Parse multiline JSON with grok in logstash

Question

I've got a JSON of the format:

{
    "SOURCE":"Source A",
    "Model":"ModelABC",
    "Qty":"3"
}

I'm trying to parse this JSON using logstash. Basically I want the logstash output to be a list of key:value pairs that I can analyze using kibana. I thought this could be done out of the box. From a lot of reading, I understand I must use the grok plugin (I am still not sure what the json plugin is for). But I am unable to get an event with all the fields. I get multiple events (one even for each attribute of my JSON). Like so:

{
       "message" => "  \"SOURCE\": \"Source A\",",
      "@version" => "1",
    "@timestamp" => "2014-08-31T01:26:23.432Z",
          "type" => "my-json",
          "tags" => [
        [0] "tag-json"
    ],
          "host" => "myserver.example.com",
          "path" => "/opt/mount/ELK/json/mytestjson.json"
}
{
       "message" => "  \"Model\": \"ModelABC\",",
      "@version" => "1",
    "@timestamp" => "2014-08-31T01:26:23.438Z",
          "type" => "my-json",
          "tags" => [
        [0] "tag-json"
    ],
          "host" => "myserver.example.com",
          "path" => "/opt/mount/ELK/json/mytestjson.json"
}
{
       "message" => "  \"Qty\": \"3\",",
      "@version" => "1",
    "@timestamp" => "2014-08-31T01:26:23.438Z",
          "type" => "my-json",
          "tags" => [
        [0] "tag-json"
    ],
          "host" => "myserver.example.com",
          "path" => "/opt/mount/ELK/json/mytestjson.json"
}

Should I use the multiline codec or the json_lines codec? If so, how can I do that? Do I need to write my own grok pattern or is there something generic for JSONs that will give me ONE EVENT with key:value pairs that I get for one event above? I couldn't find any documentation that sheds light on this. Any help would be appreciated. My conf file is shown below:

input
{
        file
        {
                type => "my-json"
                path => ["/opt/mount/ELK/json/mytestjson.json"]
                codec => json
                tags => "tag-json"
        }
}

filter
{
   if [type] == "my-json"
   {
        date { locale => "en"  match => [ "RECEIVE-TIMESTAMP", "yyyy-mm-dd HH:mm:ss" ] }
   }
}

output
{
        elasticsearch
        {
                host => localhost
        }
        stdout { codec => rubydebug }
}

Answer 1

I think I found a working answer to my problem. I am not sure if it's a clean solution, but it helps parse multiline JSONs of the type above.

input 
{   
    file 
    {
        codec => multiline
        {
            pattern => '^\{'
            negate => true
            what => previous                
        }
        path => ["/opt/mount/ELK/json/*.json"]
        start_position => "beginning"
        sincedb_path => "/dev/null"
        exclude => "*.gz"
    }
}

filter 
{
    mutate
    {
        replace => [ "message", "%{message}}" ]
        gsub => [ 'message','\n','']
    }
    if [message] =~ /^{.*}$/ 
    {
        json { source => message }
    }

}

output 
{ 
    stdout { codec => rubydebug }
}

My mutliline codec doesn't handle the last brace and therefore it doesn't appear as a JSON to json { source => message }. Hence the mutate filter:

replace => [ "message", "%{message}}" ]

That adds the missing brace. and the

gsub => [ 'message','\n','']

removes the \n characters that are introduced. At the end of it, I have a one-line JSON that can be read by json { source => message }

If there's a cleaner/easier way to convert the original multi-line JSON to a one-line JSON, please do POST as I feel the above isn't too clean.