From a020219183884dbc5c3188053ad3c31af835e6aa Mon Sep 17 00:00:00 2001
From: Ted Tuckman <ted.tuckman@mongodb.com>
Date: Mon, 13 Feb 2023 15:06:27 +0000
Subject: SERVER-73878 Don't append hashedTemetryKey to commands if telemetry
 is disabled

---
 src/mongo/db/pipeline/sharded_agg_helpers.cpp |  3 +++
 src/mongo/db/query/telemetry.cpp              | 19 +++++++++++++++++--
 src/mongo/db/query/telemetry.h                |  3 +++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/mongo/db/pipeline/sharded_agg_helpers.cpp b/src/mongo/db/pipeline/sharded_agg_helpers.cpp
index f6c7bb7e6fb..f0d7923322c 100644
--- a/src/mongo/db/pipeline/sharded_agg_helpers.cpp
+++ b/src/mongo/db/pipeline/sharded_agg_helpers.cpp
@@ -741,6 +741,9 @@ void abandonCacheIfSentToShards(Pipeline* shardsPipeline) {
 }
 
 void setTelemetryKeyOnAggRequest(AggregateCommandRequest& request, ExpressionContext* expCtx) {
+    if (!telemetry::isTelemetryEnabled()) {
+        return;
+    }
     request.setHashedTelemetryKey(telemetry::telemetryKeyToShardedStoreId(
         telemetry::getTelemetryKeyFromOpCtx(expCtx->opCtx), getHostNameCachedAndPort()));
 }
diff --git a/src/mongo/db/query/telemetry.cpp b/src/mongo/db/query/telemetry.cpp
index 32cca0821c1..33fab1b5fc2 100644
--- a/src/mongo/db/query/telemetry.cpp
+++ b/src/mongo/db/query/telemetry.cpp
@@ -60,7 +60,11 @@ namespace telemetry {
 static const std::string kTelemetryKeyInShardedCommand = "hashedTelemetryKey";
 
 bool isTelemetryEnabled() {
-    return feature_flags::gFeatureFlagTelemetry.isEnabledAndIgnoreFCV();
+    // During initialization FCV may not yet be setup but queries could be run. We can't
+    // check whether telemetry should be enabled without FCV, so default to not recording
+    // those queries.
+    return serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+        feature_flags::gFeatureFlagTelemetry.isEnabled(serverGlobalParams.featureCompatibility);
 }
 
 ShardedTelemetryStoreKey telemetryKeyToShardedStoreId(const BSONObj& key, std::string hostAndPort) {
@@ -78,6 +82,9 @@ BSONObj getTelemetryKeyFromOpCtx(OperationContext* opCtx) {
 void appendShardedTelemetryKeyIfApplicable(MutableDocument& objToModify,
                                            std::string hostAndPort,
                                            OperationContext* opCtx) {
+    if (!isTelemetryEnabled()) {
+        return;
+    }
     auto telemetryKey = getTelemetryKeyFromOpCtx(opCtx);
     if (telemetryKey.isEmpty()) {
         return;
@@ -90,6 +97,9 @@ void appendShardedTelemetryKeyIfApplicable(MutableDocument& objToModify,
 void appendShardedTelemetryKeyIfApplicable(BSONObjBuilder& objToModify,
                                            std::string hostAndPort,
                                            OperationContext* opCtx) {
+    if (!isTelemetryEnabled()) {
+        return;
+    }
     auto telemetryKey = getTelemetryKeyFromOpCtx(opCtx);
     if (telemetryKey.isEmpty()) {
         return;
@@ -179,7 +189,12 @@ public:
 
 ServiceContext::ConstructorActionRegisterer telemetryStoreManagerRegisterer{
     "TelemetryStoreManagerRegisterer", [](ServiceContext* serviceCtx) {
-        if (!isTelemetryEnabled()) {
+        // It is possible that this is called before FCV is properly set up. Setting up the store if
+        // the flag is enabled but FCV is incorrect is safe, and guards against the FCV being
+        // changed to a supported version later.
+        // TODO SERVER-73907. Move this to run after FCV is initialized. It could be we'd have to
+        // re-run this function if FCV changes later during the life of the process.
+        if (!feature_flags::gFeatureFlagTelemetry.isEnabledAndIgnoreFCV()) {
             // featureFlags are not allowed to be changed at runtime. Therefore it's not an issue
             // to not create a telemetry store in ConstructorActionRegisterer at start up with the
             // flag off - because the flag can not be turned on at any point afterwards.
diff --git a/src/mongo/db/query/telemetry.h b/src/mongo/db/query/telemetry.h
index 3f29f9ecc77..258324290e5 100644
--- a/src/mongo/db/query/telemetry.h
+++ b/src/mongo/db/query/telemetry.h
@@ -53,6 +53,9 @@ using BSONNumeric = long long;
 }  // namespace
 
 namespace telemetry {
+
+bool isTelemetryEnabled();
+
 /**
  * Generate a Telemetry Store key to be used on a shard from a Telemetry Store key that is being
  * used on mongos.
-- 
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