logstash grok multiline - how to merge to previous line any line that doesn't start with timestamp

Question

sometimes I print to log indented pretty jsons which printed in multiple lines. so I need to be able to tell logstash to append these prints to the original line of the original event.

example:

xxx p:INFO d:2015-07-21 11:11:58,906 sourceThread:3iMind-Atlas-akka.actor.default-dispatcher-2 queryUserId: queryId: hrvJobId:6c1a4d60-e5e6-40d8-80aa-a4dc00e9f0c4 etlStreamId:70 etlOmdId: etlDocId: logger:tim.atlas.module.etl.mq.MQConnectorEtl msg:(st:Consuming) received NotifyMQ. sending to [openmind_exchange/job_ack] message:
{
  "JobId" : "6c1a4d60-e5e6-40d8-80aa-a4dc00e9f0c4",
  "Time" : "2015-07-21T11:11:58.904Z",
  "Errors" : [ ],
  "FeedItemSchemaCounts" : {
    "Document" : 1,
    "DocumentMetadata" : 1
  },
  "OtherSchemaCounts" : { }
}

Since I've set a special log4j appender to function solely as logstash input, this task should be quiet easy. I control the layout of the log, so I can add as many prefix/suffix indicators as I please.

here's how my appender look like:

log4j.appender.logstash-input.layout.ConversionPattern=xxx p:%p d:%d{yyyy-MM-dd HH:mm:ss,SSS}{UTC} sourceThread:%X{sourceThread} queryUserId:%X{userId} queryId:%X{queryId} hrvJobId:%X{hrvJobId} etlStreamId:%X{etlStreamId} etlOmdId:%X{etlOmdId} etlDocId:%X{etlDocId} logger:%c msg:%m%n

as you can see I've prefixed every message with 'xxx' so I could tell logstash to append any line which doesn't start with 'xxx' to the previous line

here's my logstash configuration:

if [type] == "om-svc-atlas" {
    grok {
        match => [ "message" , "(?m)p:%{LOGLEVEL:loglevel} d:%{TIMESTAMP_ISO8601:logdate} sourceThread:%{GREEDYDATA:sourceThread} queryUserId:%{GREEDYDATA:userId} queryId:%{GREEDYDATA:queryId} hrvJobId:%{GREEDYDATA:hrvJobId} etlStreamId:%{GREEDYDATA:etlStreamId} etlOmdId:%{GREEDYDATA:etlOmdId} etlDocId:%{GREEDYDATA:etlDocId} logger:%{GREEDYDATA:logger} msg:%{GREEDYDATA:msg}" ]
        add_tag => "om-svc-atlas"
    }
    date {
        match => [ "logdate" , "YYYY-MM-dd HH:mm:ss,SSS" ]
        timezone => "UTC"
    }
    multiline {
        pattern => "<please tell me what to put here to tell logstash to append any line which doesnt start with xxx to the previous line>"
        what => "previous"
    }
  }

Answer 1

yes it was easy indeed :

if [type] == "om-svc-atlas" {
    grok {
        match => [ "message" , "(?m)p:%{LOGLEVEL:loglevel} d:%{TIMESTAMP_ISO8601:logdate} sourceThread:%{GREEDYDATA:sourceThread} queryUserId:%{GREEDYDATA:userId} queryId:%{GREEDYDATA:queryId} hrvJobId:%{GREEDYDATA:hrvJobId} etlStreamId:%{GREEDYDATA:etlStreamId} etlOmdId:%{GREEDYDATA:etlOmdId} etlDocId:%{GREEDYDATA:etlDocId} logger:%{GREEDYDATA:logger} msg:%{GREEDYDATA:msg}" ]
        add_tag => "om-svc-atlas"
    }
    date {
        match => [ "logdate" , "YYYY-MM-dd HH:mm:ss,SSS" ]
        timezone => "UTC"
    }
    multiline {
        pattern => "^(?!xxx).+"
        what => "previous"
    }
  }