Collect action cache hits, misses, and reasons for the misses.

As a bonus, this brings in a bunch of new unit tests for the
ActionCacheChecker.

RELNOTES: None.
PiperOrigin-RevId: 170059577

1 files changed, 25 insertions, 1 deletions

diff --git a/src/main/protobuf/action_cache.proto b/src/main/protobuf/action_cache.proto
index 429990dda0..5694ebe34a 100644
--- a/src/main/protobuf/action_cache.proto
+++ b/src/main/protobuf/action_cache.proto
@@ -31,5 +31,29 @@ message ActionCacheStatistics {
   // Time it took to save the action cache to disk.
   uint64 save_time_in_ms = 2;
 
-  // NEXT TAG: 3
+  // Reasons for not finding an action in the cache.
+  enum MissReason {
+    DIFFERENT_ACTION_KEY = 0;
+    DIFFERENT_DEPS = 1;
+    DIFFERENT_ENVIRONMENT = 2;
+    DIFFERENT_FILES = 3;
+    CORRUPTED_CACHE_ENTRY = 4;
+    NOT_CACHED = 5;
+    UNCONDITIONAL_EXECUTION = 6;
+  }
+
+  // Detailed information for a particular miss reason.
+  message MissDetail {
+    MissReason reason = 1;
+    int32 count = 2;
+  }
+
+  // Cache counters.
+  int32 hits = 3;
+  int32 misses = 4;
+
+  // Breakdown of the cache misses based on the reasons behind them.
+  repeated MissDetail miss_details = 5;
+
+  // NEXT TAG: 6
 }