Package org.apache.lucene.index

# Interface TwoPhaseCommit

All Known Implementing Classes:
  `IndexWriter`

public interface TwoPhaseCommit
An interface for implementations that support 2-phase commit. You can use `TwoPhaseCommitTool` to execute a 2-phase commit algorithm over several `TwoPhaseCommit`s.

WARNING: This API is experimental and might change in incompatible ways in the next release.

## Method Summary

Modifier and Type
Method
Description
`long`
`commit()`
The second phase of a 2-phase commit.
`long`
`prepareCommit()`
The first stage of a 2-phase commit.
`void`
`rollback()`
Discards any changes that have occurred since the last commit.

## Method Details

### prepareCommit

long prepareCommit() throws IOException
The first stage of a 2-phase commit. Implementations should do as much work as possible in this method, but avoid actual committing changes. If the 2-phase commit fails, `rollback()` is called to discard all changes since last successful commit.

Throws:
  `IOException`

### commit

long commit() throws IOException
The second phase of a 2-phase commit. Implementations should ideally do very little work in this method (following `prepareCommit()`, and after it returns, the caller can assume that the changes were successfully committed to the underlying storage.

Throws:
  `IOException`

### rollback

void rollback() throws IOException
Discards any changes that have occurred since the last commit. In a 2-phase commit algorithm, where one of the objects failed to `commit()` or `prepareCommit()`, this method is used to roll all other objects back to their previous state.

Throws:
  `IOException`