Splunk is a great tool for searching logs, but its high cost makes it prohibitive for many teams. In this article, we present a free and open-source alternative to Splunk by combining three open source projects: Elasticsearch, Kibana, and Fluentd.
Elasticsearch is an open-source search engine well-known for its ease of use. Kibana is an open-source Web UI that makes Elasticsearch user friendly for marketers, engineers and data scientists alike.
By combining these three tools (Fluentd + Elasticsearch + Kibana) we get a scalable, flexible, easy to use the log search engine with a great Web UI that provides an open-source Splunk alternative, all for free.
In this guide, we will go over the installation, setup, and basic use of this combined log search solution. This article was tested on Ubuntu 16.04 and CentOS 7.4. If you're not familiar with Fluentd, please learn more about Fluentd first.
Please confirm that Java version 8 or higher is installed:
$ java -versionopenjdk version "1.8.0_151"OpenJDK Runtime Environment (build 1.8.0_151-b12)OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode)
To install Elasticsearch, please download and extract the Elasticsearch package as shown below:
$ curl -O https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.1.0.tar.gz$ tar -xf elasticsearch-6.1.0.tar.gz$ cd elasticsearch-6.1.0
Once the installation is complete, start Elasticsearch:
Note: You can also install ElasticSearch (and Kibana) using RPM/DEB packages. For details, please refer to the official instructions.
$ curl -O https://artifacts.elastic.co/downloads/kibana/kibana-6.1.0-linux-x86_64.tar.gz$ tar -xf kibana-6.1.0-linux-x86_64.tar.gz$ cd kibana-6.1.0-linux-x86_64
Once the installation is complete, start Kibana i.e.
./bin/kibana. You can modify its configuration file (
http://localhost:5601 in your browser.
In this section, we'll install
td-agent, the stable release of Fluentd. Please refer to the guides below for detailed instructions:
Next, we'll install the Elasticsearch plugin for Fluentd: fluent-plugin-elasticsearch. Then, install
fluent-plugin-elasticsearch as follows:
$ sudo /usr/sbin/td-agent-gem install fluent-plugin-elasticsearch --no-document
We'll configure td-agent (Fluentd) to interface properly with Elasticsearch. Please modify
/etc/td-agent/td-agent.conf as shown below:
# get logs from syslog<source>@type syslogport 42185tag syslog</source># get logs from fluent-logger, fluent-cat or other fluentd instances<source>@type forward</source><match syslog.**>@type elasticsearchlogstash_format true<buffer>flush_interval 10s # for testing</buffer></match>
fluent-plugin-elasticsearch comes with a
logstash_format option that allows Kibana to search through the stored event logs in Elasticsearch.
Once everything has been set up and configured, start
# init$ sudo /etc/init.d/td-agent start# or systemd$ sudo systemctl start td-agent.service
The final step is to forward the logs from your
fluentd. Please add the following line to
/etc/rsyslog.conf, and restart
rsyslog. This will forward the local syslogs to Fluentd, and Fluentd in turn will forward the logs to Elasticsearch.
Please restart the
rsyslog service once the modification is complete:
# init$ sudo /etc/init.d/rsyslog restart# or systemd$ sudo systemctl restart rsyslog
Once Fluentd receives some event logs from
rsyslog and has flushed them to Elasticsearch, you can view, search and visualize the log data using Kibana.
For starters, let's access
http://localhost:5601 and click the
Set up index patters button in the upper-right corner of the screen.
Kibana will start a wizard that guides you through configuring the data sets to visualize. If you want a quick start, use
logstash-* as the index pattern, and select
@timestamp as the time-filter field.
After setting up an index pattern, you can view the system logs as they flow in:
For more detail on how to use Kibana, please read the official manual.
To manually send logs to Elasticsearch, please use the
$ logger -t test foobar
When debugging your
td-agent configuration, using
filter_stdout will be useful. All the logs including errors can be found at
<filter syslog.**>@type stdout</filter><match syslog.**>@type elasticsearchlogstash_format true<buffer>flush_interval 10s # for testing</buffer></match>
This article introduced the combination of Fluentd and Kibana (with Elasticsearch) which achieves a free alternative to Splunk: storing and searching machine logs. The examples provided in this article have not been tuned.
If you will be using these components in production, you may want to modify some of the configurations (e.g. JVM, Elasticsearch, Fluentd buffer, etc.) according to your needs.
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.