init: initialize spack.store lazily

- spack.store was previously initialized at the spack.store module level,
  but this means the store has to be initialized on every spack call.

- this moves the state in spack.store to a singleton so that the store is
  only initialized when needed.

36 files changed, 239 insertions, 198 deletions

diff --git a/lib/spack/spack/binary_distribution.py b/lib/spack/spack/binary_distribution.py
index 2a0dd7633d..a5bce56c79 100644
--- a/lib/spack/spack/binary_distribution.py
+++ b/lib/spack/spack/binary_distribution.py
@@ -148,8 +148,8 @@ def write_buildinfo_file(prefix, workdir, rel=False):
             #  Check if the file contains a string with the installroot.
             #  This cuts down on the number of files added to the list
             #  of files potentially needing relocation
-            if relocate.strings_contains_installroot(path_name,
-                                                     spack.store.layout.root):
+            if relocate.strings_contains_installroot(
+                    path_name, spack.store.store().layout.root):
                 filetype = relocate.get_filetype(path_name)
                 if relocate.needs_binary_relocation(filetype, os_id):
                     rel_path_name = os.path.relpath(path_name, prefix)
@@ -161,9 +161,9 @@ def write_buildinfo_file(prefix, workdir, rel=False):
     # Create buildinfo data and write it to disk
     buildinfo = {}
     buildinfo['relative_rpaths'] = rel
-    buildinfo['buildpath'] = spack.store.layout.root
-    buildinfo['relative_prefix'] = os.path.relpath(prefix,
-                                                   spack.store.layout.root)
+    buildinfo['buildpath'] = spack.store.store().layout.root
+    buildinfo['relative_prefix'] = os.path.relpath(
+        prefix, spack.store.store().layout.root)
     buildinfo['relocate_textfiles'] = text_to_relocate
     buildinfo['relocate_binaries'] = binary_to_relocate
     filename = buildinfo_file_name(workdir)
@@ -333,8 +333,8 @@ def build_tarball(spec, outdir, force=False, rel=False, unsigned=False,
     # Add original install prefix relative to layout root to spec.yaml.
     # This will be used to determine is the directory layout has changed.
     buildinfo = {}
-    buildinfo['relative_prefix'] = os.path.relpath(spec.prefix,
-                                                   spack.store.layout.root)
+    buildinfo['relative_prefix'] = os.path.relpath(
+        spec.prefix, spack.store.store().layout.root)
     spec_dict['buildinfo'] = buildinfo
     with open(specfile_path, 'w') as outfile:
         outfile.write(yaml.dump(spec_dict))
@@ -414,7 +414,7 @@ def relocate_package(workdir, allow_root):
     Relocate the given package
     """
     buildinfo = read_buildinfo_file(workdir)
-    new_path = spack.store.layout.root
+    new_path = spack.store.store().layout.root
     old_path = buildinfo['buildpath']
     rel = buildinfo.get('relative_rpaths', False)
     if rel:
@@ -493,7 +493,7 @@ def extract_tarball(spec, filename, allow_root=False, unsigned=False,
             "It cannot be installed.")
 
     new_relative_prefix = str(os.path.relpath(spec.prefix,
-                                              spack.store.layout.root))
+                                              spack.store.store().layout.root))
     # if the original relative prefix is in the spec file use it
     buildinfo = spec_dict.get('buildinfo', {})
     old_relative_prefix = buildinfo.get('relative_prefix', new_relative_prefix)
diff --git a/lib/spack/spack/build_environment.py b/lib/spack/spack/build_environment.py
index cdf3e86577..4619c4c206 100644
--- a/lib/spack/spack/build_environment.py
+++ b/lib/spack/spack/build_environment.py
@@ -256,7 +256,7 @@ def set_build_environment_variables(pkg, env, dirty):
     env.set(SPACK_PREFIX, pkg.prefix)
 
     # Install root prefix
-    env.set(SPACK_INSTALL, spack.store.root)
+    env.set(SPACK_INSTALL, spack.store.store().root)
 
     # Stuff in here sanitizes the build environment to eliminate
     # anything the user has set that may interfere.
diff --git a/lib/spack/spack/cmd/__init__.py b/lib/spack/spack/cmd/__init__.py
index f57e86ee27..8aab63d4f3 100644
--- a/lib/spack/spack/cmd/__init__.py
+++ b/lib/spack/spack/cmd/__init__.py
@@ -182,7 +182,7 @@ def elide_list(line_list, max_num=10):
 
 
 def disambiguate_spec(spec):
-    matching_specs = spack.store.db.query(spec)
+    matching_specs = spack.store.store().db.query(spec)
     if not matching_specs:
         tty.die("Spec '%s' matches no installed packages." % spec)
 
diff --git a/lib/spack/spack/cmd/activate.py b/lib/spack/spack/cmd/activate.py
index b7b953d153..6c0e5f767d 100644
--- a/lib/spack/spack/cmd/activate.py
+++ b/lib/spack/spack/cmd/activate.py
@@ -54,9 +54,10 @@ def activate(parser, args):
     if not spec.package.is_extension:
         tty.die("%s is not an extension." % spec.name)
 
-    layout = spack.store.extensions
+    layout = spack.store.store().extensions
     if args.view is not None:
-        layout = YamlViewExtensionsLayout(args.view, spack.store.layout)
+        layout = YamlViewExtensionsLayout(
+            args.view, spack.store.store().layout)
 
     if spec.package.is_activated(extensions_layout=layout):
         tty.msg("Package %s is already activated." % specs[0].short_spec)
diff --git a/lib/spack/spack/cmd/bootstrap.py b/lib/spack/spack/cmd/bootstrap.py
index 80abbd8045..650e0a8e8d 100644
--- a/lib/spack/spack/cmd/bootstrap.py
+++ b/lib/spack/spack/cmd/bootstrap.py
@@ -68,7 +68,7 @@ def bootstrap(parser, args, **kwargs):
     requirement_dict = {'environment-modules': 'environment-modules~X'}
 
     for requirement in requirement_dict:
-        installed_specs = spack.store.db.query(requirement)
+        installed_specs = spack.store.store().db.query(requirement)
         if(len(installed_specs) > 0):
             tty.msg("Requirement %s is satisfied with installed "
                     "package %s" % (requirement, installed_specs[0]))
diff --git a/lib/spack/spack/cmd/buildcache.py b/lib/spack/spack/cmd/buildcache.py
index a9f9b6d6b8..6d6c49c5bd 100644
--- a/lib/spack/spack/cmd/buildcache.py
+++ b/lib/spack/spack/cmd/buildcache.py
@@ -116,7 +116,7 @@ def find_matching_specs(pkgs, allow_multiple_matches=False, force=False):
     has_errors = False
     specs = spack.cmd.parse_specs(pkgs)
     for spec in specs:
-        matching = spack.store.db.query(spec)
+        matching = spack.store.store().db.query(spec)
         # For each spec provided, make sure it refers to only one package.
         # Fail and ask user to be unambiguous if it doesn't
         if not allow_multiple_matches and len(matching) > 1:
@@ -254,7 +254,7 @@ def install_tarball(spec, args):
             tty.msg('Installing buildcache for spec %s' % spec.format())
             bindist.extract_tarball(spec, tarball, args.allow_root,
                                     args.unsigned, args.force)
-            spack.store.db.reindex(spack.store.layout)
+            spack.store.store().reindex()
         else:
             tty.die('Download of binary cache file for spec %s failed.' %
                     spec.format())
diff --git a/lib/spack/spack/cmd/common/arguments.py b/lib/spack/spack/cmd/common/arguments.py
index ea5bc1c25d..2b1a47c8df 100644
--- a/lib/spack/spack/cmd/common/arguments.py
+++ b/lib/spack/spack/cmd/common/arguments.py
@@ -73,12 +73,12 @@ class ConstraintAction(argparse.Action):
 
         # return everything for an empty query.
         if not qspecs:
-            return spack.store.db.query(**kwargs)
+            return spack.store.store().db.query(**kwargs)
 
         # Return only matching stuff otherwise.
         specs = set()
         for spec in qspecs:
-            for s in spack.store.db.query(spec, **kwargs):
+            for s in spack.store.store().db.query(spec, **kwargs):
                 specs.add(s)
         return sorted(specs)
 
diff --git a/lib/spack/spack/cmd/deactivate.py b/lib/spack/spack/cmd/deactivate.py
index 575ba05a1d..adac9e5e0f 100644
--- a/lib/spack/spack/cmd/deactivate.py
+++ b/lib/spack/spack/cmd/deactivate.py
@@ -60,14 +60,15 @@ def deactivate(parser, args):
     spec = spack.cmd.disambiguate_spec(specs[0])
     pkg = spec.package
 
-    layout = spack.store.extensions
+    layout = spack.store.store().extensions
     if args.view is not None:
-        layout = YamlViewExtensionsLayout(args.view, spack.store.layout)
+        layout = YamlViewExtensionsLayout(
+            args.view, spack.store.store().layout)
 
     if args.all:
         if pkg.extendable:
             tty.msg("Deactivating all extensions of %s" % pkg.spec.short_spec)
-            ext_pkgs = spack.store.db.activated_extensions_for(
+            ext_pkgs = spack.store.store().db.activated_extensions_for(
                 spec, extensions_layout=layout)
 
             for ext_pkg in ext_pkgs:
diff --git a/lib/spack/spack/cmd/debug.py b/lib/spack/spack/cmd/debug.py
index 2a85be8a00..4aa6f25fa0 100644
--- a/lib/spack/spack/cmd/debug.py
+++ b/lib/spack/spack/cmd/debug.py
@@ -76,16 +76,16 @@ def create_db_tarball(args):
     tarball_name = "spack-db.%s.tar.gz" % _debug_tarball_suffix()
     tarball_path = os.path.abspath(tarball_name)
 
-    base = os.path.basename(spack.store.root)
+    base = os.path.basename(spack.store.store().root)
     transform_args = []
     if 'GNU' in tar('--version', output=str):
         transform_args = ['--transform', 's/^%s/%s/' % (base, tarball_name)]
     else:
         transform_args = ['-s', '/^%s/%s/' % (base, tarball_name)]
 
-    wd = os.path.dirname(spack.store.root)
+    wd = os.path.dirname(spack.store.store().root)
     with working_dir(wd):
-        files = [spack.store.db._index_path]
+        files = [spack.store.store().db._index_path]
         files += glob('%s/*/*/*/.spack/spec.yaml' % base)
         files = [os.path.relpath(f) for f in files]
 
diff --git a/lib/spack/spack/cmd/dependencies.py b/lib/spack/spack/cmd/dependencies.py
index ad34fa16ce..f39ddb4dab 100644
--- a/lib/spack/spack/cmd/dependencies.py
+++ b/lib/spack/spack/cmd/dependencies.py
@@ -60,7 +60,7 @@ def dependencies(parser, args):
         spec = spack.cmd.disambiguate_spec(specs[0])
 
         tty.msg("Dependencies of %s" % spec.format('$_$@$%@$/', color=True))
-        deps = spack.store.db.installed_relatives(
+        deps = spack.store.store().db.installed_relatives(
             spec, 'children', args.transitive)
         if deps:
             spack.cmd.display_specs(deps, long=True)
diff --git a/lib/spack/spack/cmd/dependents.py b/lib/spack/spack/cmd/dependents.py
index 602d386c0a..129ee56435 100644
--- a/lib/spack/spack/cmd/dependents.py
+++ b/lib/spack/spack/cmd/dependents.py
@@ -103,7 +103,7 @@ def dependents(parser, args):
         spec = spack.cmd.disambiguate_spec(specs[0])
 
         tty.msg("Dependents of %s" % spec.cformat('$_$@$%@$/'))
-        deps = spack.store.db.installed_relatives(
+        deps = spack.store.store().db.installed_relatives(
             spec, 'parents', args.transitive)
         if deps:
             spack.cmd.display_specs(deps, long=True)
diff --git a/lib/spack/spack/cmd/extensions.py b/lib/spack/spack/cmd/extensions.py
index 6ea115e42f..56463ae7c2 100644
--- a/lib/spack/spack/cmd/extensions.py
+++ b/lib/spack/spack/cmd/extensions.py
@@ -113,16 +113,17 @@ def extensions(parser, args):
             tty.msg("%d extensions:" % len(extensions))
             colify(ext.name for ext in extensions)
 
-    layout = spack.store.extensions
+    layout = spack.store.store().extensions
     if args.view is not None:
-        layout = YamlViewExtensionsLayout(args.view, spack.store.layout)
+        layout = YamlViewExtensionsLayout(
+            args.view, spack.store.store().layout)
 
     if show_installed:
         #
         # List specs of installed extensions.
         #
-        installed = [s.spec
-                     for s in spack.store.db.installed_extensions_for(spec)]
+        store = spack.store.store()
+        installed = [s.spec for s in store.db.installed_extensions_for(spec)]
 
         if show_all:
             print
diff --git a/lib/spack/spack/cmd/graph.py b/lib/spack/spack/cmd/graph.py
index 305835ff34..81e6e6119c 100644
--- a/lib/spack/spack/cmd/graph.py
+++ b/lib/spack/spack/cmd/graph.py
@@ -77,7 +77,7 @@ def graph(parser, args):
         if args.specs:
             tty.die("Can't specify specs with --installed")
         args.dot = True
-        specs = spack.store.db.query()
+        specs = spack.store.store().db.query()
 
     else:
         specs = spack.cmd.parse_specs(
diff --git a/lib/spack/spack/cmd/install.py b/lib/spack/spack/cmd/install.py
index 93aeb1009a..9c074a5794 100644
--- a/lib/spack/spack/cmd/install.py
+++ b/lib/spack/spack/cmd/install.py
@@ -244,7 +244,7 @@ def install(parser, args, **kwargs):
                 "only one spec is allowed when overwriting an installation"
 
             spec = specs[0]
-            t = spack.store.db.query(spec)
+            t = spack.store.store().db.query(spec)
             assert len(t) == 1, "to overwrite a spec you must install it first"
 
             # Give the user a last chance to think about overwriting an already
diff --git a/lib/spack/spack/cmd/reindex.py b/lib/spack/spack/cmd/reindex.py
index 33207d5ddf..647c4b73a9 100644
--- a/lib/spack/spack/cmd/reindex.py
+++ b/lib/spack/spack/cmd/reindex.py
@@ -31,4 +31,4 @@ level = "long"
 
 
 def reindex(parser, args):
-    spack.store.db.reindex(spack.store.layout)
+    spack.store.store().reindex()
diff --git a/lib/spack/spack/cmd/setup.py b/lib/spack/spack/cmd/setup.py
index abf1e2957b..60b814b6c2 100644
--- a/lib/spack/spack/cmd/setup.py
+++ b/lib/spack/spack/cmd/setup.py
@@ -135,7 +135,7 @@ def setup(self, args):
         tty.die("spack setup only takes one spec.")
 
     # Take a write lock before checking for existence.
-    with spack.store.db.write_transaction():
+    with spack.store.store().db.write_transaction():
         spec = specs[0]
         if not spack.repo.path().exists(spec.name):
             tty.die("No package for '{0}' was found.".format(spec.name),
diff --git a/lib/spack/spack/cmd/uninstall.py b/lib/spack/spack/cmd/uninstall.py
index b9f3833999..f3c7b77b1d 100644
--- a/lib/spack/spack/cmd/uninstall.py
+++ b/lib/spack/spack/cmd/uninstall.py
@@ -93,7 +93,7 @@ def find_matching_specs(specs, allow_multiple_matches=False, force=False):
     specs_from_cli = []
     has_errors = False
     for spec in specs:
-        matching = spack.store.db.query(spec)
+        matching = spack.store.store().db.query(spec)
         # For each spec provided, make sure it refers to only one package.
         # Fail and ask user to be unambiguous if it doesn't
         if not allow_multiple_matches and len(matching) > 1:
@@ -128,7 +128,8 @@ def installed_dependents(specs):
     """
     dependents = {}
     for item in specs:
-        installed = spack.store.db.installed_relatives(item, 'parents', True)
+        installed = spack.store.store().db.installed_relatives(
+            item, 'parents', True)
         lst = [x for x in installed if x not in specs]
         if lst:
             lst = list(set(lst))
@@ -157,7 +158,7 @@ def do_uninstall(specs, force):
     # Sort packages to be uninstalled by the number of installed dependents
     # This ensures we do things in the right order
     def num_installed_deps(pkg):
-        dependents = spack.store.db.installed_relatives(
+        dependents = spack.store.store().db.installed_relatives(
             pkg.spec, 'parents', True)
         return len(dependents)
 
diff --git a/lib/spack/spack/cmd/view.py b/lib/spack/spack/cmd/view.py
index 71333a088f..009529d848 100644
--- a/lib/spack/spack/cmd/view.py
+++ b/lib/spack/spack/cmd/view.py
@@ -93,7 +93,7 @@ def relaxed_disambiguate(specs, view):
             return matching_specs[0]
 
     # make function always return a list to keep consistency between py2/3
-    return list(map(squash, map(spack.store.db.query, specs)))
+    return list(map(squash, map(spack.store.store().db.query, specs)))
 
 
 def setup_parser(sp):
@@ -176,7 +176,7 @@ def view(parser, args):
     path = args.path[0]
 
     view = YamlFilesystemView(
-        path, spack.store.layout,
+        path, spack.store.store().layout,
         ignore_conflicts=getattr(args, "ignore_conflicts", False),
         link=os.link if args.action in ["hardlink", "hard"]
         else os.symlink,
diff --git a/lib/spack/spack/database.py b/lib/spack/spack/database.py
index 0e98cffc69..97954d67f9 100644
--- a/lib/spack/spack/database.py
+++ b/lib/spack/spack/database.py
@@ -223,7 +223,7 @@ class Database(object):
 
         Prefix lock is a byte range lock on the nth byte of a file.
 
-        The lock file is ``spack.store.db.prefix_lock`` -- the DB
+        The lock file is ``spack.store.store().db.prefix_lock`` -- the DB
         tells us what to call it and it lives alongside the install DB.
 
         n is the sys.maxsize-bit prefix of the DAG hash.  This makes
@@ -366,7 +366,7 @@ class Database(object):
         if version > _db_version:
             raise InvalidDatabaseVersionError(_db_version, version)
         elif version < _db_version:
-            self.reindex(spack.store.layout)
+            self.reindex(spack.store.store().layout)
             installs = dict((k, v.to_dict()) for k, v in self._data.items())
 
         def invalid_record(hash_key, error):
@@ -499,7 +499,7 @@ class Database(object):
                     tty.debug(
                         'RECONSTRUCTING FROM OLD DB: {0}'.format(entry.spec))
                     try:
-                        layout = spack.store.layout
+                        layout = spack.store.store().layout
                         if entry.spec.external:
                             layout = None
                             install_check = True
@@ -609,7 +609,7 @@ class Database(object):
             # reindex() takes its own write lock, so no lock here.
             with WriteTransaction(self.lock, timeout=_db_lock_timeout):
                 self._write(None, None, None)
-            self.reindex(spack.store.layout)
+            self.reindex(spack.store.store().layout)
 
     def _add(
             self,
@@ -823,7 +823,7 @@ class Database(object):
         the given spec
         """
         if extensions_layout is None:
-            extensions_layout = spack.store.extensions
+            extensions_layout = spack.store.store().extensions
         for spec in self.query():
             try:
                 extensions_layout.check_activated(extendee_spec, spec)
diff --git a/lib/spack/spack/filesystem_view.py b/lib/spack/spack/filesystem_view.py
index f374bccd1f..0c5f9a6a6c 100644
--- a/lib/spack/spack/filesystem_view.py
+++ b/lib/spack/spack/filesystem_view.py
@@ -267,7 +267,7 @@ class YamlFilesystemView(FilesystemView):
             # Check for globally activated extensions in the extendee that
             # we're looking at.
             activated = [p.spec for p in
-                         spack.store.db.activated_extensions_for(spec)]
+                         spack.store.store().db.activated_extensions_for(spec)]
             if activated:
                 tty.error("Globally activated extensions cannot be used in "
                           "conjunction with filesystem views. "
@@ -390,7 +390,8 @@ class YamlFilesystemView(FilesystemView):
             tty.info(self._croot + 'Removed package: %s' % colorize_spec(spec))
 
     def get_all_specs(self):
-        dotspack = join_path(self.root, spack.store.layout.metadata_dir)
+        dotspack = join_path(self.root,
+                             spack.store.store().layout.metadata_dir)
         if os.path.exists(dotspack):
             return list(filter(None, map(self.get_spec, os.listdir(dotspack))))
         else:
@@ -407,12 +408,14 @@ class YamlFilesystemView(FilesystemView):
 
     def get_path_meta_folder(self, spec):
         "Get path to meta folder for either spec or spec name."
-        return join_path(self.root, spack.store.layout.metadata_dir,
+        return join_path(self.root,
+                         spack.store.store().layout.metadata_dir,
                          getattr(spec, "name", spec))
 
     def get_spec(self, spec):
         dotspack = self.get_path_meta_folder(spec)
-        filename = join_path(dotspack, spack.store.layout.spec_file_name)
+        filename = join_path(dotspack,
+                             spack.store.store().layout.spec_file_name)
 
         try:
             with open(filename, "r") as f:
@@ -421,7 +424,7 @@ class YamlFilesystemView(FilesystemView):
             return None
 
     def link_meta_folder(self, spec):
-        src = spack.store.layout.metadata_path(spec)
+        src = spack.store.store().layout.metadata_path(spec)
         tgt = self.get_path_meta_folder(spec)
 
         tree = LinkTree(src)
@@ -547,4 +550,4 @@ def get_dependencies(specs):
 
 
 def ignore_metadata_dir(f):
-    return f in spack.store.layout.hidden_file_paths
+    return f in spack.store.store().layout.hidden_file_paths
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index b046a6c661..f361763878 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -949,7 +949,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             raise ValueError(
                 "is_extension called on package that is not an extension.")
         if extensions_layout is None:
-            extensions_layout = spack.store.extensions
+            extensions_layout = spack.store.store().extensions
         exts = extensions_layout.extension_map(self.extendee_spec)
         return (self.name in exts) and (exts[self.name] == self.spec)
 
@@ -1003,7 +1003,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         Removes the prefix for a package along with any empty parent
         directories
         """
-        spack.store.layout.remove_install_directory(self.spec)
+        spack.store.store().layout.remove_install_directory(self.spec)
 
     def do_fetch(self, mirror_only=False):
         """
@@ -1241,7 +1241,8 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         # Install fake man page
         mkdirp(self.prefix.man.man1)
 
-        packages_dir = spack.store.layout.build_packages_path(self.spec)
+        store = spack.store.store()
+        packages_dir = store.layout.build_packages_path(self.spec)
         dump_packages(self.spec, packages_dir)
 
     def _if_make_target_execute(self, target):
@@ -1304,7 +1305,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
     def _stage_and_write_lock(self):
         """Prefix lock nested in a stage."""
         with self.stage:
-            with spack.store.db.prefix_write_lock(self.spec):
+            with spack.store.store().db.prefix_write_lock(self.spec):
                 yield
 
     def _process_external_package(self, explicit):
@@ -1328,7 +1329,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         try:
             # Check if the package was already registered in the DB
             # If this is the case, then just exit
-            rec = spack.store.db.get_record(self.spec)
+            rec = spack.store.store().db.get_record(self.spec)
             message = '{s.name}@{s.version} : already registered in DB'
             tty.msg(message.format(s=self))
             # Update the value of rec.explicit if it is necessary
@@ -1344,12 +1345,12 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             # Add to the DB
             message = '{s.name}@{s.version} : registering into DB'
             tty.msg(message.format(s=self))
-            spack.store.db.add(self.spec, None, explicit=explicit)
+            spack.store.store().db.add(self.spec, None, explicit=explicit)
 
     def _update_explicit_entry_in_db(self, rec, explicit):
         if explicit and not rec.explicit:
-            with spack.store.db.write_transaction():
-                rec = spack.store.db.get_record(self.spec)
+            with spack.store.store().db.write_transaction():
+                rec = spack.store.store().db.get_record(self.spec)
                 rec.explicit = True
                 message = '{s.name}@{s.version} : marking the package explicit'
                 tty.msg(message.format(s=self))
@@ -1366,7 +1367,8 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         binary_distribution.extract_tarball(
             binary_spec, tarball, allow_root=False,
             unsigned=False, force=False)
-        spack.store.db.add(self.spec, spack.store.layout, explicit=explicit)
+        spack.store.store().db.add(
+            self.spec, spack.store.layout, explicit=explicit)
         return True
 
     def do_install(self,
@@ -1423,15 +1425,15 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         partial = self.check_for_unfinished_installation(keep_prefix, restage)
 
         # Ensure package is not already installed
-        layout = spack.store.layout
-        with spack.store.db.prefix_read_lock(self.spec):
+        layout = spack.store.store().layout
+        with spack.store.store().db.prefix_read_lock(self.spec):
             if partial:
                 tty.msg(
                     "Continuing from partial install of %s" % self.name)
             elif layout.check_installed(self.spec):
                 msg = '{0.name} is already installed in {0.prefix}'
                 tty.msg(msg.format(self))
-                rec = spack.store.db.get_record(self.spec)
+                rec = spack.store.store().db.get_record(self.spec)
                 # In case the stage directory has already been created,
                 # this ensures it's removed after we checked that the spec
                 # is installed
@@ -1566,7 +1568,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         try:
             # Create the install prefix and fork the build process.
             if not os.path.exists(self.prefix):
-                spack.store.layout.create_install_directory(self.spec)
+                spack.store.store().layout.create_install_directory(self.spec)
 
             # Fork a child to do the actual installation
             # we preserve verbosity settings across installs.
@@ -1577,8 +1579,8 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             keep_prefix = self.last_phase is None or keep_prefix
             # note: PARENT of the build process adds the new package to
             # the database, so that we don't need to re-read from file.
-            spack.store.db.add(
-                self.spec, spack.store.layout, explicit=explicit
+            spack.store.store().db.add(
+                self.spec, spack.store.store().layout, explicit=explicit
             )
         except directory_layout.InstallDirectoryAlreadyExistsError:
             # Abort install if install directory exists.
@@ -1632,9 +1634,9 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             raise ExternalPackageError("Attempted to repair external spec %s" %
                                        self.spec.name)
 
-        with spack.store.db.prefix_write_lock(self.spec):
+        with spack.store.store().db.prefix_write_lock(self.spec):
             try:
-                record = spack.store.db.get_record(self.spec)
+                record = spack.store.store().db.get_record(self.spec)
                 installed_in_db = record.installed if record else False
             except KeyError:
                 installed_in_db = False
@@ -1669,9 +1671,10 @@ class PackageBase(with_metaclass(PackageMeta, object)):
 
     def log(self):
         # Copy provenance into the install directory on success
-        log_install_path = spack.store.layout.build_log_path(self.spec)
-        env_install_path = spack.store.layout.build_env_path(self.spec)
-        packages_dir = spack.store.layout.build_packages_path(self.spec)
+        store = spack.store.store()
+        log_install_path = store.layout.build_log_path(self.spec)
+        env_install_path = store.layout.build_env_path(self.spec)
+        packages_dir = store.layout.build_packages_path(self.spec)
 
         # Remove first if we're overwriting another build
         # (can happen with spack setup)
@@ -1690,8 +1693,9 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         with working_dir(self.stage.source_path):
             errors = StringIO()
             target_dir = os.path.join(
-                spack.store.layout.metadata_path(self.spec), 'archived-files'
-            )
+                spack.store.store().layout.metadata_path(self.spec),
+                'archived-files')
+
             for glob_expr in self.archive_files:
                 # Check that we are trying to copy things that are
                 # in the source_path tree (not arbitrary files)
@@ -1750,7 +1754,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
 
         installed = set(os.listdir(self.prefix))
         installed.difference_update(
-            spack.store.layout.hidden_file_paths)
+            spack.store.store().layout.hidden_file_paths)
         if not installed:
             raise InstallError(
                 "Install failed for %s.  Nothing was installed!" % self.name)
@@ -1758,7 +1762,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
     @property
     def build_log_path(self):
         if self.installed:
-            return spack.store.layout.build_log_path(self.spec)
+            return spack.store.store().layout.build_log_path(self.spec)
         else:
             return join_path(self.stage.source_path, 'spack-build.out')
 
@@ -1916,16 +1920,16 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         if not os.path.isdir(spec.prefix):
             # prefix may not exist, but DB may be inconsistent. Try to fix by
             # removing, but omit hooks.
-            specs = spack.store.db.query(spec, installed=True)
+            specs = spack.store.store().db.query(spec, installed=True)
             if specs:
-                spack.store.db.remove(specs[0])
+                spack.store.store().db.remove(specs[0])
                 tty.msg("Removed stale DB entry for %s" % spec.short_spec)
                 return
             else:
                 raise InstallError(str(spec) + " is not installed.")
 
         if not force:
-            dependents = spack.store.db.installed_relatives(
+            dependents = spack.store.store().db.installed_relatives(
                 spec, 'parents', True)
             if dependents:
                 raise PackageStillNeededError(spec, dependents)
@@ -1937,7 +1941,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             pkg = None
 
         # Pre-uninstall hook runs first.
-        with spack.store.db.prefix_write_lock(spec):
+        with spack.store.store().db.prefix_write_lock(spec):
 
             if pkg is not None:
                 spack.hooks.pre_uninstall(spec)
@@ -1946,11 +1950,11 @@ class PackageBase(with_metaclass(PackageMeta, object)):
             if not spec.external:
                 msg = 'Deleting package prefix [{0}]'
                 tty.debug(msg.format(spec.short_spec))
-                spack.store.layout.remove_install_directory(spec)
+                spack.store.store().layout.remove_install_directory(spec)
             # Delete DB entry
             msg = 'Deleting DB entry [{0}]'
             tty.debug(msg.format(spec.short_spec))
-            spack.store.db.remove(spec)
+            spack.store.store().db.remove(spec)
 
         if pkg is not None:
             spack.hooks.post_uninstall(spec)
@@ -1996,7 +2000,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         self._sanity_check_extension()
 
         if extensions_layout is None:
-            extensions_layout = spack.store.extensions
+            extensions_layout = spack.store.store().extensions
 
         extensions_layout.check_extension_conflict(
             self.extendee_spec, self.spec)
@@ -2040,11 +2044,11 @@ class PackageBase(with_metaclass(PackageMeta, object)):
 
         """
         extensions_layout = kwargs.get("extensions_layout",
-                                       spack.store.extensions)
+                                       spack.store.store().extensions)
         target = extensions_layout.extendee_target_directory(self)
 
         def ignore(filename):
-            return (filename in spack.store.layout.hidden_file_paths or
+            return (filename in spack.store.store().layout.hidden_file_paths or
                     kwargs.get('ignore', lambda f: False)(filename))
 
         tree = LinkTree(extension.prefix)
@@ -2072,7 +2076,7 @@ class PackageBase(with_metaclass(PackageMeta, object)):
         verbose = kwargs.get("verbose", True)
         remove_dependents = kwargs.get("remove_dependents", False)
         extensions_layout = kwargs.get("extensions_layout",
-                                       spack.store.extensions)
+                                       spack.store.store().extensions)
 
         # Allow a force deactivate to happen.  This can unlink
         # spurious files if something was corrupted.
@@ -2124,11 +2128,11 @@ class PackageBase(with_metaclass(PackageMeta, object)):
 
         """
         extensions_layout = kwargs.get("extensions_layout",
-                                       spack.store.extensions)
+                                       spack.store.store().extensions)
         target = extensions_layout.extendee_target_directory(self)
 
         def ignore(filename):
-            return (filename in spack.store.layout.hidden_file_paths or
+            return (filename in spack.store.store().layout.hidden_file_paths or
                     kwargs.get('ignore', lambda f: False)(filename))
 
         tree = LinkTree(extension.prefix)
@@ -2273,7 +2277,7 @@ def flatten_dependencies(spec, flat_dir):
     for dep in spec.traverse(root=False):
         name = dep.name
 
-        dep_path = spack.store.layout.path_for_spec(dep)
+        dep_path = spack.store.store().layout.path_for_spec(dep)
         dep_files = LinkTree(dep_path)
 
         os.mkdir(flat_dir + '/' + name)
@@ -2302,7 +2306,7 @@ def dump_packages(spec, path):
         if node is not spec:
             # Locate the dependency package in the install tree and find
             # its provenance information.
-            source = spack.store.layout.build_packages_path(node)
+            source = spack.store.store().layout.build_packages_path(node)
             source_repo_root = join_path(source, node.namespace)
 
             # There's no provenance installed for the source package.  Skip it.
diff --git a/lib/spack/spack/relocate.py b/lib/spack/spack/relocate.py
index ffda18f350..303776557b 100644
--- a/lib/spack/spack/relocate.py
+++ b/lib/spack/spack/relocate.py
@@ -110,7 +110,7 @@ def get_placeholder_rpaths(path_name, orig_rpaths):
     Replaces original layout root dir with a placeholder string in all rpaths.
     """
     rel_rpaths = []
-    orig_dir = spack.store.layout.root
+    orig_dir = spack.store.store().layout.root
     for rpath in orig_rpaths:
         if re.match(orig_dir, rpath):
             placeholder = set_placeholder(orig_dir)
@@ -186,7 +186,7 @@ def macho_make_paths_placeholder(rpaths, deps, idpath):
     replacement are returned.
     """
     new_idpath = None
-    old_dir = spack.store.layout.root
+    old_dir = spack.store.store().layout.root
     placeholder = set_placeholder(old_dir)
     if idpath:
         new_idpath = re.sub(old_dir, placeholder, idpath)
@@ -425,9 +425,9 @@ def make_binary_placeholder(cur_path_names, allow_root):
                                 new_rpaths, new_deps, new_idpath)
             if (not allow_root and
                 strings_contains_installroot(cur_path,
-                                             spack.store.layout.root)):
-                raise InstallRootStringException(cur_path,
-                                                 spack.store.layout.root)
+                                             spack.store.store().layout.root)):
+                raise InstallRootStringException(
+                    cur_path, spack.store.store().layout.root)
     elif platform.system() == 'Linux':
         for cur_path in cur_path_names:
             orig_rpaths = get_existing_elf_rpaths(cur_path)
@@ -435,10 +435,10 @@ def make_binary_placeholder(cur_path_names, allow_root):
                 new_rpaths = get_placeholder_rpaths(cur_path, orig_rpaths)
                 modify_elf_object(cur_path, new_rpaths)
                 if (not allow_root and
-                    strings_contains_installroot(cur_path,
-                                                 spack.store.layout.root)):
-                    raise InstallRootStringException(cur_path,
-                                                     spack.store.layout.root)
+                    strings_contains_installroot(
+                        cur_path, spack.store.store().layout.root)):
+                    raise InstallRootStringException(
+                        cur_path, spack.store.store().layout.root)
     else:
         tty.die("Placeholder not implemented for %s" % platform.system())
 
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 896927e3fd..e81d913631 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1402,7 +1402,7 @@ class Spec(object):
     @property
     def prefix(self):
         if self._prefix is None:
-            self.prefix = spack.store.layout.path_for_spec(self)
+            self.prefix = spack.store.store().layout.path_for_spec(self)
         return self._prefix
 
     @prefix.setter
@@ -3107,7 +3107,7 @@ class Spec(object):
                 elif named_str == 'SPACK_ROOT':
                     out.write(fmt % token_transform(spack.paths.prefix))
                 elif named_str == 'SPACK_INSTALL':
-                    out.write(fmt % token_transform(spack.store.root))
+                    out.write(fmt % token_transform(spack.store.store().root))
                 elif named_str == 'PREFIX':
                     out.write(fmt % token_transform(self.prefix))
                 elif named_str.startswith('HASH'):
@@ -3149,7 +3149,7 @@ class Spec(object):
         if not self.concrete:
             return None
         try:
-            record = spack.store.db.get_record(self)
+            record = spack.store.store().db.get_record(self)
             return record.installed
         except KeyError:
             return None
@@ -3159,7 +3159,7 @@ class Spec(object):
         if not self.concrete:
             return None
         try:
-            record = spack.store.db.get_record(self)
+            record = spack.store.store().db.get_record(self)
             return record.explicit
         except KeyError:
             return None
@@ -3382,7 +3382,7 @@ class SpecParser(spack.parse.Parser):
     def spec_by_hash(self):
         self.expect(ID)
 
-        specs = spack.store.db.query()
+        specs = spack.store.store().db.query()
         matches = [spec for spec in specs if
                    spec.dag_hash()[:len(self.token.value)] == self.token.value]
 
diff --git a/lib/spack/spack/store.py b/lib/spack/spack/store.py
index ca6eb37361..9bd8166c16 100644
--- a/lib/spack/spack/store.py
+++ b/lib/spack/spack/store.py
@@ -45,32 +45,59 @@ configuration.
 import os
 import spack.paths
 import spack.config
-from spack.util.path import canonicalize_path
-from spack.database import Database
-from spack.directory_layout import YamlDirectoryLayout
-from spack.directory_layout import YamlExtensionsLayout
+import spack.util.path
+import spack.database
+import spack.directory_layout
 
-__author__ = "Benedikt Hegner (CERN)"
-__all__ = ['db', 'extensions', 'layout', 'root']
+#: default installation root, relative to the Spack install path
+default_root = os.path.join(spack.paths.opt_path, 'spack')
 
-#
-# Set up the install path
-#
-root = canonicalize_path(spack.config.get(
-    'config:install_tree', os.path.join(spack.paths.opt_path, 'spack')))
 
-#
-# Set up the installed packages database
-#
-db = Database(root)
+class Store(object):
+    """A store is a path full of installed Spack packages.
 
-#
-# This controls how spack lays out install prefixes and
-# stage directories.
-#
-layout = YamlDirectoryLayout(
-    root,
-    hash_len=spack.config.get('config:install_hash_length'),
-    path_scheme=spack.config.get('config:install_path_scheme'))
+    Stores consist of packages installed according to a
+    ``DirectoryLayout``, along with an index, or _database_ of their
+    contents.  The directory layout controls what paths look like and how
+    Spack ensures that each uniqe spec gets its own unique directory (or
+    not, though we don't recommend that). The database is a signle file
+    that caches metadata for the entire Spack installation.  It prevents
+    us from having to spider the install tree to figure out what's there.
+
+    Args:
+        root (str): path to the root of the install tree
+        path_scheme (str): expression according to guidelines in
+            ``spack.util.path`` that describes how to construct a path to
+            a package prefix in this store
+        hash_length (int): length of the hashes used in the directory
+            layout; spec hash suffixes will be truncated to this length
+    """
+    def __init__(self, root, path_scheme, hash_length):
+        self.root = root
+        self.db = spack.database.Database(root)
+        self.layout = spack.directory_layout.YamlDirectoryLayout(
+            root, hash_len=hash_length, path_scheme=path_scheme)
+        self.extensions = spack.directory_layout.YamlExtensionsLayout(
+            root, self.layout)
+
+    def reindex(self):
+        """Convenience function to reindex the store DB with its own layout."""
+        return self.db.reindex(self.layout)
+
+
+#: Singleton store instance
+_store = None
+
+
+def store():
+    """Get the singleton store instance."""
+    global _store
+
+    if _store is None:
+        root = spack.config.get('config:install_tree', default_root)
+        root = spack.util.path.canonicalize_path(root)
 
-extensions = YamlExtensionsLayout(root, layout)
+        _store = Store(root,
+                       spack.config.get('config:install_path_scheme'),
+                       spack.config.get('config:install_hash_length'))
+    return _store
diff --git a/lib/spack/spack/test/cmd/dependencies.py b/lib/spack/spack/test/cmd/dependencies.py
index 015eac589c..f211737e4b 100644
--- a/lib/spack/spack/test/cmd/dependencies.py
+++ b/lib/spack/spack/test/cmd/dependencies.py
@@ -60,7 +60,7 @@ def test_immediate_installed_dependencies(mock_packages, database):
     lines = [l for l in out.strip().split('\n') if not l.startswith('--')]
     hashes = set([re.split(r'\s+', l)[0] for l in lines])
 
-    expected = set([spack.store.db.query_one(s).dag_hash(7)
+    expected = set([spack.store.store().db.query_one(s).dag_hash(7)
                     for s in ['mpich', 'callpath^mpich']])
 
     assert expected == hashes
@@ -74,7 +74,7 @@ def test_transitive_installed_dependencies(mock_packages, database):
     lines = [l for l in out.strip().split('\n') if not l.startswith('--')]
     hashes = set([re.split(r'\s+', l)[0] for l in lines])
 
-    expected = set([spack.store.db.query_one(s).dag_hash(7)
+    expected = set([spack.store.store().db.query_one(s).dag_hash(7)
                     for s in ['zmpi', 'callpath^zmpi', 'fake',
                               'dyninst', 'libdwarf', 'libelf']])
 
diff --git a/lib/spack/spack/test/cmd/dependents.py b/lib/spack/spack/test/cmd/dependents.py
index c6a5b01111..6d85596c37 100644
--- a/lib/spack/spack/test/cmd/dependents.py
+++ b/lib/spack/spack/test/cmd/dependents.py
@@ -58,10 +58,10 @@ def test_immediate_installed_dependents(mock_packages, database):
     lines = [l for l in out.strip().split('\n') if not l.startswith('--')]
     hashes = set([re.split(r'\s+', l)[0] for l in lines])
 
-    expected = set([spack.store.db.query_one(s).dag_hash(7)
+    expected = set([spack.store.store().db.query_one(s).dag_hash(7)
                     for s in ['dyninst', 'libdwarf']])
 
-    libelf = spack.store.db.query_one('libelf')
+    libelf = spack.store.store().db.query_one('libelf')
     expected = set([d.dag_hash(7) for d in libelf.dependents()])
 
     assert expected == hashes
@@ -75,7 +75,7 @@ def test_transitive_installed_dependents(mock_packages, database):
     lines = [l for l in out.strip().split('\n') if not l.startswith('--')]
     hashes = set([re.split(r'\s+', l)[0] for l in lines])
 
-    expected = set([spack.store.db.query_one(s).dag_hash(7)
+    expected = set([spack.store.store().db.query_one(s).dag_hash(7)
                     for s in ['zmpi', 'callpath^zmpi', 'mpileaks^zmpi']])
 
     assert expected == hashes
diff --git a/lib/spack/spack/test/cmd/install.py b/lib/spack/spack/test/cmd/install.py
index e7b0fb9693..5635fbdf09 100644
--- a/lib/spack/spack/test/cmd/install.py
+++ b/lib/spack/spack/test/cmd/install.py
@@ -387,7 +387,7 @@ def test_extra_files_are_archived(mock_packages, mock_archive, mock_fetch,
     install('archive-files')
 
     archive_dir = os.path.join(
-        spack.store.layout.metadata_path(s), 'archived-files'
+        spack.store.store().layout.metadata_path(s), 'archived-files'
     )
     config_log = os.path.join(archive_dir, 'config.log')
     assert os.path.exists(config_log)
diff --git a/lib/spack/spack/test/cmd/uninstall.py b/lib/spack/spack/test/cmd/uninstall.py
index 1c187431d1..d81ab13a57 100644
--- a/lib/spack/spack/test/cmd/uninstall.py
+++ b/lib/spack/spack/test/cmd/uninstall.py
@@ -61,7 +61,7 @@ def test_recursive_uninstall():
     """Test recursive uninstall."""
     uninstall('-y', '-a', '--dependents', 'callpath')
 
-    all_specs = spack.store.layout.all_specs()
+    all_specs = spack.store.store().layout.all_specs()
     assert len(all_specs) == 8
     # query specs with multiple configurations
     mpileaks_specs = [s for s in all_specs if s.satisfies('mpileaks')]
diff --git a/lib/spack/spack/test/conftest.py b/lib/spack/spack/test/conftest.py
index 46767133b2..c405d1246a 100644
--- a/lib/spack/spack/test/conftest.py
+++ b/lib/spack/spack/test/conftest.py
@@ -283,18 +283,18 @@ def database(tmpdir_factory, mock_packages, config):
 
     # Make a fake install directory
     install_path = tmpdir_factory.mktemp('install_for_database')
-    spack_install_path = spack.store.root
+    spack_install_path = spack.store.store().root
 
-    spack.store.root = str(install_path)
+    spack.store.store().root = str(install_path)
     install_layout = spack.directory_layout.YamlDirectoryLayout(
         str(install_path))
-    spack_install_layout = spack.store.layout
-    spack.store.layout = install_layout
+    spack_install_layout = spack.store.store().layout
+    spack.store.store().layout = install_layout
 
     # Make fake database and fake install directory.
     install_db = spack.database.Database(str(install_path))
-    spack_install_db = spack.store.db
-    spack.store.db = install_db
+    spack_install_db = spack.store.store().db
+    spack.store.store().db = install_db
 
     Entry = collections.namedtuple('Entry', ['path', 'layout', 'db'])
     Database = collections.namedtuple(
@@ -316,8 +316,8 @@ def database(tmpdir_factory, mock_packages, config):
         spec.package.do_uninstall(spec)
 
     def _refresh():
-        with spack.store.db.write_transaction():
-            for spec in spack.store.db.query():
+        with spack.store.store().db.write_transaction():
+            for spec in spack.store.store().db.query():
                 _uninstall(spec)
             _install('mpileaks ^mpich')
             _install('mpileaks ^mpich2')
@@ -332,7 +332,7 @@ def database(tmpdir_factory, mock_packages, config):
         refresh=_refresh)
 
     # Transaction used to avoid repeated writes.
-    with spack.store.db.write_transaction():
+    with spack.store.store().db.write_transaction():
         t.install('mpileaks ^mpich')
         t.install('mpileaks ^mpich2')
         t.install('mpileaks ^zmpi')
@@ -340,17 +340,17 @@ def database(tmpdir_factory, mock_packages, config):
 
     yield t
 
-    with spack.store.db.write_transaction():
-        for spec in spack.store.db.query():
+    with spack.store.store().db.write_transaction():
+        for spec in spack.store.store().db.query():
             if spec.package.installed:
                 t.uninstall(spec)
             else:
-                spack.store.db.remove(spec)
+                spack.store.store().db.remove(spec)
 
     install_path.remove(rec=1)
-    spack.store.root = spack_install_path
-    spack.store.layout = spack_install_layout
-    spack.store.db = spack_install_db
+    spack.store.store().root = spack_install_path
+    spack.store.store().layout = spack_install_layout
+    spack.store.store().db = spack_install_db
 
 
 @pytest.fixture()
@@ -363,26 +363,27 @@ def refresh_db_on_exit(database):
 @pytest.fixture()
 def install_mockery(tmpdir, config, mock_packages):
     """Hooks a fake install directory, DB, and stage directory into Spack."""
-    layout = spack.store.layout
-    extensions = spack.store.extensions
-    db = spack.store.db
+    layout = spack.store.store().layout
+    extensions = spack.store.store().extensions
+    db = spack.store.store().db
     new_opt = str(tmpdir.join('opt'))
 
     # Use a fake install directory to avoid conflicts bt/w
     # installed pkgs and mock packages.
-    spack.store.layout = spack.directory_layout.YamlDirectoryLayout(new_opt)
-    spack.store.extensions = spack.directory_layout.YamlExtensionsLayout(
-        new_opt, spack.store.layout)
-    spack.store.db = spack.database.Database(new_opt)
+    store = spack.store.store()
+    store.layout = spack.directory_layout.YamlDirectoryLayout(new_opt)
+    store.extensions = spack.directory_layout.YamlExtensionsLayout(
+        new_opt, spack.store.store().layout)
+    store.db = spack.database.Database(new_opt)
 
     # We use a fake package, so temporarily disable checksumming
     with spack.config.override('config:checksum', False):
         yield
 
     # Restore Spack's layout.
-    spack.store.layout = layout
-    spack.store.extensions = extensions
-    spack.store.db = db
+    store.layout = layout
+    store.extensions = extensions
+    store.db = db
 
 
 @pytest.fixture()
diff --git a/lib/spack/spack/test/database.py b/lib/spack/spack/test/database.py
index 147a61ad81..b0ee343095 100644
--- a/lib/spack/spack/test/database.py
+++ b/lib/spack/spack/test/database.py
@@ -47,16 +47,16 @@ def _print_ref_counts():
     recs = []
 
     def add_rec(spec):
-        cspecs = spack.store.db.query(spec, installed=any)
+        cspecs = spack.store.store().db.query(spec, installed=any)
 
         if not cspecs:
             recs.append("[ %-7s ] %-20s-" % ('', spec))
         else:
             key = cspecs[0].dag_hash()
-            rec = spack.store.db.get_record(cspecs[0])
+            rec = spack.store.store().db.get_record(cspecs[0])
             recs.append("[ %-7s ] %-20s%d" % (key[:7], spec, rec.ref_count))
 
-    with spack.store.db.read_transaction():
+    with spack.store.store().db.read_transaction():
         add_rec('mpileaks ^mpich')
         add_rec('callpath ^mpich')
         add_rec('mpich')
@@ -79,7 +79,7 @@ def _print_ref_counts():
 
 def _check_merkleiness():
     """Ensure the spack database is a valid merkle graph."""
-    all_specs = spack.store.db.query(installed=any)
+    all_specs = spack.store.store().db.query(installed=any)
 
     seen = {}
     for spec in all_specs:
@@ -93,7 +93,7 @@ def _check_merkleiness():
 
 def _check_db_sanity(install_db):
     """Utiilty function to check db against install layout."""
-    pkg_in_layout = sorted(spack.store.layout.all_specs())
+    pkg_in_layout = sorted(spack.store.store().layout.all_specs())
     actual = sorted(install_db.query())
 
     externals = sorted([x for x in actual if x.external])
@@ -129,7 +129,7 @@ def _check_remove_and_add_package(install_db, spec):
     assert concrete_spec not in remaining
 
     # add it back and make sure everything is ok.
-    install_db.add(concrete_spec, spack.store.layout)
+    install_db.add(concrete_spec, spack.store.store().layout)
     installed = install_db.query()
     assert concrete_spec in installed
     assert installed == original
@@ -147,7 +147,7 @@ def _mock_install(spec):
 
 
 def _mock_remove(spec):
-    specs = spack.store.db.query(spec)
+    specs = spack.store.store().db.query(spec)
     assert len(specs) == 1
     spec = specs[0]
     spec.package.do_uninstall(spec)
@@ -206,7 +206,7 @@ def test_005_db_exists(database):
 
 def test_010_all_install_sanity(database):
     """Ensure that the install layout reflects what we think it does."""
-    all_specs = spack.store.layout.all_specs()
+    all_specs = spack.store.store().layout.all_specs()
     assert len(all_specs) == 14
 
     # Query specs with multiple configurations
@@ -241,12 +241,12 @@ def test_010_all_install_sanity(database):
 
 def test_015_write_and_read(database):
     # write and read DB
-    with spack.store.db.write_transaction():
-        specs = spack.store.db.query()
-        recs = [spack.store.db.get_record(s) for s in specs]
+    with spack.store.store().db.write_transaction():
+        specs = spack.store.store().db.query()
+        recs = [spack.store.store().db.get_record(s) for s in specs]
 
     for spec, rec in zip(specs, recs):
-        new_rec = spack.store.db.get_record(spec)
+        new_rec = spack.store.store().db.get_record(spec)
         assert new_rec.ref_count == rec.ref_count
         assert new_rec.spec == rec.spec
         assert new_rec.path == rec.path
@@ -262,7 +262,7 @@ def test_020_db_sanity(database):
 def test_025_reindex(database):
     """Make sure reindex works and ref counts are valid."""
     install_db = database.mock.db
-    spack.store.db.reindex(spack.store.layout)
+    spack.store.store().reindex()
     _check_db_sanity(install_db)
 
 
@@ -293,7 +293,7 @@ def test_050_basic_query(database):
     """Ensure querying database is consistent with what is installed."""
     install_db = database.mock.db
     # query everything
-    assert len(spack.store.db.query()) == 16
+    assert len(spack.store.store().db.query()) == 16
 
     # query specs with multiple configurations
     mpileaks_specs = install_db.query('mpileaks')
@@ -350,7 +350,7 @@ def test_080_root_ref_counts(database):
     assert install_db.get_record('mpich').ref_count == 1
 
     # Put the spec back
-    install_db.add(rec.spec, spack.store.layout)
+    install_db.add(rec.spec, spack.store.store().layout)
 
     # record is present again
     assert len(install_db.query('mpileaks ^mpich', installed=any)) == 1
@@ -436,7 +436,7 @@ def test_115_reindex_with_packages_not_in_repo(database, refresh_db_on_exit):
     # packages should not have to be defined in the repository once they
     # are installed
     with spack.repo.swap(MockPackageMultiRepo([])):
-        spack.store.db.reindex(spack.store.layout)
+        spack.store.store().reindex()
         _check_db_sanity(install_db)
 
 
diff --git a/lib/spack/spack/test/spec_syntax.py b/lib/spack/spack/test/spec_syntax.py
index 76867cec73..5f5c1fd3ee 100644
--- a/lib/spack/spack/test/spec_syntax.py
+++ b/lib/spack/spack/test/spec_syntax.py
@@ -336,8 +336,8 @@ class TestSpecSyntax(object):
         x2 = Spec('a')
         x2._hash = 'xx'
         x2._concrete = True
-        database.mock.db.add(x1, spack.store.layout)
-        database.mock.db.add(x2, spack.store.layout)
+        database.mock.db.add(x1, spack.store.store().layout)
+        database.mock.db.add(x2, spack.store.store().layout)
 
         # ambiguity in first hash character
         self._check_raises(AmbiguousHashError, ['/x'])
diff --git a/var/spack/repos/builtin/packages/aspell/package.py b/var/spack/repos/builtin/packages/aspell/package.py
index 66eeb9e7cb..1b23258099 100644
--- a/var/spack/repos/builtin/packages/aspell/package.py
+++ b/var/spack/repos/builtin/packages/aspell/package.py
@@ -50,8 +50,8 @@ class Aspell(AutotoolsPackage):
     #   - dest_dir instead of self.prefix in tree.(find_conflict|merge)()
     def activate(self, extension, **kwargs):
         extensions_layout = kwargs.get("extensions_layout",
-                                       spack.store.extensions)
-        if extensions_layout is not spack.store.extensions:
+                                       spack.store.store().extensions)
+        if extensions_layout is not spack.store.store().extensions:
             raise ExtensionError(
                 'aspell does not support non-global extensions')
 
@@ -60,7 +60,7 @@ class Aspell(AutotoolsPackage):
         tree = LinkTree(extension.prefix.lib)
 
         def ignore(filename):
-            return (filename in spack.store.layout.hidden_file_paths or
+            return (filename in spack.store.store().layout.hidden_file_paths or
                     kwargs.get('ignore', lambda f: False)(filename))
 
         conflict = tree.find_conflict(dest_dir, ignore=ignore)
@@ -71,8 +71,8 @@ class Aspell(AutotoolsPackage):
 
     def deactivate(self, extension, **kwargs):
         extensions_layout = kwargs.get("extensions_layout",
-                                       spack.store.extensions)
-        if extensions_layout is not spack.store.extensions:
+                                       spack.store.store().extensions)
+        if extensions_layout is not spack.store.store().extensions:
             raise ExtensionError(
                 'aspell does not support non-global extensions')
 
@@ -80,7 +80,7 @@ class Aspell(AutotoolsPackage):
         dest_dir = aspell('dump', 'config', 'dict-dir', output=str).strip()
 
         def ignore(filename):
-            return (filename in spack.store.layout.hidden_file_paths or
+            return (filename in spack.store.store().layout.hidden_file_paths or
                     kwargs.get('ignore', lambda f: False)(filename))
 
         tree = LinkTree(extension.prefix.lib)
diff --git a/var/spack/repos/builtin/packages/cbtf-krell/package.py b/var/spack/repos/builtin/packages/cbtf-krell/package.py
index 15ea33dd79..9ec7853abf 100644
--- a/var/spack/repos/builtin/packages/cbtf-krell/package.py
+++ b/var/spack/repos/builtin/packages/cbtf-krell/package.py
@@ -193,15 +193,16 @@ class CbtfKrell(CMakePackage):
         # the login node components with this spack invocation. We
         # need these paths to be the ones created in the CNL
         # spack invocation.
-        be_cbtf = spack.store.db.query_one('cbtf arch=cray-CNL-haswell')
-        be_cbtfk = spack.store.db.query_one('cbtf-krell arch=cray-CNL-haswell')
-        be_papi = spack.store.db.query_one('papi arch=cray-CNL-haswell')
-        be_boost = spack.store.db.query_one('boost arch=cray-CNL-haswell')
-        be_mont = spack.store.db.query_one('libmonitor arch=cray-CNL-haswell')
-        be_unw = spack.store.db.query_one('libunwind arch=cray-CNL-haswell')
-        be_xer = spack.store.db.query_one('xerces-c arch=cray-CNL-haswell')
-        be_dyn = spack.store.db.query_one('dyninst arch=cray-CNL-haswell')
-        be_mrnet = spack.store.db.query_one('mrnet arch=cray-CNL-haswell')
+        store = spack.store.store()
+        be_cbtf = store.db.query_one('cbtf arch=cray-CNL-haswell')
+        be_cbtfk = store.db.query_one('cbtf-krell arch=cray-CNL-haswell')
+        be_papi = store.db.query_one('papi arch=cray-CNL-haswell')
+        be_boost = store.db.query_one('boost arch=cray-CNL-haswell')
+        be_mont = store.db.query_one('libmonitor arch=cray-CNL-haswell')
+        be_unw = store.db.query_one('libunwind arch=cray-CNL-haswell')
+        be_xer = store.db.query_one('xerces-c arch=cray-CNL-haswell')
+        be_dyn = store.db.query_one('dyninst arch=cray-CNL-haswell')
+        be_mrnet = store.db.query_one('mrnet arch=cray-CNL-haswell')
 
         CrayLoginNodeOptions.append('-DCN_RUNTIME_PLATFORM=%s'
                                     % rt_platform)
diff --git a/var/spack/repos/builtin/packages/openspeedshop/package.py b/var/spack/repos/builtin/packages/openspeedshop/package.py
index 237784e42d..2663a3ff33 100644
--- a/var/spack/repos/builtin/packages/openspeedshop/package.py
+++ b/var/spack/repos/builtin/packages/openspeedshop/package.py
@@ -197,7 +197,8 @@ class Openspeedshop(CMakePackage):
         # spec['cbtf'].prefix is the login node value for this build, as
         # we only get here when building the login node components and
         # that is all that is known to spack.
-        be_ck = spack.store.db.query_one('cbtf-krell arch=cray-CNL-haswell')
+        store = spack.store.store()
+        be_ck = store.db.query_one('cbtf-krell arch=cray-CNL-haswell')
 
         # Equivalent to install-tool cmake arg:
         # '-DCBTF_KRELL_CN_RUNTIME_DIR=%s'
diff --git a/var/spack/repos/builtin/packages/perl/package.py b/var/spack/repos/builtin/packages/perl/package.py
index 1759c15d86..192e31f32f 100644
--- a/var/spack/repos/builtin/packages/perl/package.py
+++ b/var/spack/repos/builtin/packages/perl/package.py
@@ -264,7 +264,7 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
         super(Perl, self).activate(ext_pkg, **args)
 
         extensions_layout = args.get("extensions_layout",
-                                     spack.store.extensions)
+                                     spack.store.store().extensions)
 
         exts = extensions_layout.extension_map(self.spec)
         exts[ext_pkg.name] = ext_pkg.spec
@@ -276,7 +276,7 @@ class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
         super(Perl, self).deactivate(ext_pkg, **args)
 
         extensions_layout = args.get("extensions_layout",
-                                     spack.store.extensions)
+                                     spack.store.store().extensions)
 
         exts = extensions_layout.extension_map(self.spec)
         # Make deactivate idempotent
diff --git a/var/spack/repos/builtin/packages/python/package.py b/var/spack/repos/builtin/packages/python/package.py
index 34e1e0ea6d..b2ca9a29b4 100644
--- a/var/spack/repos/builtin/packages/python/package.py
+++ b/var/spack/repos/builtin/packages/python/package.py
@@ -320,7 +320,7 @@ class Python(AutotoolsPackage):
             output_filename = None
             try:
                 output_filename = join_path(
-                    spack.store.layout.metadata_path(self.spec),
+                    spack.store.store().layout.metadata_path(self.spec),
                     Python._DISTUTIL_CACHE_FILENAME)
                 with open(output_filename, 'w') as output_file:
                     sjson.dump(self._distutil_vars, output_file)
@@ -342,7 +342,7 @@ class Python(AutotoolsPackage):
         if not self._distutil_vars and self.installed:
             try:
                 input_filename = join_path(
-                    spack.store.layout.metadata_path(self.spec),
+                    spack.store.store().layout.metadata_path(self.spec),
                     Python._DISTUTIL_CACHE_FILENAME)
                 if os.path.isfile(input_filename):
                     with open(input_filename) as input_file:
@@ -680,7 +680,7 @@ class Python(AutotoolsPackage):
         args.update(ignore=ignore)
 
         extensions_layout = args.get("extensions_layout",
-                                     spack.store.extensions)
+                                     spack.store.store().extensions)
 
         super(Python, self).activate(ext_pkg, **args)
 
@@ -696,7 +696,7 @@ class Python(AutotoolsPackage):
         super(Python, self).deactivate(ext_pkg, **args)
 
         extensions_layout = args.get("extensions_layout",
-                                     spack.store.extensions)
+                                     spack.store.store().extensions)
 
         exts = extensions_layout.extension_map(self.spec)
         # Make deactivate idempotent