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>

etc/spack/defaults/config.yaml

@@ -201,3 +201,7 @@ config:
   # building and installing packages. This gives information about Spack's
   # current progress as well as the current and total number of packages.
   terminal_title: false
+
+  # Number of seconds a buildcache's index.json is cached locally before probing
+  # for updates, within a single Spack invocation. Defaults to 10 minutes.
+  binary_index_ttl: 600

lib/spack/spack/binary_distribution.py

@@ -12,6 +12,7 @@
 import sys
 import tarfile
 import tempfile
+import time
 import traceback
 import warnings
 from contextlib import closing
@@ -105,6 +106,9 @@ def __init__(self, cache_root):
         # 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 @@ def clear(self):
             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 @@ def find_built_spec(self, spec, mirrors_to_check=None):
                         }
                     ]
         """
-        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):
@@ -253,6 +257,9 @@ def find_by_hash(self, find_hash, mirrors_to_check=None):
             mirrors_to_check: Optional mapping containing mirrors to check.  If
                 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]
@@ -283,7 +290,7 @@ def update_spec(self, spec, found_list):
                         "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
@@ -325,17 +332,30 @@ def update(self):
 
         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:
+                # 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
+                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
@@ -351,6 +371,8 @@ def update(self):
                         "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 @@ def update(self):
                 # 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
+    # The index may be out-of-date. If we aren't only considering indices, try
-    # try to fetch directly, unless we are only considering the indices.
+    # 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

lib/spack/spack/schema/config.py

@@ -73,6 +73,7 @@
             "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"],

lib/spack/spack/test/bindist.py

@@ -453,6 +453,7 @@ def test_generate_index_missing(monkeypatch, tmpdir, mutable_config):
     # Update index
     buildcache_cmd("update-index", "-d", mirror_dir.strpath)
 
+    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