SERVER-43698 Don't allow atClusterTime whwere number of seconds in Timestamp is 0

Author: lankas

jstests/noPassthrough/readConcern_atClusterTime.js

@@ -56,6 +56,16 @@ session.startTransaction({readConcern: {level: "snapshot", atClusterTime: "bad"}
 assert.commandFailedWithCode(sessionDb.runCommand({find: collName}), ErrorCodes.TypeMismatch);
 assert.commandFailedWithCode(session.abortTransaction_forTesting(), ErrorCodes.NoSuchTransaction);
 
+// 'atClusterTime' cannot specify a null Timestamp.
+session.startTransaction({readConcern: {level: "snapshot", atClusterTime: Timestamp(0, 0)}});
+assert.commandFailedWithCode(sessionDb.runCommand({find: collName}), ErrorCodes.InvalidOptions);
+assert.commandFailedWithCode(session.abortTransaction_forTesting(), ErrorCodes.NoSuchTransaction);
+
+// 'atClusterTime' cannot specify a Timestamp with zero seconds.
+session.startTransaction({readConcern: {level: "snapshot", atClusterTime: Timestamp(0, 1)}});
+assert.commandFailedWithCode(sessionDb.runCommand({find: collName}), ErrorCodes.InvalidOptions);
+assert.commandFailedWithCode(session.abortTransaction_forTesting(), ErrorCodes.NoSuchTransaction);
+
 // 'atClusterTime' cannot be used with readConcern level 'majority'.
 session.startTransaction({readConcern: {level: "majority", atClusterTime: clusterTime}});
 assert.commandFailedWithCode(sessionDb.runCommand({find: collName}), ErrorCodes.InvalidOptions);

src/mongo/db/repl/read_concern_args.cpp

@@ -220,14 +220,17 @@ Status ReadConcernArgs::parse(const BSONObj& readConcernObj) {
                           << kLevelFieldName << " is equal to " << kSnapshotReadConcernStr);
     }
 
-    if (_afterClusterTime && _afterClusterTime == LogicalTime::kUninitialized) {
+    // Make sure that atClusterTime wasn't specified with zero seconds.
+    if (_atClusterTime && _atClusterTime->asTimestamp().isNull()) {
         return Status(ErrorCodes::InvalidOptions,
-                      str::stream() << kAfterClusterTimeFieldName << " cannot be a null timestamp");
+                      str::stream() << kAtClusterTimeFieldName << " cannot be a null timestamp");
     }
 
-    if (_atClusterTime && _atClusterTime == LogicalTime::kUninitialized) {
+    // It's okay for afterClusterTime to be specified with zero seconds, but not an uninitialized
+    // timestamp.
+    if (_afterClusterTime && _afterClusterTime == LogicalTime::kUninitialized) {
         return Status(ErrorCodes::InvalidOptions,
-                      str::stream() << kAtClusterTimeFieldName << " cannot be a null timestamp");
+                      str::stream() << kAfterClusterTimeFieldName << " cannot be a null timestamp");
     }
 
     return Status::OK();