SERVER-39520 Use database IX lock for dropCollection

2 files changed, 76 insertions, 43 deletions

diff --git a/jstests/core/txns/drop_collection_not_blocked_by_txn.js b/jstests/core/txns/drop_collection_not_blocked_by_txn.js
new file mode 100644
index 00000000000..626a7128a5c
--- /dev/null
+++ b/jstests/core/txns/drop_collection_not_blocked_by_txn.js
@@ -0,0 +1,32 @@
+/**
+ * Test that drop collection only takes database IX lock and will not be blocked by transactions.
+ *
+ * @tags: [uses_transactions, requires_db_locking, assumes_unsharded_collection]
+ */
+
+(function() {
+    "use strict";
+
+    let rst = new ReplSetTest({nodes: 1});
+    rst.startSet();
+    rst.initiate();
+
+    let db = rst.getPrimary().getDB("test");
+
+    assert.commandWorked(db.runCommand({insert: "a", documents: [{x: 1}]}));
+    assert.commandWorked(db.runCommand({insert: "b", documents: [{x: 1}]}));
+
+    const session = db.getMongo().startSession();
+    const sessionDb = session.getDatabase("test");
+
+    session.startTransaction();
+    // This holds a database IX lock and a collection IX lock on "a".
+    sessionDb.a.insert({y: 1});
+
+    // This only requires database IX lock.
+    assert.commandWorked(db.runCommand({drop: "b"}));
+
+    session.commitTransaction();
+
+    rst.stopSet();
+})();
diff --git a/jstests/core/txns/transactions_profiling_with_drops.js b/jstests/core/txns/transactions_profiling_with_drops.js
index 418bc45330b..4c2c1c0047a 100644
--- a/jstests/core/txns/transactions_profiling_with_drops.js
+++ b/jstests/core/txns/transactions_profiling_with_drops.js
@@ -7,20 +7,17 @@
 
     const dbName = "test";
     const collName = "transactions_profiling_with_drops";
-    const otherCollName = "other";
     const adminDB = db.getSiblingDB("admin");
     const testDB = db.getSiblingDB(dbName);
-    const otherColl = testDB[otherCollName];
     const session = db.getMongo().startSession({causalConsistency: false});
     const sessionDb = session.getDatabase(dbName);
     const sessionColl = sessionDb[collName];
 
     sessionDb.runCommand({dropDatabase: 1, writeConcern: {w: "majority"}});
     assert.commandWorked(sessionColl.insert({_id: "doc"}, {w: "majority"}));
-    assert.commandWorked(otherColl.insert({_id: "doc"}, {w: "majority"}));
     assert.commandWorked(sessionDb.runCommand({profile: 1, slowms: 1}));
 
-    jsTest.log("Test read profiling with drops.");
+    jsTest.log("Test read profiling with operation holding database X lock.");
 
     jsTest.log("Start transaction.");
     session.startTransaction();
@@ -32,39 +29,50 @@
     profilerHasSingleMatchingEntryOrThrow(
         {profileDB: testDB, filter: {"command.comment": "read success"}});
 
-    jsTest.log("Start a drop, which will hang.");
-    let awaitDrop = startParallelShell(function() {
-        db.getSiblingDB("test").runCommand({drop: "other", writeConcern: {w: "majority"}});
+    // Lock 'test' database in X mode.
+    let lockShell = startParallelShell(function() {
+        assert.commandFailed(db.adminCommand({
+            sleep: 1,
+            secs: 500,
+            lock: "w",
+            lockTarget: "test",
+            $comment: "transaction_profiling_with_drops lock sleep"
+        }));
     });
 
-    // Wait for the drop to have a pending MODE_X lock on the database.
-    assert.soon(
-        function() {
-            return adminDB
-                       .aggregate([
-                           {$currentOp: {}},
-                           {$match: {"command.drop": otherCollName, waitingForLock: true}}
-                       ])
-                       .itcount() === 1;
-        },
-        function() {
-            return "Failed to find drop in currentOp output: " +
-                tojson(adminDB.aggregate([{$currentOp: {}}]));
+    const waitForCommand = function(opFilter) {
+        let opId = -1;
+        assert.soon(function() {
+            const curopRes = testDB.currentOp();
+            assert.commandWorked(curopRes);
+            const foundOp = curopRes["inprog"].filter(opFilter);
+
+            if (foundOp.length == 1) {
+                opId = foundOp[0]["opid"];
+            }
+            return (foundOp.length == 1);
         });
+        return opId;
+    };
+
+    // Wait for sleep to appear in currentOp
+    let opId = waitForCommand(
+        op => (op["ns"] == "admin.$cmd" &&
+               op["command"]["$comment"] == "transaction_profiling_with_drops lock sleep"));
 
     jsTest.log("Run a slow read. Profiling in the transaction should fail.");
     assert.sameMembers(
         [{_id: "doc"}],
         sessionColl.find({$where: "sleep(1000); return true;"}).comment("read failure").toArray());
     session.commitTransaction();
-    awaitDrop();
+
+    assert.commandWorked(testDB.killOp(opId));
+    lockShell();
+
     profilerHasZeroMatchingEntriesOrThrow(
         {profileDB: testDB, filter: {"command.comment": "read failure"}});
 
-    jsTest.log("Test write profiling with drops.");
-
-    // Recreate the "other" collection so it can be dropped again.
-    assert.commandWorked(otherColl.insert({_id: "doc"}, {w: "majority"}));
+    jsTest.log("Test write profiling with operation holding database X lock.");
 
     jsTest.log("Start transaction.");
     session.startTransaction();
@@ -75,31 +83,24 @@
     profilerHasSingleMatchingEntryOrThrow(
         {profileDB: testDB, filter: {"command.collation": {locale: "en"}}});
 
-    jsTest.log("Start a drop, which will hang.");
-    awaitDrop = startParallelShell(function() {
-        db.getSiblingDB("test").runCommand({drop: "other", writeConcern: {w: "majority"}});
+    // Lock 'test' database in X mode.
+    lockShell = startParallelShell(function() {
+        assert.commandFailed(db.getSiblingDB("test").adminCommand(
+            {sleep: 1, secs: 500, lock: "w", lockTarget: "test", $comment: "lock sleep"}));
     });
 
-    // Wait for the drop to have a pending MODE_X lock on the database.
-    assert.soon(
-        function() {
-            return adminDB
-                       .aggregate([
-                           {$currentOp: {}},
-                           {$match: {"command.drop": otherCollName, waitingForLock: true}}
-                       ])
-                       .itcount() === 1;
-        },
-        function() {
-            return "Failed to find drop in currentOp output: " +
-                tojson(adminDB.aggregate([{$currentOp: {}}]));
-        });
+    // Wait for sleep to appear in currentOp
+    opId = waitForCommand(
+        op => (op["ns"] == "admin.$cmd" && op["command"]["$comment"] == "lock sleep"));
 
     jsTest.log("Run a slow write. Profiling in the transaction should fail.");
     assert.commandWorked(sessionColl.update(
         {$where: "sleep(1000); return true;"}, {$inc: {bad: 1}}, {collation: {locale: "fr"}}));
     session.commitTransaction();
-    awaitDrop();
+
+    assert.commandWorked(testDB.killOp(opId));
+    lockShell();
+
     profilerHasZeroMatchingEntriesOrThrow(
         {profileDB: testDB, filter: {"command.collation": {locale: "fr"}}});