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Chapter 23. Large Messages

23.1. Configuring the server
23.2. Configuring Parameters
23.2.1. Using Core API
23.2.2. Using JMS
23.2.3. Compressed Large Messages
23.3. Streaming large messages
23.3.1. Streaming over Core API
23.3.2. Streaming over JMS
23.4. Streaming Alternative
23.5. Large message example

HornetQ supports sending and receiving of huge messages, even when the client and server are running with limited memory. The only realistic limit to the size of a message that can be sent or consumed is the amount of disk space you have available. We have tested sending and consuming messages up to 8 GiB in size with a client and server running in just 50MiB of RAM!

To send a large message, the user can set an InputStream on a message body, and when that message is sent, HornetQ will read the InputStream. A FileInputStream could be used for example to send a huge message from a huge file on disk.

As the InputStream is read the data is sent to the server as a stream of fragments. The server persists these fragments to disk as it receives them and when the time comes to deliver them to a consumer they are read back of the disk, also in fragments and sent down the wire. When the consumer receives a large message it initially receives just the message with an empty body, it can then set an OutputStream on the message to stream the huge message body to a file on disk or elsewhere. At no time is the entire message body stored fully in memory, either on the client or the server.

Large messages are stored on a disk directory on the server side, as configured on the main configuration file.

The configuration property large-messages-directory specifies where large messages are stored.

<configuration xmlns="urn:hornetq"
   xsi:schemaLocation="urn:hornetq /schema/hornetq-configuration.xsd">

By default the large message directory is data/largemessages

For the best performance we recommend large messages directory is stored on a different physical volume to the message journal or paging directory.

Any message larger than a certain size is considered a large message. Large messages will be split up and sent in fragments. This is determined by the parameter min-large-message-size

The default value is 100KiB.

HornetQ supports setting the body of messages using input and output streams (java.lang.io)

These streams are then used directly for sending (input streams) and receiving (output streams) messages.

When receiving messages there are 2 ways to deal with the output stream; you may choose to block while the output stream is recovered using the method ClientMessage.saveOutputStream or alternatively using the method ClientMessage.setOutputstream which will asynchronously write the message to the stream. If you choose the latter the consumer must be kept alive until the message has been fully received.

You can use any kind of stream you like. The most common use case is to send files stored in your disk, but you could also send things like JDBC Blobs, SocketInputStream, things you recovered from HTTPRequests etc. Anything as long as it implements java.io.InputStream for sending messages or java.io.OutputStream for receiving them.

When using JMS, HornetQ maps the streaming methods on the core API (see Table 23.1, “org.hornetq.api.core.client.ClientMessage API”) by setting object properties . You can use the method Message.setObjectProperty to set the input and output streams.

The InputStream can be defined through the JMS Object Property JMS_HQ_InputStream on messages being sent:

BytesMessage message = session.createBytesMessage();

FileInputStream fileInputStream = new FileInputStream(fileInput);

BufferedInputStream bufferedInput = new BufferedInputStream(fileInputStream);

message.setObjectProperty("JMS_HQ_InputStream", bufferedInput);


The OutputStream can be set through the JMS Object Property JMS_HQ_SaveStream on messages being received in a blocking way.

BytesMessage messageReceived = (BytesMessage)messageConsumer.receive(120000);
File outputFile = new File("huge_message_received.dat");
FileOutputStream fileOutputStream = new FileOutputStream(outputFile);
BufferedOutputStream bufferedOutput = new BufferedOutputStream(fileOutputStream);
// This will block until the entire content is saved on disk
messageReceived.setObjectProperty("JMS_HQ_SaveStream", bufferedOutput);

Setting the OutputStream could also be done in a non blocking way using the property JMS_HQ_OutputStream.

// This won't wait the stream to finish. You need to keep the consumer active.
messageReceived.setObjectProperty("JMS_HQ_OutputStream", bufferedOutput);


When using JMS, Streaming large messages are only supported on StreamMessage and BytesMessage.

Please see Section 11.1.31, “Large Message” for an example which shows how large message is configured and used with JMS.