Add A REST End point to Cluster Management Service

Here is the list of REST API that's currently available in CMS. This article gives you instructions on how to add a new REST end point in CMS.

Add A New Type of Element to be managed by REST CMS

From this diagram, you can actually see the FOUR major components you need to create in order to have your element managed by the REST CMS: a controller, a configuration manager, a configuration validator and a configuration realizer. 

Controller

In order to add a rest end point, we will need a controller entry point to handle the request. You can see RegionManagementController as an example. Here is a few things you need to pay attention to:

1. @ApiOperation: this is to make your rest end point available in Cli. The value attribute of this annotation will be the name of the command line to invoke this rest end point. If this rest end point is a list/get type of operation, you can provide an optional 'jqFilter' attribute to filter out the json response as a tabular result to this cli command. Command line users can override this jqFilter by providing their own when executing this command, this attribute is there only as a default filter.
2. @PreAuthorize: specifies the permission needed to execute this rest end point.
3. Don't put too much logic in the controllers. The controller should simply use the request parameters, form them into the arguments that cluster management service API accepts and return the results.

The moment you want to call the CMS API, you find yourself in need of  two basic types for your Element: a Configuration object and a RuntimeInfo.

Configuration ObjectConfigurationConverterConfigurationConverter

This objects specifies how you want to configure this element like Region, Index, GatewayReceiver etc. To get started, consider only adding those attributes that you want to expose through rest api. For example, although according to the cache.xsd, a region can be configured with many attributes (see RegionConfig, which is generated by the jaxb service using the cache.xsd file), in rest management api, we don't want to overwhelm users, so we only expose those that are more commonly used. That would require us to expose a different configuration object called Region (better to put all configuration object in one package). 

Your configuration object should either extend AbstractConfiguratioin if you can only configure one of it in the entire cluster (like PDX, can only be defined in the cluster level), or GroupableConfiguration if there could be one per server group (like region). There are also interfaces your configuration needs to consider adding: RegionScoped and HasFile. If your configuration lives under the Region element in cache.xml (like Index), then your configuration object needs to implement RegionScoped. If your object has file content (like Deployment), then it needs to implement HasFile.  Note if your object implement RegionScoped, then you need to extend AbstractConfiguration, not GroupableConfguration.

When you create your Configuration object, you notice you will need to type it with a RuntimeInfo. This is used to tell the framework what's the corresponding RuntimeInfo object this configuration object is related to. For example, Region is related to RuntimeRegionInfo, which give more information about the state of the region on each server, that's why Region extends GroupableConfiguration<RuntimeRegionInfo>. If your configuration object doesn't have any corresponding runtime information, you can simply type it with the abstract class itself, like <code>class XYZ extends AbstractConfiguration<RuntimeInfo></code>.

RuntimeInfo Object

Like said above, this object collects runtime information about this configuration object on each server. For example, entry count for the region, specific jar location on each server about each deployment etc. If you don't need to collect any runtime information for your configuration object, you don't need to implement this.

Configuration Manager

Now that you have the configuration object ready, you will need to create a ConfigurationManager that tells the framework how this object is to be managed by the configuration service. If your configuration object is part of the cache xml, your configuration manager should extend CacheConfigurationManager. If your object affects other parts outside cache.xml, like jar deployment or runtime properties, you will need to extend its parent class ConfigurationManager.

For now, after you created a configuration manager, you will need to manually add it to the map in the list of managers in LocatorClusterManagementService.

Note the configuration managers are run on the locators.

CacheConfigurationManager

To extend this class, you will need to implement a few methods, basically to tell the framework how your element will be added/deleted/updated/found in the CacheConfig (an object represent the cache.xml). You can see examples in RegionConfigManager. In there you find yourself in need of a ConfigurationConverter.

ConfigurationConverter

ConfigurationConverter specifies how you convert between your configuration object and the xml representation of it.

As we mentioned before, we don't use jaxb generated object as our configuration object but create our own configuration object. Since CacheConfig uses these jaxb-generated objects inside (because they are all auto-generated by the jaxb service), we will need a way to convert our configuration object to/from these xml objects. Hence, in order to implement the CacheConfigurationManager, we will need a converter first. You can also the usage and the implementation of a converter in RegionConfigManager. 

ConfigurationManager

If your configuration is not part of the cache.xml, but something else, like deployment or runtime properties, you will need to implement this interface instead.

Configuration Validator

Configuration Validator is called when CMS receives the configuration for operations like create or delete. You can use this to validate if the attributes set on the configuration is valid or not.

For now, after you created a configuration validator, you will need to manually add it to the map in the list of validators in LocatorClusterManagementService.

Note the configuration validators are run on the locators.

Configuration Realizer

Configuration Realizer controls how the entity represented by this configuration is created/deleted/updated on the servers. For example, after we have this region configuration, how we actually create it on the servers. See RegionConfigRealizer.java for example. 

For now, after you created a configuration realizer, you will need to manually add it to the map in the list of validators in CacheRealizationFunction

Note the configuration realizers are run on the servers.

A New Operation to be started by REST CMS