dropwizard-runtime-config-example
Example application demonstrating how to update your dropwizard configuration at runtime.
Usage
To build and start the server run:
./gradlew clean build install && \
./build/install/dropwizard-runtime-config-example/bin/dropwizard-runtime-config-example server config.ymlGet the initial config value:
$ curl 'http://localhost:8080/config'
helloUpdate the config value (to the hardcoded string):
$ curl -X POST 'http://localhost:8081/tasks/updateconfig'Then get the config value that is now updated:
$ curl 'http://localhost:8080/config'
goodbyeDiscussion
This works because you are referencing the same instance in memory when you update the config via the
/tasks/updateconfig admin endpoint. You instantiate ConfigResource.java
and UpdateConfigTask.java
with the same instance of ExampleConfiguration.java.
If instead you initialized both with the String returned from config.getMyConfigValue() this would no longer work.
Limitations
When you update the config value, note that these config values won't be written to config.yml.
This also means that when you restart the application, these values will be reset to those in the config.yml.
However, if you'd like the values to persist between restarts, it shouldn't be too hard to implement this
yourself, say, by writing the file yourself.
You should also pay close attention to how you're using your config values. These values are now dynamic, and it's possible they could be changed in the middle of processing, so you need to handle them with care. You should copy them once to separate references at the beginning of processing. If you're adding this feature to an existing application I'd recommend reviewing their usage patterns.
Examples in action
If you'd like to see this feature used in the wild, take a look at my other project:
If you implement this feature yourself, please ping me. I'd be happy to link your project here as well :)