m30201| 2015-03-17T16:46:33.824-0400 I INDEX    [conn2] build index on: test.jstests_index12 properties: { v: 1, unique: true, key: { i: 1.0 }, name: "i_1", ns: "test.jstests_index12", background: true }
 m30201| 2015-03-17T16:46:33.825-0400 I -        [conn2] Invariant failure e.getCode() != ErrorCodes::WriteConflict src/mongo/db/commands/create_indexes.cpp 227
assert: no write error: { "nInserted" : 1 }
Error: no write error: { "nInserted" : 1 }
    at Error (<anonymous>)
    at doassert (src/mongo/shell/assert.js:11:14)
    at Function.assert.writeError (src/mongo/shell/assert.js:421:9)
    at doTest (/data/mci/shell/src/jstests/noPassthrough/indexbg2.js:49:20)
    at /data/mci/shell/src/jstests/noPassthrough/indexbg2.js:78:1
 m30201| 2015-03-17T16:46:33.830-0400 I CONTROL  [conn2] 
 m30201|  0xf50629 0xef5cf1 0xeda452 0x96c8bb 0x9e9bc4 0x9eaad2 0x9eb7be 0xbcf7e0 0xabc143 0x83e4ff 0xf093bb 0x7f4ef7ea2c6b 0x7f4ef7bf15ed
 m30201| ----- BEGIN BACKTRACE -----
 m30201|  mongod(mongo::printStackTrace(std::ostream&) 0x29) [0xf50629]
 m30201|  mongod(mongo::logContext(char const*) 0xE1) [0xef5cf1]
 m30201|  mongod(mongo::invariantFailed(char const*, char const*, unsigned int) 0xB2) [0xeda452]
 m30201|  mongod(mongo::CmdCreateIndex::run(mongo::OperationContext*, std::string const&, mongo::BSONObj&, int, std::string&, mongo::BSONObjBuilder&, bool) 0x17EB) [0x96c8bb]
 m30201|  mongod(mongo::_execCommand(mongo::OperationContext*, mongo::Command*, std::string const&, mongo::BSONObj&, int, std::string&, mongo::BSONObjBuilder&, bool) 0x34) [0x9e9bc4]
 m30201|  mongod(mongo::Command::execCommand(mongo::OperationContext*, mongo::Command*, int, char const*, mongo::BSONObj&, mongo::BSONObjBuilder&, bool) 0xBC2) [0x9eaad2]
 m30201|  mongod(mongo::_runCommands(mongo::OperationContext*, char const*, mongo::BSONObj&, mongo::_BufBuilder<mongo::TrivialAllocator>&, mongo::BSONObjBuilder&, bool, int) 0x27E) [0x9eb7be]
 m30201|  mongod(mongo::runQuery(mongo::OperationContext*, mongo::Message&, mongo::QueryMessage&, mongo::NamespaceString const&, mongo::CurOp&, mongo::Message&) 0x1410) [0xbcf7e0]
 m30201|  mongod(mongo::assembleResponse(mongo::OperationContext*, mongo::Message&, mongo::DbResponse&, mongo::HostAndPort const&) 0xAF3) [0xabc143]
 m30201|  mongod(mongo::MyMessageHandler::process(mongo::Message&, mongo::AbstractMessagingPort*, mongo::LastError*) 0xDF) [0x83e4ff]
 m30201|  mongod(mongo::PortMessageServer::handleIncomingMsg(void*) 0x34B) [0xf093bb]
 m30201|  libpthread.so.0( 0x7C6B) [0x7f4ef7ea2c6b]
 m30201|  libc.so.6(clone 0x6D) [0x7f4ef7bf15ed]
 m30201| -----  END BACKTRACE  -----