By default deployed in Kubernetes outputs logging to disk and console output. If persistent disk storage is enabled, the logs end up on the mounted shared disk. But persistent disk is not always the desired log target, especially in a cloud environment where persistent data is typically accessed through services and APIs rather than as files. The console logs can be accessed through the "kubectl logs" command or from a Kubernetes dashboard. The buffer for storing the Kubernetes console logs is stored in memory only though and thus will be lost when a Pod terminates.
To get a production ready log configuration you can use tools from the Kubernetes ecosystem. In this guide we show you how to set up:
- Fluent for log collection
- Elasticsearch for log storage
- Kibana for log visualization
These tools give you powerful and flexible log collection, storage, and visualization. The Elasticsearch database storage also provides powerful tools to perform analytics on the log data. It is outside the scope of this guide to describe those capabilities.
Note!
This guide includes the steps for installing the tools in the Kubernetes cluster. If you deploy in a cloud environment, these tools may already be configured. In that case, it is enough to perform the configuration and skip the installation steps.
Enable JSON Logging in 
Before setting up log collection, make sure that JSON formatted logging is enabled in using the setting:
log: # Format can be "json" or "raw". Default is "raw" format: json
in values.yaml.
Create a Namespace
To isolate the logging functionality from the rest of the system and make it possible to reuse it from multiple instances, a separate namespace is created to host the installed tools.
kubectl create namespace logging
Add Helm Repos
helm repo add elastic https://helm.elastic.co helm repo add fluent https://fluent.github.io/helm-charts
Install Elasticsearch
helm fetch elastic/elasticsearch --untar
It is recommended to enable Elasticsearch security before proceeding with installation:
Note!
For simplicity this example installs Elasticsearch without persistent storage. Refer to Elasticsearch Helm chart documentation for help to enable persistent storage:
https://github.com/elastic/helm-charts/tree/master/elasticsearch
helm upgrade --install elasticsearch elasticsearch -n logging --set=persistence.enabled=false
Install Kibana
helm fetch elastic/kibana --untar
helm upgrade --install kibana kibana -n logging --set=service.type=LoadBalancer --set=service.port=80
Install Fluentd
helm fetch fluent/fluentd --untar
Edit values.yaml to enable System Log collection over syslog. Add the following source to section 01_sources.conf (leaving existing sources unaltered):
01_sources.conf: |-
<source>
@type syslog
port 5140
bind 0.0.0.0
tag system
</source>
Edit values.yaml to specify the JSON based log format:
02_filters.conf: |-
<label @KUBERNETES>
<match kubernetes.var.log.containers.fluentd**>
@type relabel
@label @FLUENT_LOG
</match>
<filter kubernetes.**>
@type kubernetes_metadata
@id filter_kube_metadata
skip_labels false
skip_container_metadata false
skip_namespace_metadata true
skip_master_url true
</filter>
<filter kubernetes.var.log.containers.**>
@type parser
<parse>
@type json
json_parser json
</parse>
replace_invalid_sequence true
emit_invalid_record_to_error false
key_name log
reserve_data true
remove_key_name_field true
</filter>
<match **>
@type relabel
@label @DISPATCH
</match>
</label>
helm upgrade --install fluentd fluentd -n logging
Enable System Log forwarding over Syslog
Configure according to:
Log Forwarding[hide]3.0[/hide]
The parameters are set in Helm values.yaml file as described in Installation Instructions[hide]3.0[/hide].
Verify that all services are up and running
$ kubectl get pod -n logging NAME READY STATUS RESTARTS AGE elasticsearch-master-0 1/1 Running 0 43m elasticsearch-master-1 1/1 Running 0 44m elasticsearch-master-2 1/1 Running 0 44m fluentd-8g95p 1/1 Running 0 19h fluentd-sqv7j 1/1 Running 0 19h fluentd-zgx6t 1/1 Running 0 19h kibana-kibana-56c9f469d-l7dtv 1/1 Running 0 105m
If all looks good, you can get the URL for the Kibana dashboard with the below command:
kubectl get service -n logging kibana-kibana -o jsonpath={.status.loadBalancer.ingress[0].hostname}
Open the Kibana dashboard and create a new Index Pattern matching the "fluentd" index.
Go to Discover view to search collected log data. For instance, to search the platform log file, enter the search query "kubernetes.pod_name:platform" in the KQL field.
Log records that are properly JSON formatted will be parsed into fields, like:
"thread": "main",
"level": "WARN",
"loggerName": "com.digitalroute.picostart.PlatformClassLoader",
"marker": {
"name": "PS",
"parents": [
{
"name": "LIFECYCLE"
}
]
},
"message": "Starting Web Server",
"endOfBatch": false,
"loggerFqcn": "org.apache.logging.log4j.spi.AbstractLogger",
"instant": {
"epochSecond": 1614690212,
"nanoOfSecond": 819721000
},
"threadId": 1,
"threadPriority": 5,
"timestamp": "2021-03-02T13:03:32.819+0000"
While records that are not JSON formatted will be displayed per row in the "log" field, like:
"log": "2021-03-02 13:03:35.788:INFO:oejs.Server:pool-10-thread-1: Started @33338ms\n",
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