Logging API

The Logging API exposes node, component, and container (task) logs.

The Logging API is backed by the DC/OS Log component, which runs on all nodes in the cluster. For more information about using the Logging API, see Logging. For usage examples, see Logging API Examples.

Compatibility

The Logging API has been updated significantly for DC/OS 1.11 and later.

In versions of DC/OS prior to 1.11, task logs were available via files API. Now you can leverage the consolidated API for both component and task logs.

In versions of DC/OS prior to 1.11, node and component logs were managed by journald. However, the [Mesos task journald log sink was disabled due to journald performance issues. So container log files for older versions are only accessible via the Mesos task sandbox files API.

The following code may be useful:

FRAMEWORK_NAME="marathon"
APP_ID="nginx"

# get the mesos task state json
MESOS_STATE="$(curl -k -H "Authorization: token=${DCOS_AUTH_TOKEN}" ${DCOS_URL}/mesos/state)"
TASK_STATE="$(echo "${MESOS_STATE}" | jq ".frameworks[] | select(.name == \"${FRAMEWORK_NAME}\") | .tasks[] | select(.name == \"${APP_ID}\")")"

# extract values from the task json
AGENT_ID="$(echo "${TASK_STATE}" | jq -r '.slave_id')"
TASK_ID="$(echo "${TASK_STATE}" | jq -r '.id')"
FRAMEWORK_ID="$(echo "${TASK_STATE}" | jq -r '.framework_id')"
EXECUTOR_ID="$(echo "${TASK_STATE}" | jq -r '.executor_id')"
CONTAINER_ID="$(echo "${TASK_STATE}" | jq -r '.statuses[0].container_status.container_id.value')"

# default to container ID when executor ID is empty
EXECUTOR_ID="${EXECUTOR_ID:-${TASK_ID}}"

# Using Mesos API, agent/files endpoint
curl -k -H "Authorization: token=${DCOS_AUTH_TOKEN}" "${DCOS_URL}/agent/${AGENT_ID}/files/read?path=/var/lib/mesos/slave/slaves/${AGENT_ID}/frameworks/${FRAMEWORK_ID}/executors/${EXECUTOR_ID}/runs/${CONTAINER_ID}/stdout&offset=0&length=50000"

Routes

Access to the Logging API is proxied through Admin Router on each node using the following route:

/system/v1/logs/

Access to the Logging API of the agent nodes is proxied through the master node to the appropriate agent node based on {agent_id}:

/system/v1/agent/{agent_id}/

To determine the address of your cluster, see Cluster Access.

Discovery Endpoints

Master routes which are serving task logs are also called ‘discovery endpoints’. When the user makes a GET request to a discovery endpoint, the user is redirected to the agent node with the desired endpoint.

The parameters used in the request come from mesos state.json and are called “task metadata”.

Auth

All Logging API routes require authentication to use. To authenticate API requests, see Obtaining an authentication token and Passing an authentication token.

The Logging API also requires authorization via the following permissions:

All routes may also be reached by users with the dcos:superuser permission. To assign permissions to your account, see Permissions Reference.

Format

The API request header can be any of the following:

• text/plain, text/html, */* request logs in text format, ending with \n.
• application/json request logs in JSON format.
• text/event-stream request logs in Server-Sent-Events format.

DC/OS Logging follows the Server-Sent-Event specifications. It supports reading the log entry from a specific cursor position, if the client specifies a request header Last-Event-ID as defined in SSE specifications. Every log entry in SSE format contains an ID with a token ID: . This allows the client to know the current log entry and gives you the ability to resume logs consumption if it was interrupted.

Resources

The following resources are available under both of the above routes:

[ Base URL: / ]

Fluent Bit

Tags

Fluent Bit’s default configuration tags logs emitted by systemd units with host.<unit-name>. For example, logs for dcos-mesos-master.service are tagged with host.dcos-mesos-master.service.