caching_ext: introduce noop-mode for cachelib and memcache caches

Summary: Sometimes we just don't want to cache at all.  Add a no-op mode so we can use the same code.

Differential Revision: D43410853

fbshipit-source-id: 20dd632df66dc85b4da18678ff56e5b83e987326

eden/mononoke/changesets/changesets_impl/src/caching.rs

@@ -126,7 +126,7 @@ impl CachingChangesets {
     #[cfg(test)]
     pub fn cachelib_stats(&self) -> MockStoreStats {
         match self.cachelib {
-            CachelibHandler::Real(_) => unimplemented!(),
+            CachelibHandler::Real(_) | CachelibHandler::Noop => unimplemented!(),
             CachelibHandler::Mock(ref mock) => mock.stats(),
         }
     }
@@ -134,7 +134,7 @@ impl CachingChangesets {
     #[cfg(test)]
     pub fn memcache_stats(&self) -> MockStoreStats {
         match self.memcache {
-            MemcacheHandler::Real(_) => unimplemented!(),
+            MemcacheHandler::Real(_) | MemcacheHandler::Noop => unimplemented!(),
             MemcacheHandler::Mock(ref mock) => mock.stats(),
         }
     }
@@ -286,7 +286,7 @@ impl EntityStore<ChangesetEntryWrapper> for CacheRequest<'_> {
 
         match mapping.memcache {
             MemcacheHandler::Real(_) => true,
-            MemcacheHandler::Mock(..) => false,
+            MemcacheHandler::Mock(..) | MemcacheHandler::Noop => false,
         }
     }
 }

eden/mononoke/common/rust/caching_ext/src/cachelib_utils.rs

@@ -22,6 +22,7 @@ use crate::CachelibKey;
 pub enum CachelibHandler<T> {
     Real(VolatileLruCachePool),
     Mock(MockStore<T>),
+    Noop,
 }
 
 impl<T> From<VolatileLruCachePool> for CachelibHandler<T> {
@@ -56,6 +57,7 @@ impl<T: Abomonation + Clone + Send + 'static> CachelibHandler<T> {
         match self {
             CachelibHandler::Real(ref cache) => get_cached(cache, key),
             CachelibHandler::Mock(store) => Ok(store.get(key)),
+            CachelibHandler::Noop => Ok(None),
         }
     }
 
@@ -66,6 +68,7 @@ impl<T: Abomonation + Clone + Send + 'static> CachelibHandler<T> {
                 store.set(key, value.clone());
                 Ok(true)
             }
+            CachelibHandler::Noop => Ok(false),
         }
     }
 
@@ -73,11 +76,15 @@ impl<T: Abomonation + Clone + Send + 'static> CachelibHandler<T> {
         CachelibHandler::Mock(MockStore::new())
     }
 
+    pub fn create_noop() -> Self {
+        CachelibHandler::Noop
+    }
+
     #[cfg(test)]
     pub(crate) fn gets_count(&self) -> usize {
         use std::sync::atomic::Ordering;
         match self {
-            CachelibHandler::Real(_) => unimplemented!(),
+            CachelibHandler::Real(_) | CachelibHandler::Noop => unimplemented!(),
             CachelibHandler::Mock(MockStore { ref get_count, .. }) => {
                 get_count.load(Ordering::SeqCst)
             }
@@ -86,7 +93,7 @@ impl<T: Abomonation + Clone + Send + 'static> CachelibHandler<T> {
 
     pub fn mock_store(&self) -> Option<&MockStore<T>> {
         match self {
-            CachelibHandler::Real(_) => None,
+            CachelibHandler::Real(_) | CachelibHandler::Noop => None,
             CachelibHandler::Mock(ref mock) => Some(mock),
         }
     }

eden/mononoke/common/rust/caching_ext/src/memcache_utils.rs

@@ -18,6 +18,7 @@ use crate::mock_store::MockStore;
 pub enum MemcacheHandler {
     Real(MemcacheClient),
     Mock(MockStore<Bytes>),
+    Noop,
 }
 
 impl From<MemcacheClient> for MemcacheHandler {
@@ -33,6 +34,7 @@ impl MemcacheHandler {
                 client.get(key).await.map(|value| value.map(Bytes::from))
             }
             MemcacheHandler::Mock(store) => Ok(store.get(&key)),
+            MemcacheHandler::Noop => Ok(None),
         }
     }
 
@@ -48,6 +50,7 @@ impl MemcacheHandler {
                 store.set(&key, value.into());
                 Ok(())
             }
+            MemcacheHandler::Noop => Ok(()),
         }
     }
 
@@ -63,6 +66,7 @@ impl MemcacheHandler {
                 // For now we ignore TTLs here
                 self.set(key, value).await
             }
+            MemcacheHandler::Noop => Ok(()),
         }
     }
 
@@ -70,11 +74,15 @@ impl MemcacheHandler {
         MemcacheHandler::Mock(MockStore::new())
     }
 
+    pub fn create_noop() -> Self {
+        MemcacheHandler::Noop
+    }
+
     #[cfg(test)]
     pub(crate) fn gets_count(&self) -> usize {
         use std::sync::atomic::Ordering;
         match self {
-            MemcacheHandler::Real(_) => unimplemented!(),
+            MemcacheHandler::Real(_) | MemcacheHandler::Noop => unimplemented!(),
             MemcacheHandler::Mock(MockStore { ref get_count, .. }) => {
                 get_count.load(Ordering::SeqCst)
             }

eden/mononoke/repo_attributes/commit_graph/caching_commit_graph_storage/src/lib.rs

@@ -186,7 +186,7 @@ impl EntityStore<CachedChangesetEdges> for CacheRequest<'_> {
     fn spawn_memcache_writes(&self) -> bool {
         match self.caching_storage.memcache {
             MemcacheHandler::Real(_) => true,
-            MemcacheHandler::Mock(..) => false,
+            MemcacheHandler::Mock(..) | MemcacheHandler::Noop => false,
         }
     }
 }