Managing a Broker

5 Managing a Broker

This chapter explains how to use the Message Queue Command utility (imqcmd) to manage a broker. The chapter has the following sections:

Command Utility Preliminaries
Using the Command Utility
Managing Brokers

This chapter does not cover all topics related to managing a broker. Additional topics are covered in the following separate chapters:

For information on configuring and managing connection services, see Configuring and Managing Connection Services.
For information on managing message delivery services, including how to create, display, update, and destroy physical destinations, see Managing Message Delivery.
For information on configuring and managing persistence services, for both flat-file and JDBC-based data stores, see Configuring Persistence Services.
For information about setting up security for the broker, such as user authentication, access control, encryption, and password files, see Configuring and Managing Security Services.
For information on configuring and managing clustering services, for both conventional and enhanced broker clusters, see Configuring and Managing Broker Clusters.
For information about monitoring a broker, see Monitoring Broker Operations.

Command Utility Preliminaries

Before using the Command utility to manage a broker, you must do the following:

Start the broker using the imqbrokerd command. You cannot use the Command utility subcommands l until a broker is running.
Determine whether you want to set up a Message Queue administrative user or use the default account. You must specify a user name and password to use all Command utility subcommands (except to display command help and version information).
When you install Message Queue, a default flat-file user repository is installed. The repository is shipped with two default entries: an administrative user and a guest user. If you are testing Message Queue, you can use the default user name and password (admin/admin) to run the Command utility.
If you are setting up a production system, you must set up authentication and authorization for administrative users. See Configuring and Managing Security Services for information on setting up a file-based user repository or configuring the use of an LDAP directory server. In a production environment, it is a good security practice to use a nondefault user name and password.
If you want to use a secure connection to the broker, set up and enable the ssladmin service on the target broker instance, For more information, see Message Encryption.

Using the Command Utility

The Message Queue Command utility (imqcmd) enables you to manage the broker and its services interactively from the command line. See Command Utility for general reference information about the syntax, subcommands, and options of the imqcmd command, and Broker Properties Reference for specific information on the configuration properties used to specify broker behavior.

Specifying the User Name and Password

Because each imqcmd subcommand is authenticated against the user repository, it requires a user name and password. The only exceptions are commands that use the -h or -H option to display help, and those that use the -v option to display the product version.

Use the -u option to specify an administrative user name. For example, the following command displays information about the default broker:

imqcmd query bkr  -u admin

If you omit the user name, the command will prompt you for it.

Note	For simplicity, the examples in this chapter use the default user name `admin` as the argument to the `-u` option. In a real-life production environment, you would use a custom user name.

Specify the password using one of the following methods:

Create a password file and enter the password into that file as the value of the imq.imqcmd.password property. On the command line, use the -passfile option to provide the name of the password file.
Let the imqcmd command prompt you for the password.

Note	In previous versions of Message Queue, you could use the `-p` option to specify a password on the `imqcmd` command line. As of Message Queue 4.0, this option is deprecated and is no longer supported; you must instead use one of the methods listed above.

Specifying the Broker Name and Port

Most imqcmd subcommands use the -b option to specify the host name and the port mapper port number of the broker to which the command applies:

-b hostName:portNumber

If no broker is specified, the command applies by default to a broker running on the local host (localhost) at port mapper port number 7676. See "Port Mapper" for more information.

To issue a command to a broker that is running on a remote host, listening on a non-default port, or both, you must use the -b option to specify the host and port explicitly.

Literal IP addresses as host names: You can use a literal IPv4 or IPv6 address as a host name. If you use a literal IPv6 address, its format must conform to RFC2732, Format for Literal IPv6 Addresses in URL’s.

Displaying the Product Version

To display the Message Queue product version, use the -v option. For example:

imqcmd  -v

If you enter an imqcmd command line containing the -v option in addition to a subcommand or other options, the Command utility processes only the -v option. All other items on the command line are ignored.

Displaying Help

To display help on the imqcmd command, use the -h or -H option, and do not use a subcommand. You cannot get help about specific subcommands.

For example, the following command displays help about imqcmd:

imqcmd  -H

If you enter an imqcmd command line containing the -h or -H option in addition to a subcommand or other options, the Command utility processes only the -h or -H option. All other items on the command line are ignored.

Examples

The examples in this section illustrate how to use the imqcmd command.

The following example lists the properties of the broker running on host localhost at port 7676, so the -b option is unnecessary:

imqcmd query bkr  -u admin

The command uses the default administrative user name (admin) and omits the password, so that the command will prompt for it.

The following example lists the properties of the broker running on the host myserver at port 1564. The user name is aladdin:

imqcmd query bkr  -b myserver:1564  -u aladdin

(For this command to work, the user repository would need to be updated to add the user name aladdin to the admin group.)

The following example lists the properties of the broker running on localhost at port 7676. The initial timeout for the command is set to 20 seconds and the number of retries after timeout is set to 7. The user’s password is in a password file called myPassfile, located in the current directory at the time the command is invoked.

imqcmd query bkr  -u admin  -passfile myPassfile  -rtm 20  -rtr 7

For a secure connection to the broker, these examples could include the -secure option. This option causes the Command utility to use the ssladmin service if that service has been configured and started.

Managing Brokers

This section describes how to use Command utility subcommands to perform the following broker management tasks:

Shutting Down and Restarting a Broker
Quiescing a Broker
Pausing and Resuming a Broker
Updating Broker Properties
Viewing Broker Information

In addition to using the subcommands described in the following sections, imqcmd allows you to set system properties using the -D option. This is useful for setting or overriding connection factory properties or connection-related Java system properties.

For example, the following command changes the default value of imqSSLIsHostTrusted:

imqcmd list svc -secure -DimqSSLIsHostTrusted=true

The following command specifies the password file and the password used for the SSL trust store that is used by the imqcmd command:

imqcmd list svc -secure -DJavax.net.ssl.trustStore=/tmp/MyTruststore
              -Djavax.net.ssl.trustStorePassword=MyTrustword

Shutting Down and Restarting a Broker

The subcommand imqcmd shutdown bkr shuts down a broker:

imqcmd shutdown bkr  [-b hostName:portNumber]
[-time nSeconds]
[-nofailover]

The broker stops accepting new connections and messages, completes delivery of existing messages, and terminates the broker process.

The -time option, if present, specifies the interval, in seconds, to wait before shutting down the broker. For example, the following command delays 90 seconds and then shuts down the broker running on host wolfgang at port 1756:

imqcmd shutdown bkr  -b wolfgang:1756  -time 90  -u admin

The broker will not block, but will return immediately from the delayed shutdown request. During the shutdown interval, the broker will not accept any new jms connections; admin connections will be accepted, and existing jms connections will continue to operate. If the broker belongs to an enhanced broker cluster, it will not attempt to take over for any other broker during the shutdown interval.

If the broker is part of an enhanced broker cluster (see "Enhanced Clusters" in Open Message Queue Technical Overview), another broker in the cluster will ordinarily attempt to take over its persistent data on shutdown; the -nofailover option to the imqcmd shutdown bkr subcommand suppresses this behavior. Conversely, you can use the imqcmd takeover bkr subcommand to force such a takeover manually (for instance, if the takeover broker were to fail before completing the takeover process); see Preventing or Forcing Broker Failover for more information.

Note	The `imqcmd` `takeover` `bkr` subcommand is intended only for use in failed-takeover situations. You should use it only as a last resort, and not as a general way of forcibly taking over a running broker.

To shut down and restart a broker, use the subcommand imqcmd restart bkr:

imqcmd restart bkr  [-b hostName:portNumber]

This shuts down the broker and then restarts it using the same options that were specified when it was first started. To choose different options, shut down the broker with imqcmd shutdown bkr and then start it again with the Broker utility (imqbrokerd), specifying the options you want.

Quiescing a Broker

The subcommand imqcmd quiesce bkr quiesces a broker, causing it to refuse any new client connections while continuing to service old ones:

imqcmd quiesce bkr  [-b hostName:portNumber]

If the broker is part of an enhanced broker cluster, this allows its operations to wind down normally without triggering a takeover by another broker, for instance in preparation for shutting it down administratively for upgrade or similar purposes. For example, the following command quiesces the broker running on host hastings at port 1066:

imqcmd quiesce bkr  -b hastings:1066  -u admin

To reverse the process and return the broker to normal operation, use the imqcmd unquiesce bkr subcommand:

imqcmd unquiesce bkr  [-b hostName:portNumber]

For example, the following command unquiesces the broker that was quiesced in the preceding example:

imqcmd unquiesce bkr  -b hastings:1066  -u admin

Pausing and Resuming a Broker

The subcommand imqcmd pause bkr pauses a broker, suspending its connection service threads and causing it to stop listening on the connection ports:

imqcmd pause bkr  [-b hostName:portNumber]

For example, the following command pauses the broker running on host myhost at port 1588:

imqcmd pause bkr  -b myhost:1588  -u admin

Because its connection service threads are suspended, a paused broker is unable to accept new connections, receive messages, or dispatch messages. The admin connection service is not suspended, allowing you to continue performing administrative tasks needed to regulate the flow of messages to the broker. Pausing a broker also does not suspend the cluster connection service; however, since message delivery within a cluster depends on the delivery functions performed by the different brokers in the cluster, pausing a broker in a cluster may result in a slowing of some message traffic.

You can also pause individual connection services and physical destinations. For more information, see Pausing and Resuming a Connection Service and Pausing and Resuming a Physical Destination.

The subcommand imqcmd resume bkr reactivates a broker’s service threads, causing it to resume listening on the ports:

imqcmd resume bkr  [-b hostName:portNumber]

For example, the following command resumes the default broker (host localhost at port 7676):

imqcmd resume bkr  -u admin

Updating Broker Properties

The subcommand imqcmd update bkr can be used to change the values of a subset of broker properties for the default broker (or for the broker at a specified host and port):

imqcmd update bkr [-b hostName:portNumber]
-o property1=value1  [ [-o property2=value2] … ]

For example, the following command turns off the auto-creation of queue destinations for the default broker:

imqcmd update bkr  -o imq.autocreate.queue=false  -u admin

You can use imqcmd update bkr to update any of the following broker properties:

imq.autocreate.queue
imq.autocreate.topic
imq.autocreate.queue.maxNumActiveConsumers
imq.autocreate.queue.maxNumBackupConsumers
imq.cluster.url
imq.destination.DMQ.truncateBody
imq.destination.logDeadMsgs
imq.log.level
imq.log.file.rolloversecs
imq.log.file.rolloverbytes
imq.system.max_count
imq.system.max_size
imq.message.max_size
imq.portmapper.port

See Broker Properties Reference for detailed information about these properties.

Viewing Broker Information

To display information about a single broker, use the imqcmd query bkr subcommand:

imqcmd query bkr  -b hostName:portNumber

This lists the current settings of the broker’s properties, as shown in Example 5-1.

Example 5-1 Broker Information Listing

Querying the broker specified by:
-------------------------
Host         Primary Port
-------------------------
localHost    7676

Version                                              5.0
Instance Name                                        imqbroker
Broker ID                                            mybroker
Primary Port                                         7676
Broker is Embedded                                   false
Instance Configuration/Data Root Directory           /var/imq

Current Number of Messages in System                 0
Current Total Message Bytes in System                0

Current Number of Messages in Dead Message Queue     0
Current Total Message Bytes in Dead Message Queue    0
Log Dead Messages                                    true
Truncate Message Body in Dead Message Queue          false

Max Number of Messages in System                     unlimited (-1)
Max Total Message Bytes in System                    unlimited (-1)
Max Message Size                                     70m

Auto Create Queues                                   true
Auto Create Topics                                   true
Auto Created Queue Max Number of Active Consumers    1
Auto Created Queue Max Number of Backup Consumers    0

Cluster ID                                           myClusterID
Cluster Is Highly Available                          true
Cluster Broker List (active)
Cluster Broker List (configured)
Cluster Master Broker
Cluster URL

Log Level                                            INFO
Log Rollover Interval (seconds)                      604800
Log Rollover Size (bytes)                            unlimited (-1)

The imqcmd metrics bkr subcommand displays detailed metric information about a broker’s operation:

imqcmd metrics bkr  [-b hostName:portNumber]
[-m metricType]
[-int interval]
[-msp numSamples]

The -m option specifies the type of metric information to display:

ttl (default): Messages and packets flowing into and out of the broker
rts: Rate of flow of messages and packets into and out of the broker per second
cxn: Connections, virtual memory heap, and threads

The -int and -msp options specify, respectively, the interval (in seconds) at which to display the metrics and the number of samples to display in the output. The default values are 5 seconds and an unlimited number of samples.

For example, the following command displays the rate of message flow into and out of the default broker (host localhost at port 7676) at 10-second intervals:

imqcmd metrics bkr  -m rts  -int 10  -u admin

Example 5-2 shows an example of the resulting output.

Example 5-2 Broker Metrics Listing

--------------------------------------------------------
 Msgs/sec   Msg Bytes/sec   Pkts/sec    Pkt Bytes/sec
 In   Out     In      Out     In   Out     In      Out
--------------------------------------------------------
 0     0      27      56      0     0      38      66
 10    0     7365     56      10    10    7457    1132
 0     0      27      56      0     0      38      73
 0     10     27     7402     10    20    1400    8459
 0     0      27      56      0     0      38      73

For a more detailed description of the data gathered and reported by the broker, see Brokerwide Metrics.

For brokers belonging to a broker cluster, the imqcmd list bkr subcommand displays information about the configuration of the cluster; see Displaying a Cluster Configuration for more information.