Starting Brokers and Clients

3 Starting Brokers and Clients

After installing Message Queue and performing some preparatory steps, you can begin starting brokers and clients. A broker’s configuration is governed by a set of configuration files, which can be overridden by command line options passed to the Broker utility (imqbrokerd); see Configuring a Broker for more information.

This chapter contains the following sections:

Preparing System Resources
Starting Brokers
Deleting a Broker Instance
Starting Clients

Preparing System Resources

Before starting a broker, there are two preliminary system-level tasks to perform: synchronizing system clocks and (on the Solaris or Linux platform) setting the file descriptor limit. The following sections describe these tasks.

Synchronizing System Clocks

Before starting any brokers or clients, it is important to synchronize the clocks on all hosts that will interact with the Message Queue system. Synchronization is particularly crucial if you are using message expiration (time-to-live). Time stamps from clocks that are not synchronized could prevent message expiration from working as expected and prevent the delivery of messages. Synchronization is also crucial for broker clusters.

Configure your systems to run a time synchronization protocol, such as Simple Network Time Protocol (SNTP). Time synchronization is generally supported by the xntpd daemon on Solaris and Linux, and by the W32Time service on Windows. (See your operating system documentation for information about configuring this service.) After the broker is running, avoid setting the system clock backward.

Setting the File Descriptor Limit

On the Solaris and Linux platforms, the shell in which a client or broker is running places a soft limit on the number of file descriptors that a process can use. In Message Queue, each connection a client makes, or a broker accepts, uses one of these file descriptors. Each physical destination that has persistent messages also uses a file descriptor.

As a result, the file descriptor limit constrains the number of connections a broker or client can have. By default, the maximum is 256 connections on Solaris or 1024 on Linux. (In practice, the connection limit is actually lower than this because of the use of file descriptors for persistent data storage.) If you need more connections than this, you must raise the file descriptor limit in each shell in which a client or broker will be executing. For information on how to do this, see the man page for the ulimit command.

Starting Brokers

You can start a broker either interactively, using the Message Queue command line utilities or the Windows Start menu, or by arranging for it to start automatically at system startup. The following sections describe how.

Starting Brokers Interactively

You can start a broker interactively from the command line, using the Broker utility (imqbrokerd). (Alternatively, on Windows, you can start a broker from the Start menu.) You cannot use the Administration Console (imqadmin) or the Command utility (imqcmd) to start a broker; the broker must already be running before you can use these tools.

On the Solaris and Linux platforms, a broker instance must always be started by the same user who initially started it. Each broker instance has its own set of configuration properties and file-based persistent data store. When the broker instance first starts, Message Queue uses the user’s file creation mode mask (umask) to set permissions on directories containing the configuration information and persistent data for that broker instance.

A broker instance has the instance name imqbroker by default. To start a broker from the command line with this name and the default configuration, simply use the command

imqbrokerd

This starts a broker instance named imqbroker on the local machine, with the Port Mapper at the default port of 7676 (see Port Mapper).

To specify an instance name other than the default, use the`-name` option to the imqbrokerd command. The following command starts a broker with the instance name myBroker:

imqbrokerd  -name myBroker

Other options are available on the imqbrokerd command line to control various aspects of the broker’s operation. See Broker Utility for complete information on the syntax, subcommands, and options of the imqbrokerd command. For a quick summary of this information, enter the following command:

imqbrokerd  -help

For example, the following command uses the`-tty` option to send errors and warnings to the command window (standard output):

imqbrokerd  -name myBroker  -tty

You can also use the -D option on the command line to override the values of properties specified in the broker’s instance configuration file (config.properties). The instance configuration file is described under Modifying Configuration Files. The following example sets a broker’s imq.jms.max_threads property, raising the maximum number of threads available to the jms connection service to 2000:

imqbrokerd  -name myBroker  -Dimq.jms.max_threads=2000

Starting Brokers Automatically

Instead of starting a broker explicitly from the command line, you can set it up to start automatically at system startup. How you do this depends on the platform (Solaris, Linux, or Windows) on which you are running the broker:

Automatic Broker Startup on the Solaris Platforms
Automatic Broker Startup on the Linux Platform
Automatic Broker Startup on Windows

Automatic Broker Startup on the Solaris Platforms

The method for enabling automatic startup on the Solaris 10 platforms is different from that for Solaris 9. Both are described below.

Automatic Broker Startup on the Solaris 9 Platform

On Solaris 9 operating system, scripts that enable automatic startup are placed in the /etc/rc* directory tree during Message Queue installation. To enable the use of these scripts, you must edit the configuration file imqbrokerd.conf (located in the IMQ_HOME/etc/ directory) as follows:

To start the broker automatically at system startup, set the AUTOSTART property to YES.
To have the broker restart automatically after an abnormal exit, set the RESTART property to YES.
To set startup command line arguments for the broker, specify one or more values for the ARGS property.

To disable automatic broker startup at system startup, edit the configuration file /etc/imq/imqbrokerd.conf and set the AUTOSTART property to NO.

Automatic Broker Startup on the Solaris 10 Platform

Rather than using an rc file to implement automatic broker startup when a computer reboots, the following procedure makes use of the Solaris 10 Service Management Facility (SMF).

For more information on using the Service Management Facility, please refer to Solaris 10 documentation.

To Implement Automatic Broker Startup on Solaris 10 OS

Copy and change permissions on the mqbroker startup script.
# cp /var/svc/manifest/application/sun/mq/mqbroker /lib/svc/method
# chmod 555 /lib/svc/method/mqbroker
Import the mqbroker service into the SMF repository.
# svccfg import /var/svc/manifest/application/sun/mq/mqbroker.xml
Verify that the import was successful by checking the state of the mqbroker service.
# svcs mqbroker
Output resembles the following:

STATE STIME FMRI
disabled 16:22:50 svc:/application/sun/mq/mqbroker:default

The service is initially shown as disabled. 4. Eanable the mqbroker service.
# svcadm enable svc:/application/sun/mq/mqbroker:default
Enabling the mqbroker service will start the imqbrokerd process. A reboot will subsequently restart the broker. 5. Configure the mqbroker service to pass any desired arguments to the imqbrokerd command.
The options/broker_args property is used to pass arguments to`imqbrokerd`. For example to add -loglevel DEBUGHIGH, do the following:

# svccfg
svc:> select svc:/application/sun/mq/mqbroker
svc:/application/sun/mq/mqbroker> setprop options/broker_args="-loglevel DEBUGHIGH"
svc:/application/sun/mq/mqbroker> exit

To Disable Automatic Broker Startup on Solaris 10 OS

Disable the mqbroker service.
# svcadm disable svc:/application/sun/mq/mqbroker:default
A subsequent reboot will not restart the broker.

Automatic Broker Startup on the Linux Platform

On Linux systems, scripts that enable automatic startup are placed in the /etc/rc* directory tree during Message Queue installation. To enable the use of these scripts, you must edit the configuration file imqbrokerd.conf (located in the IMQ_HOME/etc/ directory) as follows:

To start the broker automatically at system startup, set the AUTOSTART property to YES.
To have the broker restart automatically after an abnormal exit, set the RESTART property to YES.
To set startup command line arguments for the broker, specify one or more values for the ARGS property.

To disable automatic broker startup at system startup, edit the configuration file /etc/opt/sun/mq/imqbrokerd.conf and set the AUTOSTART property to NO.

Automatic Broker Startup on Windows

To start a broker automatically at Windows system startup, you must define the broker as a Windows service. The broker will then start at system startup time and run in the background until system shutdown. Consequently, you will not need to use the Message Queue Broker utility (imqbrokerd) unless you want to start an additional broker.

A system can have no more than one broker running as a Windows service. The Windows Task Manager lists such a broker as two executable processes:

The native Windows service wrapper, imqbrokersvc.exe
The Java runtime that is running the broker

You can install a broker as a service when you install Message Queue on a Windows system. After installation, you can use the Service Administrator utility (imqsvcadmin) to perform the following operations:

Add a broker as a Windows service
Determine the startup options for the broker service
Disable a broker from running as a Windows service

To pass startup options to the broker, use the -args option to the imqsvcadmin command. This works the same way as the imqbrokerd command’s -D option, as described under Starting Brokers. Use the Command utility (imqcmd) to control broker operations as usual.

See Service Administrator Utility for complete information on the syntax, subcommands, and options of the imqsvcadmin command.

Reconfiguring the Broker Service

The procedure for reconfiguring a broker installed as a Windows service is as follows:

To Reconfigure a Broker Running as a Windows Service

Stop the service:
From the Settings submenu of the Windows Start menu, choose Control Panel.
Open the Administrative Tools control panel.
Run the Services tool by selecting its icon and choosing Open from the File menu or the pop-up context menu, or simply by double-clicking the icon.
Under Services (Local), select the Message Queue Broker service and choose Properties from the Action menu.
Alternatively, you can right-click on Message Queue Broker and choose Properties from the pop-up context menu, or simply double-click on Message Queue Broker. In either case, the Message Queue Broker Properties dialog box will appear.
Under the General tab in the Properties dialog, click Stop to stop the broker service.
Remove the service.
On the command line, enter the command

imqsvcadmin remove

Reinstall the service, specifying different broker startup options with the -args option or different Java version arguments with the -vmargs option.
For example, to change the service’s host name and port number to broker1 and 7878, you could use the command

imqsvcadmin install  -args "-name broker1  -port 7878"

Using an Alternative Java Runtime

You can use either the imqsvcadmin command’s -javahome or -jrehome option to specify the location of an alternative Java runtime. (You can also specify these options in the Start Parameters field under the General tab in the service’s Properties dialog window.)

Note	The Start Parameters field treats the backslash character (`\`) as an escape character, so you must type it twice when using it as a path delimiter: for example, `-javahome c:\\j2sdk1.4.0`

Displaying Broker Service Startup Options

To determine the startup options for the broker service, use the imqsvcadmin query command, as shown in Example 3-1.

Example 3-1 Displaying Broker Service Startup Options

imqsvcadmin query

Service Message Queue Broker is installed.
Display Name: Message Queue Broker
Start Type: Automatic
Binary location: C:\Sun\MessageQueue\bin\imqbrokersvc.exe
JavaHome: c:\j2sdk1.4.0
Broker Args: -name broker1 -port 7878

Disabling a Broker From Running as a Windows Service

To disable a broker from running as a Windows service, use the command

imqcmd shutdown bkr

to shut down the broker, followed by

imqsvcadmin remove

to remove the service.

Alternatively, you can use the Windows Services tool, reached via the Administrative Tools control panel, to stop and remove the broker service.

Restart your computer after disabling the broker service.

Troubleshooting Service Startup Problems

If you get an error when you try to start a broker as a Windows service, you can view error events that were logged:

To See Logged Service Error Events

Open the Windows Administrative Tools control panel.
Start the Event Viewer tool.
Select the Application event log.
Choose Refresh from the Action menu to display any error events.

Deleting a Broker Instance

To delete a broker instance, use the imqbrokerd command with the -remove option:

imqbrokerd  [options…]-remove instance

For example, if the name of the broker is myBroker, the command would be

imqbrokerd  -name myBroker  -remove instance

The command deletes the entire instance directory for the specified broker.

See Broker Utility for complete information on the syntax, subcommands, and options of the imqbrokerd command. For a quick summary of this information, enter the command

imqbrokerd  -help

Starting Clients

Before starting a client application, obtain information from the application developer about how to set up the system. If you are starting Java client applications, you must set the CLASSPATH variable appropriately and make sure you have the correct .jar files installed. The Open Message Queue Developer’s Guide for Java Clients contains information about generic steps for setting up the system, but your developer may have additional information to provide.

To start a Java client application, use the following command line format:

java clientAppName

To start a C client application, use the format supplied by the application developer (see "Building and Running C Clients" in Open Message Queue Developer’s Guide for C Clients).

The application’s documentation should provide information on attribute values that the application sets; you may want to override some of these from the command line. You may also want to specify attributes on the command line for any Java client that uses a Java Naming and Directory Interface (JNDI) lookup to find its connection factory. If the lookup returns a connection factory that is older than the application, the connection factory may lack support for more recent attributes. In such cases, Message Queue sets those attributes to default values; if necessary, you can use the command line to override these default values.

To specify attribute values from the command line for a Java application, use the following syntax:

java  [ [-Dattribute=value] … ]clientAppName

The value for attribute must be a connection factory administered object attribute, as described in Administered Object Attribute Reference. If there is a space in the value, put quotation marks around the

attribute=value

part of the command line.

The following example starts a client application named MyMQClient , connecting to a broker on the host OtherHost at port 7677:

java  -DimqAddressList=mq://OtherHost:7677/jms  MyMQClient

The host name and port specified on the command line override any others set by the application itself.

In some cases, you cannot use the command line to specify attribute values. An administrator can set an administered object to allow read access only, or an application developer can code the client application to do so. Communication with the application developer is necessary to understand the best way to start the client program.