MB-31869: Remove the ReplicationThrottle class

A lot of unnecessary boilerplate for making just a simple check on the
bucket memory state.

This is in preparation for further changes in the PassiveStream code.

Change-Id: Ib8a94621bef329cb6f8768b4fda61ec91340a56b
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/202686
Tested-by: Paolo Cocchi <[email protected]>
Reviewed-by: Vesko Karaganev <[email protected]>

Author: paolococchi

engines/ep/CMakeLists.txt

@@ -374,7 +374,6 @@ ADD_LIBRARY(ep_objs OBJECT
             src/probabilistic_counter.cc
             src/progress_tracker.cc
             src/quota_sharing_item_pager.cc
-            src/replicationthrottle.cc
             src/linked_list.cc
             src/range_lock_manager.cc
             src/range_scans/range_scan.cc

engines/ep/src/dcp/consumer.cc

@@ -23,10 +23,9 @@
 #include "failover-table.h"
 #include "kv_bucket.h"
 #include "objectregistry.h"
-#include "replicationthrottle.h"
 #include "vbucket.h"
-#include <fmt/chrono.h>
 #include <executor/executorpool.h>
+#include <fmt/chrono.h>
 #include <phosphor/phosphor.h>
 #include <xattr/utils.h>
 
@@ -1314,13 +1313,13 @@ process_items_error_t DcpConsumer::drainStreamsBufferedItems(
     uint32_t bytesProcessed = 0;
     size_t iterations = 0;
     do {
-        switch (engine_.getReplicationThrottle().getStatus()) {
-        case ReplicationThrottle::Status::Pause:
+        switch (engine_.getKVBucket()->getReplicationThrottleStatus()) {
+        case KVBucket::ReplicationThrottleStatus::Pause:
             backoffs++;
             vbReady.pushUnique(stream->getVBucket());
             return cannot_process;
 
-        case ReplicationThrottle::Status::Disconnect:
+        case KVBucket::ReplicationThrottleStatus::Disconnect:
             backoffs++;
             vbReady.pushUnique(stream->getVBucket());
             logger->warn(
@@ -1329,7 +1328,7 @@ process_items_error_t DcpConsumer::drainStreamsBufferedItems(
                     stream->getVBucket());
             return stop_processing;
 
-        case ReplicationThrottle::Status::Process:
+        case KVBucket::ReplicationThrottleStatus::Process:
             bytesProcessed = 0;
             rval = stream->processBufferedMessages(
                     bytesProcessed, processBufferedMessagesBatchSize);

engines/ep/src/dcp/passive_stream.cc

@@ -21,7 +21,6 @@
 #include "ep_engine.h"
 #include "failover-table.h"
 #include "kv_bucket.h"
-#include "replicationthrottle.h"
 #include "vbucket.h"
 
 #include <gsl/gsl-lite.hpp>
@@ -350,20 +349,21 @@ cb::engine_errc PassiveStream::messageReceived(
         }
     }
 
-    switch (engine->getReplicationThrottle().getStatus()) {
-    case ReplicationThrottle::Status::Disconnect:
+    const auto& bucket = *engine->getKVBucket();
+    switch (bucket.getReplicationThrottleStatus()) {
+    case KVBucket::ReplicationThrottleStatus::Disconnect:
         log(spdlog::level::level_enum::warn,
             "{} Disconnecting the connection as there is "
             "no memory to complete replication",
             vb_);
         return cb::engine_errc::disconnect;
-    case ReplicationThrottle::Status::Process:
+    case KVBucket::ReplicationThrottleStatus::Process:
         if (buffer.empty() && !alwaysBufferOperations) {
             // Memory available and no message buffered -> process the response
             const auto ret = processMessage(dcpResponse.get());
             const auto err = ret.getError();
             if (err == cb::engine_errc::no_memory) {
-                if (engine->getReplicationThrottle().doDisconnectOnNoMem()) {
+                if (bucket.disconnectReplicationAtOOM()) {
                     log(spdlog::level::level_enum::warn,
                         "{} Disconnecting the connection as there is no "
                         "memory to complete replication; process dcp "
@@ -381,7 +381,7 @@ cb::engine_errc PassiveStream::messageReceived(
             }
         }
         break;
-    case ReplicationThrottle::Status::Pause:
+    case KVBucket::ReplicationThrottleStatus::Pause:
         /* Do nothing specific here, we buffer item for this case and
            other cases below */
         break;
@@ -476,7 +476,7 @@ process_items_error_t PassiveStream::processBufferedMessages(
     processed_bytes = total_bytes_processed;
 
     if (failed) {
-        if (noMem && engine->getReplicationThrottle().doDisconnectOnNoMem()) {
+        if (noMem && engine->getKVBucket()->disconnectReplicationAtOOM()) {
             log(spdlog::level::level_enum::warn,
                 "{} Processor task indicating disconnection as "
                 "there is no memory to complete replication; process dcp "

engines/ep/src/ep_bucket.cc

@@ -29,7 +29,6 @@
 #include "kvstore/persistence_callback.h"
 #include "kvstore/rollback_callback.h"
 #include "range_scans/range_scan_callbacks.h"
-#include "replicationthrottle.h"
 #include "rollback_result.h"
 #include "tasks.h"
 #include "vb_commit.h"
@@ -254,7 +253,6 @@ EPBucket::EPBucket(EventuallyPersistentEngine& engine)
     } else {
         eviction_policy = EvictionPolicy::Full;
     }
-    replicationThrottle = std::make_unique<ReplicationThrottleEP>(engine);
 
     // Pre 7.0.0 Flushers were a part of KVShard so keep the same default
     // scaling.
@@ -2715,3 +2713,7 @@ cb::engine_errc EPBucket::prepareForResume() {
 
     return cb::engine_errc::success;
 }
+
+bool EPBucket::disconnectReplicationAtOOM() const {
+    return false;
+}

engines/ep/src/ep_bucket.h

@@ -360,6 +360,8 @@ class EPBucket : public KVBucket {
      */
     std::shared_ptr<RangeScan> takeNextRangeScan(size_t taskId);
 
+    bool disconnectReplicationAtOOM() const override;
+
     /// Hook that gets called from prepareForPause. Phase of prepareForPause()
     /// specified by the single string_view arg
     TestingHook<std::string_view> prepareForPauseTestingHook;

engines/ep/src/ep_engine.cc

@@ -41,7 +41,6 @@
 #include "kvstore/kvstore.h"
 #include "quota_sharing_item_pager.h"
 #include "range_scans/range_scan_callbacks.h"
-#include "replicationthrottle.h"
 #include "stats-info.h"
 #include "string_utils.h"
 #include "trace_helpers.h"
@@ -7036,10 +7035,6 @@ EventuallyPersistentEngine::~EventuallyPersistentEngine() {
     /* Unique_ptr(s) are deleted in the reverse order of the initialization */
 }
 
-ReplicationThrottle& EventuallyPersistentEngine::getReplicationThrottle() {
-    return getKVBucket()->getReplicationThrottle();
-}
-
 const std::string& EpEngineTaskable::getName() const {
     return myEngine->getName();
 }

engines/ep/src/ep_engine.h

@@ -56,7 +56,6 @@ class VBucketCountVisitor;
 
 // Forward decl
 class EventuallyPersistentEngine;
-class ReplicationThrottle;
 
 namespace cb::prometheus {
 enum class MetricGroup;
@@ -730,13 +729,6 @@ class EventuallyPersistentEngine : public EngineIface, public DcpIface {
         return *dcpFlowControlManager;
     }
 
-    /**
-     * Returns the replication throttle instance
-     *
-     * @return Ref to replication throttle
-     */
-    ReplicationThrottle& getReplicationThrottle();
-
     CheckpointConfig& getCheckpointConfig() {
         return *checkpointConfig;
     }

engines/ep/src/ephemeral_bucket.cc

@@ -20,7 +20,6 @@
 #include "ephemeral_vb.h"
 #include "ephemeral_vb_count_visitor.h"
 #include "failover-table.h"
-#include "replicationthrottle.h"
 #include "rollback_result.h"
 #include "seqno_persistence_notify_task.h"
 #include <executor/executorpool.h>
@@ -103,8 +102,6 @@ EphemeralBucket::EphemeralBucket(EventuallyPersistentEngine& engine)
     // in initialize().
     tombstonePurgerTask =
             std::make_shared<EphTombstoneHTCleaner>(engine, *this);
-
-    replicationThrottle = std::make_unique<ReplicationThrottleEphe>(engine);
 }
 
 EphemeralBucket::~EphemeralBucket() = default;
@@ -462,3 +459,8 @@ cb::engine_errc EphemeralBucket::getImplementationStats(
     collector.addStat(Key::ep_pending_compactions, 0);
     return cb::engine_errc::success;
 }
+
+bool EphemeralBucket::disconnectReplicationAtOOM() const {
+    return engine.getConfiguration().getEphemeralFullPolicy() ==
+           "fail_new_data";
+}

engines/ep/src/ephemeral_bucket.h

@@ -181,6 +181,8 @@ class EphemeralBucket : public KVBucket {
         return true;
     }
 
+    bool disconnectReplicationAtOOM() const override;
+
 protected:
     std::unique_ptr<VBucketCountVisitor> makeVBCountVisitor(
             vbucket_state_t state) override;

engines/ep/src/kv_bucket.cc

@@ -41,7 +41,6 @@
 #include "kvshard.h"
 #include "kvstore/kvstore.h"
 #include "range_scans/range_scan_callbacks.h"
-#include "replicationthrottle.h"
 #include "rollback_result.h"
 #include "seqno_persistence_notify_task.h"
 #include "tasks.h"
@@ -64,6 +63,7 @@
 #include <platform/timeutils.h>
 #include <statistics/collector.h>
 #include <statistics/labelled_collector.h>
+#include <utilities/math_utilities.h>
 
 #include <chrono>
 #include <cstring>
@@ -3368,3 +3368,15 @@ bool KVBucket::isCompactionExpiryFetchInline() const {
 size_t KVBucket::getNumCheckpointDestroyers() const {
     return ckptDestroyerTasks.rlock()->size();
 }
+
+KVBucket::ReplicationThrottleStatus KVBucket::getReplicationThrottleStatus()
+        const {
+    const auto& stats = engine.getEpStats();
+    const auto memoryUsed = stats.getEstimatedTotalMemoryUsed();
+    const auto bucketQuota = stats.getMaxDataSize();
+    if (memoryUsed <= cb::fractionOf(bucketQuota, mutationMemRatio)) {
+        return ReplicationThrottleStatus::Process;
+    }
+    return disconnectReplicationAtOOM() ? ReplicationThrottleStatus::Disconnect
+                                        : ReplicationThrottleStatus::Pause;
+}