Pipelines: use shared pr mirror for pipeline generation and builds (#25529)

Once PR binary graduation is deployed, the shared PR mirror will
contain binaries just built by a merged PR, before the subsequent
develop pipeline has had time to finish.  Using the shared PR mirror
as a source of binaries will reduce the number of times we have to
rebuild the same full hash.

2 files changed, 19 insertions, 2 deletions

diff --git a/lib/spack/spack/ci.py b/lib/spack/spack/ci.py
index 0ada128f64..6fbddf6385 100644
--- a/lib/spack/spack/ci.py
+++ b/lib/spack/spack/ci.py
@@ -45,6 +45,8 @@ JOB_RETRY_CONDITIONS = [
 ]
 
 SPACK_PR_MIRRORS_ROOT_URL = 's3://spack-binaries-prs'
+SPACK_SHARED_PR_MIRROR_URL = url_util.join(SPACK_PR_MIRRORS_ROOT_URL,
+                                           'shared_pr_mirror')
 TEMP_STORAGE_MIRROR_NAME = 'ci_temporary_mirror'
 
 spack_gpg = spack.main.SpackCommand('gpg')
@@ -612,11 +614,14 @@ def generate_gitlab_ci_yaml(env, print_summary, output_file,
         'strip-compilers': False,
     })
 
-    # Add this mirror if it's enabled, as some specs might be up to date
-    # here and thus not need to be rebuilt.
+    # Add per-PR mirror (and shared PR mirror) if enabled, as some specs might
+    # be up to date in one of those and thus not need to be rebuilt.
     if pr_mirror_url:
         spack.mirror.add(
             'ci_pr_mirror', pr_mirror_url, cfg.default_modify_scope())
+        spack.mirror.add('ci_shared_pr_mirror',
+                         SPACK_SHARED_PR_MIRROR_URL,
+                         cfg.default_modify_scope())
 
     pipeline_artifacts_dir = artifacts_root
     if not pipeline_artifacts_dir:
diff --git a/lib/spack/spack/test/cmd/ci.py b/lib/spack/spack/test/cmd/ci.py
index a9891796ac..fad1cd5351 100644
--- a/lib/spack/spack/test/cmd/ci.py
+++ b/lib/spack/spack/test/cmd/ci.py
@@ -617,6 +617,8 @@ spack:
             os.environ['SPACK_PR_BRANCH'] = 'fake-test-branch'
             monkeypatch.setattr(
                 ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+            monkeypatch.setattr(
+                ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
             try:
                 ci_cmd('generate', '--output-file', outputfile)
             finally:
@@ -668,6 +670,8 @@ spack:
         with ev.read('test'):
             monkeypatch.setattr(
                 ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+            monkeypatch.setattr(
+                ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
             ci_cmd('generate', '--output-file', outputfile)
 
         with open(outputfile) as f:
@@ -1153,6 +1157,8 @@ spack:
                 spack.main, 'get_version', lambda: '0.15.3-416-12ad69eb1')
             monkeypatch.setattr(
                 ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+            monkeypatch.setattr(
+                ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
             ci_cmd('generate', '--output-file', outputfile)
 
         with open(outputfile) as f:
@@ -1257,6 +1263,8 @@ spack:
         with ev.read('test'):
             monkeypatch.setattr(
                 ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+            monkeypatch.setattr(
+                ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
             ci_cmd('generate', '--output-file', outputfile, '--dependencies')
 
             with open(outputfile) as f:
@@ -1417,6 +1425,8 @@ spack:
         with ev.read('test'):
             monkeypatch.setattr(
                 ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+            monkeypatch.setattr(
+                ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
 
             ci_cmd('generate', '--output-file', outputfile)
 
@@ -1568,6 +1578,8 @@ spack:
 
         monkeypatch.setattr(
             ci, 'SPACK_PR_MIRRORS_ROOT_URL', r"file:///fake/mirror")
+        monkeypatch.setattr(
+            ci, 'SPACK_SHARED_PR_MIRROR_URL', r"file:///fake/mirror_two")
 
         with ev.read('test'):
             ci_cmd('generate', '--output-file', outputfile)