Update the binary index before attempting direct fetches (#32137)

"spack install" will not update the binary index if given a concrete
spec, which causes it to fall back to direct fetches when a simple
index update would have helped. For S3 buckets in particular, this
significantly and needlessly slows down the install process.

This commit alters the logic so that the binary index is updated
whenever a by-hash lookup fails. The lookup is attempted again with
the updated index before falling back to direct fetches. To avoid
updating too frequently (potentially once for each spec being
installed), BinaryCacheIndex.update now includes a "cooldown"
option, and when this option is enabled it will not update more
than once in a cooldown window (set in config.yaml).

Co-authored-by: Tamara Dahlgren <35777542+tldahlgren@users.noreply.github.com>

3 files changed, 44 insertions, 19 deletions

diff --git a/lib/spack/spack/binary_distribution.py b/lib/spack/spack/binary_distribution.py
index c329287de8..cfd7d0ec1b 100644
--- a/lib/spack/spack/binary_distribution.py
+++ b/lib/spack/spack/binary_distribution.py
@@ -12,6 +12,7 @@ import shutil
 import sys
 import tarfile
 import tempfile
+import time
 import traceback
 import warnings
 from contextlib import closing
@@ -105,6 +106,9 @@ class BinaryCacheIndex(object):
         # cache (_mirrors_for_spec)
         self._specs_already_associated = set()
 
+        # mapping from mirror urls to the time.time() of the last index fetch.
+        self._last_fetch_times = {}
+
         # _mirrors_for_spec is a dictionary mapping DAG hashes to lists of
         # entries indicating mirrors where that concrete spec can be found.
         # Each entry is a dictionary consisting of:
@@ -137,6 +141,7 @@ class BinaryCacheIndex(object):
             self._index_file_cache = None
         self._local_index_cache = None
         self._specs_already_associated = set()
+        self._last_fetch_times = {}
         self._mirrors_for_spec = {}
 
     def _write_local_index_cache(self):
@@ -242,7 +247,6 @@ class BinaryCacheIndex(object):
                         }
                     ]
         """
-        self.regenerate_spec_cache()
         return self.find_by_hash(spec.dag_hash(), mirrors_to_check=mirrors_to_check)
 
     def find_by_hash(self, find_hash, mirrors_to_check=None):
@@ -254,6 +258,9 @@ class BinaryCacheIndex(object):
                 None, just assumes all configured mirrors.
         """
         if find_hash not in self._mirrors_for_spec:
+            # Not found in the cached index, pull the latest from the server.
+            self.update(with_cooldown=True)
+        if find_hash not in self._mirrors_for_spec:
             return None
         results = self._mirrors_for_spec[find_hash]
         if not mirrors_to_check:
@@ -283,7 +290,7 @@ class BinaryCacheIndex(object):
                         "spec": new_entry["spec"],
                     }
 
-    def update(self):
+    def update(self, with_cooldown=False):
         """Make sure local cache of buildcache index files is up to date.
         If the same mirrors are configured as the last time this was called
         and none of the remote buildcache indices have changed, calling this
@@ -325,24 +332,37 @@ class BinaryCacheIndex(object):
 
         fetch_errors = []
         all_methods_failed = True
+        ttl = spack.config.get("config:binary_index_ttl", 600)
+        now = time.time()
 
         for cached_mirror_url in self._local_index_cache:
             cache_entry = self._local_index_cache[cached_mirror_url]
             cached_index_hash = cache_entry["index_hash"]
             cached_index_path = cache_entry["index_path"]
             if cached_mirror_url in configured_mirror_urls:
-                # May need to fetch the index and update the local caches
-                try:
-                    needs_regen = self._fetch_and_cache_index(
-                        cached_mirror_url, expect_hash=cached_index_hash
-                    )
+                # Only do a fetch if the last fetch was longer than TTL ago
+                if (
+                    with_cooldown
+                    and ttl > 0
+                    and cached_mirror_url in self._last_fetch_times
+                    and now - self._last_fetch_times[cached_mirror_url] < ttl
+                ):
+                    # The fetch worked last time, so don't error
                     all_methods_failed = False
-                except FetchCacheError as fetch_error:
-                    needs_regen = False
-                    fetch_errors.extend(fetch_error.errors)
-                # The need to regenerate implies a need to clear as well.
-                spec_cache_clear_needed |= needs_regen
-                spec_cache_regenerate_needed |= needs_regen
+                else:
+                    # May need to fetch the index and update the local caches
+                    try:
+                        needs_regen = self._fetch_and_cache_index(
+                            cached_mirror_url, expect_hash=cached_index_hash
+                        )
+                        self._last_fetch_times[cached_mirror_url] = now
+                        all_methods_failed = False
+                    except FetchCacheError as fetch_error:
+                        needs_regen = False
+                        fetch_errors.extend(fetch_error.errors)
+                    # The need to regenerate implies a need to clear as well.
+                    spec_cache_clear_needed |= needs_regen
+                    spec_cache_regenerate_needed |= needs_regen
             else:
                 # No longer have this mirror, cached index should be removed
                 items_to_remove.append(
@@ -351,6 +371,8 @@ class BinaryCacheIndex(object):
                         "cache_key": os.path.join(self._index_cache_root, cached_index_path),
                     }
                 )
+                if cached_mirror_url in self._last_fetch_times:
+                    del self._last_fetch_times[cached_mirror_url]
                 spec_cache_clear_needed = True
                 spec_cache_regenerate_needed = True
 
@@ -369,6 +391,7 @@ class BinaryCacheIndex(object):
                 # Need to fetch the index and update the local caches
                 try:
                     needs_regen = self._fetch_and_cache_index(mirror_url)
+                    self._last_fetch_times[mirror_url] = now
                     all_methods_failed = False
                 except FetchCacheError as fetch_error:
                     fetch_errors.extend(fetch_error.errors)
@@ -1878,8 +1901,8 @@ def get_mirrors_for_spec(spec=None, mirrors_to_check=None, index_only=False):
 
     results = binary_index.find_built_spec(spec, mirrors_to_check=mirrors_to_check)
 
-    # Maybe we just didn't have the latest information from the mirror, so
-    # try to fetch directly, unless we are only considering the indices.
+    # The index may be out-of-date. If we aren't only considering indices, try
+    # to fetch directly since we know where the file should be.
     if not results and not index_only:
         results = try_direct_fetch(spec, mirrors=mirrors_to_check)
         # We found a spec by the direct fetch approach, we might as well
diff --git a/lib/spack/spack/schema/config.py b/lib/spack/spack/schema/config.py
index 4ed6e7fc2d..c82990da5c 100644
--- a/lib/spack/spack/schema/config.py
+++ b/lib/spack/spack/schema/config.py
@@ -73,6 +73,7 @@ properties = {
             "binary_index_root": {"type": "string"},
             "url_fetch_method": {"type": "string", "enum": ["urllib", "curl"]},
             "additional_external_search_paths": {"type": "array", "items": {"type": "string"}},
+            "binary_index_ttl": {"type": "integer", "minimum": 0},
         },
         "deprecatedProperties": {
             "properties": ["module_roots"],
diff --git a/lib/spack/spack/test/bindist.py b/lib/spack/spack/test/bindist.py
index 68ea2cb734..7e9066ccbf 100644
--- a/lib/spack/spack/test/bindist.py
+++ b/lib/spack/spack/test/bindist.py
@@ -453,10 +453,11 @@ def test_generate_index_missing(monkeypatch, tmpdir, mutable_config):
     # Update index
     buildcache_cmd("update-index", "-d", mirror_dir.strpath)
 
-    # Check dependency not in buildcache
-    cache_list = buildcache_cmd("list", "--allarch")
-    assert "libdwarf" in cache_list
-    assert "libelf" not in cache_list
+    with spack.config.override("config:binary_index_ttl", 0):
+        # Check dependency not in buildcache
+        cache_list = buildcache_cmd("list", "--allarch")
+        assert "libdwarf" in cache_list
+        assert "libelf" not in cache_list
 
 
 def test_generate_indices_key_error(monkeypatch, capfd):