# Kubernetes Fluentd ![](https://3804023877-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LR7OsqPORtP86IQxs6E%2F-LWNPJuIG9Ym5ELlFCti%2F-LWNPNc_sauS5nBsx4bE%2Ffluentd_kubernetes.png?generation=1547671553339032\&alt=media) [Kubernetes](http://kubernetes.io) provides two logging end-points for applications and cluster logs: Stackdriver Logging for use with Google Cloud Platform and Elasticsearch. Behind the scenes there is a logging agent that take cares of log collection, parsing and distribution: [Fluentd](http://www.fluentd.org). The following document focuses on how to deploy Fluentd in Kubernetes and extend the possibilities to have different destinations for your logs. ## Getting Started The following document assumes that you have a Kubernetes cluster running or at least a local (single) node that can be used for testing purposes. Before getting started, make sure you understand or have a basic idea about the following concepts from Kubernetes: * [Node](https://kubernetes.io/docs/admin/node/) > A node is a worker machine in Kubernetes, previously known as a minion. A node may be a VM or physical machine, depending on the cluster. Each node has the services necessary to run pods and is managed by the master components... * [Pod](https://kubernetes.io/docs/user-guide/pods/) > A pod (as in a pod of whales or pea pod) is a group of one or more containers (such as Docker containers), the shared storage for those containers, and options about how to run the containers. Pods are always co-located and co-scheduled, and run in a shared context... * [DaemonSet](https://kubernetes.io/docs/admin/daemons/) > A DaemonSet ensures that all (or some) nodes run a copy of a pod. As nodes are added to the cluster, pods are added to them. As nodes are removed from the cluster, those pods are garbage collected. Deleting a DaemonSet will clean up the pods it created... Since applications run in Pods, and multiple Pods might exist across multiple nodes, we need a special Fluentd-Pod that takes care of log collection on each node: [Fluentd DaemonSet](https://github.com/fluent/fluentd-docs-gitbook/tree/507e377b7e8e78a312dc49e76bd9a302c33fd058/articles/fluentd_daemonset.md). ## Fluentd DaemonSet For [Kubernetes](https://kubernetes.io), a [DaemonSet](https://kubernetes.io/docs/admin/daemons/) ensures that all (or some) nodes run a copy of a *pod*. In order to solve log collection we are going to implement a Fluentd DaemonSet. Fluentd is flexible enough and has proper plugins to distribute logs to different third party applications like databases or cloud services, so the principal question is: *where will the logs be stored?* Once we answer this question, we can move forward to configuring our DaemonSet. The below steps will focus on sending the logs to an Elasticsearch Pod. ### Get Fluentd DaemonSet sources We have created a Fluentd DaemonSet that has proper rules and container image ready to get started: * Please grab a copy of the repository from the command line using GIT: ``` $ git clone https://github.com/fluent/fluentd-kubernetes-daemonset ``` ### DaemonSet Content The cloned repository contains several configurations that allow to deploy Fluentd as a DaemonSet, the Docker container image distributed on the repository also comes pre-configured so Fluentd can gather all logs from the Kubernetes node environment and also it appends the proper metadata to the logs. This repository has several presets for alpine/debian with popular outputs. * [DaemonSet preset settings](https://github.com/fluent/fluentd-kubernetes-daemonset/tree/master/docker-image/v0.12) ## Logging to Elasticsearch ### Requirements From the fluentd-kubernetes-daemonset/ directory, find the Yaml configuration file: * [fluentd-daemonset-elasticsearch.yaml](https://github.com/fluent/fluentd-kubernetes-daemonset/blob/master/fluentd-daemonset-elasticsearch.yaml) As an example let's see a part of the file content: ``` apiVersion: extensions/v1beta1 kind: DaemonSet metadata: name: fluentd namespace: kube-system ... spec: ... spec: containers: - name: fluentd image: quay.io/fluent/fluentd-kubernetes-daemonset env: - name: FLUENT_ELASTICSEARCH_HOST value: "elasticsearch-logging" - name: FLUENT_ELASTICSEARCH_PORT value: "9200" ... ``` The Yaml file has two relevant environment variables that are used by Fluentd when the container starts: | Environment Variable | Description | Default | | --------------------------- | ------------------------------------ | --------------------- | | FLUENT\_ELASTICSEARCH\_HOST | Specify the host name or IP address. | elasticsearch-logging | | FLUENT\_ELASTICSEARCH\_PORT | Elasticsearch TCP port | 9200 | Any relevant change needs to be done to the Yaml file before the deployment. Using the default values assumes that at least one Elasticsearch Pod **elasticsearch-logging** exists in the cluster. If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is a open source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.fluentd.org/0.12/articles/kubernetes-fluentd.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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