What is Fluentd and why is it useful for cloud-native logging?

Let's say we have a microservices application deployed in a Kubernetes cluster. This setup might include two applications in Node.js, a few Python applications, Kafka, some databases, and other services. Each service logs information about its operations, capturing details about its interactions and actions within the application.

 Figure 1: Microservices generating logs

Now, what kind of information are these applications logging?

Let's say you wanted to perform an in-depth analysis of application performance or identify the source of an error. You'd need a way to access and understand the logs generated by each service. However, if all these individual logs are scattered across different containers and sources, how'd you do that?

In this series, we'll introduce you to why Fluentd is important for logging in cloud native environments. We'll break down the Fluentd architecture and go through all its moving parts, and provide step-by-step guidance on how to install and configure it on your machine. By the end of this series, you'll manage your cloud-native logs like a pro.

What is Fluentd?

Fluentd is an open-source tool designed to collect and organize logs from the different sources in your application and then send them to specific destinations.

Figure 2: How Fluentd works by Fluentd.org

Once Fluentd collects logs from a source, it processes them through a series of steps, such as filtering, transforming, or enriching the data.

For example, Fluentd might add tags to log entries to indicate which service they came from or enrich logs with timestamps, making it easier to understand when each action occurred.

One of Fluentd's key strengths is its support for plugins, which let you configure and modify its behavior to suit your system's needs. These plugins are organized into two main types: input plugins and output plugins.

Input plugins gather data from various sources, such as web servers, application logs, or cloud services, while output plugins send the processed data to destinations like Elasticsearch, Amazon S3, or Prometheus.

These logs are processed as a "stream" of data, which means that Fluentd handles data continuously as it's produced.

One of Fluentd's core design principles is to handle data using JavaScript Object Notation (JSON). This makes it easier for systems to understand and work with, and it also includes options to compress or buffer logs to reduce the load on the network or storage system.

Why is Fluentd important for cloud-native logging?

In cloud-native environments, applications are built as microservices that can scale, change, or move across different servers or even data centers.

This setup generates a good number of log data from multiple sources that need to work together. So much so that an average microservices application can produce gigabytes of logs daily

The following are a few reasons why relying on Fluentd is important, especially in cloud-native environments:

• Compliance: Many industries require specific information to be logged to meet regulatory standards. Fluentd helps gather and organize these logs, making it easier to comply with industry regulations.
• Security: Logs can detect suspicious activity in your application by capturing access attempts, IP addresses, or user IDs. Fluentd centralizes and structures these logs, which is critical for monitoring access and identifying potential security threats.
• Debugging: An obvious reason is to debug errors. When an error occurs, it needs to be addressed immediately to avoid downtime or degraded performance. Fluentd collects, processes, and forwards your application logs in real-time, so you're always seeing the latest state of the system. This will help you detect and fix issues faster.

Its compatibility with cloud platforms and monitoring tools, such as AWS CloudWatch, Google Stackdriver, Prometheus, etc., make it a good choice for managing all your service logs.

Follow through to the next article where we'll give you a thorough breakdown of each component in the Fluentd architecture!

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