SERVER-23427 Add jstest of read-only commands run against config db when config server primary is unreachable by mongos

Author: stbrody

jstests/sharding/primary_config_server_blackholed_from_mongos.js

@@ -0,0 +1,63 @@
+// Ensures that if the primary config server is blackholed from the point of view of mongos, CRUD
+// and read-only config operations continue to work.
+(function() {
+    'use strict';
+
+    var st = new ShardingTest({
+        name: 'primary_config_server_blackholed_from_mongos',
+        shards: 2,
+        mongos: 1,
+        useBridge: true
+    });
+
+    var testDB = st.s.getDB('BlackHoleDB');
+    var configDB = st.s.getDB('config');
+
+    assert.commandWorked(testDB.adminCommand({enableSharding: 'BlackHoleDB'}));
+    assert.commandWorked(
+        testDB.adminCommand({shardCollection: testDB.ShardedColl.getFullName(), key: {_id: 1}}));
+
+    var bulk = testDB.ShardedColl.initializeUnorderedBulkOp();
+    for (var i = 0; i < 1000; i++) {
+        bulk.insert({_id: i});
+    }
+    assert.writeOK(bulk.execute());
+
+    jsTest.log('Partitioning the config server primary from the mongos');
+    var configPrimary = st.configRS.getPrimary();
+    configPrimary.discardMessagesFrom(st.s, 1.0);
+    st.s.discardMessagesFrom(configPrimary, 1.0);
+
+    assert.commandWorked(testDB.adminCommand({flushRouterConfig: 1}));
+
+    // This should fail, because the primary is not available
+    jsTest.log('Doing write operation on a new database and collection');
+    assert.writeError(st.s.getDB('NonExistentDB')
+                          .TestColl.insert({_id: 0, value: 'This value will never be inserted'}));
+
+    jsTest.log('Doing CRUD operations on the sharded collection');
+    assert.eq(1000, testDB.ShardedColl.find().itcount());
+    assert.writeOK(testDB.ShardedColl.insert({_id: 1000}));
+    assert.eq(1001, testDB.ShardedColl.find().count());
+
+    jsTest.log('Doing read operations on a config server collection');
+    // Should fail due to primary read preference
+    assert.throws(function() {
+        configDB.chunks.find().itcount();
+    });
+    assert.throws(function() {
+        configDB.chunks.find().count();
+    });
+    assert.throws(function() {
+        configDB.chunks.aggregate().itcount();
+    });
+
+    // With secondary read pref config server reads should work
+    st.s.setReadPref('secondary');
+    assert.lt(0, configDB.chunks.find().itcount());
+    assert.lt(0, configDB.chunks.find().count());
+    assert.lt(0, configDB.chunks.aggregate().itcount());
+
+    st.stop();
+
+}());