The TCP RTT check reports on roundtrip times between the host the agent is running on and any host it is communicating with. This check is passive and will only report RTT times for packets being sent and received from outside the check. The check itself will not send any packets.

This check is only shipped in the 64-bit DEB and RPM Datadog Agent v5 packages. The check is currently not available with Datadog Agent v6.

Follow the instructions below to install and configure this check for an Agent running on a host. For containerized environments, see the Autodiscovery Integration Templates for guidance on applying these instructions.

The TCP RTT check-also known as go-metro-is packaged with the Agent, but requires additional system libraries. The check uses timestamps provided by the PCAP library to compute the time between any outgoing packet and the corresponding TCP acknowledgement. As such, PCAP must be installed and configured.

Debian-based systems should use one of the following:

$ sudo apt-get install libcap
$ sudo apt-get install libcap2-bin

Redhat-based systems should use one of these:

$ sudo yum install libcap
$ sudo yum install compat-libcap1

Finally, configure PCAP:

$ sudo setcap cap_net_raw+ep /opt/datadog-agent/bin/go-metro

Edit the go-metro.yaml file in your agent's conf.d directory. See the sample go-metro.yaml for all available configuration options. The following is an example file that will show the TCP RTT times for app.datadoghq.com and 192.168.0.22:

  init_config:
    snaplen: 512
    idle_ttl: 300
    exp_ttl: 60
    statsd_ip: 127.0.0.1
    statsd_port: 8125
    log_to_file: true
    log_level: info
  instances:
    - interface: eth0
      tags:
        - env:prod
      ips:
        - 45.33.125.153
      hosts:
        - app.datadoghq.com

To validate that the check is running correctly, you should see system.net.tcp.rtt metrics showing in the Datadog interface. Also, if you Run the Agent's status subcommand, you should see something similar to the following:

● datadog-agent.service - "Datadog Agent"
    Loaded: loaded (/lib/...datadog-agent.service; enabled; vendor preset: enabled)
    Active: active (running) since Thu 2016-03-31 20:35:27 UTC; 42min ago
  Process: 10016 ExecStop=/opt/.../supervisorctl -c /etc/dd-....conf shutdown (code=exited, status=0/SUCCESS)
  Process: 10021 ExecStart=/opt/.../start_agent.sh (code=exited, status=0/SUCCESS)
  Main PID: 10025 (supervisord)
    CGroup: /system.slice/datadog-agent.service
            ├─10025 /opt/datadog-...python /opt/datadog-agent/bin/supervisord -c /etc/dd-agent/supervisor.conf
            ├─10043 /opt/datadog-...python /opt/datadog-agent/agent/dogstatsd.py --use-local-forwarder
            ├─10044 /opt/datadog-agent/bin/go-metro -cfg=/etc/dd-agent/conf.d/go-metro.yaml
            ├─10046 /opt/datadog-.../python /opt/datadog-agent/agent/ddagent.py
            └─10047 /opt/datadog-.../python /opt/datadog-agent/agent/agent.py foreground --use-local-forwarder

If the TCP RTT check has started you should see something similar to the go-metro line above.

This is a passive check, so unless there are packets actively being sent to the hosts mentioned in the yaml file, the metrics are not reported.

See metadata.csv for a list of metrics provided by this check.

The Go-metro check does not include any events.

The Go-metro check does not include any service checks.

Need help? Contact Datadog support.