Monitoring

Learn how to monitor your Fluent Bit data pipelines

Fluent Bit comes with built-it features to allow you to monitor the internals of your pipeline, connect to Prometheus and Grafana, Health checks and also connectors to use external services for such purposes:

HTTP Server

Fluent Bit comes with a built-in HTTP Server that can be used to query internal information and monitor metrics of each running plugin.

The monitoring interface can be easily integrated with Prometheus since we support it native format.

Getting Started

To get started, the first step is to enable the HTTP Server from the configuration file:

[SERVICE]
HTTP_Server On
HTTP_Listen 0.0.0.0
HTTP_PORT 2020
[INPUT]
Name cpu
[OUTPUT]
Name stdout
Match *

the above configuration snippet will instruct Fluent Bit to start it HTTP Server on TCP Port 2020 and listening on all network interfaces:

$ bin/fluent-bit -c fluent-bit.conf
Fluent Bit v1.4.0
* Copyright (C) 2019-2020 The Fluent Bit Authors
* Copyright (C) 2015-2018 Treasure Data
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io
[2020/03/10 19:08:24] [ info] [engine] started
[2020/03/10 19:08:24] [ info] [http_server] listen iface=0.0.0.0 tcp_port=2020

now with a simple curl command is enough to gather some information:

$ curl -s http://127.0.0.1:2020 | jq
{
"fluent-bit": {
"version": "0.13.0",
"edition": "Community",
"flags": [
"FLB_HAVE_TLS",
"FLB_HAVE_METRICS",
"FLB_HAVE_SQLDB",
"FLB_HAVE_TRACE",
"FLB_HAVE_HTTP_SERVER",
"FLB_HAVE_FLUSH_LIBCO",
"FLB_HAVE_SYSTEMD",
"FLB_HAVE_VALGRIND",
"FLB_HAVE_FORK",
"FLB_HAVE_PROXY_GO",
"FLB_HAVE_REGEX",
"FLB_HAVE_C_TLS",
"FLB_HAVE_SETJMP",
"FLB_HAVE_ACCEPT4",
"FLB_HAVE_INOTIFY"
]
}
}

Note that we are sending the curl command output to the jq program which helps to make the JSON data easy to read from the terminal. Fluent Bit don't aim to do JSON pretty-printing.

REST API Interface

Fluent Bit aims to expose useful interfaces for monitoring, as of Fluent Bit v0.14 the following end points are available:

URI

Description

Data Format

/

Fluent Bit build information

JSON

/api/v1/uptime

Get uptime information in seconds and human readable format

JSON

/api/v1/metrics

Internal metrics per loaded plugin

JSON

/api/v1/metrics/prometheus

Internal metrics per loaded plugin ready to be consumed by a Prometheus Server

Prometheus Text 0.0.4

/api/v1/storage

Get internal metrics of the storage layer / buffered data. This option is enabled only if in the SERVICE section the property storage.metrics has been enabled

JSON

/api/v1/health

Fluent Bit health check result

String

Uptime Example

Query the service uptime with the following command:

$ curl -s http://127.0.0.1:2020/api/v1/uptime | jq

it should print a similar output like this:

{
"uptime_sec": 8950000,
"uptime_hr": "Fluent Bit has been running: 103 days, 14 hours, 6 minutes and 40 seconds"
}

Metrics Examples

Query internal metrics in JSON format with the following command:

$ curl -s http://127.0.0.1:2020/api/v1/metrics | jq

it should print a similar output like this:

{
"input": {
"cpu.0": {
"records": 8,
"bytes": 2536
}
},
"output": {
"stdout.0": {
"proc_records": 5,
"proc_bytes": 1585,
"errors": 0,
"retries": 0,
"retries_failed": 0
}
}
}

Metrics in Prometheus format

Query internal metrics in Prometheus Text 0.0.4 format:

$ curl -s http://127.0.0.1:2020/api/v1/metrics/prometheus

this time the same metrics will be in Prometheus format instead of JSON:

fluentbit_input_records_total{name="cpu.0"} 57 1509150350542
fluentbit_input_bytes_total{name="cpu.0"} 18069 1509150350542
fluentbit_output_proc_records_total{name="stdout.0"} 54 1509150350542
fluentbit_output_proc_bytes_total{name="stdout.0"} 17118 1509150350542
fluentbit_output_errors_total{name="stdout.0"} 0 1509150350542
fluentbit_output_retries_total{name="stdout.0"} 0 1509150350542
fluentbit_output_retries_failed_total{name="stdout.0"} 0 1509150350542

Configuring Aliases

By default configured plugins on runtime get an internal name in the format plugin_name.ID. For monitoring purposes, this can be confusing if many plugins of the same type were configured. To make a distinction each configured input or output section can get an alias that will be used as the parent name for the metric.

The following example set an alias to the INPUT section which is using the CPU input plugin:

[SERVICE]
HTTP_Server On
HTTP_Listen 0.0.0.0
HTTP_PORT 2020
[INPUT]
Name cpu
Alias server1_cpu
[OUTPUT]
Name stdout
Alias raw_output
Match *

Now when querying the metrics we get the aliases in place instead of the plugin name:

{
"input": {
"server1_cpu": {
"records": 8,
"bytes": 2536
}
},
"output": {
"raw_output": {
"proc_records": 5,
"proc_bytes": 1585,
"errors": 0,
"retries": 0,
"retries_failed": 0
}
}
}

Grafana Dashboard and Alerts

Fluent Bit's exposed prometheus style metrics can be leveraged to create dashboards and alerts.

The provided example dashboard is heavily inspired by Banzai Cloud's logging operator dashboard but with a few key differences such as the use of the instance label (see why here), stacked graphs and a focus on Fluent Bit metrics.

dashboard

Alerts

Sample alerts are available here.

Health Check for Fluent Bit

Fluent bit now supports four new configs to set up the health check.

Config Name

Description

Default Value

Health_Check

enable Health check feature

Off

HC_Errors_Count

the error count to meet the unhealthy requirement

5

HC_Retry_Failure_Count

the retry failure count to meet the unhealthy requirement

5

HC_Period

The time period by second to count the error and retry failure data point

60

So the feature works as: Based on the HC_Period customer setup, if the real error number is over HC_Errors_Count or retry failure is over HC_Retry_Failure_Count, fluent bit will be considered as unhealthy. The health endpoint will return HTTP status 500 and String error. Otherwise it's healthy, will return HTTP status 200 and string ok

See the config example:

[SERVICE]
HTTP_Server On
HTTP_Listen 0.0.0.0
HTTP_PORT 2020
Health_Check On
HC_Errors_Count 5
HC_Retry_Failure_Count 5
HC_Period 5
[INPUT]
Name cpu
[OUTPUT]
Name stdout
Match *

The command to call health endpoint

$ curl -s http://127.0.0.1:2020/api/v1/health

Based on the fluent bit status, the result will be:

  • HTTP status 200 and "ok" in response to healthy status

  • HTTP status 500 and "error" in response for unhealthy status

Calyptia Cloud

Calyptia Cloud is a hosted service that allows you to monitor your Fluent Bit agents including data flow, metrics and configurations.

Get Started with Calyptia Cloud

Register your Fluent Bit agent will take less than one minute, steps:

In your Fluent Bit configuration file, append the following configuration section:

[CUSTOM]
name calyptia
api_key <YOUR_API_KEY>

Make sure to replace your API key in the configuration. After a few seconds upon restart your Fluent Bit agent, the Calyptia Cloud Dashboard will list your agent. Metrics will take around 30 seconds to shows up.

Contact Calyptia

If want to get in touch with Calyptia team, just send an email to [email protected]