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Logging - Syslog, stdout and GELF

When the service starts, if no logging configuration is set, all the log events are sent to the standard output using the basic logger capabilities of the KrakenD framework. The reporting level, in that case, is DEBUG and adds no prefix to the logs.

Extending the logging capabilities

Different logging components allow you to extend the logging functionality, such as sending the events to the syslog, choosing the verbosity level or use the Graylog Extended Log Format (GELF).

Improved logging with gologging.

The component gologging extends the default logging capabilities with the following capabilities:

  • Option to write to the stdout
  • Option to write to the syslog
  • Add a prefix to log lines
  • Select the reporting level

Enabling gologging

To enjoy the extended logging capabilitites the component needs to be added in the krakend.json configuration. Add its namespace in the extra_config at the root level:

  "version": 2,
  "extra_config": {
    "github_com/devopsfaith/krakend-gologging": {
      "level": "INFO",
      "prefix": "[KRAKEND]",
      "syslog": true,
      "stdout": true

The snippet above shows the four options you can configure, explained below.

Set the reporting level

Define the severity you would like to see in the logs with level. The recognized options from more to less verbosity are:

  • INFO

Write to Syslog or Stdout

For each log event triggered, the output can write to the syslog, the stdout, or both. The accepted values are a boolean. When true, the log writes in the selected target:

  • "syslog": true
  • "stdout": true

Add a prefix to all lines

Besides, you might want to choose to add a string to every logged line, so you can quickly filter messages with external tools later.

  • "prefix": "[ANY STRING]"

Graylog and the GELF format

KrakenD supports sending structured events in GELF format to your Graylog Cluster (KrakenD 0.7+) thanks to the krakend-gelf integration.

The setup of GELF is straightforward and requires only to set two parameters:

  • address: The address (including the port) of your Graylog cluster (or any other service that receives GELF inputs).
  • enable_tcp: Set to false (recommended) to use UDP. When using TCP performance might be affected.

Enabling GELF

Add the krakend-gelf integration in the root level of your krakend.json, inside the extra_config section. The gologging needs to be enabled too.

For instance:

"extra_config": {
  "github_com/devopsfaith/krakend-gelf": {
    "address": "myGraylogInstance:12201",
    "enable_tcp": false
  "github_com/devopsfaith/krakend-gologging": {
      "level": "INFO",
      "prefix": "[KRAKEND]",
      "syslog": false,
      "stdout": true
Unresolved issues?

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