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https://issues.apache.org/jira/browse/IGNITE-17148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kirill Tkalenko reassigned IGNITE-17148:
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Assignee: Kirill Tkalenko
> Support for abstract configuration
> ----------------------------------
>
> Key: IGNITE-17148
> URL: https://issues.apache.org/jira/browse/IGNITE-17148
> Project: Ignite
> Issue Type: Task
> Reporter: Kirill Tkalenko
> Assignee: Kirill Tkalenko
> Priority: Major
> Labels: iep-55, ignite-3
> Fix For: 3.0.0-alpha6
>
>
> *NOTE*
> Description may not be complete.
> *Problem*
> We need the ability to create a basic configuration schema so that we can
> define a common configuration schema and inherit from it with additional
> configuration added.
> Let's look at an example:
> We need to create two configuration schemes for the PageMemory based storage
> engine, they should have a common property "page size in bytes" and then they
> should be different, let's sketch an example scheme.
> {code:java}
> public class BasePageMemoryStorageEngineConfigurationSchema {
> @Value(hasDefault = true)
> public int pageSize = 16 * 1024;
> }
> @ConfigurationRoot(rootName = "in-memory-page-memory", type = DISTRIBUTED)
> public class VolatilePageMemoryStorageEngineConfigurationSchema extends
> BasePageMemoryStorageEngineConfigurationSchema{
> @ConfigValue
> public VolatilePageMemoryDataRegionConfigurationSchema defaultRegion;
> @NamedConfigValue
> public VolatilePageMemoryDataRegionConfigurationSchema regions;
> }
> @ConfigurationRoot(rootName = "persistent-page-memory", type = DISTRIBUTED)
> public class PersistentPageMemoryStorageEngineConfigurationSchema extends
> BasePageMemoryStorageEngineConfigurationSchema{
> @ConfigValue
> public PersistentPageMemoryDataRegionConfigurationSchema defaultRegion;
> @NamedConfigValue
> public PersistentPageMemoryDataRegionConfigurationSchema regions;
> @ConfigValue
> public PageMemoryCheckpointConfigurationSchema checkpoint;
> }{code}
> How can we implement this at the moment:
> * internal extension of the configuration: then the user will not be able to
> see and change it - not suitable;
> * polymorphic configuration:
> ** by design, we cannot create root config schemas for polymorphic config or
> instances;
> ** by design, we can change the type of polymorphic configuration to any
> instance, we do not fix its type, which does not suit us;
> ** by design, we cannot expose a polymorphic instance as a configuration
> schema property;
> ** hocon will display the type of polymorphic configuration, which is not
> necessary in this case and will look a little strange.
> The possible options do not suit us, so I propose to add another solution.
> *Proposal*
> Add an abstract configuration schema from which we can inherit, add
> properties, but only its heirs could be used as properties of other
> configurations schemas or configuration roots. Unlike a polymorphic
> configuration, it will not store and display the type in hocon, and the type
> cannot be changed.
> The abstract configuration schema from which will be inherited will contain
> the annotation {*}@AbstractConfiguration{*}, and any successor must extend it
> and contain *@Config* or {*}@ConfigurationRoot{*}, consider examples:
> {code:java}
> @AbstractConfiguration
> public class BasePageMemoryStorageEngineConfigurationSchema {
> @Value(hasDefault = true)
> public int pageSize = 16 * 1024;
> }
> @ConfigurationRoot(rootName = "in-memory-page-memory", type = DISTRIBUTED)
> public class VolatilePageMemoryStorageEngineConfigurationSchema extends
> BasePageMemoryStorageEngineConfigurationSchema{
> @ConfigValue
> public VolatilePageMemoryDataRegionConfigurationSchema defaultRegion;
> @NamedConfigValue
> public VolatilePageMemoryDataRegionConfigurationSchema regions;
> }
> @Config
> public class PersistentPageMemoryStorageEngineConfigurationSchema extends
> BasePageMemoryStorageEngineConfigurationSchema{
> @ConfigValue
> public PersistentPageMemoryDataRegionConfigurationSchema defaultRegion;
> @NamedConfigValue
> public PersistentPageMemoryDataRegionConfigurationSchema regions;
> @ConfigValue
> public PageMemoryCheckpointConfigurationSchema checkpoint;
> }{code}
> *Further development*
> * Merge with internal configuration extension;
> * Consider joining with a polymorphic configuration.
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