Sun Java System Messaging Server 6.3 Administration Guide Examples of Use

Typically, you would add additional pool definitions to the Job Controller configuration if you wanted to differentiate processing of some channels from that of other channels. You might also choose to use pools with different characteristics. For example, you might need to control the number of simultaneous requests that some channels are allowed to process. You can do this by creating a new pool with the job limit, then use the pool channel keyword to direct those channels to the new, more appropriate pool.

In addition to the definition of pools, the Job Controller configuration file also contains a table of the MTA channels and the commands that the Job Controller must use to process requests for each channel. The two types of requests are termed “master” and “slave.” Typically, a channel master program is invoked when there is a message stored in an MTA message queue for the channel. The master program dequeues the message.

A slave program is invoked to poll a channel and pick up any messages inbound on that channel. While nearly all MTA channels have a master program, many do not have or need a slave program. For example, a channel that handles SMTP over TCP/IP doesn’t use a slave program because a network service, the SMTP server, receives incoming SMTP messages upon request by any SMTP server. The SMTP channel's master program is the MTA’s SMTP client.

If the destination system associated with the channel cannot handle more than one message at a time, you need to create a new type of pool whose job limit is one:


On the other hand, if the destination system has enough parallelism, you can set the job limit to a higher value.

Example 10–1 shows a sample Job Controller configuration file. Table 10–6 shows the available options.

Example 10–1 Sample Job Controller Configuration File in UNIX

!MTA Job Controller configuration file
!Global defaults
tcp_port=27442         (1)
secret=never mind
slave_command=NULL     (2)
max_life_age=3600      (3)
!Pool definitions
[POOL=DEFAULT]         (4)
job_limit=10           (5)
!Channel definitions
[CHANNEL=l]             (6)
[CHANNEL=tcp_*]         (7)

The key items in the preceding example (numbered, enclosed in parentheses, and in bold font) are:

  1. This global option defines the TCP port number on which the Job Controller listens for requests.

  2. Sets a default SLAVE_COMMAND for subsequent [CHANNEL] sections.

  3. Sets a default MAX_LIFE_AGE for subsequent [CHANNEL] sections.

  4. This [POOL] section defines a pool named DEFAULT.

  5. Set the JOB_LIMIT for this pool to 10.

  6. This [CHANNEL] section applies to a channel named l, the UNIX local channel. The only definition required in this section is the master_command, which the Job Controller issues to run this channel. Since no wildcard appears in the channel name, the channel must match exactly.

  7. This [CHANNEL] section applies to any channel whose name begins with tcp_*. Since this channel name includes a wildcard, it will match any channel whose name begins with tcp_.

Example of Adding Additional Pools

The Job Controller creates and manages channel jobs for delivering messages. These channel jobs run inside processing pools within the Job Controller. A pool can be thought of a “place” where the channel jobs are run. The pool provides a computing area where a set of jobs can operate without vying for resources with jobs outside of the pool. Note that the job limit that is set in the job_controller is per pool. So, for example, if you have your SMTP_POOL defined with a job_limit of 10, then only 10 tcp_smtp client processes can run in that pool at any given time.

There are situations where one may want to create additional tcp_* channels (say, for example, a tcp channel for particularly slow mail sites). It is a good idea to have these channels run in different pools. The reason for this is if we created ten different tcp_* channels and they were all running in SMTP_POOL, it is possible to only have one tcp_smtp client running per tcp_* channel at any given time (depending on whether or not there is mail destined for all the tcp_* channels and given that SMTP_POOL defined with a job_limit of 10). Assuming there is heavy load on the system and that all queues have messages waiting to go out the various tcp_* channels, this would not be efficient. It is much more likely that one would want to define additional pools for the additional tcp_* channels so that there is no contention for slots.

For example, suppose we set up the following tcp_* channels:

tcp_yahoo smtp mx pool yahoo_pool keyword keyword keyword

tcp_aol smtp mx keyword keyword keyword pool aol_pool

tcp_hotmail smtp mx pool hotmail_pool keyword keyword keyword 
tcp_sun smtp mx pool sun_pool keyword keyword keyword

In order to add have ten tcp_smtp_client processes for each of the new channels we would add the following in the job_controller.cnf file:






For more information about pools, see 12.5.4 Processing Pools for Channel Execution Jobs.

Table 10–6 Job Controller Configuration File Options



General Options



Specifies the IP address interface to which the Job Controller should bind. The value specified (adapter) can be one of ANY, ALL, LOCALHOST, or an IP address. By default the Job Controller binds to all addresses (equivalent to specifying ALL or ANY). Specifying INTERFACE_ADDRESS=LOCALHOST means that the Job Controller only accepts connections from within the local machine. This does not affect normal operation, since no inter-machine operation is supported by the Job Controller. However, this may be inappropriate in an HA environment where an HA agent may be checking if the Job Controller is responding. If the machine on which the Messaging Server is running is in an HA environment, has an “internal network” adapter and an “external network” adapter, and you are not confident of your firewall’s ability to block connections to high port numbers, you should consider specifying the IP address of the “internal network” adapter.


The Job Controller keeps information about messages in an in-memory structure. In the event that a large backlog builds, it may need to limit the size of this structure. If the number of messages in the backlog exceeds the parameter specified here, information about subsequent messages is not kept in memory. Mail messages are not lost because they are always written to disk, but they are not considered for delivery until the number of messages known by the Job Controller drops to half this number. At this point, the Job Controller scans the queue directory mimicking an imsimta cache -sync command. The minimum value is 10. See 8.7 The Job Controller for more information.

The default is 100000. 


Shared secret used to protect requests sent to the Job Controller. 


The Job Controller occasionally scans the queue files on disk to check for missing files. By default, this takes place every four hours, starting four hours after the Job Controller is started. The format of the time_spec is HH:MM/hh:mm or /hh:mm. The variable is the interval between the events in hours (h) and minutes (m). The variable HH:MM is the first time in a day the even should take place. For example specifying, 15:45/7:15 starts the event at 15:45 and every seven hours and fifteen minutes from then.


Specifies the TCP port on which the Job Controller should listen for request packets. Do not change this unless the default conflicts with another TCP application on your system. If you do change this option, change the corresponding IMTA_JBC_SERVICE option in the MTA tailor file, msg-svr-base/config/imta_tailor, so that it matches. The TCP_PORT option applies globally and is ignored if it appears in a [CHANNEL] or [POOL] section.

Pool Option



Specifies the maximum number of processes that the pool can use simultaneously (in parallel). The JOB_LIMIT applies to each pool individually; the maximum total number of jobs is the sum of the JOB_LIMIT parameters for all pools. If set outside of a section, it is used as the default by any [POOL] section that doesn’t specify JOB_LIMIT. This option is ignored inside of a [CHANNEL] section.

Channel Option



Specifies the full path to the command to be executed by the UNIX system process created by the Job Controller to run the channel and dequeue messages outbound on that channel. If set outside of a section, it is used as the default by any [CHANNEL] section that doesn’t specify a MASTER_COMMAND. This option is ignored inside of a [POOL] section.


Specifies the maximum life time for a channel master job in seconds. If this parameter is not specified for a channel, then the global default value is used. If no default value is specified, 14400 (240 minutes) is used. 


In addition to the maximum life age parameter, the life expectancy of a channel master job is limited by the number of times it can ask the Job Controller if there are any messages. If this parameter is not specified for a channel, then the global default value is used. If no default value is specified, 300 is used. 


Specifies the full path to the command to be executed by the UNIX system process created by the Job Controller in order to run the channel and poll for any messages inbound on the channel. Most MTA channels do not have a SLAVE_COMMAND. If that is the case, the reserved value NULL should be specified. If set outside of a section, it is used as the default by any [CHANNEL] section that doesn’t specify a SLAVE_COMMAND. This option is ignored inside of a [POOL] section.