SERVER-26169 added startup parameter for linearizable read support defaulting to disabled

13 files changed, 81 insertions, 1 deletions

diff --git a/jstests/replsets/linearizable_read_concern.js b/jstests/replsets/linearizable_read_concern.js
index 4cbef17b568..f7f7d3b9228 100644
--- a/jstests/replsets/linearizable_read_concern.js
+++ b/jstests/replsets/linearizable_read_concern.js
@@ -31,9 +31,39 @@ load('jstests/libs/write_concern_util.js');
             ErrorCodes.InterruptedDueToReplStateChange);
     };
 
+    // Linearizable read concern is an opt-in feature. Replica sets started with the startup
+    // parameter --setParameter enableLinearizableReadConcern=true should error on receiving a
+    // linearizable read command.
+    {
+        jsTestLog('Testing that linearizable read is disabled by default');
+        let replTest = new ReplSetTest({nodes: 1});
+        replTest.startSet();
+        replTest.initiate();
+        let primary = replTest.getPrimary();
+
+        // Linearizable read concern is a startup-only server parameter.
+        assert.commandFailed(
+            primary.adminCommand({setParameter: 1, enableLinearizableReadConcern: true}));
+        assert.commandFailed(
+            primary.adminCommand({setParameter: 1, enableLinearizableReadConcern: false}));
+
+        let coll = primary.getDB('test').foo;
+        assert.writeOK(coll.insert({x: 1}));
+        assert.commandFailedWithCode(
+            coll.runCommand(
+                {'find': coll.getName(), readConcern: {level: "linearizable"}, maxTimeMS: 60000}),
+            ErrorCodes.LinearizableReadConcernNotEnabled);
+        replTest.stopSet();
+    }
+
     var num_nodes = 3;
     var name = 'linearizable_read_concern';
-    var replTest = new ReplSetTest({name: name, nodes: num_nodes, useBridge: true});
+    var replTest = new ReplSetTest({
+        name: name,
+        nodes: num_nodes,
+        nodeOptions: {setParameter: 'enableLinearizableReadConcern=true'},
+        useBridge: true,
+    });
     var config = replTest.getReplSetConfig();
 
     // Increased election timeout to avoid having the primary step down while we are
diff --git a/src/mongo/base/error_codes.err b/src/mongo/base/error_codes.err
index cb524d53263..c6a0e7d014b 100644
--- a/src/mongo/base/error_codes.err
+++ b/src/mongo/base/error_codes.err
@@ -194,6 +194,7 @@ error_code("FailPointEnabled", 192)
 error_code("NoShardingEnabled", 193)
 error_code("BalancerInterrupted", 194)
 error_code("ViewPipelineMaxSizeExceeded", 195)
+error_code("LinearizableReadConcernNotEnabled", 196)
 
 # Non-sequential error codes (for compatibility only)
 error_code("SocketException", 9001)
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index 432c630166d..a25288efa8e 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -1403,6 +1403,22 @@ bool Command::run(OperationContext* txn,
         return result;
     }
 
+    if (readConcernArgsStatus.getValue().getLevel() ==
+        repl::ReadConcernLevel::kLinearizableReadConcern) {
+        auto replCoord = repl::ReplicationCoordinator::get(txn);
+        if (!replCoord->isLinearizableReadConcernEnabled()) {
+            Status status(ErrorCodes::LinearizableReadConcernNotEnabled,
+                          "Linearizable read concern requested, but server was not started with "
+                          "--setParameter enableLinearizableReadConcern=true");
+            inPlaceReplyBob.resetToEmpty();
+            auto result = appendCommandStatus(inPlaceReplyBob, status);
+            inPlaceReplyBob.doneFast();
+            replyBuilder->setMetadata(rpc::makeEmptyMetadata());
+            return result;
+        }
+    }
+
+
     Status rcStatus = waitForReadConcern(txn, readConcernArgsStatus.getValue());
     if (!rcStatus.isOK()) {
         if (rcStatus == ErrorCodes::ExceededTimeLimit) {
diff --git a/src/mongo/db/repl/replication_coordinator.h b/src/mongo/db/repl/replication_coordinator.h
index 019add3e0cf..e2a6ff4e76b 100644
--- a/src/mongo/db/repl/replication_coordinator.h
+++ b/src/mongo/db/repl/replication_coordinator.h
@@ -794,6 +794,11 @@ public:
 
     virtual Status stepUpIfEligible() = 0;
 
+    /**
+     * Returns true if linearizable read concern is supported.
+     */
+    virtual bool isLinearizableReadConcernEnabled() const = 0;
+
 protected:
     ReplicationCoordinator();
 };
diff --git a/src/mongo/db/repl/replication_coordinator_external_state.h b/src/mongo/db/repl/replication_coordinator_external_state.h
index 73e99635c36..fbb8d365dbb 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state.h
@@ -355,6 +355,11 @@ public:
      * Stops periodic noop writes to oplog.
      */
     virtual void stopNoopWriter() = 0;
+
+    /**
+     * Returns true if linearizable read concern is supported.
+     */
+    virtual bool isLinearizableReadConcernEnabled() const = 0;
 };
 
 }  // namespace repl
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
index 21708c3ebff..b3d4b4ffbb4 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
@@ -118,6 +118,8 @@ const char kBlockingQueueOplogBufferName[] = "inMemoryBlockingQueue";
 // repl::SnapshotThread introduces.
 MONGO_EXPORT_STARTUP_SERVER_PARAMETER(enableReplSnapshotThread, bool, false);
 
+MONGO_EXPORT_STARTUP_SERVER_PARAMETER(enableLinearizableReadConcern, bool, false);
+
 MONGO_EXPORT_STARTUP_SERVER_PARAMETER(use3dot2InitialSync, bool, false);
 
 // Set this to specify whether to use a collection to buffer the oplog on the destination server
@@ -899,6 +901,10 @@ std::size_t ReplicationCoordinatorExternalStateImpl::getOplogFetcherMaxFetcherRe
     return oplogFetcherMaxFetcherRestarts;
 }
 
+bool ReplicationCoordinatorExternalStateImpl::isLinearizableReadConcernEnabled() const {
+    return enableLinearizableReadConcern;
+}
+
 JournalListener::Token ReplicationCoordinatorExternalStateImpl::getToken() {
     return repl::getGlobalReplicationCoordinator()->getMyLastAppliedOpTime();
 }
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.h b/src/mongo/db/repl/replication_coordinator_external_state_impl.h
index 372a1661e37..9c173a97823 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.h
@@ -113,6 +113,7 @@ public:
         OperationContext* txn) const override;
     virtual bool shouldUseDataReplicatorInitialSync() const override;
     virtual std::size_t getOplogFetcherMaxFetcherRestarts() const override;
+    virtual bool isLinearizableReadConcernEnabled() const override;
 
     // Methods from JournalListener.
     virtual JournalListener::Token getToken();
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp b/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
index 700d1608880..087e8d84ab0 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_mock.cpp
@@ -294,6 +294,10 @@ std::size_t ReplicationCoordinatorExternalStateMock::getOplogFetcherMaxFetcherRe
     return 0;
 }
 
+bool ReplicationCoordinatorExternalStateMock::isLinearizableReadConcernEnabled() const {
+    return false;
+}
+
 void ReplicationCoordinatorExternalStateMock::setIsReadCommittedEnabled(bool val) {
     _isReadCommittedSupported = val;
 }
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_mock.h b/src/mongo/db/repl/replication_coordinator_external_state_mock.h
index 35ff01d5585..fcc6eea1d4b 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_external_state_mock.h
@@ -107,6 +107,7 @@ public:
         OperationContext* txn) const override;
     virtual bool shouldUseDataReplicatorInitialSync() const override;
     virtual std::size_t getOplogFetcherMaxFetcherRestarts() const override;
+    virtual bool isLinearizableReadConcernEnabled() const override;
 
     /**
      * Adds "host" to the list of hosts that this mock will match when responding to "isSelf"
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 81c8cef4821..481c4f86c7a 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -3878,6 +3878,9 @@ void ReplicationCoordinatorImpl::setIndexPrefetchConfig(
     _indexPrefetchConfig = cfg;
 }
 
+bool ReplicationCoordinatorImpl::isLinearizableReadConcernEnabled() const {
+    return _externalState->isLinearizableReadConcernEnabled();
+}
 
 }  // namespace repl
 }  // namespace mongo
diff --git a/src/mongo/db/repl/replication_coordinator_impl.h b/src/mongo/db/repl/replication_coordinator_impl.h
index df76c251c0b..d66dd431279 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_impl.h
@@ -339,6 +339,8 @@ public:
 
     virtual Status stepUpIfEligible() override;
 
+    virtual bool isLinearizableReadConcernEnabled() const override;
+
     // ================== Test support API ===================
 
     /**
diff --git a/src/mongo/db/repl/replication_coordinator_mock.cpp b/src/mongo/db/repl/replication_coordinator_mock.cpp
index 03878cc300c..3b1aa2e8960 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.cpp
+++ b/src/mongo/db/repl/replication_coordinator_mock.cpp
@@ -467,5 +467,9 @@ Status ReplicationCoordinatorMock::stepUpIfEligible() {
     return Status::OK();
 }
 
+bool ReplicationCoordinatorMock::isLinearizableReadConcernEnabled() const {
+    return false;
+}
+
 }  // namespace repl
 }  // namespace mongo
diff --git a/src/mongo/db/repl/replication_coordinator_mock.h b/src/mongo/db/repl/replication_coordinator_mock.h
index 4daf24d894e..96dd2486e98 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_mock.h
@@ -262,6 +262,8 @@ public:
 
     virtual Status stepUpIfEligible() override;
 
+    virtual bool isLinearizableReadConcernEnabled() const override;
+
     /**
      * Sets the return value for calls to getConfig.
      */