Distributed configuration for Kong using decK
decK can operate on a sub-set of configuration instead of taking care of managing the entire configuration of Kong.
This can be very useful in a variety of scenarios, some examples include:
- Your organization uses a single Kong installation whose configuration is built from multiple teams. For example, one team manages the inventory API, while another team manages the users API and both APIs are exposed via Kong. In such a case, you want team inventory to manage it’s configuration without worrying about the configuration of the other team. The two teams should be able to push out configuration changes as they see fit and when they see fit.
- Kong’s configuration is very large, and you would like to manage it using different files, where you different parts take care of different problems.
- You want to declaratively manage all of the configuration for Kong except consumers and their credentials. The consumers are being managed by another service or you are dynamically creating them or the number of consumer is just so large that it makes no sense to manage them in a declarative fashion.
In such case, you can use decK’s
select-tag feature to export, sync, reset
only a sub-set of configuration.
Tags, introduced in Kong 1.1, provide a way to associate metadata with entities in Kong. You can also filter entities by tags on the list endpoints in Kong.
Using this feature, decK associates tags with entities and can manage a group of entities which share a common tag(s).
When multiple tags are specified in decK, decK ANDs those tags together, meaning only entities containing all the tags will be managed by decK. You can specify a combination of up-to 5 tags but it is recommended to use fewer or only on tag, for performance reasons in Kong’s codebase.
You can export a sub-set of entities in Kong by specifying common tags
$ deck dump --select-tag foo-tag --select-tag bar-tag # generates a kong.yaml file with all entities which have both the tags
If you observe the file generated by decK, you will see the following section:
_info: select_tags: - foo-tag - bar-tag
This sub-section tells decK to filter out entities containing select-tags during a sync operation.
You don’t need to specify
The commands will use the tags present in the state file and perform the diff
Since the state files have the tagging information, different teams can make updates to the part of configuration in Kong, without worrying about configuration of other teams. You no longer need to maintain Kong’s configuration in a single repository, where multiple teams need to co-ordinate.
--select-tagflag is present on those two commands for use-cases where the file cannot have
select_tagsdefined inside it. It is strongly advised that you do not supply select-tags to sync and diff commands via flags. The reason being that the tag information should be part of the declarative configuration file itself in order to provide a practical declarative file. The tagging information and entity definitions should be present in one place, else an error in supplying the wrong tag via the CLI can break the configuration.
You can delete only a sub-set of entities sharing a tag using the
flag on the
Initial setup problem
When you initially get started with a distributed configuration management, you will likely run into a problem where the related entities you would like to manage don’t share a single database.
To get around this problem, you can use one of the following approaches:
- Go through each entity in Kong, and patch those entities with the common
tag(s) you’d like and then use decK’s
dumpcommand to export by different tags.
- Export the entire configuration of Kong, and divide up the configuration
into different files. And then add the
select_tagsinfo to the file. This will require recreation of the database now, since decK will not detect any of the entities present (as they are missing the common tag).