spring-cloud-consul allow key deletion to trigger configuration refresh

see https://github.com/spring-cloud/spring-cloud-consul/issues/780

Adding/changing a key triggers refreshing values for Environment and @value. But deleting a key does not. This is a strange behavior. e.g., you have two paths to watch in Consul: /default/config and /my-service/config, if I add a key to my-service/config I can override the default settings in /default/config, but when I delete the key, nothing happens and I have to restart my app.

Moreover, when I delete a key, in ConfigWatch.watchConfigKeyValues(), the index will stop increasing. Suppose you get an index 16866 previously, then for the deletion event we should increase the current index to the new index in the response, maybe 16914. Currently the watch just stops at 16866 and retry and retry over again. If you set timeout shorter to 3 second you will see this busy loop behavior from log. Without increasing the index, it's a little less efficient and we will waste some resources.

I think the problem is, when 404 with a higher index is returned, it means the key was deleted, and we should publish the RefreshEvent and increase the index. Then the spring config framework should listen to the event and change accordingly, maybe delete the key from ConsulPropertySource.

May 19 '22 02:05 DanielYWoo

can somebody approve the initial code check workflow to run?

May 24 '22 05:05 DanielYWoo

@spencergibb could you take a look and approve it?

Jun 01 '22 12:06 DanielYWoo

@marcingrzejszczak @ryanjbaxter hi, could you take a look?

Jun 06 '22 15:06 DanielYWoo

Please be patient

Jun 06 '22 15:06 spencergibb

I approved the checks, you have checkstyle errors

Jun 06 '22 15:06 ryanjbaxter

Hi Ryan, many thanks, I fixed checkstyle errors. BTW, the unit test currently has a minor problem on a slow machines, I also put a comment into the unit test.

Jun 08 '22 11:06 DanielYWoo

@ryanjbaxter I am working on another PR, similar to this one, there are some checkstyle errors on some classes that I did not touch. I need to fix them even they are unrelated and untouched, right?

Jun 10 '22 02:06 DanielYWoo

I dont see how that would be possible, that would imply that there are checkstyle errors in the code and if that was the case our builds would be failing because of them. I just checked and our builds are all green.

Jun 10 '22 12:06 ryanjbaxter

@ryanjbaxter I am thinking exactly the same as you. Anyway, just curious but it's not a big deal, I have fixed them all in another PR.

Jun 10 '22 12:06 DanielYWoo

I also think we are at odds with #223. What would be the difference between a prefix not existing and a key deletion?

Mar 09 '23 19:03 spencergibb