storage-extention.md

# Extend storage
SkyWalking has already provided several storage solutions. In this document, you could 
learn how to implement a new storage easily. 

## Define your storage provider
1. Define a class extends `org.apache.skywalking.oap.server.library.module.ModuleProvider`.
2. Set this provider targeting to Storage module.
```java
@Override 
public Class<? extends ModuleDefine> module() {
    return StorageModule.class;
}
```

## Implement all DAOs
Here is the list of all DAO interfaces in storage
1. IServiceInventoryCacheDAO
1. IServiceInstanceInventoryCacheDAO
1. H2EndpointInventoryCacheDAO
1. H2NetworkAddressInventoryCacheDAO
1. IBatchDAO
1. StorageDAO
1. IRegisterLockDAO
1. H2TopologyQueryDAO
1. IMetricQueryDAO
1. ITraceQueryDAO
1. IMetadataQueryDAO
1. IAggregationQueryDAO
1. IAlarmQueryDAO
1. IHistoryDeleteDAO

## Register all service implementations
In `public void prepare()`, use `this#registerServiceImplementation` method to do register binding your implementation with the above interfaces.

## Example
Take `org.apache.skywalking.oap.server.storage.plugin.elasticsearch.StorageModuleElasticsearchProvider` 
or `org.apache.skywalking.oap.server.storage.plugin.jdbc.mysql.MySQLStorageProvider`  as a good example.

## Redistribution with new storage implementation.
You don't have to clone the main repo just for implementing the storage. You could just easy depend our Apache releases.
Take a look at [SkyAPM/SkyWalking-With-Es5x-Storage](https://github.com/SkyAPM/SkyWalking-With-Es5x-Storage) repo, SkyWalking v6 redistribution with ElasticSearch 5 TCP connection storage implemention.