SERVER-35365 MapReduce should write "inc" collections to "local" db.

(cherry picked from commit 30ac39448a0c83bb12fd4d0fa537e8292be20d08)

1 files changed, 83 insertions, 0 deletions

diff --git a/jstests/replsets/mr_nonrepl_coll_in_local_db.js b/jstests/replsets/mr_nonrepl_coll_in_local_db.js
new file mode 100644
index 00000000000..2b6cd66617e
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+++ b/jstests/replsets/mr_nonrepl_coll_in_local_db.js
@@ -0,0 +1,83 @@
+// All collections created during a map-reduce should be replicated to secondaries unless they are
+// in the "local" or "admin" databases. Any collection outside of "local" that does not get
+// replicated is a potential problem for workloads with transactions (see SERVER-35365 and
+// SERVER-35282).
+//
+// We verify this requirement by running a map-reduce, examining the logs to find the names of
+// all collections created, and checking the oplog for entries logging the creation of each of those
+// collections.
+(function() {
+    "use strict";
+
+    load("jstests/libs/check_log.js");
+
+    const name = "mr_nonrepl_coll_in_local_db";
+    const replSet = new ReplSetTest({name: name, nodes: 2});
+    replSet.startSet();
+    replSet.initiate();
+
+    const dbName = name;
+    const collName = "test";
+
+    const primary = replSet.getPrimary();
+    const primaryDB = primary.getDB(dbName);
+    const coll = primaryDB[collName];
+
+    // Insert 1000 documents in the "test" collection.
+    const bulk = coll.initializeUnorderedBulkOp();
+    for (let i = 0; i < 1000; i++) {
+        const array = Array.from({lengthToInsert: 10000}, _ => Math.floor(Math.random() * 100));
+        bulk.insert({arr: array});
+    }
+    assert.writeOK(bulk.execute());
+
+    // Run a simple map-reduce.
+    const result = coll.mapReduce(
+        function map() {
+            return this.arr.forEach(element => emit(element, 1));
+        },
+        function reduce(key, values) {
+            return Array.sum(values);
+        },
+        {query: {arr: {$exists: true}}, out: "mr_result"});
+    assert.commandWorked(result);
+
+    // Examine the logs to find a list of created collections.
+    const logLines = checkLog.getGlobalLog(primaryDB);
+    let createdCollections = [];
+    logLines.forEach(function(line) {
+        let matchResult = line.match(/createCollection: (.+) with/);
+        if (matchResult) {
+            createdCollections.push(matchResult[1]);
+        }
+    });
+
+    createdCollections.forEach(function(createdCollectionName) {
+        if (createdCollectionName.startsWith("admin.")) {
+            // Although the "admin.system.version" collection is replicated, no "c" entry gets
+            // created for it in the oplog, so this test would see it as unreplicated. In general,
+            // this test is not concerned with the "admin" database, so we don't examine any "admin"
+            // collections.
+            return;
+        }
+
+        // Search for a log entry for the creation of this collection.
+        const oplogEntries = primaryDB.getSiblingDB("local")["oplog.rs"]
+                                 .find({op: "c", "o.idIndex.ns": createdCollectionName})
+                                 .toArray();
+        if (createdCollectionName.startsWith("local.")) {
+            // We do not want to see any replication of "local" collections.
+            assert.eq(oplogEntries.length,
+                      0,
+                      "Found unexpected oplog entry for creation of " + createdCollectionName +
+                          ": " + tojson(oplogEntries));
+        } else {
+            assert.eq(oplogEntries.length,
+                      1,
+                      "Found no oplog entry or too many entries for creation of " +
+                          createdCollectionName + ": " + tojson(oplogEntries));
+        }
+    });
+
+    replSet.stopSet();
+}());