Collect stats on stalecache hits and misses.

r2/r2/lib/app_globals.py

@@ -61,7 +61,12 @@ from r2.lib.lock import make_lock_factory
 from r2.lib.manager import db_manager
 from r2.lib.plugin import PluginLoader
 from r2.lib.providers import select_provider
-from r2.lib.stats import Stats, CacheStats, StatsCollectingConnectionPool
+from r2.lib.stats import (
+    CacheStats,
+    StaleCacheStats,
+    Stats,
+    StatsCollectingConnectionPool,
+)
 from r2.lib.translation import get_active_langs, I18N_PATH
 from r2.lib.utils import config_gold_price, thread_dump
 
@@ -774,7 +779,10 @@ class Globals(object):
         def reset_caches():
             for name, chain in cache_chains.iteritems():
                 chain.reset()
-                chain.stats = CacheStats(self.stats, name)
+                if isinstance(chain, StaleCacheChain):
+                    chain.stats = StaleCacheStats(self.stats, name)
+                else:
+                    chain.stats = CacheStats(self.stats, name)
         self.cache_chains = cache_chains
 
         self.reset_caches = reset_caches

r2/r2/lib/cache.py

@@ -694,10 +694,13 @@ class StaleCacheChain(CacheChain):
             if stale_value is not None:
                 if self.stats:
                     self.stats.cache_hit()
+                    self.stats.stale_hit()
                 return stale_value # never return stale data into the
                                    # LocalCache, or people that didn't
                                    # say they'll take stale data may
                                    # get it
+            else:
+                self.stats.stale_miss()
 
         value = self.realcache.get(key)
         if value is None:
@@ -735,6 +738,12 @@ class StaleCacheChain(CacheChain):
                 ret[k] = v
                 keys.remove(k)
 
+            stale_hits = len(stale_values)
+            stale_misses = len(keys)
+            if self.stats:
+                self.stats.stale_hit(stale_hits)
+                self.stats.stale_miss(stale_misses)
+
         if keys:
             values = self.realcache.simple_get_multi(keys)
             if values and stale:

r2/r2/lib/stats.py

@@ -449,6 +449,30 @@ class CacheStats:
             self.parent.cache_count_multi(data, sample_rate=sample_rate)
 
 
+class StaleCacheStats(CacheStats):
+    def __init__(self, parent, cache_name):
+        CacheStats.__init__(self, parent, cache_name)
+        self.stale_hit_name = '%s.stale.hit' % self.cache_name
+        self.stale_miss_name = '%s.stale.miss' % self.cache_name
+        self.stale_total_name = '%s.stale.total' % self.cache_name
+
+    def stale_hit(self, delta=1):
+        if delta:
+            data = {
+                self.stale_hit_name: delta,
+                self.stale_total_name: delta,
+            }
+            self.parent.cache_count_multi(data)
+
+    def stale_miss(self, delta=1):
+        if delta:
+            data = {
+                self.stale_miss_name: delta,
+                self.stale_total_name: delta,
+            }
+            self.parent.cache_count_multi(data)
+
+
 class StatsCollectingConnectionPool(pool.ConnectionPool):
     def __init__(self, keyspace, stats=None, *args, **kwargs):
         pool.ConnectionPool.__init__(self, keyspace, *args, **kwargs)