Revert "SERVER-25158 fail gracefully when attempting to join a cluster with featureCompatibilityVersion 3.4"

This reverts commit 85a326b84ce1d1009bfbb97dbce934383d802883.

4 files changed, 0 insertions, 28 deletions

diff --git a/src/mongo/client/replica_set_monitor.cpp b/src/mongo/client/replica_set_monitor.cpp
index 8cf534b3fd5..0a471ffd088 100644
--- a/src/mongo/client/replica_set_monitor.cpp
+++ b/src/mongo/client/replica_set_monitor.cpp
@@ -835,14 +835,6 @@ HostAndPort Refresher::_refreshUntilMatches(const ReadPreferenceSetting* criteri
                     conn->isMaster(ignoredOutParam, &reply);
                     pingMicros = timer.micros();
                     conn.done();  // return to pool on success.
-                } catch (const DBException& ex) {
-                    // If this mongos is being used in an illegal configuration and must be
-                    // upgraded, bubble up the error.
-                    Status status = ex.toStatus();
-                    if (status == ErrorCodes::MustUpgrade) {
-                        throw;
-                    }
-                    reply = BSONObj();  // should be a no-op but want to be sure
                 } catch (...) {
                     reply = BSONObj();  // should be a no-op but want to be sure
                 }
diff --git a/src/mongo/s/client/sharding_connection_hook.cpp b/src/mongo/s/client/sharding_connection_hook.cpp
index f1db2092a6f..bb368f443d1 100644
--- a/src/mongo/s/client/sharding_connection_hook.cpp
+++ b/src/mongo/s/client/sharding_connection_hook.cpp
@@ -159,15 +159,6 @@ void ShardingConnectionHook::onCreate(DBClientBase* conn) {
             return;
         }
 
-        // Report a useful error message when we are illegally attempting to connect to 3.4 config
-        // servers in 3.4 feature compatibility mode.
-        uassert(ErrorCodes::MustUpgrade,
-                str::stream() << "Using a 3.2 mongos with a cluster that has "
-                                 "featureCompatibilityVersion 3.4 is not a supported "
-                                 "configuration. See "
-                                 "http://dochub.mongodb.org/core/3.4-feature-compatibility.",
-                configServerModeNumber < 2);
-
         uassert(28785,
                 str::stream() << "Unrecognized configsvr version number: " << configServerModeNumber
                               << ". Expected either 0 or 1",
diff --git a/src/mongo/s/server.cpp b/src/mongo/s/server.cpp
index 2200143c5bd..e68fd12b66f 100644
--- a/src/mongo/s/server.cpp
+++ b/src/mongo/s/server.cpp
@@ -296,12 +296,6 @@ static ExitCode runMongosServer() {
                 return EXIT_CLEAN;
             }
             error() << "Error initializing sharding system: " << status;
-
-            // Exit gracefully if this mongos is being used incorrectly in a mixed 3.2/3.4 cluster.
-            if (status == ErrorCodes::MustUpgrade) {
-                dbexit(EXIT_SHARDING_ERROR);
-            }
-
             return EXIT_SHARDING_ERROR;
         }
 
diff --git a/src/mongo/s/sharding_initialization.cpp b/src/mongo/s/sharding_initialization.cpp
index 99079c97c8c..36a074742dd 100644
--- a/src/mongo/s/sharding_initialization.cpp
+++ b/src/mongo/s/sharding_initialization.cpp
@@ -199,11 +199,6 @@ Status initializeGlobalShardingState(OperationContext* txn,
                 // retry.
                 return status;
             }
-
-            if (status == ErrorCodes::MustUpgrade) {
-                return status;
-            }
-
             if (status == ErrorCodes::ReplicaSetNotFound) {
                 // ReplicaSetNotFound most likely means we've been waiting for the config replica
                 // set to come up for so long that the ReplicaSetMonitor stopped monitoring the set.