SERVER-31885 Prohibit $changeStream from running on a non-existent database

3 files changed, 24 insertions, 2 deletions

diff --git a/jstests/change_streams/change_stream.js b/jstests/change_streams/change_stream.js
index 80356aa3b48..59e8df872f1 100644
--- a/jstests/change_streams/change_stream.js
+++ b/jstests/change_streams/change_stream.js
@@ -6,10 +6,18 @@
     load("jstests/libs/change_stream_util.js");
     load('jstests/libs/uuid_util.js');
 
+    jsTestLog("Testing $changeStream on non-existent database");
+    const dbDoesNotExist = db.getSiblingDB("database-does-not-exist");
+    assert.commandWorked(dbDoesNotExist.dropDatabase());
+    assert.commandFailedWithCode(
+        dbDoesNotExist.runCommand(
+            {aggregate: dbDoesNotExist.getName(), pipeline: [{$changeStream: {}}], cursor: {}}),
+        ErrorCodes.NamespaceNotFound);
+
     let cst = new ChangeStreamTest(db);
 
     jsTestLog("Testing single insert");
-    assertDropCollection(db, "t1");
+    assertDropAndRecreateCollection(db, "t1");
     let cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
     // Test that if there are no changes, we return an empty batch.
     assert.eq(0, cursor.firstBatch.length, "Cursor had changes: " + tojson(cursor));
diff --git a/jstests/change_streams/change_stream_collation.js b/jstests/change_streams/change_stream_collation.js
index 314e7b08954..b20d33e1981 100644
--- a/jstests/change_streams/change_stream_collation.js
+++ b/jstests/change_streams/change_stream_collation.js
@@ -11,6 +11,10 @@
 
     const caseInsensitive = {locale: "en_US", strength: 2};
 
+    // $changeStream cannot run on a non-existent database. Create an unrelated collection to ensure
+    // that the database is present before testing.
+    assertDropAndRecreateCollection(db, "change_stream_ensure_db_exists");
+
     let caseInsensitiveCollection = "change_stream_case_insensitive";
     assertDropCollection(db, caseInsensitiveCollection);
 
diff --git a/jstests/noPassthrough/unsupported_change_stream_deployments.js b/jstests/noPassthrough/unsupported_change_stream_deployments.js
index 82a497bf19b..90b494654e8 100644
--- a/jstests/noPassthrough/unsupported_change_stream_deployments.js
+++ b/jstests/noPassthrough/unsupported_change_stream_deployments.js
@@ -22,18 +22,22 @@
 
     const conn = MongoRunner.runMongod({enableMajorityReadConcern: ""});
     assert.neq(null, conn, "mongod was unable to start up");
+    // $changeStream cannot run on a non-existent database.
+    assert.writeOK(conn.getDB("test").ensure_db_exists.insert({}));
     assertChangeStreamNotSupportedOnConnection(conn);
     assert.eq(0, MongoRunner.stopMongod(conn));
 
     // Test master/slave deployments.
     const masterSlaveFixture = new ReplTest("change_stream");
     const master = masterSlaveFixture.start(true, {enableMajorityReadConcern: ""});
+    assert.writeOK(master.getDB("test").ensure_db_exists.insert({}));
     assertChangeStreamNotSupportedOnConnection(master);
 
     const slave = masterSlaveFixture.start(false);
     // Slaves start in FCV 3.4; we need to wait for it to sync the FCV document from the master
     // before trying a change stream, or the change stream will fail for the wrong reason.
     assert.soonNoExcept(() => checkFCV(slave.getDB("admin"), "3.6") || true);
+    assert.soonNoExcept(() => slave.getDB("test").ensure_db_exists.exists());
     assertChangeStreamNotSupportedOnConnection(slave);
 
     // Test a sharded cluster with standalone shards.
@@ -41,8 +45,14 @@
         {shards: 2, other: {shardOptions: {enableMajorityReadConcern: ""}}, config: 1});
     // Make sure the database exists before running any commands.
     const mongosDB = clusterWithStandalones.getDB("test");
-    assert.writeOK(mongosDB.unrelated.insert({}));
+    // enableSharding will create the db at the cluster level but not on the shards. $changeStream
+    // through mongoS will be allowed to run on the shards despite the lack of a database.
+    assert.commandWorked(mongosDB.adminCommand({enableSharding: "test"}));
     assertChangeStreamNotSupportedOnConnection(clusterWithStandalones.s);
+    // Shard the 'ensure_db_exists' collection on a hashed key before running $changeStream on the
+    // shards directly. This will ensure that the database is created on both shards.
+    assert.commandWorked(
+        mongosDB.adminCommand({shardCollection: "test.ensure_db_exists", key: {_id: "hashed"}}));
     assertChangeStreamNotSupportedOnConnection(clusterWithStandalones.shard0);
     assertChangeStreamNotSupportedOnConnection(clusterWithStandalones.shard1);
 }());