SERVER-33223 Add transaction resource stash

1 files changed, 119 insertions, 0 deletions

diff --git a/jstests/noPassthrough/snapshot_reads.js b/jstests/noPassthrough/snapshot_reads.js
new file mode 100644
index 00000000000..8f17d25e8b8
--- /dev/null
+++ b/jstests/noPassthrough/snapshot_reads.js
@@ -0,0 +1,119 @@
+// Tests snapshot isolation on readConcern level snapshot read.
+// @tags: [requires_replication]
+(function() {
+    "use strict";
+
+    const dbName = "test";
+    const collName = "coll";
+
+    const rst = new ReplSetTest({nodes: 2});
+    rst.startSet();
+    rst.initiate();
+
+    function runTest({useCausalConsistency}) {
+        const primaryDB = rst.getPrimary().getDB(dbName);
+        primaryDB.coll.drop();
+
+        const session =
+            primaryDB.getMongo().startSession({causalConsistency: useCausalConsistency});
+        const sessionDb = session.getDatabase(dbName);
+
+        if (!primaryDB.serverStatus().storageEngine.supportsSnapshotReadConcern) {
+            rst.stopSet();
+            return;
+        }
+
+        const bulk = primaryDB.coll.initializeUnorderedBulkOp();
+        for (let x = 0; x < 10; ++x) {
+            bulk.insert({_id: x});
+        }
+        assert.commandWorked(bulk.execute({w: "majority"}));
+
+        let txnNumber = 0;
+
+        // Establish a snapshot cursor, fetching the first 5 documents.
+        let res = assert.commandWorked(sessionDb.runCommand({
+            find: collName,
+            sort: {_id: 1},
+            batchSize: 5,
+            readConcern: {level: "snapshot"},
+            txnNumber: NumberLong(txnNumber)
+        }));
+
+        assert(res.hasOwnProperty("cursor"));
+        assert(res.cursor.hasOwnProperty("id"));
+        const cursorId = res.cursor.id;
+
+        // Insert an 11th document which should not be visible to the snapshot cursor. This write is
+        // performed outside of the session.
+        assert.writeOK(primaryDB.coll.insert({_id: 10}, {writeConcern: {w: "majority"}}));
+
+        // Fetch the 6th document. This confirms that the transaction stash is preserved across
+        // multiple getMore invocations.
+        res = assert.commandWorked(sessionDb.runCommand({
+            getMore: cursorId,
+            collection: collName,
+            batchSize: 1,
+            txnNumber: NumberLong(txnNumber)
+        }));
+        assert(res.hasOwnProperty("cursor"));
+        assert(res.cursor.hasOwnProperty("id"));
+        assert.neq(0, res.cursor.id);
+
+        // Exhaust the cursor, retrieving the remainder of the result set.
+        res = assert.commandWorked(sessionDb.runCommand({
+            getMore: cursorId,
+            collection: collName,
+            batchSize: 10,
+            txnNumber: NumberLong(txnNumber++)
+        }));
+
+        // The cursor has been exhausted.
+        assert(res.hasOwnProperty("cursor"));
+        assert(res.cursor.hasOwnProperty("id"));
+        assert.eq(0, res.cursor.id);
+
+        // Only the remaining 4 of the initial 10 documents are returned. The 11th document is not
+        // part of the result set.
+        assert(res.cursor.hasOwnProperty("nextBatch"));
+        assert.eq(4, res.cursor.nextBatch.length);
+
+        // Perform a second snapshot read under a new transaction.
+        res = assert.commandWorked(sessionDb.runCommand({
+            find: collName,
+            sort: {_id: 1},
+            batchSize: 20,
+            readConcern: {level: "snapshot"},
+            txnNumber: NumberLong(txnNumber++)
+        }));
+
+        // The cursor has been exhausted.
+        assert(res.hasOwnProperty("cursor"));
+        assert(res.cursor.hasOwnProperty("id"));
+        assert.eq(0, res.cursor.id);
+
+        // All 11 documents are returned.
+        assert(res.cursor.hasOwnProperty("firstBatch"));
+        assert.eq(11, res.cursor.firstBatch.length);
+
+        // Reject snapshot reads without txnNumber.
+        assert.commandFailed(sessionDb.runCommand(
+            {find: collName, sort: {_id: 1}, batchSize: 20, readConcern: {level: "snapshot"}}));
+
+        // Reject snapshot reads without session.
+        assert.commandFailed(primaryDB.runCommand({
+            find: collName,
+            sort: {_id: 1},
+            batchSize: 20,
+            readConcern: {level: "snapshot"},
+            txnNumber: NumberLong(txnNumber++)
+        }));
+
+        session.endSession();
+    }
+
+    runTest({useCausalConsistency: false});
+    runTest({useCausalConsistency: true});
+
+    rst.stopSet();
+})();