Routing your logs with Fluentd match directives
Note: This page describes routing logs with Fluentd. If you are using syslog-ng to route your log messages, see Routing your logs with syslog-ng.
The first step to process your logs is to select which logs go where. The Logging operator uses Kubernetes labels, namespaces and other metadata to separate different log flows.
Available routing metadata keys:
Name | Type | Description | Empty |
---|---|---|---|
namespaces | []string | List of matching namespaces | All namespaces |
labels | map[string]string | Key - Value pairs of labels | All labels |
hosts | []string | List of matching hosts | All hosts |
container_names | []string | List of matching containers (not Pods) | All containers |
Match statement
To select or exclude logs you can use the match
statement. Match is a collection
of select
and exclude
expressions. In both expression you can use the labels
attribute to filter for pod’s labels. Moreover, in Cluster flow you can use namespaces
as a selecting or excluding criteria.
If you specify more than one label in a select
or exclude
expression, the labels have a logical AND connection between them. For example, an exclude
expression with two labels excludes messages that have both labels. If you want an OR connection between labels, list them in separate expressions. For example, to exclude messages that have one of two specified labels, create a separate exclude
expression for each label.
The select
and exclude
statements are evaluated in order!
Without at least one select
criteria, no messages will be selected!
Flow:
ClusterFlow:
Examples
Example 0. Select all logs
To select all logs, or if you only want to exclude some logs but retain others you need an empty select statement.
Example 1. Select logs by label
Select logs with app: nginx
labels from the namespace:
Example 2. Exclude logs by label
Exclude logs with app: nginx
labels from the namespace
Example 3. Exclude and select logs by label
Select logs with app: nginx
labels from the default
namespace but exclude logs with env: dev
labels
Example 4. Exclude cluster logs by namespace
Select app: nginx
from all namespaces except from dev
and sandbox
Example 5. Exclude and select cluster logs by namespace
Select app: nginx
from all prod
and infra
namespaces but exclude cluster logs from dev
, sandbox
namespaces
Example 6. Multiple labels - AND
Exclude logs that have both the app: nginx
and app.kubernetes.io/instance: nginx-demo
labels
Example 6. Multiple labels - OR
Exclude logs that have either the app: nginx
or the app.kubernetes.io/instance: nginx-demo
labels