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Overriding configuration with environment vars

Document updated on Oct 10, 2022

When KrakenD runs, all the behavior is loaded from the configuration file. Through environment variables, you can override some of its values. There are two different ways of injecting environment vars.

  • Replacing existing values in the configuration
  • Setting new values when using the {{env}} function in flexible configuration

Value replacement with env vars

You can override configuration values with an environment variable for each configuration value that isn’t nested (meaning first-level properties of the configuration). However, with this technique, you cannot override parameters that aren’t declared in the configuration.

Examples of values you can replace are the port, timeout, or the configuration name to name a few.

To replace configuration parameters during runtime, capitalize them and add a prefix KRAKEND_. The configuration file is not changed. Only the values hold in memory.

For instance, take the following krakend.json configuration as an example:

    "version": 3,
    "timeout": "3s",
    "name": "Example gateway.",
    "cache_ttl": "0s"

To replace values using env vars, you could start krakend with the following command:

Example: Override configuration with env vars 
$KRAKEND_NAME="Build ABC0123" \
krakend run -c krakend.json

The resulting configuration will be:

    "version": 3,
    "timeout": "500ms",
    "name": "Build ABC0123"

Notice that the port attribute is not present in the configuration, despite passing a KRAKEND_PORT parameter. This is because the port didn’t exist previously in the configuration file, and the environment variables can only override values.

Setting new values

If you need to set content using environment variables at any level, you have to use the flexible configuration. It includes a series of advanced functions including an env function that can write in the config any value.

Here is an example:

    "version": 3,
    "name": "Configuration for {{ env "MY_POD_NAMESPACE" }}"

Usage reporting env var

When KrakenD starts, it sends a request to our stats server with anonymous non-sensitive information. Our Telemetry system sends 1 request every 12 hours and contains the following data:

  • The KrakenD Version you are running
  • The architecture (e.g: amd64)
  • The operating system /linux/ darwin)
  • A random unique ID

That’s all we collect (source code here). We are well aware of the importance of privacy. However, we are not in the data-mining business, so we selected a set of minimal details to share from your KrakenD instances that would give us enough insights into the matter without being invasive. We decided that we’d rather lose some accuracy than collect (maybe) sensible information, so we went for this anonymous approach.

We don’t collect typical system metrics like the number of CPU/cores, CPU usage, available and consumed ram, network throughput, etc. That’s something more related to system monitoring than KrakenD, and we felt that collecting these metrics generates friction with the acceptance of a telemetry system.

If you are not comfortable sharing your KrakenD version, you can disable it in the open-source version by passing an environment variable USAGE_DISABLE=1. If you want to know how it’s built, read this blog post.


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