SERVER-34575: Only downgrade to 3.6 when oplog was replayed on startup.

1 files changed, 91 insertions, 0 deletions

diff --git a/jstests/multiVersion/downgrade_to_36_only_with_recovered_data.js b/jstests/multiVersion/downgrade_to_36_only_with_recovered_data.js
new file mode 100644
index 00000000000..2803273524e
--- /dev/null
+++ b/jstests/multiVersion/downgrade_to_36_only_with_recovered_data.js
@@ -0,0 +1,91 @@
+/**
+ * Test that a node that is shutdown without running replication recovery does not downgrade to
+ * 3.6 compatible data files, even when FCV is 3.6.
+ *
+ * @tags: [requires_wiredtiger, requires_persistence, requires_replication]
+ */
+
+// Steps:
+// 1) Setup a one node replica set with `--shardsvr`. Shards are born in FCV 3.6
+// 2) Initiate the replica set.
+// 3) Wait for the first stable checkpoint.
+// 4) Set FCV to 4.0
+// 5) Insert a document.
+// 6) Hard crash the server. The checkpoint does not contain (4) nor (5), but
+//    the oplog does.
+// 7) Start the node as a standalone. Confirm the write at (5) is missing.
+// 8) Shutdown the node. Run `--repair`. This will not play oplog recovery.
+//    When this process shuts down, it must not downgrade the files.
+// 9) Restart the node as a replica set/shard. Assert oplog recovery went well
+//    by observing the write at (5).
+(function() {
+    "use strict";
+
+    const name = "rs";
+    let conn = MongoRunner.runMongod(
+        {binVersion: "latest", shardsvr: "", replSet: name, syncdelay: "600"});
+
+    assert.neq(conn, null, "mongod was unable to start up");
+
+    let options = conn.fullOptions;
+
+    assert.commandWorked(conn.adminCommand({replSetInitiate: 1}));
+    assert.soon(function() {
+        let status = assert.commandWorked(conn.adminCommand("replSetGetStatus"));
+        return status["lastStableCheckpointTimestamp"].t > 0;
+    });
+
+    assert.commandWorked(conn.adminCommand({setFeatureCompatibilityVersion: "4.0"}));
+    assert.commandWorked(
+        conn.getDB("foo")["bar"].insert({_id: 0}, {writeConcern: {w: 1, j: true}}));
+
+    jsTestLog("Oplog entries:");
+    let cursor = conn.getDB("local").oplog.rs.find();
+    while (cursor.hasNext()) {
+        printjson(cursor.next());
+    }
+
+    MongoRunner.stopMongod(conn, 9, {allowedExitCode: MongoRunner.EXIT_SIGKILL});
+
+    jsTestLog("Running as standalone.");
+    options.shardsvr = undefined;
+    options.replSet = undefined;
+    options.restart = true;
+    conn = MongoRunner.runMongod(options);
+
+    assert.eq(0, conn.getDB("foo")["bar"].find({_id: 0}).itcount());
+    MongoRunner.stopMongod(conn);
+
+    jsTestLog("Restarting after standalone with replication.");
+    options.shardsvr = "";
+    options.replSet = name;
+
+    conn = MongoRunner.runMongod(options);
+    assert.neq(conn, null, "mongod was unable to start up");
+
+    assert.soon(function() {
+        return conn.adminCommand("ismaster")["ismaster"];
+    });
+    assert.eq(1, conn.getDB("foo")["bar"].find({_id: 0}).itcount());
+    MongoRunner.stopMongod(conn);
+
+    jsTestLog("Running repair. The process will automatically exit when complete.");
+    options.shardsvr = undefined;
+    options.replSet = undefined;
+    options.repair = '';
+    MongoRunner.runMongod(options);
+
+    jsTestLog("Restarting after repair with replication.");
+    options.shardsvr = '';
+    options.replSet = name;
+    options.repair = undefined;
+
+    conn = MongoRunner.runMongod(options);
+    assert.neq(conn, null, "mongod was unable to start up");
+
+    assert.soon(function() {
+        return conn.adminCommand("ismaster")["ismaster"];
+    });
+    assert.eq(1, conn.getDB("foo")["bar"].find({_id: 0}).itcount());
+    MongoRunner.stopMongod(conn);
+})();