- RpcResult<Void> result = Rpcs.<Void> getRpcResult(false, null, Arrays.asList(
- RpcErrors.getRpcError( "", "in-use", null, ErrorSeverity.WARNING,
- "Toaster is busy", ErrorType.APPLICATION, null ) ) );
- return Futures.immediateFuture(result);
- }
- else if( outOfBread() ) {
- RpcResult<Void> result = Rpcs.<Void> getRpcResult(false, null, Arrays.asList(
- RpcErrors.getRpcError( "out-of-stock", "resource-denied", null, null,
- "Toaster is out of bread",
- ErrorType.APPLICATION, null ) ) );
- return Futures.immediateFuture(result);
- }
- else {
- // Notice that we are moving the actual call to another thread,
- // allowing this thread to return immediately.
- // The MD-SAL design encourages asynchronus programming. If the
- // caller needs to block until the call is
- // complete then they can leverage the blocking methods on the
- // Future interface.
- currentTask = executor.submit(new MakeToastTask(input));
+ checkStatusAndMakeToast( input, futureResult );
+
+ return futureResult;
+ }
+
+ private List<RpcError> makeToasterOutOfBreadError() {
+ return Arrays.asList(
+ RpcErrors.getRpcError( "out-of-stock", "resource-denied", null, null,
+ "Toaster is out of bread",
+ ErrorType.APPLICATION, null ) );
+ }
+
+ private List<RpcError> makeToasterInUseError() {
+ return Arrays.asList(
+ RpcErrors.getRpcError( "", "in-use", null, ErrorSeverity.WARNING,
+ "Toaster is busy", ErrorType.APPLICATION, null ) );
+ }
+
+ private void checkStatusAndMakeToast( final MakeToastInput input,
+ final SettableFuture<RpcResult<Void>> futureResult ) {
+
+ // Read the ToasterStatus and, if currently Up, try to write the status to Down.
+ // If that succeeds, then we essentially have an exclusive lock and can proceed
+ // to make toast.
+
+ final ReadWriteTransaction tx = dataProvider.newReadWriteTransaction();
+ ListenableFuture<Optional<DataObject>> readFuture =
+ tx.read( LogicalDatastoreType.OPERATIONAL, TOASTER_IID );
+
+ final ListenableFuture<RpcResult<TransactionStatus>> commitFuture =
+ Futures.transform( readFuture, new AsyncFunction<Optional<DataObject>,
+ RpcResult<TransactionStatus>>() {
+
+ @Override
+ public ListenableFuture<RpcResult<TransactionStatus>> apply(
+ Optional<DataObject> toasterData ) throws Exception {
+
+ ToasterStatus toasterStatus = ToasterStatus.Up;
+ if( toasterData.isPresent() ) {
+ toasterStatus = ((Toaster)toasterData.get()).getToasterStatus();
+ }
+
+ LOG.debug( "Read toaster status: {}", toasterStatus );
+
+ if( toasterStatus == ToasterStatus.Up ) {
+
+ if( outOfBread() ) {
+ LOG.debug( "Toaster is out of bread" );
+
+ return Futures.immediateFuture( Rpcs.<TransactionStatus>getRpcResult(
+ false, null, makeToasterOutOfBreadError() ) );
+ }
+
+ LOG.debug( "Setting Toaster status to Down" );
+
+ // We're not currently making toast - try to update the status to Down
+ // to indicate we're going to make toast. This acts as a lock to prevent
+ // concurrent toasting.
+ tx.put( LogicalDatastoreType.OPERATIONAL, TOASTER_IID,
+ buildToaster( ToasterStatus.Down ) );
+ return tx.commit();
+ }
+
+ LOG.debug( "Oops - already making toast!" );
+
+ // Return an error since we are already making toast. This will get
+ // propagated to the commitFuture below which will interpret the null
+ // TransactionStatus in the RpcResult as an error condition.
+ return Futures.immediateFuture( Rpcs.<TransactionStatus>getRpcResult(
+ false, null, makeToasterInUseError() ) );
+ }
+ } );
+
+ Futures.addCallback( commitFuture, new FutureCallback<RpcResult<TransactionStatus>>() {
+ @Override
+ public void onSuccess( RpcResult<TransactionStatus> result ) {
+ if( result.getResult() == TransactionStatus.COMMITED ) {
+
+ // OK to make toast
+ currentMakeToastTask.set( executor.submit(
+ new MakeToastTask( input, futureResult ) ) );
+ } else {
+
+ LOG.debug( "Setting error result" );
+
+ // Either the transaction failed to commit for some reason or, more likely,
+ // the read above returned ToasterStatus.Down. Either way, fail the
+ // futureResult and copy the errors.
+
+ futureResult.set( Rpcs.<Void>getRpcResult( false, null, result.getErrors() ) );
+ }
Code Review / controller.git / commitdiff