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Debugging Ory Kratos in Docker with Delve

Very often, there is a need to debug Kratos being deployed as a Docker image. To support this, Kratos ships with a couple of files:

  • The Dockerfile-debug file, which you can find in the .docker directory.
  • The docker-compose.template.dbg file, which you can find in the same directory. This file defines a template for a service, one would like to debug in Docker
  • and a supplementary skript, located in the script directory.

Actually, these files don't include any Kratos specifica and thus can be used for any Golang based project. As you already could infer, this support is meant to be used in a docker-compose setup as described below. You can however run it as a standalone Docker container as well. You can find some information on how to achieve this at the end of this document.

As part of a docker-compose setup

Imagine you have the following project structure:

  • docker-compose - a directory containing your docker-compose.yaml file
  • kratos - a directory containing the Kratos code
  • kratos-frontend - a directory containing a frontend application for Kratos

The docker-compose.yml mentioned above could look as follows:

version: "3.7"


image: postgres:9.6
- "5432:5432"
- type: volume
source: postgres-db
target: /var/lib/postgresql/data
read_only: false
- PGDATA=/var/lib/postgresql/data/pgdata

image: kratos
context: ../kratos
dockerfile: ./.docker/Dockerfile-build
- DSN=postgres://kratos:secret@postgresd:5432/kratos?sslmode=disable&max_conns=20&max_idle_conns=4
- type: bind
source: path-to-kratos-config
target: /etc/config/kratos
command: migrate sql -e --yes
- postgresd

image: kratos
context: ../kratos
dockerfile: ./.docker/Dockerfile-build
- kratos-migrate
- "4433:4433" # public
- "4434:4434" # admin
command: serve -c /etc/config/kratos/kratos.yml --watch-courier --dev
- type: bind
source: path-to-kratos-config
target: /etc/config/kratos

image: kratos-frontend
context: ../kratos-kratos-frontend
dockerfile: ./Dockerfile
- file-containing-all-required-configuration.env

To enable debugging of Kratos without changing the above docker-compose file, you can do the following (from the docker-compose directory):

SERVICE_NAME=kratos SERVICE_ROOT=../kratos REMOTE_DEBUGGING_PORT=9999 envsubst < ../kratos/.docker/docker-compose.template.dbg \
> docker-compose.kratos.tmp
docker-compose -f docker-compose.yaml -f docker-compose.kratos.tmp up --build -d kratos

The first line will create an overwrite docker-compose file to have a debug configuration for the kratos service. The second line will start a debug container by

  • mounting your kratos directory into the resulting Docker container,
  • downloading Delve,
  • building Kratos inside the container,
  • starting it in Delve with the arguments, you've defined in your regular docker-compose file - in the example above, this would be serve -c /etc/config/kratos/kratos.yml --watch-courier --dev - and
  • watching for changes on any go file within the mounted code base.

Each time you change a .go file, the Delve process will be stopped, Kratos will be recompiled and Delve will be started again. With other words, you'll have to re-connect with your debugger again after each change.

As you can see from the above usage, the docker-compose.template.dbg template expects the following variables to be defined:

  • SERVICE_ROOT - the root directory of the service to be started in the debug mode.
  • SERVICE_NAME - the name of the service from the docker-compose file.
  • REMOTE_DEBUGGING_PORT - the host port, the Delve listening port should be exposed as. This is the port you should connect your remote debugger to.

If you run docker-compose this way, the container run with debugging enabled will wait until the debugger connects. If your IDE supports remote debugging, set host to localhost and port to the value, you've used for REMOTE_DEBUGGING_PORT in your remote debugging configuration.

As a standalone Docker container

If you just would like to start Kratos in a container in debug mode, you can just use the Dockerfile-debug file instead of the regular Dockerfile. Make however sure your build context in the root directory of Kratos and not the .docker directory. In your IDE the debug configuration has to reference that file. In addition, you'll have to expose the Delve service port 40000 under the port 8000, as well as the actual port of the service, you'll like to access from your host, configure the bind mounts and set the run options to --security-opt="apparmor=unconfined" --cap-add=SYS_PTRACE.