# Kubernetes
[Fluent Bit](http://fluentbit.io) is a lightweight and extensible **Log Processor** that comes with full support for Kubernetes:
* Read Kubernetes/Docker log files from the file system or through Systemd Journal.
* Enrich logs with Kubernetes metadata.
* Deliver logs to third party storage services like Elasticsearch, InfluxDB, HTTP, etc.
Content:
* [Concepts](#concepts)
* [Installation Steps](#installation)
## Concepts
Before geting started it is important to understand how Fluent Bit will be deployed. Kubernetes manages a cluster of *nodes*, so our log agent tool will need to run on every node to collect logs from every *POD*, hence Fluent Bit is deployed as a DaemonSet (a POD that runs on every *node* of the cluster).
When Fluent Bit runs, it will read, parse and filter the logs of every POD and will enrich each entry with the following information (metadata):
* POD Name
* POD ID
* Container Name
* Container ID
* Labels
* Annotations
To obtain these information, a built-in filter plugin called *kubernetes* talks to the Kubernetes API Server to retrieve relevant information such as the *pod\_id*, *labels* and *annotations*, other fields such as *pod\_name*, *container\_id* and *container\_name* are retrieved locally from the log file names. All of this is handled automatically, no intervention is required from a configuration aspect.
> Our Kubernetes Filter plugin is fully inspired on the [Fluentd Kubernetes Metadata Filter](https://github.com/fabric8io/fluent-plugin-kubernetes_metadata_filter) written by [Jimmi Dyson](https://github.com/jimmidyson).
## Installation
[Fluent Bit](http://fluentbit.io) must be deployed as a DaemonSet, so on that way it will be available on every node of your Kubernetes cluster. To get started run the following commands to create the namespace, service account and role setup:
```
$ kubectl create namespace logging
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/fluent-bit-service-account.yaml
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/fluent-bit-role.yaml
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/fluent-bit-role-binding.yaml
```
The next step is to create a ConfigMap that will be used by our Fluent Bit DaemonSet:
```
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/output/elasticsearch/fluent-bit-configmap.yaml
```
### Note for Kubernetes v1.16
Starting from Kubernetes v1.16, DaemonSet resources are not longer served from `extensions/v1beta` . Our current Daemonset Yaml files uses the old `apiVersion`.
If you are using Kubernetes v1.16, grab manually a copy of your Daemonset Yaml file and replace the value of `apiVersion` from:
```yaml
apiVersion: extensions/v1beta1
```
to
```yaml
apiVersion: apps/v1
```
You can read more about this deprecation on Kubernetes v1.14 Changelog here:
### Fluent Bit to Elasticsearch
Fluent Bit DaemonSet ready to be used with Elasticsearch on a normal Kubernetes Cluster:
```
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/output/elasticsearch/fluent-bit-ds.yaml
```
### Fluent Bit to Elasticsearch on Minikube
If you are using Minikube for testing purposes, use the following alternative DaemonSet manifest:
```
$ kubectl create -f https://raw.githubusercontent.com/fluent/fluent-bit-kubernetes-logging/master/output/elasticsearch/fluent-bit-ds-minikube.yaml
```
## Details
The default configuration of Fluent Bit makes sure of the following:
* Consume all containers logs from the running Node.
* The [Tail input plugin](https://docs.fluentbit.io/manual/v/1.0/input/tail) will not append more than **5MB** into the engine until they are flushed to the Elasticsearch backend. This limit aims to provide a workaround for [backpressure](https://docs.fluentbit.io/manual/v/1.0/configuration/backpressure) scenarios.
* The Kubernetes filter will enrich the logs with Kubernetes metadata, specifically *labels* and *annotations*. The filter only goes to the API Server when it cannot find the cached info, otherwise it uses the cache.
* The default backend in the configuration is Elasticsearch set by the [Elasticsearch Ouput Plugin](https://docs.fluentbit.io/manual/v/1.0/output/elasticsearch). It uses the Logstash format to ingest the logs. If you need a different Index and Type, please refer to the plugin option and do your own adjustments.
* There is an option called **Retry\_Limit** set to False, that means if Fluent Bit cannot flush the records to Elasticsearch it will re-try indefinitely until it succeed.
---
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