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101 lines
4.3 KiB
Markdown
101 lines
4.3 KiB
Markdown
<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
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<!-- BEGIN STRIP_FOR_RELEASE -->
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<h1>PLEASE NOTE: This document applies to the HEAD of the source
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tree only. If you are using a released version of Kubernetes, you almost
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certainly want the docs that go with that version.</h1>
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<strong>Documentation for specific releases can be found at
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[releases.k8s.io](http://releases.k8s.io).</strong>
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<!-- END STRIP_FOR_RELEASE -->
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<!-- END MUNGE: UNVERSIONED_WARNING -->
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# Logging
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## Logging by Kubernetes Components
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Kubernetes components, such as kubelet and apiserver, use the [glog](https://godoc.org/github.com/golang/glog) logging library. Developer conventions for logging severity are described in [docs/devel/logging.md](../devel/logging.md).
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## Examining the logs of running containers
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The logs of a running container may be fetched using the command `kubectl logs`. For example, given
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this pod specification which has a container which writes out some text to standard
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output every second [counter-pod.yaml](../../examples/blog-logging/counter-pod.yaml):
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```
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apiVersion: v1
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kind: Pod
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metadata:
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name: counter
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spec:
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containers:
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- name: count
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image: ubuntu:14.04
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args: [bash, -c,
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'for ((i = 0; ; i++)); do echo "$i: $(date)"; sleep 1; done']
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```
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we can run the pod:
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```
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$ kubectl create -f counter-pod.yaml
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pods/counter
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```
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and then fetch the logs:
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```
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$ kubectl logs counter
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0: Tue Jun 2 21:37:31 UTC 2015
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1: Tue Jun 2 21:37:32 UTC 2015
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2: Tue Jun 2 21:37:33 UTC 2015
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3: Tue Jun 2 21:37:34 UTC 2015
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4: Tue Jun 2 21:37:35 UTC 2015
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5: Tue Jun 2 21:37:36 UTC 2015
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...
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```
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If a pod has more than one container then you need to specify which container's log files should
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be fetched e.g.
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```
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$ kubectl logs kube-dns-v3-7r1l9 etcd
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2015/06/23 00:43:10 etcdserver: start to snapshot (applied: 30003, lastsnap: 20002)
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2015/06/23 00:43:10 etcdserver: compacted log at index 30003
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2015/06/23 00:43:10 etcdserver: saved snapshot at index 30003
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2015/06/23 02:05:42 etcdserver: start to snapshot (applied: 40004, lastsnap: 30003)
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2015/06/23 02:05:42 etcdserver: compacted log at index 40004
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2015/06/23 02:05:42 etcdserver: saved snapshot at index 40004
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2015/06/23 03:28:31 etcdserver: start to snapshot (applied: 50005, lastsnap: 40004)
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2015/06/23 03:28:31 etcdserver: compacted log at index 50005
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2015/06/23 03:28:31 etcdserver: saved snapshot at index 50005
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2015/06/23 03:28:56 filePurge: successfully removed file default.etcd/member/wal/0000000000000000-0000000000000000.wal
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2015/06/23 04:51:03 etcdserver: start to snapshot (applied: 60006, lastsnap: 50005)
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2015/06/23 04:51:03 etcdserver: compacted log at index 60006
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2015/06/23 04:51:03 etcdserver: saved snapshot at index 60006
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...
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```
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## Cluster level logging to Google Cloud Logging
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The getting started guide [Cluster Level Logging to Google Cloud Logging](../getting-started-guides/logging.md)
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explains how container logs are ingested into [Google Cloud Logging](https://cloud.google.com/logging/docs/)
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and shows how to query the ingested logs.
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## Cluster level logging with Elasticsearch and Kibana
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The getting started guide [Cluster Level Logging with Elasticsearch and Kibana](../getting-started-guides/logging-elasticsearch.md)
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describes how to ingest cluster level logs into Elasticsearch and view them using Kibana.
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## Ingesting Application Log Files
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Cluster level logging only collects the standard output and standard error output of the applications
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running in containers. The guide [Collecting log files within containers with Fluentd](../../contrib/logging/fluentd-sidecar-gcp/README.md) explains how the log files of applications can also be ingested into Google Cloud logging.
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## Known issues
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Kubernetes does log rotation for kubernetes components and docker containers. The command `kubectl logs` currently only read the latest logs, not all historical ones.
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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