bmqa_confirmeventbuilder.h File Reference

Provide a builder for batching confirmation messages. More...

#include <bmqa_message.h>
#include <bmqt_resultcode.h>
#include <bdlbb_blob.h>
#include <bsls_alignedbuffer.h>

Go to the source code of this file.

Classes
class	BloombergLP::bmqa::ConfirmEventBuilder
	Mechanism to build a batch of CONFIRM messages. More...

Namespaces
namespace	BloombergLP
namespace	BloombergLP::bmqa

Detailed Description

This component implements a mechanism, bmqa::ConfirmEventBuilder, that can be used for batching CONFIRM messages. The resulting batch can be sent to the BlazingMQ broker using the bmqa::Session (refer to bmqa_session.h for details). Wherever possible, a BlazingMQ consumer should try to send a batch of CONFIRM messages, which is more efficient than confirming messages individually.

The builder holds a batch of CONFIRM messages under construction, and provides two flavors of addMessageConfirmation method to add a CONFIRM message to the batch. It also provides a routine to retrieve number of CONFIRM messages added to the batch. Once application is done creating the batch, it can retrieve the blob (wire-representation) of the batch and send it via bmqa::Session. See the usage section for more details.

Usage

• An instance of bmqa::ConfirmEventBuilder (the builder) can be used to create multiple batches of CONFIRM messages. The recommended approach is to create one instance of the builder and use it throughout the lifetime of the task (if the task is multi-threaded, an instance per thread must be created and maintained). See usage example 1 for an illustration.
• The lifetime of an instance of the builder is bound by the bmqa::Session from which it was created. In other words, bmqa::Session instance must outlive the builder instance.

Example 1 - Basic Usage

// In this snippet, we will send a batch of CONFIRMs for all the
// 'bmqa::Message' messages received in a 'bmqa::MessageEvent'.
 
// Note that error handling is omitted from the snippet for the sake of
// brevity.
 
bmqa::Session session;
    // Session start up logic elided.
 
// Create and load an instance of the ConfirmEventBuilder.  Note that in
// this example, we are creating the builder on the stack everytime a
// message event is received.  Another approach can be to maintain the
// builder as a data member and use it everytime.
 
bmqa::ConfirmEventBuilder builder;
session.loadConfirmEventBuilder(&builder);
 
// Assuming that a 'bmqa::MessageEvent' is received.
 
bmqa::MessageIterator iter = messageEvent.messageIterator();
while (iter.nextMessage()) {
    const bmqa::Message& msg = iter.message();
 
    // Business logic for processing 'msg' elided.
 
    int rc = builder.addMessageConfirmation(msg);
        // Error handling elided.
}
 
// All messages in the event have been processed and their corresponding
// CONFIRM messages have been batched.  Now its time to send the batch to
// the BlazingMQ broker.
 
int rc = session.confirmMessages(&builder);
    // Error handling elided.  Note that in case of success, above method
    // will also reset the 'builder'.

Thread Safety

This component is NOT thread safe. If it is desired to create a batch of CONFIRM messages from multiple threads, an instance of the builder must be created and maintained per thread.