Intermittently unable to insert data

[theburn]

The data flow is as follows：

wrk(Modern HTTP benchmarking tool) ---> logstash ----> mongodb

• Version:

1. logstash-5.6.7
2. logstash-output-mongo: 3.1.3
3. MongoDB: 3.4.13

• Operating System:

1. CentOS 7.2 (4 Core and 8G Mem)

• Config File

jvm、startup、logstash is default config

input {
        http {
            host => "0.0.0.0"
            port => 50001
            type => "metric"
            threads => 256
        }
}

filter {
    
        if [type] == "metric" {

            if [message] == "epoch,value"{
                drop { }
            }

            ruby {

                code => "
                        event.set('insertdate', event.get('@timestamp'))
                        event.set('[@metadata][type]', event.get('type'))
                        event.set('[@metadata][collection]', event.get('collection'))
                        event.set('expireAt', Time.now + (7*24*60*60))
                        "
            }

             mutate {
                split => {"message" => ","}
                add_field => {
                        "time" => "%{message[0]}"
                }
            }

            ruby {
                code => "
                        event.set('value', event.get('message').drop(1))
                        "
            }

            mutate {
                join => {
                    "value" => ","
                }
                
                remove_field => ["host","@timestamp","@version","headers","tags","message","type","collection"]
            }
  
        }
}


output {

        if  [@metadata][type] == "metric"  {
            mongodb {
                bulk => true
                bulk_interval => 1
                bulk_size => 900
                codec => json
                collection => "%{[@metadata][collection]}"
                isodate => true
                database => "metric"
                uri => "mongodb://aaa:bbb@xxx.xxx.xxx.xxx27017/admin"
            }
}

• Sample Data:

{
    "collection":"03406bdd-560f-4525-89a1-8929dbe72e16.app.rsptime'",
    "message":"1488181693.035,xxxxxxxxxxxxxxxxxxxxxxxxxxx..."  # avg length is  512Byte
}

• Steps to Reproduce:

1. start logstash by config
2. wrk process post request
3. logstash insert data
4. use mongostat to monitor ， a continuous 0 value （insert column）appears

Shell> mongostat -u xxx -p xxxx --authenticationDatabase admin
insert query update delete getmore command ... ...
1000
1440
....
0
0
... // about 1-2 minutes
0
1200
1100
... // about 1-3 minutes
0
0
...
(repeat)

5. At the moment, mongodb can't query（ db.xxx.find() is blocked）

---

At the same time, I wrote a test program with golang（use bulk）, and it's work well,
the value of the inserted column is around 5000，and mongo query is work well