docker-logstash-kubernetes

Logstash container for pulling docker logs with kubernetes metadata support. Additionally logs are pulled from systemd journal too. Events can be pushed to Cloudwatch Logs and or ElasticSearch.

Logstash tails docker logs and extracts pod, container_name, namespace, etc. The way this works is very simple. Logstash looks at an event field which contains full path to kubelet created symlinks to docker container logs, and extracts useful information from a symlink name. No access to Kubernetes API is required.

Events can then pushed to Cloudwatch logs (disabled by default). An example event in Cloudwatch Logs looks like below:

{
    "log": "10.10.112.0 - - [02/Oct/2015:15:20:38 +0000] \"GET /dataset HTTP/1.1\" 200 2 \"-\" \"axios/0.5.4\" 6\n",
    "stream": "stdout",
    "time": "2015-10-02T15:20:38.706043658Z",
    "replication_controller": "data-example-api",
    "pod": "data-example-api-p82sy",
    "namespace": "hoapi-catalogue",
    "container_name": "data-example-api",
    "container_id": "df1874255f0c85d18747b5edfc8dc372dbebf725b9ccbfb37549f5f81bba8326"
}

Other outputs can be added in the future.

Requirements

You need to have kubelet process running on the host. Normally kubelet creates symlinks to container logs from /var/log/containers/ to /var/lib/docker/containers/. So for that you need to make sure that logstash has access to both directories.

For logstash to be able to pull logs from journal, you need to make sure that logstash can read /var/log/journal.

Also, logstash writes sincedb file to its home directory, which by default is /var/lib/logstash. If you don't want logstash to start reading docker or journal logs from the beginning after a restart, make sure you mount /var/lib/logstash somewhere on the host.

If you want to push events to Cloudwatch Logs, then you will have to set AWS access keys via environment variables.

Configuration

As usual, configuration is passed through environment variables.

• LS_HEAP_SIZE - logstash JVM heap size. Defaults to 500m.
• OUTPUT_CLOUDWATCH - whether to enable this output. Defaults to false.
• AWS_REGION - defaults to eu-west-1.
• AWS_ACCESS_KEY_ID - must be set.
• AWS_SECRET_ACCESS_KEY - must be set.
• LOG_GROUP_NAME - Cloudwatch logs group name. Defaults to logstash.
• LOG_STREAM_NAME - Cloudwatch logs stream name. Defaults to hostname().
• INPUT_JOURNALD - Enable logs ingestion from journald. Default: true.
• OUTPUT_ELASTICSEARCH - Enable logs output to ElasticSearch. Default true.
• ELASTICSEARCH_HOST - ElasticSearch host, can be comma separated. Default: 127.0.0.1:9200.
• ELASTICSEARCH_INDEX_SUFFIX - ElasticSearch index suffix. Default: "".
• LOGSTASH_ARGS - Sets additional logstash command line arguments.

Running

$ docker run -ti --rm \
    -v /var/lib/logstash-kubernetes:/var/lib/logstash:z \
    -v /var/log/journal:/var/log/journal:ro \
    -v /var/lib/docker/containers:/var/lib/docker/containers:ro \
    -v /var/log/containers:/var/log/containers:ro \
    -e ELASTICSEARCH_HOST=my-est-host.local:9200 \
    quay.io/ukhomeofficedigital/logstash-kubernetes:v0.4.0