![]() ![]() The second method uses a sidecar pattern, where every Pod contains a sidecar container that captures logs and sends those logs to an external service. In a later section of this guide, we will show how to use this approach for effective logging. A DaemonSet is a Kubernetes feature where every node (or some of them) runs a copy of the Pod. The first method uses a node-level agent configured as a DaemonSet. There are two ways to achieve cluster-level logging. This solves the problem of losing node-level logs by pushing all the node-level logs to a backend service. Cluster-level loggingĬluster-level logging involves a centralized logging service aggregating logs from all the nodes. Node-level logging, however, has a significant shortcoming: A Pod’s logs are lost if the node goes down or Kubernetes evicts that Pod. You can use the following command to check which logs use the default driver. If there’s no driver configured, logging defaults to json-file. ![]() The node’s logging driver picks up the messages and writes them to the appropriate log file. The container engine redirects any application log message to the stdout or stderr streams. In node-level logging, the Pod writes application logs to the node where it’s running. In a Kubernetes environment, the node or the cluster manages the application logs. The kubelet and the container runtime write logs to the systemd journal if it’s present or to the /var/log directory if it’s not. The Kubernetes scheduler and kube-proxy run inside a container and always write logs to the local /var/log directory irrespective of the driver used. Kubernetes system components include the Kubernetes Scheduler, kube-proxy, kubelet, and the container runtime. Kubernetes logs can come from the container orchestration system and from containerized applications. Other logging drivers like FluentD, AWS CloudWatch, and GCP Logs facilitate writing logs to external log aggregator services. The syslog and journald logging drivers help writing to Linux log systems. By default, Kubernetes uses the json-file driver, which formats all log entries to JSON and internally caches them. However, it ships with some logging drivers to facilitate storing and aggregating logs. Kubernetes doesn’t provide a native solution for storing logs. In a production Kubernetes environment, hundreds or even thousands of containers can exist in different states-running, stopping, restarting, or terminating-at any given moment. We will introduce the Kubernetes logging architectures and explain the node-level logging patterns in detail.Įxplore the complete Kubernetes Logging Guide series: This article is part one of a guide that covers Kubernetes Logging fundamentals. Therefore, a different approach is necessary to capture logs from Kubernetes-hosted applications. Storing logs in containers or virtual machines isn’t practical because both are ephemeral. With this shift in deployment infrastructure from bare metal to containers, logging and monitoring techniques have changed. These applications often rely on Kubernetes for container orchestration that yields seamless scaling and robust fault tolerance. Modern cloud-based, distributed applications depend heavily on container technology.
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