Upgrader (Apache Accumulo Manager Server 2.1.0 API)

All Known Implementing Classes:

Upgrader8to9, Upgrader9to10
```
public interface Upgrader
```
The purpose of this interface is to allow per version upgrade implementations to be created. Keeping the code for upgrading each version separate makes it easier to maintain and understand the upgrade code over time.
Upgrade operations should be idempotent. For failure cases upgrade operations may partially complete and then be run again later.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`upgradeMetadata(ServerContext context)`	Update the metadata table - called after the metadata table is loaded and before loading user tablets.
`void`	`upgradeRoot(ServerContext context)`	Update the root tablet - called after the root tablet is loaded and before the metadata table is loaded.
`void`	`upgradeZookeeper(ServerContext context)`	Update entries in ZooKeeper - called before the root tablet is loaded.

- Method Detail
  - upgradeZookeeper
```
void upgradeZookeeper(ServerContext context)
```
    Update entries in ZooKeeper - called before the root tablet is loaded.
    
    Parameters:
    
    context - the server context.
  - upgradeRoot
```
void upgradeRoot(ServerContext context)
```
    Update the root tablet - called after the root tablet is loaded and before the metadata table is loaded.
    
    Parameters:
    
    context - the server context.
  - upgradeMetadata
```
void upgradeMetadata(ServerContext context)
```
    Update the metadata table - called after the metadata table is loaded and before loading user tablets.
    
    Parameters:
    
    context - the server context.