Free Alternative To Splunk

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​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.
Kibana Visualization
​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 log search engine with a great Web UI that provides an open-source Splunk alternative, all for free.
Fluentd + Elasticsearch + Kibana
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.
Prerequisites
Java for Elasticsearch
Please confirm that Java version 8 or higher is installed:
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$ java -version
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openjdk version "1.8.0_151"
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OpenJDK Runtime Environment (build 1.8.0_151-b12)
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OpenJDK 64-Bit Server VM (build 25.151-b12, mixed mode)
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Set Up Elasticsearch
To install Elasticsearch, please download and extract the Elasticsearch package as shown below:
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$ curl -O https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.1.0.tar.gz
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$ tar -xf elasticsearch-6.1.0.tar.gz
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$ cd elasticsearch-6.1.0
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Once the installation is complete, start Elasticsearch:
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$ ./bin/elasticsearch
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Note: You can also install Elasticsearch (and Kibana) using RPM/DEB packages. For details, please refer to the official instructions.
Set Up Kibana
To install Kibana, download it from the official website and extract it. Kibana is an HTML/CSS/JavaScript application (download). Use the binary for 64-bit Linux systems.
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$ curl -O https://artifacts.elastic.co/downloads/kibana/kibana-6.1.0-linux-x86_64.tar.gz
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$ tar -xf kibana-6.1.0-linux-x86_64.tar.gz
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$ cd kibana-6.1.0-linux-x86_64
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Once the installation is complete, start Kibana i.e. ./bin/kibana. You can modify its configuration file (config/kibana.yml).
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$ ./bin/kibana
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Access http://localhost:5601 in your browser.
Set Up Fluentd (td-agent)
In this section, we'll install td-agent, the stable release of Fluentd. Please refer to the guides below for detailed instructions:
​Debian Package​
​RPM Package​
​Ruby gem​
Next, we'll install the Elasticsearch plugin for Fluentd: fluent-plugin-elasticsearch. Then, install fluent-plugin-elasticsearch as follows:
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$ sudo /usr/sbin/td-agent-gem install fluent-plugin-elasticsearch --no-document
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We'll configure td-agent (Fluentd) to interface properly with Elasticsearch. Please modify /etc/td-agent/td-agent.conf as shown below:
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# get logs from syslog
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<source>
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  @type syslog
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  port 42185
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  tag syslog
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</source>
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​
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# get logs from fluent-logger, fluent-cat or other fluentd instances
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<source>
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  @type forward
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</source>
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​
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<match syslog.**>
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  @type elasticsearch
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  logstash_format true
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  <buffer>
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    flush_interval 10s # for testing
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  </buffer>
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</match>
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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 td-agent:
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# init
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$ sudo /etc/init.d/td-agent start
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# or systemd
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$ sudo systemctl start td-agent.service
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Set Up rsyslogd
The final step is to forward the logs from your rsyslogd to 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.
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*.* @127.0.0.1:42185
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Please restart the rsyslog service once the modification is complete:
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# init
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$ sudo /etc/init.d/rsyslog restart
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# or systemd
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$ sudo systemctl restart rsyslog
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Store and Search Event Logs
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 Top Menu
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:
Kibana: Discover
For more detail on how to use Kibana, please read the official manual.
To manually send logs to Elasticsearch, please use the logger command:
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$ logger -t test foobar
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When debugging your td-agent configuration, using filter_stdout will be useful. All the logs including errors can be found at /etc/td-agent/td-agent.log.
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<filter syslog.**>
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  @type stdout
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</filter>
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​
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<match syslog.**>
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  @type elasticsearch
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  logstash_format true
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  <buffer>
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    flush_interval 10s # for testing
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  </buffer>
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</match>
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Conclusion
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.
Learn More
​Fluentd Architecture​
​Fluentd Get Started​
​Downloading Fluentd​
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.