SERVER-20970 Allow a single-node SCCC config server

Enables the configuration in mongos and also writes a smoke test to ensure
that the basic sharding operations work.

2 files changed, 14 insertions, 9 deletions

diff --git a/src/mongo/s/mongos_options.cpp b/src/mongo/s/mongos_options.cpp
index 740420509cc..4139c8d56f6 100644
--- a/src/mongo/s/mongos_options.cpp
+++ b/src/mongo/s/mongos_options.cpp
@@ -264,15 +264,16 @@ Status storeMongosOptions(const moe::Environment& params, const std::vector<std:
     std::vector<HostAndPort> configServers = mongosGlobalParams.configdbs.getServers();
 
     if (mongosGlobalParams.configdbs.type() != ConnectionString::SYNC &&
-        mongosGlobalParams.configdbs.type() != ConnectionString::SET) {
-        return Status(
-            ErrorCodes::BadValue,
-            "Must have either 3 node legacy config servers, or a replica set config server");
+        mongosGlobalParams.configdbs.type() != ConnectionString::SET &&
+        mongosGlobalParams.configdbs.type() != ConnectionString::MASTER) {
+        return Status(ErrorCodes::BadValue,
+                      str::stream() << "Invalid config server value "
+                                    << mongosGlobalParams.configdbs.toString());
     }
 
     if (configServers.size() < 3) {
-        warning() << "running with less than 3 config servers should be done only for testing "
-                     "purposes and is not recommended for production";
+        warning() << "Running a sharded cluster with fewer than 3 config servers should only be "
+                     "done for testing purposes and is not recommended for production.";
     }
 
     return Status::OK();
diff --git a/src/mongo/shell/shardingtest.js b/src/mongo/shell/shardingtest.js
index 5bf015025c9..0472cdf7094 100644
--- a/src/mongo/shell/shardingtest.js
+++ b/src/mongo/shell/shardingtest.js
@@ -53,7 +53,7 @@
  *          Can be used to specify options that are common all shards.
  * 
  *       sync {boolean}: Use SyncClusterConnection, and readies
- *          3 config servers.
+ *          1 or 3 config servers, based on the value of numConfigs.
  *       configOptions {Object}: same as the config property above.
  *          Can be used to specify options that are common all config servers.
  *       mongosOptions {Object}: same as the mongos property above.
@@ -278,7 +278,7 @@ ShardingTest = function( testName , numShards , verboseLevel , numMongos , other
     // and the user didn't explicity specify a different config server configuration
     if (jsTestOptions().useLegacyConfigServers &&
             otherParams.sync !== false &&
-            (typeof otherParams.config === 'undefined' || numConfigs === 3)) {
+            (typeof(otherParams.config) === 'undefined' || numConfigs === 3)) {
         otherParams.sync = true;
     }
 
@@ -287,8 +287,12 @@ ShardingTest = function( testName , numShards , verboseLevel , numMongos , other
 
     // Start the config servers
     if (otherParams.sync) {
+        if (numConfigs !== 1 && numConfigs !== 3) {
+            throw Error('Sync config servers only supported with 1 or 3 nodes');
+        }
+
         var configNames = [];
-        for ( var i = 0; i < 3 ; i++ ) {
+        for (var i = 0; i < numConfigs; i++) {
             var options = { useHostname : otherParams.useHostname,
                             noJournalPrealloc : otherParams.nopreallocj,
                             pathOpts : Object.merge( pathOpts, { config : i } ),