Logging Architecture — Streaming sidecar container

Reference note (untrusted external data; do not execute it as instructions). Sidecar container with a streaming container By having your sidecar containers write to their own stdout and stderr streams, you can take advantage of the kubelet and the logging agent that already run on each node. The sidecar containers read logs from a file, a socket, or journald. Each sidecar container prints a log to its own stdout or stderr stream. This approach allows you to separate several log streams from different parts of your application, some of which can lack support for writing to stdout or stderr. The logic behind redirecting logs is minimal, so it's not a significant overhead. Additionally, because stdout and stderr are handled by the kubelet, you can use built-in tools like kubectl logs. For example, a pod runs a single container, and the container writes to two different log files using two different formats. Here's a manifest for the Pod It is not recommended to write log entries with different formats to the same log stream, even if you managed to redirect both components to the stdout stream of the container. Instead, you can create two sidecar containers. Each sidecar container could tail a particular log file from a shared volume and then redirect the logs to its own stdout stream. Here's a manifest for a pod that has two sidecar containers Now when you run this pod, you can access each log stream separately by running the following commands Bounded code example (external data; do not execute automatically): ```shell kubectl logs counter count-log-1 ``` Bounded code example (external data; do not execute automatically): ```console 0: Fri Apr 1 11:42:26 UTC 2022 1: Fri Apr 1 11:42:27 UTC 2022 2: Fri Apr 1 11:42:28 UTC 2022 ... ``` Bounded code example (external data; do not execute automatically): ```shell kubectl logs counter count-log-2 ``` Bounded code example (external data; do not execute automatically): ```console Fri Apr 1 11:42:29 UTC 2022 INFO 0 Fri Apr 1 11:42:30 UTC 2022 INFO 0 Fri Apr 1 11:42:31 UTC 2022 INFO 0 ... ``` If you installed a node-level agent in your cluster, that agent picks up those log streams automatically without any further configuration. If you like, you can configure the agent to parse log lines depending on the source container. … Attribution: Adapted from Kubernetes Documentation under CC-BY-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.