SERVER-25694 Eliminate race in PlanExecutor cleanup.

Ensures that a collection lock is held in at least MODE_IS while
deregistering a PlanExecutor from the cursor manager. Introduces new
PlanExecutor::dispose() and ClientCursor::dispose() methods that must be
called before destruction of those classes, and ensures they are called
before destruction. These calls will thread an OperationContext all the
way through to DocumentSource::dispose() for each stage in a Pipeline,
which will give DocumentSourceCursor a chance to acquire locks and
deregister its PlanExecutor if necessary.

1 files changed, 90 insertions, 0 deletions

diff --git a/jstests/core/getmore_invalidated_cursors.js b/jstests/core/getmore_invalidated_cursors.js
new file mode 100644
index 00000000000..9b93d069d61
--- /dev/null
+++ b/jstests/core/getmore_invalidated_cursors.js
@@ -0,0 +1,90 @@
+// Tests that running a getMore on a cursor that has been invalidated by something like a collection
+// drop will return an appropriate error message.
+(function() {
+    'use strict';
+
+    const testDB = db.getSiblingDB("getmore_invalidated_cursors");
+    const coll = testDB.test;
+
+    const nDocs = 100;
+    const batchSize = nDocs - 1;
+
+    function setupCollection() {
+        coll.drop();
+        const bulk = coll.initializeUnorderedBulkOp();
+        for (let i = 0; i < nDocs; ++i) {
+            bulk.insert({_id: i, x: i});
+        }
+        assert.writeOK(bulk.execute());
+        assert.commandWorked(coll.createIndex({x: 1}));
+    }
+
+    // Test that dropping the database between a find and a getMore will return an appropriate error
+    // code and message.
+    setupCollection();
+
+    const isShardedCollection = coll.stats().sharded;
+    const shellReadMode = testDB.getMongo().readMode();
+
+    let cursor = coll.find().batchSize(batchSize);
+    cursor.next();  // Send the query to the server.
+
+    assert.commandWorked(testDB.dropDatabase());
+
+    let error = assert.throws(() => cursor.itcount());
+
+    if (testDB.runCommand({isdbgrid: 1}).isdbgrid && shellReadMode == 'legacy') {
+        // The cursor will be invalidated on mongos, and we won't be able to find it.
+        assert.neq(-1, error.message.indexOf('didn\'t exist on server'), error.message);
+    } else {
+        assert.eq(error.code, ErrorCodes.OperationFailed, tojson(error));
+        assert.neq(-1, error.message.indexOf('collection dropped'), error.message);
+    }
+
+    // Test that dropping the collection between a find and a getMore will return an appropriate
+    // error code and message.
+    setupCollection();
+    cursor = coll.find().batchSize(batchSize);
+    cursor.next();  // Send the query to the server.
+
+    coll.drop();
+
+    error = assert.throws(() => cursor.itcount());
+    if (isShardedCollection) {
+        // The cursor will be invalidated on mongos, and we won't be able to find it.
+        if (shellReadMode == 'legacy') {
+            assert.neq(-1, error.message.indexOf('didn\'t exist on server'), error.message);
+        } else {
+            assert.eq(error.code, ErrorCodes.CursorNotFound, tojson(error));
+            assert.neq(-1, error.message.indexOf('not found'), error.message);
+        }
+    } else {
+        assert.eq(error.code, ErrorCodes.OperationFailed, tojson(error));
+        assert.neq(-1, error.message.indexOf('collection dropped'), error.message);
+    }
+
+    // Test that dropping an index between a find and a getMore will return an appropriate error
+    // code and message.
+    setupCollection();
+    cursor = coll.find().batchSize(batchSize);
+    cursor.next();  // Send the query to the server.
+
+    assert.commandWorked(testDB.runCommand({dropIndexes: coll.getName(), index: {x: 1}}));
+
+    error = assert.throws(() => cursor.itcount());
+    assert.eq(error.code, ErrorCodes.QueryPlanKilled, tojson(error));
+    assert.neq(-1, error.message.indexOf('index \'x_1\' dropped'), error.message);
+
+    // Test that killing a cursor between a find and a getMore will return an appropriate error
+    // code and message.
+
+    setupCollection();
+    // Use the find command so that we can extract the cursor id to pass to the killCursors command.
+    let cursorId = assert
+                       .commandWorked(testDB.runCommand(
+                           {find: coll.getName(), filter: {}, batchSize: batchSize}))
+                       .cursor.id;
+    assert.commandWorked(testDB.runCommand({killCursors: coll.getName(), cursors: [cursorId]}));
+    assert.commandFailedWithCode(testDB.runCommand({getMore: cursorId, collection: coll.getName()}),
+                                 ErrorCodes.CursorNotFound);
+}());