Centralized logging, just like security, is a fundamental aspect of monitoring and sound management of core resources in an IT infrastructure including web applications and hardware devices. Competent operation teams always have in place a log monitoring and management system which proves beneficial especially when there’s a system failure or an application behaves weirdly.

Why is Logging so Important?

When systems crash or applications malfunction, as they will sometimes do, you need to get to the bottom of the matter and uncover the cause of failure. Log files record system activity and give insights into the possible sources of error and subsequent failure. They give an elaborate sequence of events, including a detailed timestamp, that occasioned or led to an incident.

The diagnosis and recovery of any system start with the review of system logs. Analyzing log files can help operation teams find evidence of suspicious activity such as unauthorized logins which points to a security breach. It can help database administrators to tune their database for optimal performance and also help developers troubleshoot issues with their applications and write better code.

Centralized Logging

Managing and analyzing log files from one or two servers might be an easy undertaking. The same cannot be said of an enterprise environment with dozens of servers. For this reason, centralized logging is most recommended. Centralized logging consolidates log files from all systems into one dedicated server for easy log management. It saves time and energy that would have been used in logging in and analyzing log files of individual systems.

In this guide, we feature some of the most notable open-source centralized logging management systems for Linux.

1. Elastic Stack ( Elasticsearch Logstash & Kibana)

Elastic Stack, commonly abbreviated as ELK, is a popular three-in-one log centralization, parsing, and visualization tool that centralizes large sets of data and logs from multiple servers into one server.

ELK stack comprises 3 different products:

Logstash

Logstash is a free and open-source data pipeline that collects logs and events data and even processes and transforms the data to the desired output. Data is sent to logstash from remote servers using agents called ‘beats’. The ‘beats’ ship a huge volume of system metrics and logs to Logstash whereupon they are processed. It then feeds the data to Elasticsearch.

Elasticsearch

Built on Apache Lucene, Elasticsearch is an open-source and distributed search and analytics engine for nearly all types of data – both structured and unstructured. This includes textual, numerical, and geospatial data.

It was first released in 2010. Elasticsearch is the central component of the ELK stack and is renowned for its speed, scalability, and REST APIs. It stores, indexes, and analyzes huge volumes of data passed on from Logstash.

Kibana

Data is finally passed on to Kibana, which is a WebUI visualization platform that runs alongside Elasticsearch. Kibana allows you to explore and visualize time-series data and logs from elasticsearch. It visualizes data and logs on intuitive dashboards which take various forms such as bar graphs, pie charts, histograms, etc.

2. Graylog

Graylog is yet another popular and powerful centralized log management tool that comes with both open-source and enterprise plans. It accepts data from clients installed on multiple nodes and, just like Kibana, visualizes the data on dashboards on a web interface.

Graylogs plays a monumental role in making business decisions touching on user interaction of a web application. It collects vital analytics on the apps’ behavior and visualizes the data on various graphs such as bar graphs, pie charts, and histograms to mention a few. The data collected inform key business decisions.

For example, you can determine peak hours when customers place orders using your web application. With such insights in hand, the management can make informed business decisions to scale up revenue.

Unlike Elastic Search, Graylog offers a single-application solution in data collection, parsing, and visualization. It rids the need for installation of multiple components unlike in ELK stack where you have to install individual components separately. Graylog collects and stores data in MongoDB which is then visualized on user-friendly and intuitive dashboards.

Graylog is widely used by developers in different phases of app deployment in tracking the state of web applications and obtaining information such as request times, errors, etc. This helps them to modify the code and boost performance.

3. Fluentd

Written in C, Fluentd is a cross-platform and opensource log monitoring tool that unifies log and data collection from multiple data sources. It’s completely opensource and licensed under the Apache 2.0 license. In addition, there’s a subscription model for enterprise use.

Fluentd processes both structured and semi-structured sets of data. It analyzes application logs, events logs, clickstreams and aims to be a unifying layer between log inputs and outputs of varying types.

It structures data in a JSON format allowing it to seamlessly unify all facets of data logging including the collection, filtering, parsing, and outputting logs across multiple nodes.

Fluentd comes with a small footprint and is resource-friendly, so you won’t have to worry about running out of memory or your CPU being overutilized. Additionally, it boasts of a flexible plugin architecture where users can take advantage of over 500 community-developed plugins to extend its functionality.

4. LOGalyze

LOGalyze is a powerful network monitoring and log management tool that collects and parses logs from network devices, Linux, and Windows hosts. It was initially commercial but is now completely free to download and install without any limitations.

LOGalyze is ideal for analyzing server and application logs and presents them in various report formats such as PDF, CSV, and HTML. It also provides extensive search capabilities and real-time event detection of services across multiple nodes.

Like the aforementioned log monitoring tools, LOGalyze also provides a neat and simple web interface that allows users to log in and monitor various data sources and analyze log files.

5. NXlog

NXlog is yet another powerful and versatile tool for log collection and centralization. It’s a multi-platform log management utility that is tailored to pick up policy breaches, identify security risks and analyze issues in system, application, and server logs.

NXlog has the capability of collating events logs from numerous endpoints in varying formats including Syslog and windows event logs. It can perform a range of log related tasks such as log rotation, log rewrites. log compression and can also be configured to send alerts.

You can download NXlog in two editions: The community edition, which is free to download, and use, and the enterprise edition which is subscription-based.