Loki
Loki is multi-tenant log aggregation system inspired by Prometheus. It is designed to be very cost effective and easy to operate.
The Fluent Bit loki
built-in output plugin allows you to send your log or events to a Loki service. It supports data enrichment with Kubernetes labels, custom label keys and Tenant ID within others.
Be aware there is a separate Golang output plugin provided by Grafana with different configuration options.
Configuration Parameters
Labels
Loki store the record logs inside Streams, a stream is defined by a set of labels, at least one label is required.
Fluent Bit implements a flexible mechanism to set labels by using fixed key/value pairs of text but also allowing to set as labels certain keys that exists as part of the records that are being processed. Consider the following JSON record (pretty printed for readability):
If you decide that your Loki Stream will be composed by two labels called job
and the value of the record key called stream
, your labels
configuration properties might look as follows:
As you can see the label job
has the value fluentbit
and the second label is configured to access the nested map called sub
targeting the value of the key stream
. Note that the second label name must starts with a $
, that means that's a Record Accessor pattern so it provide you the ability to retrieve values from nested maps by using the key names.
When processing above's configuration, internally the ending labels for the stream in question becomes:
Another feature of Labels management is the ability to provide custom key names, using the same record accessor pattern we can specify the key name manually and let the value to be populated automatically at runtime, e.g:
When processing that new configuration, the internal labels will be:
Using the label_keys
property
label_keys
propertyThe additional configuration property called label_keys
allow to specify multiple record keys that needs to be placed as part of the outgoing Stream Labels, yes, this is a similar feature than the one explained above in the labels
property. Consider this as another way to set a record key in the Stream, but with the limitation that you cannot use a custom name for the key value.
The following configuration examples generate the same Stream Labels:
the above configuration accomplish the same than this one:
both will generate the following Streams label:
Kubernetes & Labels
Note that if you are running in a Kubernetes environment, you might want to enable the option auto_kubernetes_labels
which will auto-populate the streams with the Pod labels for you. Consider the following configuration:
Based in the JSON example provided above, the internal stream labels will be:
Networking and TLS Configuration
This plugin inherit core Fluent Bit features to customize the network behavior and optionally enable TLS in the communication channel. For more details about the specific options available refer to the following articles:
Networking Setup: timeouts, keepalive and source address
Security & TLS: all about TLS configuration and certificates
Note that all options mentioned in the articles above must be enabled in the plugin configuration in question.
Fluent Bit + Grafana Cloud
Fluent Bit supports sending logs (and metrics) to Grafana Cloud by providing the appropriate URL and ensuring TLS is enabled.
An example configuration - make sure to set the credentials and ensure the host URL matches the correct one for your deployment:
Getting Started
The following configuration example, will emit a dummy example record and ingest it on Loki . Copy and paste the following content into a file called out_loki.conf
:
run Fluent Bit with the new configuration file:
Fluent Bit output:
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