# Qpid Java FAQ

## Purpose

Here are a list of commonly asked questions and answers. Click on the the bolded questions for the answer to unfold. If you have any questions which are not on this list, please email our qpid-user list.

### What is Qpid ?

The java implementation of Qpid is a pure Java message broker that implements the AMQP protocol. Essentially, Qpid is a robust, performant middleware component that can handle your messaging traffic.

It currently supports the following features:

- High performance header-based routing for messages

- All features required by the JMS 1.1 specification. Qpid passes all tests in the Sun JMS compliance test suite

- Transaction support

- Persistence using the high performance Berkeley DB Java Edition. The persistence layer is also pluggable should an alternative implementation be required. The BDB store is available from the page

- Pluggable security using SASL. Any Java SASL provider can be used

- Management using JMX and a custom management console built using Eclipse RCP

- Naturally, interoperability with other clients including the Qpid .NET, Python, Ruby and C++ implementations

### Why am I getting a ConfigurationException at broker startup ?

#### InvocationTargetException

If you get a java.lang.reflect.InvocationTargetException on startup, wrapped as ConfigurationException like this:

    Error configuring message broker: org.apache.commons.configuration.ConfigurationException: java.lang.reflect.InvocationTargetException
    2008-09-26 15:14:56,529 ERROR [main] server.Main (Main.java:206) - Error configuring message broker: org.apache.commons.configuration.ConfigurationException: java.lang.reflect.InvocationTargetException
    org.apache.commons.configuration.ConfigurationException: java.lang.reflect.InvocationTargetException
    at org.apache.qpid.server.security.auth.database.ConfigurationFilePrincipalDatabaseManager.initialisePrincipalDatabase(ConfigurationFilePrincipalDatabaseManager.java:158)
    at org.apache.qpid.server.security.auth.database.ConfigurationFilePrincipalDatabaseManager.initialisePrincipalDatabases(ConfigurationFilePrincipalDatabaseManager.java:87)
    at org.apache.qpid.server.security.auth.database.ConfigurationFilePrincipalDatabaseManager.<init>(ConfigurationFilePrincipalDatabaseManager.java:56)
    at org.apache.qpid.server.registry.ConfigurationFileApplicationRegistry.initialise(ConfigurationFileApplicationRegistry.java:117)
    at org.apache.qpid.server.registry.ApplicationRegistry.initialise(ApplicationRegistry.java:79)
    at org.apache.qpid.server.registry.ApplicationRegistry.initialise(ApplicationRegistry.java:67)
    at org.apache.qpid.server.Main.startup(Main.java:260)
    at org.apache.qpid.server.Main.execute(Main.java:196)
    at org.apache.qpid.server.Main.<init>(Main.java:96)
    at org.apache.qpid.server.Main.main(Main.java:454)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)
    Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.qpid.server.security.auth.database.ConfigurationFilePrincipalDatabaseManager.initialisePrincipalDatabase(ConfigurationFilePrincipalDatabaseManager.java:148)

.. then it means you have a missing password file.

You need to create a password file for your deployment and update your config.xml to reflect the location of the password file for your instance.

The config.xml can be a little confusing in terms of element names and file names for passwords.

To do this, you need to edit the passwordDir element for the broker, which may have a comment to that effect:

    <passwordDir><!-- Change to the location --></passwordDir>

The file should be named passwd by default but if you want to you can change this by editing this element:

    <value>${passwordDir}/passwd</value>

#### Cannot locate configuration source null/virtualhosts.xml

If you get this message, wrapped inside a ConfigurationException then you've come across a known issue, see JIRA

The work around is to use a qualified path as the parameter value for your -c option, rather than (as you migth be) starting the broker from your installed etc directory. Even going up one level and using a path relative to your Â£QPID_HOME directory would sort this e.g qpid-server -c ./etc/myconfig.xml

### How do I run the Qpid broker ?

The broker comes with a script for unix/linux/cygwin called qpid-server, which can be found in the bin directory of the installed package. This command can be executed without any paramters and will then use the default configuration file provided on install.

For the Windows OS, please use qpid-server.bat.

There's no need to set your classpath for QPID as the scripts take care of that by adding jar's with classpath defining manifest files to your classpath.

For more information on running the broker please see our page.

### How can I create a connection using a URL ?

Please see the documentation.

### How do I represent a JMS Destination string with QPID ?

#### Queues

A queue can be created in QPID using the following URL format.

direct://amq.direct/<Destination>/<Queue Name>

For example: direct://amq.direct/<Destination>/simpleQueue

Queue names may consist of any mixture of digits, letters, and underscores.

The is described in more detail on it's own page.

#### Topics

A topic can be created in QPID using the following URL format.

topic://amq.topic/<Topic Subscription>/

The topic subscription may only contain the letters A-Z and a-z and digits 0-9.

The topic subscription is formed from a series of words that may only contain the letters A-Z and a-z and digits 0-9. The words are delimited by dots. Each dot represents a new level.

For example: stocks.nyse.ibm

Wildcards can be used on subscription with the following meaning.

- match a single level # match zero or more levels

For example: With two clients 1 - stocks.*.ibm 2 - stocks.#.ibm

Publishing stocks.nyse.ibm will be received by both clients but stocks.ibm and stocks.world.us.ibm will only be received by client 2.

The topic currently does not support wild cards.

### How do I connect to the broker using JNDI ?

see

### I'm using Spring and Weblogic - can you help me with the configuration for moving over to Qpid ?

Here is a donated Spring configuration file appContext.zip which shows the config for Qpid side by side with Weblogic. HtH !

### How do I configure the logging level for Qpid ?

The system property

    amqj.logging.level

can be used to configure the logging level. For the broker, you can use the environment variable AMQJ_LOGGING_LEVEL which is picked up by the qpid-run script (called by qpid-server to start the broker) at runtime.

For client code that you've written, simply pass in a system property to your command line to set it to the level you'd like i.e.

    -Damqj.logging.level=INFO

The log level for the broker defaults to INFO if the env variable is not set, but you may find that your log4j properties affect this. Setting the property noted above should address this.

### How can I configure my application to use Qpid client logging?

If you don't already have a logging implementation in your classpath you should add slf4-log4j12-1.4.0.jar and log4j-1.2.12.jar.

### How can I configure the broker ?

The broker configuration is contained in the <installed-dir>/etc/config.xml file. You can copy and edit this file and then specify your own configuration file as a parameter to the startup script using the -c flag i.e. qpid-server -c <your_config_file's_path>

For more detailed information on configuration, please see

### What ports does the broker use?

The broker defaults to use port 5672 at startup for AMQP traffic. If the management interface is enabled it starts on port 8999 by default.

The JMX management interface actually requires 2 ports to operate, the second of which is indicated to the client application during connection initiation to the main (default: 8999) port. Previously this second port has been chosen at random during broker startup, however since Qpid 0.5 this has been fixed to a port 100 higher than the main port(ie Default:9099) in order to ease firewall navigation.

### How can I change the port the broker uses at runtime ?

The broker defaults to use port 5672 at startup for AMQP traffic. The broker also uses port 8999 for the JMX Management interface.

To change the AMQP traffic port use the -p flag at startup. To change the management port use -m i.e. qpid-server -p <port_number_to_use> -m <port_number_to_use>

Use this to get round any issues on your host server with port 5672/8999 being in use/unavailable.

For additional details on what ports the broker uses see FAQ entry. For more detailed information on configuration, please see

### What command line options can I pass into the qpid-server script ?

The following command line options are available:

The following options are available:

Command Line Options

Option | Long Option | Description
b | bind | Bind to the specified address overriding any value in the config file
c | config | Use the given configuration file
h | help | Prints list of options
l | logconfig | Use the specified log4j.xml file rather than that in the etc directory
m | mport | Specify port to listen on for the JMX Management. Overrides value in config file
p | port | Specify port to listen on. Overrides value in config file
v | version | Print version information and exit
w | logwatch | Specify interval for checking for logging config changes. Zero means no checking

### How do I authenticate with the broker ? What user id & password should I use ?

You should login as user guest with password guest

### How do I create queues that will always be instantiated at broker startup ?

You can configure queues which will be created at broker startup by tailoring a copy of the virtualhosts.xml file provided in the installed qpid-version/etc directory.

So, if you're using a queue called 'devqueue' you can ensure that it is created at startup by using an entry something like this:

    <virtualhosts>
      <default>test</default>
      <virtualhost>
       <name>test</name>
       <test>
       <queue>
          <name>devqueue</name>
          <devqueue>
            <exchange>amq.direct</exchange>
            <maximumQueueDepth>4235264</maximumQueueDepth>  <!-- 4Mb -->
            <maximumMessageSize>2117632</maximumMessageSize> <!-- 2Mb -->
            <maximumMessageAge>600000</maximumMessageAge>  <!-- 10 mins -->
          </devqueue>
       </queue>
       </test>
      </virtualhost>
    </virtualhosts>

Note that the name (in thie example above the name is 'test') element should match the virtualhost that you're using to create connections to the broker. This is effectively a namespace used to prevent queue name clashes etc. You can also see that we've set the 'test' virtual host to be the default for any connections which do not specify a virtual host (in the <default> tag).

You can amend the config.xml to point at a different virtualhosts.xml file by editing the <virtualhosts/> element.

So, for example, you could tell the broker to use a file in your home directory by creating a new config.xml file with the following entry:

<virtualhosts>/home/myhomedir/virtualhosts.xml</virtualhosts>

You can then pass this amended config.xml into the broker at startup using the -c flag i.e. qpid-server -c <path>/config.xml

### How do I create queues at runtime?

Queues can be dynamically created at runtime by creating a consumer for them. After they have been created and bound (which happens automatically when a JMS Consumer is created) a publisher can send messages to them.

### How do I tune the broker?

There are a number of tuning options available, please see the page for more information.

### Where do undeliverable messages end up ?

At present, messages with an invalid routing key will be returned to the sender. If you register an exception listener for your publisher (easiest to do by making your publisher implement the ExceptionListener interface and coding the onException method) you'll see that you end up in onException in this case. You can expect to be catching a subclass of org.apache.qpid.AMQUndeliveredException.

### Can I configure the name of the Qpid broker log file at runtime ?

If you simply start the Qpid broker using the default configuration, then the log file is written to $QPID_WORK/log/qpid.log

This is not ideal if you want to run several instances from one install, or acrhive logs to a shared drive from several hosts.

To make life easier, there are two optional ways to configure the naming convention used for the broker log.

#### Setting a prefix or suffix

Users should set the following environment variables before running qpid-server:

QPID_LOG_PREFIX - will prefix the log file name with the specified value e.g. if you set this value to be the name of your host (for example) it could look something like host123qpid.log

QPID_LOG_SUFFIX - will suffix the file name with the specified value e.g. if you set this value to be the name of your application (for example) if could look something like qpidMyApp.log

#### Including the PID

Setting either of these variables to the special value PID will introduce the process id of the java process into the file name as a prefix or suffix as specified**

### My client application appears to have hung?

The client code currently has various timeouts scattered throughout the code. These can cause your client to appear like it has hung when it is actually waiting for the timeout ot compelete. One example is when the broker becomes non-responsive, the client code has a hard coded 2 minute timeout that it will wait when closing a connection. These timeouts need to be consolidated and exposed. see

### How do I contact the Qpid team ?

For general questions, please subscribe to the users@qpid.apache.org mailing list.

For development questions, please subscribe to the dev@qpid.apache.org mailing list.

More details on these lists are available on our page.

### How can I change a user's password while the broker is up ?

You can do this via the . To do this simply log in to the management console as an admin user (you need to have created an admin account in the jmxremote.access file first) and then select the 'UserManagement' mbean. Select the user in the table and click the Set Password button. Alternatively, update the password file and use the management console to reload the file with the button at the bottom of the 'UserManagement' view. In both cases, this will take effect when the user next logs in i.e. will not cause them to be disconnected if they are already connected.

For more information on the Management Console please see our

### How do I know if there is a consumer for a message I am going to send?

Knowing that there is a consumer for a message is quite tricky. That said using the qpid.jms.Session#createProducer with immediate and mandatory set to true will get you part of the way there.

If you are publishing to a well known queue then immediate will let you know if there is any consumer able to pre-fetch that message at the time you send it. If not it will be returned to you on your connection listener.

If you are sending to a queue that the consumer creates then the mandatory flag will let you know if they have not yet created that queue.

These flags will not be able to tell you if the consuming application has received the message and is able to process it.

### How can I inspect the contents of my MessageStore?

There are two possibilities here:

1) The management console can be used to interogate an active broker and browse the contents of a queue.See the page for further details.

2) The can be used to inspect the contents of a persistent message store. Note: this can currently only be used when the broker is offline.

### Why are my transient messages being so slow?

You should check that you aren't sending persistent messages, this is the default. If you want to send transient messages you must explicitly set this option when instantiating your MessageProducer or on the send() method.

### Why does my producer fill up the broker with messages?

The Java broker does not currently implement producer flow control. Publishes are currently asynchronous, so there is no ability to rate limit this automatically. While this is something which will be addressed in the future, it is currently up to applications to ensure that they do not publish faster than the messages are being consumed for signifcant periods of time.

### The broker keeps throwing an OutOfMemory exception?

The broker can no longer store any more messages in memory. This is particular evident if you are using the MemoryMessageStore. To alleviate this issue you should ensure that your clients are consuming all the messages from the broker.

You may also want to increase the memory allowance to the broker though this will only delay the exception if you are publishing messages faster than you are consuming. See for details of changing the memory settings.

### Why am I getting a broker side exception when I try to publish to a queue or a topic ?

If you get a stack trace like this when you try to publish, then you may have typo'd the exchange type in your queue or topic declaration. Open your virtualhosts.xml and check that the

    <exchange>amq.direct</exchange>

    2009-01-12 15:26:27,957 ERROR [pool-11-thread-2] protocol.AMQMinaProtocolSession (AMQMinaProtocolSession.java:365) - Unexpected exception while processing frame. Closing connection.
    java.lang.NullPointerException
            at org.apache.qpid.server.security.access.PrincipalPermissions.authorise(PrincipalPermissions.java:398)
            at org.apache.qpid.server.security.access.plugins.SimpleXML.authorise(SimpleXML.java:302)
            at org.apache.qpid.server.handler.QueueBindHandler.methodReceived(QueueBindHandler.java:111)
            at org.apache.qpid.server.handler.ServerMethodDispatcherImpl.dispatchQueueBind(ServerMethodDispatcherImpl.java:498)
            at org.apache.qpid.framing.amqp_8_0.QueueBindBodyImpl.execute(QueueBindBodyImpl.java:167)
            at org.apache.qpid.server.state.AMQStateManager.methodReceived(AMQStateManager.java:204)
            at org.apache.qpid.server.protocol.AMQMinaProtocolSession.methodFrameReceived(AMQMinaProtocolSession.java:295)
            at org.apache.qpid.framing.AMQMethodBodyImpl.handle(AMQMethodBodyImpl.java:93)
            at org.apache.qpid.server.protocol.AMQMinaProtocolSession.frameReceived(AMQMinaProtocolSession.java:235)
            at org.apache.qpid.server.protocol.AMQMinaProtocolSession.dataBlockReceived(AMQMinaProtocolSession.java:191)
            at org.apache.qpid.server.protocol.AMQPFastProtocolHandler.messageReceived(AMQPFastProtocolHandler.java:244)
            at org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.messageReceived(AbstractIoFilterChain.java:703)
            at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(AbstractIoFilterChain.java:362)
            at org.apache.mina.common.support.AbstractIoFilterChain.access$1200(AbstractIoFilterChain.java:54)
            at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceived(AbstractIoFilterChain.java:800)
            at org.apache.qpid.pool.PoolingFilter.messageReceived(PoolingFilter.java:371)
            at org.apache.mina.filter.ReferenceCountingIoFilter.messageReceived(ReferenceCountingIoFilter.java:96)
            at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(AbstractIoFilterChain.java:362)
            at org.apache.mina.common.support.AbstractIoFilterChain.access$1200(AbstractIoFilterChain.java:54)
            at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceived(AbstractIoFilterChain.java:800)
            at org.apache.mina.filter.codec.support.SimpleProtocolDecoderOutput.flush(SimpleProtocolDecoderOutput.java:60)
            at org.apache.mina.filter.codec.QpidProtocolCodecFilter.messageReceived(QpidProtocolCodecFilter.java:174)
            at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(AbstractIoFilterChain.java:362)
            at org.apache.mina.common.support.AbstractIoFilterChain.access$1200(AbstractIoFilterChain.java:54)
            at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceived(AbstractIoFilterChain.java:800)
            at org.apache.qpid.pool.Event$ReceivedEvent.process(Event.java:86)
            at org.apache.qpid.pool.Job.processAll(Job.java:110)
            at org.apache.qpid.pool.Job.run(Job.java:149)
            at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
            at java.lang.Thread.run(Thread.java:619)

### Why is there a lot of AnonymousIoService threads

These threads are part of the thread pool used by Mina to process the socket. In the future we may provide tuning guidelines but at this point we have seen no performance implications from the current configuration. As the threads are part of a pool they should remain inactive until required.

### "unable to certify the provided SSL certificate using the current SSL trust store" when connecting the Management Console to the broker.

You have not configured the console's SSL trust store properly, see for more details.

### Can a use TCP_KEEPALIVE or AMQP heartbeating to keep my connection open?

See