From ada51ff12bc231269a7cd4e5dd09225b7214db5b Mon Sep 17 00:00:00 2001
From: Zhe Wu <halfprice@users.noreply.github.com>
Date: Wed, 19 Oct 2022 22:09:04 -0700
Subject: [PATCH] Add a counter to track physical shard creation throuogh moves

---
 fdbserver/DDRelocationQueue.actor.cpp         | 19 ++++++++++++++++++-
 fdbserver/DDShardTracker.actor.cpp            |  4 ++++
 .../fdbserver/DataDistribution.actor.h        |  3 +++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/fdbserver/DDRelocationQueue.actor.cpp b/fdbserver/DDRelocationQueue.actor.cpp
index 46bb435145..b460e53cf4 100644
--- a/fdbserver/DDRelocationQueue.actor.cpp
+++ b/fdbserver/DDRelocationQueue.actor.cpp
@@ -687,6 +687,9 @@ struct DDQueue : public IDDRelocationQueue {
 
 	Reference<EventCacheHolder> movedKeyServersEventHolder;
 
+	int moveReusePhysicalShard;
+	int moveCreateNewPhysicalShard;
+
 	void startRelocation(int priority, int healthPriority) {
 		// Although PRIORITY_TEAM_REDUNDANT has lower priority than split and merge shard movement,
 		// we must count it into unhealthyRelocations; because team removers relies on unhealthyRelocations to
@@ -750,7 +753,8 @@ struct DDQueue : public IDDRelocationQueue {
 	    output(output), input(input), getShardMetrics(getShardMetrics), getTopKMetrics(getTopKMetrics), lastInterval(0),
 	    suppressIntervals(0), rawProcessingUnhealthy(new AsyncVar<bool>(false)),
 	    rawProcessingWiggle(new AsyncVar<bool>(false)), unhealthyRelocations(0),
-	    movedKeyServersEventHolder(makeReference<EventCacheHolder>("MovedKeyServers")) {}
+	    movedKeyServersEventHolder(makeReference<EventCacheHolder>("MovedKeyServers")), moveReusePhysicalShard(0),
+	    moveCreateNewPhysicalShard(0) {}
 	DDQueue() = default;
 
 	void validate() {
@@ -1676,6 +1680,11 @@ ACTOR Future<Void> dataDistributionRelocator(DDQueue* self,
 					// when !rd.isRestore(), dataMoveId is just decided as physicalShardIDCandidate
 					// thus, update the physicalShardIDCandidate to related data structures
 					ASSERT(physicalShardIDCandidate != UID().first());
+					if (self->physicalShardCollection->physicalShardExists(physicalShardIDCandidate)) {
+						self->moveReusePhysicalShard++;
+					} else {
+						self->moveCreateNewPhysicalShard++;
+					}
 					rd.dataMoveId = newShardId(physicalShardIDCandidate, AssignEmptyRange::False);
 					auto inFlightRange = self->inFlight.rangeContaining(rd.keys.begin);
 					inFlightRange.value().dataMoveId = rd.dataMoveId;
@@ -2472,6 +2481,14 @@ ACTOR Future<Void> dataDistributionQueue(Reference<IDDTxnProcessor> db,
 					    .trackLatest("MovingData"); // This trace event's trackLatest lifetime is controlled by
 					                                // DataDistributor::movingDataEventHolder. The track latest
 					                                // key we use here must match the key used in the holder.
+
+					if (SERVER_KNOBS->SHARD_ENCODE_LOCATION_METADATA && SERVER_KNOBS->ENABLE_DD_PHYSICAL_SHARD) {
+						TraceEvent("PhysicalShardMoveStats")
+						    .detail("MoveCreateNewPhysicalShard", self.moveCreateNewPhysicalShard)
+						    .detail("MoveReusePhysicalShard", self.moveReusePhysicalShard);
+						self.moveCreateNewPhysicalShard = 0;
+						self.moveReusePhysicalShard = 0;
+					}
 				}
 				when(wait(self.error.getFuture())) {} // Propagate errors from dataDistributionRelocator
 				when(wait(waitForAll(ddQueueFutures))) {}
diff --git a/fdbserver/DDShardTracker.actor.cpp b/fdbserver/DDShardTracker.actor.cpp
index 5c17bc1ab5..be7343ba4c 100644
--- a/fdbserver/DDShardTracker.actor.cpp
+++ b/fdbserver/DDShardTracker.actor.cpp
@@ -2081,6 +2081,10 @@ void PhysicalShardCollection::logPhysicalShardCollection() {
 	}
 }
 
+bool PhysicalShardCollection::physicalShardExists(uint64_t physicalShardID) {
+	return physicalShardInstances.find(physicalShardID) != physicalShardInstances.end();
+}
+
 // FIXME: complete this test with non-empty range
 TEST_CASE("/DataDistributor/Tracker/FetchTopK") {
 	state DataDistributionTracker self;
diff --git a/fdbserver/include/fdbserver/DataDistribution.actor.h b/fdbserver/include/fdbserver/DataDistribution.actor.h
index e8016101e3..2389dc0ab6 100644
--- a/fdbserver/include/fdbserver/DataDistribution.actor.h
+++ b/fdbserver/include/fdbserver/DataDistribution.actor.h
@@ -322,6 +322,9 @@ public:
 	// Log physicalShard
 	void logPhysicalShardCollection();
 
+	// Checks if a physical shard exists.
+	bool physicalShardExists(uint64_t physicalShardID);
+
 private:
 	// Track physicalShard metrics by tracking keyRange metrics
 	void updatePhysicalShardMetricsByKeyRange(KeyRange keyRange,