MB-39745: Remove KVShard from BGFetcher

It's not necessary and is required to decouple BGFetchers from KVShards

Change-Id: Ifbeb2b10f2d55d16cfc53ac341dceabfd91eccf4
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/136376
Tested-by: Build Bot <[email protected]>
Reviewed-by: Dave Rigby <[email protected]>

Author: BenHuddleston

engines/ep/src/bgfetcher.cc

@@ -21,16 +21,14 @@
 #include "ep_engine.h"
 #include "executorpool.h"
 #include "kv_bucket.h"
-#include "kvshard.h"
 #include "tasks.h"
 #include "vbucket_bgfetch_item.h"
 #include <phosphor/phosphor.h>
 #include <algorithm>
 #include <climits>
 #include <vector>
 
-BgFetcher::BgFetcher(KVBucket& s, KVShard& k)
-    : BgFetcher(s, k, s.getEPEngine().getEpStats()) {
+BgFetcher::BgFetcher(KVBucket& s) : BgFetcher(s, s.getEPEngine().getEpStats()) {
 }
 
 BgFetcher::~BgFetcher() {
@@ -88,7 +86,7 @@ size_t BgFetcher::doFetch(Vbid vbId, vb_bgfetch_queue_t& itemsToFetch) {
                     startTime.time_since_epoch())
                     .count());
 
-    shard.getROUnderlying()->getMulti(vbId, itemsToFetch);
+    store.getROUnderlying(vbId)->getMulti(vbId, itemsToFetch);
 
     std::vector<bgfetched_item_t> fetchedItems;
     for (const auto& fetch : itemsToFetch) {
@@ -143,7 +141,7 @@ bool BgFetcher::run(GlobalTask *task) {
     size_t num_fetched_items = 0;
 
     for (const auto vbId : bg_vbs) {
-        VBucketPtr vb = shard.getBucket(vbId);
+        VBucketPtr vb = store.getVBucket(vbId);
         if (vb) {
             // Requeue the bg fetch task if vbucket DB file is not created yet.
             if (vb->isBucketCreation()) {
@@ -166,13 +164,3 @@ bool BgFetcher::run(GlobalTask *task) {
 
     return true;
 }
-
-bool BgFetcher::pendingJob() const {
-    for (const auto vbid : shard.getVBuckets()) {
-        VBucketPtr vb = shard.getBucket(vbid);
-        if (vb && vb->hasPendingBGFetchItems()) {
-            return true;
-        }
-    }
-    return false;
-}

engines/ep/src/bgfetcher.h

@@ -25,7 +25,6 @@
 // Forward declarations.
 class EPStats;
 class KVBucket;
-class KVShard;
 class GlobalTask;
 
 /**
@@ -38,11 +37,10 @@ class BgFetcher {
      * Construct a BgFetcher
      *
      * @param s  The store
-     * @param k  The shard to which this background fetcher belongs
      * @param st reference to statistics
      */
-    BgFetcher(KVBucket& s, KVShard& k, EPStats& st)
-        : store(s), shard(k), taskId(0), stats(st), pendingFetch(false) {
+    BgFetcher(KVBucket& s, EPStats& st)
+        : store(s), taskId(0), stats(st), pendingFetch(false) {
     }
 
     /**
@@ -52,16 +50,14 @@ class BgFetcher {
      * from KVBucket's reference to EPEngine's epstats.
      *
      * @param s The store
-     * @param k The shard to which this background fetcher belongs
      */
-    BgFetcher(KVBucket& s, KVShard& k);
+    BgFetcher(KVBucket& s);
 
     ~BgFetcher();
 
     void start();
     void stop();
     bool run(GlobalTask *task);
-    bool pendingJob() const;
     void notifyBGEvent();
     void setTaskId(size_t newId) { taskId = newId; }
     void addPendingVB(Vbid vbId) {
@@ -78,7 +74,6 @@ class BgFetcher {
     void wakeUpTaskIfSnoozed();
 
     KVBucket& store;
-    KVShard& shard;
     size_t taskId;
     std::mutex queueMutex;
     EPStats &stats;

engines/ep/src/ep_bucket.cc

@@ -962,12 +962,18 @@ bool EPBucket::startBgFetcher() {
 void EPBucket::stopBgFetcher() {
     for (const auto& shard : vbMap.shards) {
         BgFetcher* bgfetcher = shard->getBgFetcher();
-        if (bgfetcher->pendingJob()) {
-            EP_LOG_WARN(
-                    "Shutting down engine while there are still pending data "
-                    "read for shard {} from database storage",
-                    shard->getId());
+        for (const auto vbid : shard->getVBuckets()) {
+            VBucketPtr vb = shard->getBucket(vbid);
+            if (vb && vb->hasPendingBGFetchItems()) {
+                EP_LOG_WARN(
+                        "Shutting down engine while there are still pending "
+                        "data "
+                        "read for shard {} from database storage",
+                        shard->getId());
+                break;
+            }
         }
+
         EP_LOG_INFO("Stopping bg fetcher for shard:{}", shard->getId());
         bgfetcher->stop();
     }

engines/ep/src/kvshard.cc

@@ -84,7 +84,7 @@ KVShard::KVShard(EventuallyPersistentEngine& engine, id_type id)
 
 void KVShard::enablePersistence(EPBucket& ep) {
     flusher = std::make_unique<Flusher>(&ep, this);
-    bgFetcher = std::make_unique<BgFetcher>(ep, *this);
+    bgFetcher = std::make_unique<BgFetcher>(ep);
 }
 
 // Non-inline destructor so we can destruct

engines/ep/tests/module_tests/evp_vbucket_test.cc

@@ -55,7 +55,7 @@ TEST_P(EPVBucketTest, GetBGFetchItemsPerformance) {
     auto mockEPBucket =
             engine->public_makeMockBucket(engine->getConfiguration());
     KVShard kvShard(*engine.get(), 0);
-    BgFetcher bgFetcher(*mockEPBucket.get(), kvShard);
+    BgFetcher bgFetcher(*mockEPBucket.get());
 
     for (unsigned int ii = 0; ii < 100000; ii++) {
         auto fetchItem =