Monitoring Docker

Supported versions and support policy

The sensor supports the following versions of Docker:

• Docker 23.0
• Docker 25.0
• Docker 26.x
• Docker 27.x

The following table shows the latest supported version and support policy:

For more information about the support policy, see Support strategy for sensors.

Configuration data

Performance metrics

Using the Docker Engine API, the performance metrics are returned from the /containers/{id}/stats endpoint.

Health signature

For each sensor, there is a curated knowledgebase of health signatures that are evaluated continuously against the incoming metrics and are used to raise issues or incidents depending on user impact.

Built-in events trigger issues or incidents based on failing health signatures on entities, and custom events trigger issues or incidents based on the thresholds of an individual metric of any given entity.

For information about the built-in events for the Docker sensor, see the Built-in events reference.

Enabling Docker log collection

To enable log collection, complete the following steps:

1. Obtain an add-on to the Instana license. To purchase the add-on license, contact your IBM sales representative.

2. Enable log collection by configuring the Docker log sensor in the agent configuration file as shown in the following example:

   com.instana.plugin.docker:
       logs:
         enabled: true
   

   The following example shows the possible configuration options with their default values:

   com.instana.plugin.docker:
       logs:
         enabled: true
       unixSocket: "/var/run/docker.sock"
       maxBufferSize: 16777216
       minBatchSize: 1024
       minBatchWithholdCount: 2
       sendInterval: 1
       socketTimeout: 600
       maxLineLength: 16384
   

   The following table lists the configuration options and their description:

   Table 3: Configuration options for Docker log collection

   Configuration option	Description	Default value
   unixSocket	The path to the Docker daemon's socket.	"/var/run/docker.sock"
   maxBufferSize	The maximum internal buffer size in bytes. This controls how much log message data can be stored in memory inside the sensor while reading.	16777216
   minBatchSize	The minimum size of a message batch to be transmitted to the server, in characters. A batch of messages is not transmitted until it reaches at least this size (up to minBatchWithholdCount retries).	1024
   minBatchWithholdCount	The number of times a batch can be held back for being too small before it is sent anyway. If a log batch is smaller than minBatchSize, it isn't sent right away. Even if the amount of data remains smaller than minBatchSize, it is eventually sent anyway when the number of tries exceeds this number.	2
   sendInterval	The interval to be waited between attempts to send a log batch, in seconds.	1
   socketTimeout	Duration, in seconds, for establishing a socket connection before timing out.	600
   maxLineLength	The maximum length of a line in the log, in characters. Since this length is measured in characters, the actual number of bytes used varies based on the encoding.	16384

After you enable the log collection, you can view the logs in the Instana UI. For more information, see Viewing Docker logs.

Disabling Docker log collection

To disable Docker logging again, use one of the following options:

• Set the enabled flag to false in the agent configuration file:

  com.instana.plugin.docker:
      logs:
        enabled: false
  

• Remove the logs section from the agent configuration file.

Logging is disabled by default.

Avoiding duplicate logs

The agent's AutoTracing functions automatically gather trace logs from applications inside containers, so enabling both trace logs and Docker logs results in duplicate logs. To avoid this issue, enable only one or other.

Application trace logs have the advantage of being correlated with the application traces, while Docker logs are not. But application traces collect only ERROR and WARNING level logs, while the Docker log sensor collects the entire log output stream, including logs at all levels.

Streams

The Docker log sensor collects the streams stdout and stderr from Docker containers.