SERVER-31631 Bump minimum outgoing wire version for mongod when featureCompatibilityVersion is 3.6

2 files changed, 115 insertions, 0 deletions

diff --git a/jstests/multiVersion/feature_compatibility_version_lagging_secondary.js b/jstests/multiVersion/feature_compatibility_version_lagging_secondary.js
new file mode 100644
index 00000000000..b56e219cac3
--- /dev/null
+++ b/jstests/multiVersion/feature_compatibility_version_lagging_secondary.js
@@ -0,0 +1,68 @@
+// Tests that a primary with upgrade featureCompatibilityVersion cannot connect with a secondary
+// with a lower binary version.
+(function() {
+    "use strict";
+
+    load("jstests/libs/write_concern_util.js");
+
+    const latest = "latest";
+    const downgrade = "3.4";
+
+    const upgradeFCV = "3.6";
+    const downgradeFCV = "3.4";
+
+    function testProtocolVersion(protocolVersion) {
+        jsTestLog("Testing connections between mixed-version mixed-featureCompatibilityVersion " +
+                  "nodes in a replica set using protocol version " + protocolVersion);
+
+        // Start a new replica set with two latest version nodes.
+        let rst = new ReplSetTest({
+            protocolVersion: protocolVersion,
+            nodes: [{binVersion: latest}, {binVersion: latest, rsConfig: {priority: 0}}],
+            settings: {chainingAllowed: false}
+        });
+        rst.startSet();
+
+        // The default value for 'catchUpTimeoutMillis' on 3.6 is -1. A 3.4 secondary will refuse to
+        // join a replica set with catchUpTimeoutMillis=-1.
+        let replSetConfig = rst.getReplSetConfig();
+        replSetConfig.settings.catchUpTimeoutMillis = 2000;
+        rst.initiate(replSetConfig);
+
+        let primary = rst.getPrimary();
+        let latestSecondary = rst.getSecondary();
+
+        // Set the featureCompatibilityVersion to the downgrade version so that a downgrade node can
+        // join the set.
+        assert.commandWorked(
+            primary.getDB("admin").runCommand({setFeatureCompatibilityVersion: downgradeFCV}));
+
+        // Add a downgrade node to the set.
+        let downgradeSecondary = rst.add({binVersion: downgrade, rsConfig: {priority: 0}});
+        rst.reInitiate();
+
+        // Wait for the downgrade secondary to finish initial sync.
+        rst.awaitSecondaryNodes();
+        rst.awaitReplication();
+
+        // Stop replication on the downgrade secondary.
+        stopServerReplication(downgradeSecondary);
+
+        // Set the featureCompatibilityVersion to the upgrade version. This will not replicate to
+        // the downgrade secondary, but the downgrade secondary will no longer be able to
+        // communicate with the rest of the set.
+        assert.commandWorked(primary.adminCommand({setFeatureCompatibilityVersion: upgradeFCV}));
+
+        // Shut down the latest version secondary.
+        rst.stop(latestSecondary);
+
+        // The primary should step down, since it can no longer see a majority of the replica set.
+        rst.waitForState(primary, ReplSetTest.State.SECONDARY);
+
+        restartServerReplication(downgradeSecondary);
+        rst.stopSet();
+    }
+
+    testProtocolVersion(0);
+    testProtocolVersion(1);
+})();
diff --git a/jstests/multiVersion/migration_between_mixed_FCV_mixed_version_mongods.js b/jstests/multiVersion/migration_between_mixed_FCV_mixed_version_mongods.js
new file mode 100644
index 00000000000..7c79af655b0
--- /dev/null
+++ b/jstests/multiVersion/migration_between_mixed_FCV_mixed_version_mongods.js
@@ -0,0 +1,47 @@
+/**
+ * Test that it is not possible to move a chunk from an upgrade featureCompatibilityVersion node to
+ * a downgrade binary version node.
+ */
+
+// This test will not end with consistent UUIDs, since there is inconsistent
+// featureCompatibilityVersion across the cluster.
+TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
+
+(function() {
+    "use strict";
+
+    load("jstests/libs/feature_compatibility_version.js");
+
+    const upgradeVersion = "3.6";
+    const downgradeVersion = "3.4";
+
+    let st = new ShardingTest({
+        shards: [{binVersion: "latest"}, {binVersion: downgradeVersion}],
+        mongos: {binVersion: "latest"}
+    });
+
+    let testDB = st.s.getDB("test");
+
+    // Create a sharded collection with primary shard 0.
+    assert.commandWorked(st.s.adminCommand({enableSharding: testDB.getName()}));
+    st.ensurePrimaryShard(testDB.getName(), st.shard0.shardName);
+    assert.commandWorked(
+        st.s.adminCommand({shardCollection: testDB.coll.getFullName(), key: {a: 1}}));
+
+    // Set the featureCompatibilityVersion to 3.6. This will fail because the
+    // featureCompatibilityVersion cannot be set to 3.6 on shard 1, but it will set the
+    // featureCompatibilityVersion to 3.6 on shard 0.
+    assert.commandFailed(st.s.adminCommand({setFeatureCompatibilityVersion: upgradeVersion}));
+    checkFCV(st.configRS.getPrimary().getDB("admin"), downgradeVersion, upgradeVersion);
+    checkFCV(st.shard0.getDB("admin"), upgradeVersion);
+    checkFCV34(st.shard1.getDB("admin"), downgradeVersion);
+
+    // It is not possible to move a chunk from an upgrade featureCompatibilityVersion shard to a
+    // downgrade shard.
+    assert.commandFailedWithCode(
+        st.s.adminCommand(
+            {moveChunk: testDB.coll.getFullName(), find: {a: 1}, to: st.shard1.shardName}),
+        ErrorCodes.IncompatibleServerVersion);
+
+    st.stop();
+})();