org.apache.hadoop.hbase.regionserver

Interface RegionMergeTransaction

All Known Implementing Classes:

RegionMergeTransactionImpl

@InterfaceAudience.LimitedPrivate(value="Coprocesssor")
 @InterfaceStability.Evolving
public interface RegionMergeTransaction

Executes region merge as a "transaction". It is similar with SplitTransaction. Call prepare(RegionServerServices) to setup the transaction, execute(Server, RegionServerServices) to run the transaction and rollback(Server, RegionServerServices) to cleanup if execute fails.

Here is an example of how you would use this interface:

  RegionMergeTransactionFactory factory = new RegionMergeTransactionFactory(conf);
  RegionMergeTransaction mt = factory.create(parent, midKey)
    .registerTransactionListener(new TransactionListener() {
       public void transition(RegionMergeTransaction transaction,
         RegionMergeTransactionPhase from, RegionMergeTransactionPhase to) throws IOException {
         // ...
       }
       public void rollback(RegionMergeTransaction transaction,
         RegionMergeTransactionPhase from, RegionMergeTransactionPhase to) {
         // ...
       }
    });
  if (!mt.prepare()) return;
  try {
    mt.execute(server, services);
  } catch (IOException ioe) {
    try {
      mt.rollback(server, services);
      return;
    } catch (RuntimeException e) {
      // abort the server
    }
  }
 

A merge transaction is not thread safe. Callers must ensure a split is run by one thread only.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	RegionMergeTransaction.JournalEntry Split transaction journal entry
static class	RegionMergeTransaction.RegionMergeTransactionPhase Each enum is a step in the merge transaction.
static interface	RegionMergeTransaction.TransactionListener Split transaction listener

Method Summary

Modifier and Type	Method and Description
Region	execute(Server server, RegionServerServices services) Deprecated. use #execute(Server, RegionServerServices, User)
Region	execute(Server server, RegionServerServices services, User user) Run the transaction.
List<RegionMergeTransaction.JournalEntry>	getJournal() Get the journal for the transaction.
HRegionInfo	getMergedRegionInfo()
RegionServerServices	getRegionServerServices() Get the RegonServerServices of the server running the transaction or rollback
Server	getServer() Get the Server running the transaction or rollback
boolean	prepare(RegionServerServices services) Check merge inputs and prepare the transaction.
RegionMergeTransaction	registerTransactionListener(RegionMergeTransaction.TransactionListener listener) Register a listener for transaction preparation, execution, and possibly rollback phases.
boolean	rollback(Server server, RegionServerServices services) Deprecated. use #rollback(Server, RegionServerServices, User)
boolean	rollback(Server server, RegionServerServices services, User user) Roll back a failed transaction

Method Detail

prepare

boolean prepare(RegionServerServices services)
         throws IOException

Check merge inputs and prepare the transaction.

Parameters:

services -

Returns:

true if the regions are mergeable else false if they are not (e.g. its already closed, etc.).

Throws:

IOException

execute

@Deprecated
Region execute(Server server,
                           RegionServerServices services)
                    throws IOException

Deprecated. use #execute(Server, RegionServerServices, User)

Run the transaction.

Parameters:

server - Hosting server instance. Can be null when testing

services - Used to online/offline regions.

Returns:

merged region

Throws:

IOException - If thrown, transaction failed. Call rollback(Server, RegionServerServices)

IOException

See Also:

rollback(Server, RegionServerServices)

execute

Region execute(Server server,
               RegionServerServices services,
               User user)
        throws IOException

Run the transaction.

Parameters:

server - Hosting server instance. Can be null when testing

services - Used to online/offline regions.

user -

Returns:

merged region

Throws:

IOException - If thrown, transaction failed. Call rollback(Server, RegionServerServices)

IOException

See Also:

rollback(Server, RegionServerServices, User)

rollback

@Deprecated
boolean rollback(Server server,
                             RegionServerServices services)
                      throws IOException

Deprecated. use #rollback(Server, RegionServerServices, User)

Roll back a failed transaction

Parameters:

server - Hosting server instance (May be null when testing).

services - Services of regionserver, used to online regions.

Returns:

True if we successfully rolled back, false if we got to the point of no return and so now need to abort the server to minimize damage.

Throws:

IOException - If thrown, rollback failed. Take drastic action.

rollback

boolean rollback(Server server,
                 RegionServerServices services,
                 User user)
          throws IOException

Roll back a failed transaction

Parameters:

server - Hosting server instance (May be null when testing).

services - Services of regionserver, used to online regions.

user -

Returns:

True if we successfully rolled back, false if we got to the point of no return and so now need to abort the server to minimize damage.

Throws:

IOException - If thrown, rollback failed. Take drastic action.

registerTransactionListener

RegionMergeTransaction registerTransactionListener(RegionMergeTransaction.TransactionListener listener)

Register a listener for transaction preparation, execution, and possibly rollback phases.

A listener can abort a transaction by throwing an exception.

Parameters:

listener - the listener

Returns:

'this' for chaining

getMergedRegionInfo

HRegionInfo getMergedRegionInfo()

Returns:

merged region info

getJournal

List<RegionMergeTransaction.JournalEntry> getJournal()

Get the journal for the transaction.

Journal entries are an opaque type represented as JournalEntry. They can also provide useful debugging information via their toString method.

Returns:

the transaction journal

getServer

Server getServer()

Get the Server running the transaction or rollback

Returns:

server instance

getRegionServerServices

RegionServerServices getRegionServerServices()

Get the RegonServerServices of the server running the transaction or rollback

Returns:

region server services