writeConcern is not setting to Acknowledged in mongodb

Question

private val DATABASE:String   = config.getString("db.dbname")

private val SERVER:ServerAddress = {
    val hostName=config.getString("db.hostname")
    val port=config.getString("db.port").toInt
    new ServerAddress(hostName,port)
}

val connectionMongo = MongoConnection(SERVER)
def collectionMongo(name:String) = connectionMongo(DATABASE)(name)

val result:WriteResult = collectionMongo("pgroup")
    .insert(new BasicDBObject("_id",privateArtGroup.getUuid)
    .append("ArtGroupStatus",privateArtGroup.artGroupStatus.toString())
    .append("isNew",privateArtGroup.isNew), WriteConcern.Acknowledged)

log.info("what is the write concern " + collectionMongo(pgroup).getWriteConcern)

log.info("what is the write concern "+collectionMongo(pgroup).getWriteConcern) 

I am setting WriteConcern to Acknowledged but its not setting

the log stataments prints this from where i get to know its not setting

What is the write concer WriteConcern{w=0, wTimeout=null ms, fsync=null, journal=null

Why w=0 ? it should be w=1 I am using casbah V 3.1.1

Answer 1

val result:WriteResult = collectionMongo("pgroup")
.insert(new BasicDBObject("_id",privateArtGroup.getUuid)
.append("ArtGroupStatus",privateArtGroup.artGroupStatus.toString())
.append("isNew",privateArtGroup.isNew), WriteConcern.Acknowledged)

WriteConcern.Acknowledged - Write operations that use this write concern will wait for acknowledgement from the primary server before returning.

w: 1 - Requests acknowledgement that the write operation has propagated to the standalone mongod or the primary in a replica set.

Reason for Why w=0 ? i Once the given insert query is executed with writeconcern acknowledge the job is done. Moreover we are setting the writeconcern for the insert query alone and not for the collection. This could be a reason that you are getting w=0.

But still I couldn't figure out - In general we have w: 1 is the default write concern for MongoDB and why you are getting w=0.