Reduce coupling in KVShard

This class doesn't need to know about the higher-level bucket or
ep-engine classes.

Change-Id: I9c1ad7b9a08aabc8a74057b90a07dd52271daab1
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/160324
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Trond Norbye <trond.norbye@couchbase.com>

Author: daverigby

engines/ep/src/kvshard.cc

@@ -12,23 +12,22 @@
 #include <functional>
 #include <memory>
 
-#include "ep_bucket.h"
-#include "ep_engine.h"
+#include "configuration.h"
 #include "flusher.h"
 #include "kvshard.h"
 #include "kvstore/kvstore.h"
+#include "vbucket.h"
 
 /* [EPHE TODO]: Consider not using KVShard for ephemeral bucket */
-KVShard::KVShard(EventuallyPersistentEngine& engine, id_type id)
+KVShard::KVShard(Configuration& config,
+                 id_type numShards,
+                 id_type id)
     : // Size vBuckets to have sufficient slots for the maximum number of
       // vBuckets each shard is responsible for. To ensure correct behaviour
       // when vbuckets isn't a multiple of num_shards, apply ceil() to the
       // division so we round up where necessary.
-      vbuckets(std::ceil(float(engine.getConfiguration().getMaxVbuckets()) /
-                         engine.getWorkLoadPolicy().getNumShards())),
+      vbuckets(std::ceil(float(config.getMaxVbuckets()) / numShards)),
       highPriorityCount(0) {
-    const auto numShards = engine.getWorkLoadPolicy().getNumShards();
-    auto& config = engine.getConfiguration();
     const std::string backend = config.getBackend();
 
 #ifdef EP_USE_MAGMA

engines/ep/src/kvshard.h

@@ -59,15 +59,13 @@
  */
 class Configuration;
 class CookieIface;
-class EPBucket;
-class EventuallyPersistentEngine;
 class KVStoreIface;
 
 class KVShard {
 public:
     // Identifier for a KVShard
     using id_type = uint16_t;
-    KVShard(EventuallyPersistentEngine& engine, KVShard::id_type id);
+    KVShard(Configuration& config, id_type numShards, id_type id);
     ~KVShard();
 
     KVStoreIface* getRWUnderlying() {

engines/ep/src/vbucketmap.cc

@@ -23,7 +23,8 @@ VBucketMap::VBucketMap(KVBucket& bucket)
     const auto numShards = engine.getWorkLoadPolicy().getNumShards();
     shards.resize(numShards);
     for (size_t shardId = 0; shardId < numShards; shardId++) {
-        shards[shardId] = std::make_unique<KVShard>(engine, shardId);
+        shards[shardId] = std::make_unique<KVShard>(
+                bucket.getEPEngine().getConfiguration(), numShards, shardId);
     }
 
     auto& config = engine.getConfiguration();
@@ -184,4 +185,4 @@ size_t VBucketMap::getNumAliveVBuckets() const {
         res += getVBStateCount(state);
     }
     return res;
-}
+}

engines/ep/tests/module_tests/evp_vbucket_test.cc

@@ -49,7 +49,9 @@ TEST_P(EPVBucketTest, GetBGFetchItemsPerformance) {
     // bgFetcher
     auto mockEPBucket =
             engine->public_makeMockBucket(engine->getConfiguration());
-    KVShard kvShard(*engine.get(), 0);
+    KVShard kvShard(engine->getConfiguration(),
+                    engine->getConfiguration().getMaxNumShards(),
+                    0);
     BgFetcher bgFetcher(*mockEPBucket.get());
 
     for (unsigned int ii = 0; ii < 100000; ii++) {