SERVER-58367 Create Feature flag for PM-2384

5 files changed, 84 insertions, 23 deletions

diff --git a/jstests/multiVersion/upgrade_downgrade_sharded_cluster.js b/jstests/multiVersion/upgrade_downgrade_sharded_cluster.js
index 529727c0131..e245d2e38b2 100644
--- a/jstests/multiVersion/upgrade_downgrade_sharded_cluster.js
+++ b/jstests/multiVersion/upgrade_downgrade_sharded_cluster.js
@@ -20,12 +20,8 @@ function setupClusterAndDatabase(binVersion) {
         mongos: 1,
         config: 1,
         shards: 2,
-        other: {
-            mongosOptions: {binVersion: binVersion},
-            configOptions: {binVersion: binVersion},
-            shardOptions: {binVersion: binVersion},
-            rs: {nodes: 2}
-        }
+        rs: {nodes: 2, binVersion: binVersion},
+        other: {mongosOptions: {binVersion: binVersion}, configOptions: {binVersion: binVersion}}
     });
     st.configRS.awaitReplication();
 
@@ -77,7 +73,7 @@ function createShardedCollection() {
 }
 
 function testDisabledLongNameSupport(collNs) {
-    jsTestLog('Verify that long name support is properly disabled on collection ' + collNs);
+    jsTest.log('Verify that long name support is properly disabled on collection ' + collNs);
 
     const collConfigDoc = st.s.getDB('config').collections.findOne({_id: collNs});
     assert.eq(collConfigDoc.supportingLongName, undefined);
@@ -91,7 +87,7 @@ function testDisabledLongNameSupport(collNs) {
     shard1Secondary.setSecondaryOk();
 
     for (const node of [shard0Primary, shard0Secondary, shard1Primary, shard1Secondary]) {
-        jsTestLog('Verify the consistency of the persisted cache on node ' + getNodeName(node));
+        jsTest.log('Verify the consistency of the persisted cache on node ' + getNodeName(node));
 
         const configDb = node.getDB('config');
 
@@ -104,7 +100,7 @@ function testDisabledLongNameSupport(collNs) {
 }
 
 function testImplicitlyEnabledLongNameSupport(collNs) {
-    jsTestLog('Verify that long name support is properly enabled on collection ' + collNs);
+    jsTest.log('Verify that long name support is properly enabled on collection ' + collNs);
 
     const collConfigDoc = st.s.getDB('config').collections.findOne({_id: collNs});
     assert.eq(collConfigDoc.supportingLongName, 'implicitly_enabled');
@@ -118,7 +114,7 @@ function testImplicitlyEnabledLongNameSupport(collNs) {
     shard1Secondary.setSecondaryOk();
 
     for (const node of [shard0Primary, shard0Secondary, shard1Primary, shard1Secondary]) {
-        jsTestLog('Verify the consistency of the persisted cache on node ' + getNodeName(node));
+        jsTest.log('Verify the consistency of the persisted cache on node ' + getNodeName(node));
 
         const configDb = node.getDB('config');
 
@@ -130,9 +126,21 @@ function testImplicitlyEnabledLongNameSupport(collNs) {
     }
 }
 
+function isFeatureFlagLongCollectionNamesEnabled() {
+    const getClusterLookupParam =
+        st.configRS.getPrimary().adminCommand({getParameter: 1, featureFlagLongCollectionNames: 1});
+    return getClusterLookupParam.hasOwnProperty('featureFlagLongCollectionNames') &&
+        getClusterLookupParam.featureFlagLongCollectionNames.value;
+}
+
 function checkClusterBeforeUpgrade(fcv, collNs) {
     checkConfigAndShardsFCV(fcv);
-    testDisabledLongNameSupport(collNs);
+
+    if (isFeatureFlagLongCollectionNamesEnabled()) {
+        testImplicitlyEnabledLongNameSupport(collNs);
+    } else {
+        testDisabledLongNameSupport(collNs);
+    }
 }
 
 function checkClusterAfterBinaryUpgrade() {
@@ -141,8 +149,14 @@ function checkClusterAfterBinaryUpgrade() {
 
 function checkClusterAfterFCVUpgrade(fcv, call1Ns, call2Ns) {
     checkConfigAndShardsFCV(fcv);
-    testImplicitlyEnabledLongNameSupport(call1Ns);
-    testImplicitlyEnabledLongNameSupport(call2Ns);
+
+    if (isFeatureFlagLongCollectionNamesEnabled()) {
+        testImplicitlyEnabledLongNameSupport(call1Ns);
+        testImplicitlyEnabledLongNameSupport(call2Ns);
+    } else {
+        testDisabledLongNameSupport(call1Ns);
+        testDisabledLongNameSupport(call2Ns);
+    }
 }
 
 function checkClusterAfterFCVDowngrade() {
@@ -151,6 +165,7 @@ function checkClusterAfterFCVDowngrade() {
 
 function checkClusterAfterBinaryDowngrade(fcv, call1Ns, call2Ns, call3Ns) {
     checkConfigAndShardsFCV(fcv);
+
     testDisabledLongNameSupport(call1Ns);
     testDisabledLongNameSupport(call2Ns);
     testDisabledLongNameSupport(call3Ns);
diff --git a/src/mongo/db/s/config/sharding_catalog_manager.cpp b/src/mongo/db/s/config/sharding_catalog_manager.cpp
index 295fa1bc183..188279a1b7c 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager.cpp
@@ -61,6 +61,7 @@
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/database_version.h"
 #include "mongo/s/grid.h"
+#include "mongo/s/long_collection_names_gen.h"
 #include "mongo/s/write_ops/batched_command_request.h"
 #include "mongo/s/write_ops/batched_command_response.h"
 #include "mongo/transport/service_entry_point.h"
@@ -669,7 +670,9 @@ void ShardingCatalogManager::upgradeMetadataTo51Phase2(OperationContext* opCtx)
     LOGV2(5857402, "Starting metadata upgrade to FCV 5.1 (phase 2)");
 
     try {
-        _enableSupportForLongCollectionName(opCtx);
+        if (feature_flags::gFeatureFlagLongCollectionNames.isEnabledAndIgnoreFCV()) {
+            _enableSupportForLongCollectionName(opCtx);
+        }
     } catch (const DBException& e) {
         LOGV2_ERROR(
             5857403, "Failed to upgrade metadata to FCV 5.1 (phase 2)", "error"_attr = redact(e));
@@ -683,7 +686,9 @@ void ShardingCatalogManager::downgradeMetadataToPre51Phase2(OperationContext* op
     LOGV2(5857405, "Starting metadata downgrade to pre FCV 5.1 (phase 2)");
 
     try {
-        _disableSupportForLongCollectionName(opCtx);
+        if (feature_flags::gFeatureFlagLongCollectionNames.isEnabledAndIgnoreFCV()) {
+            _disableSupportForLongCollectionName(opCtx);
+        }
     } catch (const DBException& e) {
         LOGV2_ERROR(5857406,
                     "Failed to downgrade metadata to pre FCV 5.1 (phase 2)",
diff --git a/src/mongo/db/s/create_collection_coordinator.cpp b/src/mongo/db/s/create_collection_coordinator.cpp
index 9cc00c593f2..1b0621f2a94 100644
--- a/src/mongo/db/s/create_collection_coordinator.cpp
+++ b/src/mongo/db/s/create_collection_coordinator.cpp
@@ -54,6 +54,7 @@
 #include "mongo/s/cluster_commands_helpers.h"
 #include "mongo/s/cluster_write.h"
 #include "mongo/s/grid.h"
+#include "mongo/s/long_collection_names_gen.h"
 
 namespace mongo {
 namespace {
@@ -822,18 +823,21 @@ void CreateCollectionCoordinator::_commit(OperationContext* opCtx) {
 
     coll.setKeyPattern(_shardKeyPattern->getKeyPattern());
 
-    // Prevent the FCV from changing before committing the new collection to the config server. This
-    // ensures that the 'supportingLongName' field is properly set (and committed) based on the
-    // current shard's FCV.
+    // Prevent the FCV from changing before committing the new collection to the config server.
+    // This ensures that the 'supportingLongName' field is properly set (and committed) based on
+    // the current shard's FCV.
     //
     // TODO: Remove once FCV 6.0 becomes last-lts
-    FixedFCVRegion fixedFCVRegion(opCtx);
+    std::shared_ptr<FixedFCVRegion> currentFCV;
 
     // TODO: Remove condition once FCV 6.0 becomes last-lts
-    const auto& currentFCV = serverGlobalParams.featureCompatibility;
-    if (currentFCV.isGreaterThanOrEqualTo(
-            multiversion::FeatureCompatibilityVersion::kUpgradingFrom_5_0_To_5_1)) {
-        coll.setSupportingLongName(SupportingLongNameStatusEnum::kImplicitlyEnabled);
+    if (feature_flags::gFeatureFlagLongCollectionNames.isEnabledAndIgnoreFCV()) {
+        currentFCV = std::make_shared<FixedFCVRegion>(opCtx);
+        if ((*currentFCV)
+                ->isGreaterThanOrEqualTo(
+                    multiversion::FeatureCompatibilityVersion::kUpgradingFrom_5_0_To_5_1)) {
+            coll.setSupportingLongName(SupportingLongNameStatusEnum::kImplicitlyEnabled);
+        }
     }
 
     if (_doc.getCreateCollectionRequest().getTimeseries()) {
diff --git a/src/mongo/s/SConscript b/src/mongo/s/SConscript
index b9b22e5851c..52de11e1322 100644
--- a/src/mongo/s/SConscript
+++ b/src/mongo/s/SConscript
@@ -174,6 +174,7 @@ env.Library(
         'chunk_version.idl',
         'database_version.cpp',
         'database_version.idl',
+        'long_collection_names.idl',
         'mongod_and_mongos_server_parameters.idl',
         'request_types/abort_reshard_collection.idl',
         'request_types/add_shard_request_type.cpp',
diff --git a/src/mongo/s/long_collection_names.idl b/src/mongo/s/long_collection_names.idl
new file mode 100644
index 00000000000..aa5d47dad89
--- /dev/null
+++ b/src/mongo/s/long_collection_names.idl
@@ -0,0 +1,36 @@
+# Copyright (C) 2020-present MongoDB, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the Server Side Public License, version 1,
+# as published by MongoDB, Inc.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# Server Side Public License for more details.
+#
+# You should have received a copy of the Server Side Public License
+# along with this program. If not, see
+# <http://www.mongodb.com/licensing/server-side-public-license>.
+#
+# As a special exception, the copyright holders give permission to link the
+# code of portions of this program with the OpenSSL library under certain
+# conditions as described in each individual source file and distribute
+# linked combinations including the program with the OpenSSL library. You
+# must comply with the Server Side Public License in all respects for
+# all of the code used other than as permitted herein. If you modify file(s)
+# with this exception, you may extend this exception to your version of the
+# file(s), but you are not obligated to do so. If you do not wish to do so,
+# delete this exception statement from your version. If you delete this
+# exception statement from all source files in the program, then also delete
+# it in the license file.
+
+global:
+    cpp_namespace: mongo::feature_flags
+
+feature_flags:
+    featureFlagLongCollectionNames:
+        description: Extend the maximum name length of sharded collections from 236 to 256 bytes,
+                     aligning it to the limit of non-sharded collections.
+        cpp_varname: gFeatureFlagLongCollectionNames
+        default: false