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CXL. SAM - Simple Asynchronous Messaging

Introduction

This extension provides access to the functionality of messaging and queueing systems, such as the IBM WebSphere MQSeries family of products, from PHP scripts. The interface is designed to make it extremely simple to do the more commonly required tasks such as deliver simple text messages to queues while still allowing skilled users to do more complex messaging operations. For many users the complexities of setting up numerous options can be simply ignored.

The SAM extension is a framework that provides a very simple API that can be used to access a number of messaging middleware systems. Currently the package includes built-in support for the MQTT (MQ Telemetry Transport) messaging protocol and support for the IBM Messaging and Queuing middleware products. SAM is designed to be readily extended to support other messaging systems and extension modules may be written in C or PHP.

Installation

The SAM framework and MQTT support can be built and used without any other prerequisites. Support for protocols other than MQTT is provided via a set of libraries and some client side code referred to as XMS.

If you only intend to use the built-in MQTT support then you can build and configure SAM as an extension or simply refer to "php_sam.php" with a "requires" or "requires_once" clause in your PHP script. In this case you need only install the code without building the extension using the pear installer:

pecl install -B SAM

Prerequisites

The SAM extension interfaces to the IBM Messaging and Queuing middleware products using a set of libraries and some client side code referred to as XMS. This package is available as a free download in the guise of IBM support pack IA94. There is a description of this package and download links in the article Introducing XMS - The IBM Message Service API.

If you intend to use SAM to access the Messaging and Queuing infrastructure within WebSphere MQ then you will also need to have installed a local MQ queue manager or installed the WebSphere MQ clients package. The clients package is freely available as a support pack (MQC6).

If you are only aiming to experiment with sending messages to and from WebSphere Application Server queues using the WebSphere Platform Messaging protocol (WPM) then you do not need to install the MQC6 package.

After installing these packages you will need to ensure the XMS binary and, if you are using it, the MQ client bin directory are included in the PATH environment variable so that Apache and PHP can find the dependent .DLLs/libraries.

Linux installation steps

The sam extension is supplied as a PECL module, which you should be able to download and install in one step as follows:

pecl install sam

(Depending on your php environment, you will probably need to be root to do this.)

Make sure that the module is loaded by PHP, by adding following line to php.ini:

extension=sam.so

If you intend to use the XMS support to access the IBM Messaging and Queuing family you must also enable the SAM XMS extension.

extension=sam_xms.so

If you cannot use the PEAR installer, you can download the extension and build it manually:

pear download sam          #downloads sam-<version>.tgz
tar -xzf sam-<version>.tgz
cd sam-<version>
phpize
./configure
make
make install               #you may need to be root for this step

To work with the very latest source, you'll need to extract it from cvs and build manually as above.

Windows installation steps

You will probably need to build the sam extension for Windows as there are only a limited range of pre-built binaries available from the SAM website. The extension can be built using the standard Windows extension build procedures.

You will need the PHP source tree for the version of PHP you wish to build the SAM extension against which you can obtain from php.net. This should be unpacked into a working directory of your choice.

You will also need the libraries and headers used by PHP extensions available from http://www.php.net/extra/win32build.zip and this should be unzipped so that is in your working directory.

You should have something like:

c:\php-build\-
              |
              |---php-5.0.5--|---build
              |              |---ext
              |              |--- ...
              |
              |---win32build--|---bin
                              |---include
                              |---lib

You will need a compiler such as the free version of Visual Studio C++ Express from the Microsoft web site. Also you need the Microsoft Windows Platform SDK which again can be downloaded from the Microsoft web site.

Obtain the SAM extension source using pear (pecl download sam) or by using CVS and copy the files to a new "sam" directory under the "ext" directory in your PHP source tree.

To build the extension open a build environment window by going to the start menu->all programs->microsoft platform SDK for windows-> open build environment window->windows 200 build environment-> set windows 2000 build environment (retail)

This should open a command prompt with all the environment variables set up to access the platform SDK etc. You then need to set the environment variables for Visual Studio by issuing the command "vcvars32.bat" in the window.

Change directory to your working directory e.g. cd c:\php-build. Then make sure the win32build tools are accessible by adding them to the PATH environment variable:

set PATH=..\win32build\bin;%PATH%

Run the buildconf.bat command. This should rebuild the configure.js file.

Run the cscript command with the appropriate options. To build just the SAM extension framework and MQTT support use:

cscript /nologo configure.js --with-sam

To build the SAM framework and the XMS support use:

cscript /nologo configure.js --with-sam --with-sam_xms="c:\program files\ibm\xms"

The additional parameter passed for sam_xms is the installation path to the XMS libraries and runtime that were installed as described under prerequisites at the top of this page.

You can specify whatever other cscript parameters you require to include or exclude items from the php build or select options.

Assuming all has gone well so far you can now finally run a make for the SAM framework!

nmake php_sam.dll

Also if you are using the XMS support you must make the sam_xms extensions:

nmake php_sam_xms.dll

If you have used Visual Studio 2005 to build the DLLs please see below for additional steps that must be carried out before proceeding further.

The DLLs created (php_sam.dll and optionally php_sam_xms.dll) can now be copied to the subdirectory appropriate for your PHP set-up. Make sure that the module(s) are loaded by PHP, by adding following line to php.ini :

extension=php_sam.dll

If you intend to use the XMS support to access the IBM Messgaing and Queuing family you must also enable the SAM XMS extension.

extension=php_sam_xms.dll

Additional steps for Visual Studio 2005

If you build the SAM extension with the Microsoft Visual Studio 2005 compiler and tools you need to perform an additional step in the build process to ensure the php_sam.dll is able to link with the C runtime libraries at runtime. This step includes the dependancy manifest into the DLL. Switch to the directory where the php_sam.dll has been generated (usually Release_TS or Debug_TS below the php source directory) and issue the following magic incantation:

mt.exe -manifest php_sam.dll.manifest -outputresource:php_sam.dll;2

If you are using the XMS capabilities you will need to do the same with the SAM XMS DLL:

mt.exe -manifest php_sam_xms.dll.manifest -outputresource:php_sam_xms.dll;2

If you build the SAM extension using the compiler and libaries from Microsoft Visual Studio 2005 you will also need to ensure that the runtime components are installed on the system on which you intend to use SAM. This can be accomplished by installing Visual Studio 2005 or by using the freely distributable runtime package.

Protocol support and mapping

The SAM framework can be extended to support other messaging protocols and connection mechanisms. To add support for a new protocol or connection library a support class has to be defined, either as a C extension or as a PHP script, and a "factory" script must be created. The support class must implement all the methods of the SAMConnection class though it should not inherit from SAMConnection. The factory script will be called by the SAM framework to create an instance of the implemented class. The way SAM chooses which factory to call is based on the protocol specified as the first parameter of the "connect" call.

By default the built-in MQTT support will be used if a connect call specifies a protocol of SAM_MQTT ("mqtt"), for any other protocol SAM will attempt to use the XMS support extension. To add support for additional protocols or to modify the default behavior entries may be added to php.ini in the [sam] section. The default mapping is equivalent to the following entries:

[sam]
sam.factory.mqtt=mqtt
sam.factory.wmq=xms
sam.factory.wmq:client=xms
sam.factory.wmq:bindings=xms
sam.factory.wpm=xms
sam.factory.rtt=xms

As can be seen from these examples the entries take the form of "sam.factory.pppp=xxx" where pppp is the protocol string specified on the connect call and xxx is a factory suffix. Note: SAM defines constants for these protocol strings such that SAM_WMQ=wmq, SAM_WPM=wpm, SAM_RTT=rtt, SAM_MQTT=mqtt, etc.

When identifying the support code to use on a connect call SAM looks up the protocol name in the php.ini entries and then invokes a factory script named sam_factory_xxx.php. If no entry is found the support will default to XMS.

API Usage

Connections

In order to perform any messaging and queueing functions a connection must be established with a messaging server by creating a SAMConnection object and calling its "connect" method, with a set of connection properties, to connect the PHP script to the messaging server. Until such time as the SAMConnection object is destroyed the connection will be maintained and available for use. All SAMConnection objects are destroyed when the PHP script exits.

A set of default properties may be used in connecting to a messaging server but as a minimum the PHP script must specify a protocol to be used.

Example 1. Creating a connection and connecting to a remote WebSphere MQSeries Messaging Server


<?php
   $conn = new SAMConnection();
   $conn->connect(SAM_WMQ, array(SAM_HOST => 'myhost.mycompany.com',
                                 SAM_PORT => 1506,
                                 SAM_BROKER => 'mybroker'));
?>

Example 2. Creating a connection and connecting to a remote WebSphere Application Server


<?php
   $conn = new SAMConnection();
   $conn->connect(SAM_WPM, array(SAM_ENDPOINTS => 'localhost:7278:BootstrapBasicMessaging',
                                 SAM_BUS => 'Bus1',
                                 SAM_TARGETCHAIN => 'InboundBasicMessaging'));
?>

Example 3. Creating a connection and connecting to an MQTT server


<?php
   $conn = new SAMConnection();
   $conn->connect(SAM_MQTT, array(SAM_HOST => 'myhost.mycompany.com',
                                 SAM_PORT => 1883));
?>

Messages

Messages sent to and received from queues are represented by the SAMMessage object. The SAMMessage object encapsulates the body of the message (if one exists) and the header properties associated with the message. A SAMMessage object is either supplied as a parameter to a messaging operation or returned as a result.

Example 4. Creating a message with a simple text body


<?php
$msg = new SAMMessage('This is a simple text message');
?>

Messages may have header properties associated with them that provide control over the transport of the message or further information to the receiving application. By default message properties are delivered to the underlying messaging system as strings and in this case they may be set with the following simple syntax:

Example 5. Setting a text format property using the default syntax


<?php
   $msg->header->myPropertyName = 'textData';
?>

If it is desired to pass type information an alternative syntax may be used where the value and the type hint are passed in an associative array:

Example 6. Setting a property using a type hint


<?php
   $msg->header->myPropertyName = array(3.14159, SAM_FLOAT);
?>

Properties may also be extracted from the header of a message.

Example 7. Retrieving a property from a message header


<?php
   $myProperty = $msg->header->myPropertyName;
?>

Messaging operations

All messaging operations are performed through calls to methods on the connection object. To add a message to a queue the "send" method is used, to obtain a message from a queue the "receive" method is used. Other methods provide publish and subscribe functionality and control of transaction boundaries.

Example 8. Adding a message to a queue and receiving a response


<?php
$msg = new SAMMessage('This is a simple text message');
$msg->header->SAM_REPLY_TO = 'queue://receive/test';
$correlid = $conn->send('queue://send/test', $msg);

if (!$correlid) {
  // The Send failed!
  echo "Send failed ($conn->errno) $conn->error";
} else {
  $resp = $conn->receive('queue://receive/test', array(SAM_CORRELID => $correlid));
}
?>

Publish/Subscribe and suscriptions to topics

SAM allows messages to be sent either to queues or, for WebSphere MQ and WPM, to publish/subscribe topics. A topic desintation is specified to SAM in the usual way, i.e. in the form 'topic://fred', rather than the form 'queue://AQUEUE' used for point to point operation. To use publish/subscribe it is simply necessary to specify the correct broker name on the SAMConnect "connect" call and the desired topic in the destination argument to the SAMConnect "send" and "receive" calls. The PHP interface is otherwise identical to the point to point model.

By default, SAM creates non-durable subscriptions when using publish/subscribe. This means that if a client application is inactive when messages are published to a topic, then it will not receive them when it subsequently restarted. SAM does also allow durable subscriptions to be made to topics when using WPM or WebSphere MQ publish/subscribe. The purpose of these subscriptions is to allow data to be received by a client application even if that client was not active at the time the data was published.

Durable subscriptions are specified by using the SAMConnect "subscribe" call. This method takes the destination topic as an input parameter and returns a subscription identifier that may be used on subsequent "receive" calls. When the subscription is no longer required the SAMConnection "unsubscribe" method should be used to delete the subscription.

Example 9. Creating a durable subscription to a topic


<?php

$subName = $conn->subscribe('topic://A');

if (!$subName) {
   echo "Subscribe failed";
} else {
   # Subscribe was OK
   // ...
}
?>

Example 10. Subscribing to a topic using a WebSphere Platform Messaging (WPM) server


<?php
$conn = new SAMConnection();
// Note: For pub/sub on WPM, when connecting the name of a messaging engine
//   to hold the durable subscription (SAM_WPM_DUR_SUB_HOME) must be specified.
$conn->connect(SAM_WMQ, array(SAM_ENDPOINTS => 'localhost:7278:BootstrapBasicMessaging',
                              SAM_BUS => 'Bus1',
                              SAM_TARGETCHAIN => 'InboundBasicMessaging'
                              SAM_WPM_DUR_SUB_HOME => 'MyMachineNode01.server1-Bus1'));

$subName = $conn->subscribe('topic://A');

if (!$subName) {
   echo "Subscribe failed";
} else {
   # Subscribe was OK
   // ...
}
?>

Example 11. Receiving published data using a durable subscription


<?php

$msg = $conn->receive($subName);
if ($msg) {
   echo "Received a message OK";
} else {
   echo "The receive failed";
}

?>

Example 12. Deleting a durable subscription to a topic


<?php

if (!$conn->unsubscribe($subName)) {
   echo "Unsubscribe failed";
}

?>

Error handling

All SAMConnection methods that provide access to messaging operations return FALSE if an error occurred in processing the request. In addition the SAMConnection object has two properties, "errno" and "error", that provide respectively the error number and text description of the last error to occur on the connection.

Example 13. Handling an error from a method that returns no result


<?php
   if (!$conn->commit()) {
     // The commit failed!
     echo "Commit failed ($conn->errno) $conn->error";
   }
?>

Example 14. Handling an error from a method that returns a result


<?php
$correlid = $conn->send('queue://send/test', $msg);

if (!$correlid) {
  // The Send failed!
  echo "Send failed ($conn->errno) $conn->error";
} else {
  ...
}
?>

Predefined Classes

SAMConnection

Object representing a connection to a Messaging Server

Constructor

new SAMConnection - construct a new connection object to allow connection to a messaging infrastructure.

Methods

commit - a method that commits (successfully completes) an in-flight unit of work.
connect - a method that connects a PHP script to a messaging server.
disconnect - a method that disconnects a PHP script from a messaging server.
isConnected - a method that checks whether a PHP script is connected to a messaging server.
peek - a method that receives a message from a queue without removing it from the queue.
peekAll - a method that receives one or messages from a queue without removing them from the queue.
receive - a method that receives a message from a queue or subscription.
remove - a method that removes a message from a queue.
rollback - a method that cancels (rolls back) an in-flight unit of work.
send - a method that sends a message to a queue or posts to a topic
setDebug - a method that switches additional debugging output on or off
subscribe - a method that creates a subscription to one or more topics
unsubscribe - a method that destroys a subscription to one or more topics

Properties

errno - the numeric error code for the last encountered error on this connection. This property is set to 0 if the last operation was successful.
error - the text description for the last encountered error on this connection

SAMMessage

Object representing a message to be sent or received

Constructor

new SAMMessage - construct a new message.

Properties

body - the body of the message.
header - the header properties of the message.

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

SAM_AUTO (string): Automatic behaviour
SAM_BOOLEAN (string): Type specifier used when setting properties on SAM_Message objects.
SAM_BUS (string): Connect attribute used to set the name of the enterprise service bus to connect to.
SAM_BYTE (string): Type specifier used when setting properties on SAM_Message objects.
SAM_BYTES (string): Message body type descriptor.
SAM_CORRELID (string): Attribute used on receive, send and remove requests to identify specific messages.
SAM_DELIVERYMODE (string): Message header property.
SAM_DOUBLE (string): Type specifier used when setting properties on SAM_Message objects.
SAM_ENDPOINTS (string): Connect attribute used to define the possible endpoints to connect to.
SAM_FLOAT (string): Type specifier used when setting properties on SAM_Message objects.
SAM_HOST (string): Connect attribute used to set the hostname of the required messaging server.
SAM_INT (string): Type specifier used when setting properties on SAM_Message objects.
SAM_LONG (string): Type specifier used when setting properties on SAM_Message objects.
SAM_MANUAL (string): Manual (script controlled) behaviour
SAM_MESSAGEID (string): Attribute used on receive and remove requests to identify specific messages.
SAM_MQTT (string): Connect protocol definition for selecting the MQTT (MQ Telemetry Transport) protocol.
SAM_MQTT_CLEANSTART (bool): Optional connect option to indicate to an MQTT server that all previous connection data for this client should be removed and that subscriptions should be deleted when the client disconnects explicitly or unexpectedly.
SAM_NON_PERSISTENT (string): Connect attribute value used to request messages are not made persistent on the messaging server.
SAM_PASSWORD (string): Connect attribute used to define the password to be used for the user account being used to connect to a messaging server that requires authorisation for connections.
SAM_PERSISTENT (string): Connect attribute value used to request messages are made persistent on the messaging server to protect against loss of messages in the event of failure.
SAM_PORT (string): Connect attribute used to set the port number on which to communicate with the messaging server.
SAM_PRIORITY (string): Option name used on send requests to specify a delivery priority value.
SAM_REPLY_TO (string): Message propery used to specify the queue identity on to which the script expects response or reply messages to be posted.
SAM_RTT (string): Connect protocol definition for selecting the IBM Realtime Transport protocol for communication with a business integration messaging server.
SAM_STRING (string): Type specifier used when setting properties on SAM_Message objects.
SAM_TARGETCHAIN (string): Connection attribute used to set the required target chain identifier.
SAM_TEXT (string): Message body type descriptor.
SAM_TIMETOLIVE (string): Message send option name used to specify the length of time a message should be retained in milliseconds.
SAM_TRANSACTIONS (string): Connection attribute used to set required transactional behaviour. May be set to SAM_AUTO (default) or SAM_MANUAL.
SAM_USERID (string): Connect attribute used to define the account to being used to connect to a messaging server that requires authorisation for connections.
SAM_WAIT (string): Receive property used to specify the wait timeout to be used when receiving a message from a queue or subscription.
SAM_WMQ (string): Connect protocol definition for selecting the IBM WebSphere MQSeries protocol for communication with the desired messaging server.
SAM_WMQ_BINDINGS (string): Connect protocol definition for selecting the IBM WebSphere MQSeries protocol for communication with a local messaging server.
SAM_WMQ_CLIENT (string): Connect protocol definition for selecting the IBM WebSphere MQSeries protocol for communication with a remote messaging server.
SAM_WMQ_TARGET_CLIENT (string): Option name used on send requests to specify the target client mode. This can either be default to 'jms' or 'mq'. The default is 'jms' which means an RFH2 header is sent with the message whereas the 'mq' setting means no RFH2 is included.
SAM_WPM (string): Connect protocol definition for selecting the IBM WebSphere Platform Messaging protocol for communication with a WebSphere Application Server messaging server.

Table of Contents
SAMConnection->commit() -- Commits (completes) the current unit of work.
SAMConnection->connect() -- Establishes a connection to a Messaging Server
SAMConnection->__construct() -- Creates a new connection to a Messaging Server
SAMConnection->disconnect() -- Disconnects from a Messaging Server
SAMConnection->errno -- Contains the unique numeric error code of the last executed SAM operation.
SAMConnection->error -- Contains the text description of the last failed SAM operation.
SAMConnection->isConnected() -- Queries whether a connection is established to a Messaging Server
SAMConnection->peek() -- Read a message from a queue without removing it from the queue.
SAMConnection->peekAll() -- Read one or more messages from a queue without removing it from the queue.
SAMConnection->receive() -- Receive a message from a queue or subscription.
SAMConnection->remove() -- Remove a message from a queue.
SAMConnection->rollback() -- Cancels (rolls back) an in-flight unit of work.
SAMConnection->send() -- Send a message to a queue or publish an item to a topic.
SAMConnection::setDebug() -- Turn on or off additional debugging output.
SAMConnection->subscribe() -- Create a subscription to a specified topic.
SAMConnection->unsubscribe() -- Cancel a subscription to a specified topic.
SAMMessage->body -- The body of the message.
SAMMessage->__construct() -- Creates a new Message object
SAMMessage->header -- The header properties of the message.