This topic includes the following sections:
This topic provides information about using the ATMI COBOL language functions for enqueuing and dequeuing messages: TPENQUEUE(3cbl) and TPDEQUEUE(3cbl), plus some ancillary functions.
The BEA Tuxedo programmer coding client or server programs for the queued message facility should be familiar with the COBOL language binding to the BEA Tuxedo ATMI. General guidance on BEA Tuxedo programming is available in Programming BEA Tuxedo ATMI Applications Using COBOL. Detailed pages on all the ATMI functions are in the BEA Tuxedo ATMI COBOL Function Reference.
The calls used to place a message on a BEA Tuxedo /Q queue can originate from any client or server process associated with the application. The list includes:
The discussion of BEA Tuxedo /Q programming in this topic primarily reflects the client-side portion of the figure Queued Service Invocation. The figure shows how a client (or a process acting in the role of a client) queues a message by calling TPENQUEUE(3cbl) and specifying a queue space made available through a TMQUEUE(5) server. The client later retrieves a reply via a TPDEQUEUE(3cbl) call to TMQUEUE
.
The figure shows the queued message being dequeued by the server TMQFORWARD(5) and sent to an application server for processing (via TPCALL(3cbl)). When a reply to TPCALL
is received, TMQFORWARD
enqueues the reply message. Because TMQFORWARD
provides an interface between the queue space and existing application services, further application coding is not required. For that reason, this topic concentrates on the client-to-queue space side.
Some examples of customization are given after the discussion of the basic model.
The syntax for TPENQUEUE()
is as follows:
01 TPQUEDEF-REC.
COPY TPQUEDEF.
01 TPTYPE-REC.
COPY TPTYPE.
01 DATA-REC.
COPY User Data.
01 TPSTATUS-REC.
COPY TPSTATUS.
CALL "TPENQUEUE" USING TPQUEDEF-REC TPTYPE-REC DATA-REC TPSTATUS-REC.
When a TPENQUEUE()
call is issued it tells the system to store a message on the queue identified in QNAME
in TPQUEDEF-REC
in the space identified in QSPACE-NAME
in TPQUEDEF-REC
. The message is in DATA-REC
, and LEN
in TPTYPE-REC
has the length of the message. By the use of settings in TPQUEDEF-REC
, the system is informed how the call to TPENQUEUE()
is to be handled. Further information about the handling of the enqueued message and replies is provided in the TPQUEDEF-REC
structure.
There are some important arguments to control the operation of TPENQUEUE(3cbl). Lets look at some of them.
QSPACE-NAME
identifies a queue space previously created by the administrator. When a server is defined in the SERVERS
section of the configuration file, the service names it offers are aliases for the actual queue space name (which is specified as part of the OPENINFO
parameter in the GROUPS
section). For example, when your application uses the server TMQUEUE
, the value pointed at by QSPACE-NAME
is the name of a service advertised by TMQUEUE
. If no service aliases are defined, the name of the default service is the same as the server name, TMQUEUE
. In this case the configuration file might include the following:
TMQUEUE
SRVGRP = QUE1 SRVID = 1
GRACE = 0 RESTART = Y CONV = N
CLOPT = "-A"
or
CLOPT = "-s TMQUEUE"
The entry for server group QUE1
has an OPENINFO
parameter that specifies the resource manager, the pathname of the device and the queue space name. The QSPACE-NAME
argument in a client program then looks like this:
01 TPQUEDEF-REC.
COPY TPQUEDEF.
01 TPTYPE-REC.
COPY TPTYPE.
01 TPSTATUS-REC.
COPY TPSTATUS.
01 USER-DATA-REC PIC X(100).
*
*
*
MOVE LOW-VALUES TO TPQUEDEF-REC.
MOVE "TMQUEUE" TO QSPACE-NAME IN TPQUEDEF-REC.
MOVE "STRING" TO QNAME IN TPQUEDEF-REC.
SET TPTRAN IN TPQUEDEF-REC TO TRUE.
SET TPBLOCK IN TPQUEDEF-REC TO TRUE.
SET TPTIME IN TPQUEDEF-REC TO TRUE.
SET TPSIGRSTRT IN TPQUEDEF-REC TO TRUE.
MOVE LOW-VALUES TO TPTYPE-REC.
MOVE "STRING" TO REC-TYPE IN TPTYPE-REC.
MOVE LENGTH OF USER-DATA-REC TO LEN IN TPTYPE-REC.
CALL "TPENQUEUE" USING
TPQUEDEF-REC
TPTYPE-REC
USER-DATA-REC
TPSTATUS-REC.
The example shown on the TMQUEUE(5) reference page shows how alias service names can be included when the server is built and specified in the configuration file. The sample program in A Sample Application, also specifies an alias service name.
When message queues are being used within a queue space to invoke services, they are named according to application services that process the requests. QNAME
contains such a value; an exception in which QNAME
is not an application service is described in Procedure for Dequeuing Replies from Services Invoked Through TMQFORWARD.
DATA-REC
contains the message to be processed. LEN
in TPTYPE-REC
gives the length of the message. Some BEA Tuxedo record types (VIEW
, for example) do not require LEN
to be specified; in such cases, the argument is ignored. If RECTYPE
in TPTYPE-REC
is SPACES
, DATA-REC
and LEN
are ignored and the message is enqueued with no data portion.
Settings in TPQUEDEF-REC
are used to tell the BEA Tuxedo system how the TPENQUEUE()
call is handled; the following are valid settings:
TPNOTRAN
TPNOTRAN
or TPTRAN
must be set.
TPTRAN
TPNOTRAN
or TPTRAN
must be set.
TPNOBLOCK
TPNOBLOCK
is set and a blocking condition exists such as the internal buffers into which the message is transferred are full, the call fails and tperrno(5) is set to TPEBLOCK
. If TPNOBLOCK
is set and a blocking condition exists because the target queue is opened exclusively by another application, the call fails, tperrno()
is set to TPEDIAGNOSTIC
, and the diagnostic field of the TPQCTL
structure is set to QMESHARE
. In the latter case, the other application, which is based on a BEA product other than the BEA Tuxedo system, opened the queue for exclusive read and/or write using the Queuing Services API (QSAPI). Either TPNOBLOCK
or TPBLOCK
must be set.
TPBLOCK
TPBLOCK
is set and a blocking condition exists, the caller blocks until the condition subsides or a timeout occurs (either transaction or blocking timeout). Either TPNOBLOCK
or TPBLOCK
must be set.
TPNOTIME
TPNOTIME
or TPTIME
must be set.
TPTIME
TPNOTIME
or TPTIME
must be set.
TPSIGRSTRT
TPSIGRSTRT
or TPNOSIGRSTRT
must be set.
TPNOSIGRSTRT
TP-STATUS
to TPEGOTSIG
. Either TPSIGRSTRT
or TPNOSIGRSTRT
must be set.
The TPQUEDEF-REC
structure has members that are used by the application and by the BEA Tuxedo system to pass parameters in both directions between application programs and the queued message facility. It is defined in the COBOL COPY
file. The client that calls TPQUEDEF-REC
uses settings to mark members the application wants the system to fill in. The structure is also used by TPDEQUEUE()
; some of the members do not come into play until the application calls that function. The complete structure is shown in the following listing.
05 TPBLOCK-FLAG PIC S9(9) COMP-5.
88 TPBLOCK VALUE 0.
88 TPNOBLOCK VALUE 1.
05 TPTRAN-FLAG PIC S9(9) COMP-5.
88 TPTRAN VALUE 0.
88 TPNOTRAN VALUE 1.
05 TPTIME-FLAG PIC S9(9) COMP-5.
88 TPTIME VALUE 0.
88 TPNOTIME VALUE 1.
05 TPSIGRSTRT-FLAG PIC S9(9) COMP-5.
88 TPNOSIGRSTRT VALUE 0.
88 TPSIGRSTRT VALUE 1.
05 TPNOCHANGE-FLAG PIC S9(9) COMP-5.
88 TPCHANGE VALUE 0.
88 TPNOCHANGE VALUE 1.
05 TPQUE-ORDER-FLAG PIC S9(9) COMP-5.
88 TPQDEFAULT VALUE 0.
88 TPQTOP VALUE 1.
88 TPQBEFOREMSGID VALUE 2.
05 TPQUE-TIME-FLAG PIC S9(9) COMP-5.
88 TPQNOTIME VALUE 0.
88 TPQTIME-ABS VALUE 1.
88 TPQTIME-REL VALUE 2.
05 TPQUE-PRIORITY-FLAG PIC S9(9) COMP-5.
88 TPQNOPRIORITY VALUE 0.
88 TPQPRIORITY VALUE 1.
05 TPQUE-CORRID-FLAG PIC S9(9) COMP-5.
88 TPQNOCORRID VALUE 0.
88 TPQCORRID VALUE 1.
05 TPQUE-REPLYQ-FLAG PIC S9(9) COMP-5.
88 TPQNOREPLYQ VALUE 0.
88 TPQREPLYQ VALUE 1.
05 TPQUE-FAILQ-FLAG PIC S9(9) COMP-5.
88 TPQNOFAILUREQ VALUE 0.
88 TPQFAILUREQ VALUE 1.
05 TPQUE-MSGID-FLAG PIC S9(9) COMP-5.
88 TPQNOMSGID VALUE 0.
88 TPQMSGID VALUE 1.
05 TPQUE-GETBY-FLAG PIC S9(9) COMP-5.
88 TPQGETNEXT VALUE 0.
88 TPQGETBYMSGIDOLD VALUE 1.
88 TPQGETBYCORRIDOLD VALUE 2.
88 TPQGETBYMSGID VALUE 3.
88 TPQGETBYCORRID VALUE 4.
05 TPQUE-WAIT-FLAG PIC S9(9) COMP-5.
88 TPQNOWAIT VALUE 0.
88 TPQWAIT VALUE 1.
05 TPQUE-DELIVERY-FLAG PIC S9(9) COMP-5.
88 TPQNODELIVERYQOS VALUE 0.
88 TPQDELIVERYQOS VALUE 1.
05 TPQUEQOS-DELIVERY-FLAG PIC S9(9) COMP-5.
88 TPQQOSDELIVERYDEFAULTPERSIST VALUE 0.
88 TPQQOSDELIVERYPERSISTENT VALUE 1.
88 TPQQOSDELIVERYNONPERSISTENT VALUE 2.
05 TPQUE-REPLY-FLAG PIC S9(9) COMP-5.
88 TPQNOREPLYQOS VALUE 0.
88 TPQREPLYQOS VALUE 1.
05 TPQUEQOS-REPLY-FLAG PIC S9(9) COMP-5.
88 TPQQOSREPLYDEFAULTPERSIST VALUE 0.
88 TPQQOSREPLYPERSISTENT VALUE 1.
88 TPQQOSREPLYNONPERSISTENT VALUE 2.
05 TPQUE-EXPTIME-FLAG PIC S9(9) COMP-5.
88 TPQNOEXPTIME VALUE 0.
88 TPQEXPTIME-ABS VALUE 1.
88 TPQEXPTIME-REL VALUE 2.
88 TPQEXPTIME-NONE VALUE 3.
05 TPQUE-PEEK-FLAG PIC S9(9) COMP-5.
88 TPQNOPEEK VALUE 0.
88 TPQPEEK VALUE 1.
05 DIAGNOSTIC PIC S9(9) COMP-5.
88 QMEINVAL VALUE -1.
88 QMEBADRMID VALUE -2.
88 QMENOTOPEN VALUE -3.
88 QMETRAN VALUE -4.
88 QMEBADMSGID VALUE -5.
88 QMESYSTEM VALUE -6.
88 QMEOS VALUE -7.
88 QMEABORTED VALUE -8.
88 QMEPROTO VALUE -9.
88 QMEBADQUEUE VALUE -10.
88 QMENOMSG VALUE -11.
88 QMEINUSE VALUE -12.
88 QMENOSPACE VALUE -13.
88 QMERELEASE VALUE -14.
88 QMEINVHANDLE VALUE -15.
88 QMESHARE VALUE -16.
05 DEQ-TIME PIC 9(9) COMP-5.
05 EXP-TIME PIC 9(9) COMP-5.
05 PRIORITY PIC S9(9) COMP-5.
05 MSGID PIC X(32).
05 CORRID PIC X(32).
05 QNAME PIC X(15).
05 QSPACE-NAME PIC X(15).
05 REPLYQUEUE PIC X(15).
05 FAILUREQUEUE PIC X(15).
05 CLIENTID OCCURS 4 TIMES PIC S9(9) COMP-5.
05 APPL-RETURN-CODE PIC S9(9) COMP-5.
05 APPKEY PIC S9(9) COMP-5.
The following is a list of valid settings for the parameters controlling input information for TPENQUEUE
.
TPQTOP
TPQDEFAULT
to use default queue ordering. TPQTOP
, TPQBEFOREMSGID
, or TPQDEFAULT
must be set.
TPQBEFOREMSGID
MSGID
. This request may not be granted depending on whether or not the queue was configured to allow overriding the queue ordering. Set TPQDEFAULT
to use default queue ordering. TPQTOP
, TPQBEFOREMSGID
, or TPQDEFAULT
must be set.
MSGID
must be completely initialized (for example, padded with spaces).
TPQTIME-ABS
DEQ-TIME
. DEQ-TIME
is an absolute time value as generated by time
(2) or mktime(3C)
(the number of seconds since 00:00:00 Universal Coordinated Time—UTC, January 1, 1970). Set TPQNOTIME
if neither an absolute or relative time value is set. TPQTIME-ABS
, TPQTIME-REL
, or TPQNOTIME
must be set. The absolute time is determined by the clock on the machine where the queue manager process resides.
TPQTIME-REL
DEQ-TIME
specifies the number of seconds to delay after the enqueuing completes before the submitted message should be available. Set TPQNOTIME
if neither an absolute or relative time value is set. TPQTIME-ABS
, TPQTIME-REL
, or TPQNOTIME
must be set.
TPQPRIORITY
PRIORITY
. The priority must be in the range 1 to 100, inclusive. The higher the number, the higher the priority (that is, a message with a higher number is dequeued before a message with a lower number). For queues not ordered by priority, this value is informational. If TPQNOPRIORITY
is set, the priority for the message is 50 by default.
TPQCORRID
CORRID
is available when a message is dequeued with TPDEQUEUE()
. This identifier accompanies any reply or failure message that is queued so that an application can correlate a reply with a particular request. Set TPQNOCORRID
if a correlation identifier is not available.
CORRID
must be completely initialized (for example, padded with spaces).
TPQREPLYQ
REPLYQUEUE
is associated with the queued message. Any reply to the message is queued to the named queue within the same queue space as the request message. Set TPQNOREPLYQ
if a reply queue name is not available.
TPQFAILUREQ
FAILUREQUEUE
is associated with the queued message. If (1) the enqueued message is processed by TMQFORWARD()
, (2) TMQFORWARD
was started with the -d
option, and (3) the service fails and returns a non-NULL reply, a failure message consisting of the reply and its associated tpurcode
is enqueued to the named queue within the same queue space as the original request message. Set TPQNOFAILUREQ
if a failure queue name is not available.
TPQDELIVERYQOS
TPQREPLYQOS
TPQDELIVERYQOS
is set, the flags specified by TPQUEQOS-DELIVERY-FLAG
control the quality of service for message delivery. One of the following mutually exclusive flags must be set: TPQQOSDELIVERYDEFAULTPERSIST
, TPQQOSDELIVERYPERSISTENT
, or TPQQOSDELIVERYNONPERSISTENT
. If TPQDELIVERYQOS
is not set, TPQNODELIVERYQOS
must be set. When TPQNODELIVERYQOS
is set, the default delivery policy of the target queue dictates the delivery quality of service for the message.
TPQREPLYQOS
is set, the flags specified by TPQUEQOS-REPLY-FLAG
control the quality of service for reply message delivery for any reply. One of the following mutually exclusive flags must be set: TPQQOSREPLYDEFAULTPERSIST
, TPQQOSREPLYPERSISTENT
, or TPQQOSREPLYNONPERSISTENT
. The TPQREPLYQOS
flag is used when a reply is returned from messages processed by TMQFORWARD
. Applications not using TMQFORWARD
to invoke services may use the TPQREPLYQOS
flag as a hint for their own reply mechanism.
If TPQREPLYQOS
is not set, TPQNOREPLYQOS
must be set. When TPQNOREPLYQOS
is set, the default delivery policy of the REPLYQUEUE
queue dictates the delivery quality of service for any reply. Note that the default delivery policy is determined when the reply to a message is enqueued. That is, if the default delivery policy of the reply queue is modified between the time that the original message is enqueued and the reply to the message is enqueued, the policy used is the one in effect when the reply is finally enqueued.
The valid TPQUEQOS-DELIVERY-FLAG
and TPQUEQOS-REPLY-FLAG
flags are:
TPQEXPTIME-ABS
EXP-TIME
. EXP-TIME
must be set to an absolute time generated by time
(2) or mktime
(3C) (the number of seconds since 00:00:00 Universal Coordinated Time—UTC, January 1, 1970).
If an absolute time is specified that is earlier than the time of the enqueue operation, the operation succeeds, but the message is not counted for the purpose of calculating thresholds. If the expiration time is before the message availability time, the message is not available for dequeuing unless either the availability or expiration time is changed so that the availability time is before the expiration time. In addition, these messages are removed from the queue at expiration time even if they were never available for dequeuing. If a message expires during a transaction, the expiration does not cause the transaction to fail. Messages that expire while being enqueued or dequeued within a transaction are removed from the queue when the transaction ends. There is no acknowledgment that the message has expired.
One of the following must be set: TPQEXPTIME-ABS
, TPQEXPTIME-REL
, TPQEXPTIME-NONE
, or TPQNOEXPTIME
.
TPQEXPTIME-REL
EXP-TIME
.
TPQEXPTIME-ABS
, TPQEXPTIME-REL
, TPQEXPTIME-NONE
, or TPQNOEXPTIME
.
TPQEXPTIME-NONE
TPQEXPTIME-ABS
, TPQEXPTIME-REL
, TPQEXPTIME-NONE
, or TPQNOEXPTIME
.
TPQNOEXPTIME
TPQEXPTIME-ABS
, TPQEXPTIME-REL
, TPQEXPTIME-NONE
, or TPQNOEXPTIME
.
Additionally, the APPL-RETURN-CODE
member of TPQUEDEF-REC
can be set with a user-return code. This value is returned to the application that calls TPDEQUEUE()
to dequeue the message.
As output from TPENQUEUE()
, the following may be set in the TPQUEDEF-REC
structure:
05 DIAGNOSTIC PIC S9(9) COMP-5.
05 MSGID PIC X(32).
The following is a valid setting in TPQUEDEF-REC
controlling output information from TPENQUEUE()
. If this setting is true when TPENQUEUE()
is called, the BEA Tuxedo /Q server TMQUEUE(5) populates the associated element in the record with a message identifier. If this setting is not true when TPENQUEUE()
is called, TMQUEUE()
does not populate the associated element in the record with a message identifier.
TPQMSGID
TPENQUEUE()
is successful, the message identifier is stored in MSGID
. The entire 32 bytes of the message identifier value are significant, so the value stored in MSGID
is completely initialized (for example, padded with null characters). The actual padding character used for initialization varies between releases of the BEA Tuxedo /Q component. If TPQNOMSGID
is set, the message identifier is not available.
The remaining members of the control structure are not used on input to TPENQUEUE()
.
If the call to TPENQUEUE()
fails and TP-STATUS
is set to TPEDIAGNOSTIC
, a value indicating the reason for failure is returned in DIAGNOSTIC
. The following are the possible values:
QMEINVAL
]
QMEBADRMID
]
QMENOTOPEN
]
QMETRAN
]
TPNOTRAN
setting and an error occurred trying to start a transaction in which to enqueue the message. This diagnostic is not returned by a queue manager from BEA Tuxedo release 7.1 or later.
QMEBADMSGID
]
QMESYSTEM
]
QMEOS
]
QMEABORTED
]
QMEPROTO
]
QMEBADQUEUE
]
QMENOSPACE
]
QMENOSPACE
is returned when any of the following configured resources is exceeded: (1) the amount of disk (persistent) space allotted to the queue space, (2) the amount of memory (non-persistent) space allotted to the queue space, (3) the maximum number of simultaneously active transactions allowed for the queue space, (4) the maximum number of messages that the queue space can contain at any one time, (5) the maximum number of concurrent actions that the Queuing Services component can handle, or (6) the maximum number of authenticated users that may concurrently use the Queuing Services component.
QMERELEASE
]
QMESHARE
]
If the administrator, in creating a queue, allows TPENQUEUE()
calls to override the order of messages on the queue, you have two mutually exclusive ways to use the override capability. You can specify that the message is to be placed at the top of the queue by setting TPQTOP
or you can specify that it be placed ahead of a specific message by setting TPQBEFOREMSGID
and setting MSGID
to the ID of the message you wish to precede. This assumes that you saved the message-ID from a previous call in order to be able to use it here. Your administrator must tell you what the queue supports; it can be created to allow either or both of these overrides, or to allow neither.
You can set a value in PRIORITY
to specify the priority for the message. The value must be in the range 1 to 100; the higher the number, the higher the priority, unlike values specified with the UNIX nice
command. If PRIORITY
was not one of the queue ordering parameters, setting a priority here has no effect on the dequeuing order. The priority value is retained however, so that it can be inspected when the message is dequeued.
You can specify in DEQ-TIME
either an absolute time or a time relative to the completion of the enqueuing operation at which the message is made available. You set either TPQTIME-ABS
or TPQTIME-REL
to indicate how the value should be treated. A queue may be created with time
as a queue-ordering criterion, in which case messages are ordered by the message availability time.
The following example shows how to enqueue a message with a relative time. The sample message will become available sixty seconds in the future.
01 TPQUEDEF-REC.
COPY TPQUEDEF.
01 TPTYPE-REC.
COPY TPTYPE.
01 TPSTATUS-REC.
COPY TPSTATUS.
01 USER-DATA-REC PIC X(100).
*
*
*
MOVE LOW-VALUES TO TPQUEDEF-REC.
MOVE "QSPACE1" TO QSPACE-NAME IN TPQUEDEF-REC.
MOVE "Q1" TO QNAME IN TPQUEDEF-REC.
SET TPTRAN IN TPQUEDEF-REC TO TRUE.
SET TPBLOCK IN TPQUEDEF-REC TO TRUE.
SET TPTIME IN TPQUEDEF-REC TO TRUE.
SET TPSIGRSTRT IN TPQUEDEF-REC TO TRUE.
SET TPQDEFAULT IN TPQUEDEF-REC TO TRUE.
SET TPQTIME-REL IN TPQUEDEF-REC TO TRUE.
MOVE 60 TO DEQ-TIME IN TPQUEDEF-REC.
SET TPQNOPRIORITY IN TPQUEDEF-REC TO TRUE.
SET TPQNOCORRID IN TPQUEDEF-REC TO TRUE.
SET TPQNOREPLYQ IN TPQUEDEF-REC TO TRUE.
SET TPQNOFAILUREQ IN TPQUEDEF-REC TO TRUE.
SET TPQMSGID IN TPQUEDEF-REC TO TRUE.
MOVE LOW-VALUES TO TPTYPE-REC.
MOVE "STRING" TO REC-TYPE IN TPTYPE-REC.
MOVE LENGTH OF USER-DATA-REC TO LEN IN TPTYPE-REC.
CALL "TPENQUEUE" USING
TPQUEDEF-REC
TPTYPE-REC
USER-DATA-REC
TPSTATUS-REC.
If the caller of TPENQUEUE()
is in transaction mode and TPTRAN
is set, then the enqueuing is done within the caller's transaction. The caller knows for certain from the success or failure of TPENQUEUE()
whether the message was enqueued or not. If the call succeeds, the message is guaranteed to be on the queue. If the call fails, the transaction is rolled back, including the part where the message was placed on the queue.
If the caller of TPENQUEUE()
is not in transaction mode or if TPNOTRAN
is set, the message is enqueued outside of the caller's transaction. If the call to TPENQUEUE()
returns success, the message is guaranteed to be on the queue. If the call to TPENQUEUE()
fails with a communication error or with a timeout, the caller is left in doubt about whether the failure occurred before or after the message was enqueued.
Note that specifying TPNOTRAN
while the caller is not in transaction mode has no meaning.
The syntax for TPDEQUEUE()
is as follows:
01 TPQUEDEF-REC.
COPY TPQUEDEF.
01 TPTYPE-REC.
COPY TPTYPE.
01 DATA-REC.
COPY User Data.
01 TPSTATUS-REC.
COPY TPSTATUS.
CALL "TPDEQUEUE" USING TPQUEDEF-REC TPTYPE-REC DATA-REC TPSTATUS-REC.
When this call is issued it tells the system to dequeue a message from the QNAME
in TPQUEDEF-REC
queue, in the queue space named QSPACE-NAME
in TPQUEDEF-REC
. The message is placed in DATA-REC
. LEN
in
TPTYPE-REC
is set to the length of the data. If LEN
is 0 on return from TPDEQUEUE()
, the message had no data portion. By the use of settings in TPQUEDEF-REC
the system is informed how the call to TPDEQUEUE()
is to be handled.
There are some important arguments to control the operation of TPDEQUEUE(3cbl). Let's look at some of them.
QSPACE-NAME
identifies a queue space previously created by the administrator. When the TMQUEUE
server is defined in the SERVERS
section of the configuration file, the service names it offers are aliases for the actual queue space name (which is specified as part of the OPENINFO
parameter in the GROUPS
section). For example, when your application uses the server TMQUEUE
, the value pointed at by QSPACE-NAME
is the name of a service advertised by TMQUEUE
. If no service aliases are defined, the name of the default service is the same as that of the server, TMQUEUE
. In this case the configuration file may include the following:
TMQUEUE
SRVGRP = QUE1 SRVID = 1
GRACE = 0 RESTART = Y CONV = N
CLOPT = "-A"
or
CLOPT = "-s TMQUEUE"
The entry for server group QUE1
has an OPENINFO
parameter that specifies the resource manager, the pathname of the device, and the queue space name. The QSPACE-NAME
argument in a client program then looks like the following:
01 TPQUEDEF-REC.
COPY TPQUEDEF.
01 TPTYPE-REC.
COPY TPTYPE.
01 TPSTATUS-REC.
COPY TPSTATUS.
01 USER-DATA-REC PIC X(100).
*
*
*
MOVE LOW-VALUES TO TPQUEDEF-REC.
MOVE "TMQUEUE" TO QSPACE-NAME IN TPQUEDEF-REC.
MOVE "REPLYQ" TO QNAME IN TPQUEDEF-REC.
SET TPTRAN IN TPQUEDEF-REC TO TRUE.
SET TPBLOCK IN TPQUEDEF-REC TO TRUE.
SET TPTIME IN TPQUEDEF-REC TO TRUE.
SET TPSIGRSTRT IN TPQUEDEF-REC TO TRUE.
MOVE LOW-VALUES TO TPTYPE-REC.
MOVE "STRING" TO REC-TYPE IN TPTYPE-REC.
MOVE LENGTH OF USER-DATA-REC TO LEN IN TPTYPE-REC.
CALL "TPDEQUEUE" USING
TPQUEDEF-REC
TPTYPE-REC
USER-DATA-REC
TPSTATUS-REC.
The example shown on the TMQUEUE(5) reference page shows how alias service names can be included when the server is built and specified in the configuration file. The sample program in A Sample Application, also specifies an alias service name.
Queue names in a queue space must be agreed upon by the applications that will access the queue space. This requirement is especially important for reply queues. If QNAME
refers to a reply queue, the administrator creates it (and often an error queue) in the same manner that he or she creates any other queue. QNAME
contains the name of the queue from which to retrieve a message or reply.
These arguments have a different flavor than they do on TPENQUEUE()
. DATA-REC
is where the system is to place the message being dequeued.
It is an error for LEN
to be 0 on input. When TPDEQUEUE()
returns, LEN
contains the length of the data retrieved. If it is 0, it means that the reply had no data portion. This can be a legitimate and successful reply in some applications; receiving even a 0 length reply can be used to show successful processing of the enqueued request. If you wish to know whether the record has changed from before the call to TPDEQUEUE()
, save the length prior to the call to TPDEQUEUE()
and compare it to LEN
after the call completes. If the reply is larger than LEN
, then DATA-REC
will contain only as many bytes as will fit. The remainder are discarded and TPDEQUEUE()
fails with TPTRUNCATE
.
Settings in TPQUEDEF-REC
are used to tell the BEA Tuxedo system how the TPDEQUEUE()
call is handled; the following are valid settings:
TPNOTRAN
TPNOTRAN
or TPTRAN
must be set.
TPTRAN
TPNOTRAN
or TPTRAN
must be set.
TPNOBLOCK
TPNOBLOCK
is set and a blocking condition exists such as the internal buffers into which the message is transferred are full, the call fails and tperrno(5) is set to TPEBLOCK
. If TPNOBLOCK
is set and a blocking condition exists because the target queue is opened exclusively by another application, the call fails, tperrno()
is set to TPEDIAGNOSTIC
, and the diagnostic field of the TPQCTL
structure is set to QMESHARE
. In the latter case, the other application, which is based on a BEA product other than the BEA Tuxedo system, opened the queue for exclusive read and/or write using the Queuing Services API (QSAPI). Either TPNOBLOCK
or TPBLOCK
must be set.
TPBLOCK
TPBLOCK
is set and a blocking condition exists, the caller blocks until the condition subsides or a timeout occurs (either transaction or blocking timeout). This blocking condition does not include blocking on the queue itself if the TPQWAIT
setting is specified. Either TPNOBLOCK
or TPBLOCK
must be set.
TPNOTIME
TPNOTIME
or TPTIME
must be set.
TPTIME
TPNOTIME
or TPTIME
must be set.
TPNOCHANGE
DATA-REC
is not allowed to change. That is, the type and subtype of the received record must match the type and subtype of the record DATA-REC
. Either TPNOCHANGE
or TPCHANGE
must be set.
TPCHANGE
DATA-REC
, DATA-REC
's record type changes to the received record's type so long as the receiver recognizes the incoming record type. That is, the type and sub-type of the received record must match the type and sub-type of the record DATA-REC
. Either TPNOCHANGE
or TPCHANGE
must be set.
TPSIGRSTRT
TPSIGRSTRT
or TPNOSIGRSTRT
must be set.
TPNOSIGRSTRT
TP-STATUS
to TPEGOTSIG
. Either TPSIGRSTRT
or TPNOSIGRSTRT
must be set.
The first argument to TPDEQUEUE()
is the structure TPQUEDEF-REC
. The TPQUEDEF-REC
structure has members that are used by the application and by the BEA Tuxedo system to pass parameters in both directions between application programs and the queued message facility. The client that calls TPDEQUEUE()
uses settings to mark members the application wants the system to fill in. As described earlier, the structure is also used by TPENQUEUE()
; some of the members only apply to that function. The entire structure is shown in The TPQUEDEF-REC Structure.
As input to TPDEQUEUE()
, the following elements may be set in the TPQUEDEF
structure:
05 MSGID PIC X(32).
05 CORRID PIC X(32).
The following is a list of valid settings in TPQUEDEF-REC
that control input for TPDEQUEUE()
:
TPQGETNEXT
TPQGETNEXT
, TPQGETBYMSGID
, or TPQGETBYCORRID
.
TPQGETBYMSGID
MSGID
be dequeued. The message identifier is returned by a prior call to TPENQUEUE()
. Note that the message identifier is not valid if the message has moved from one queue to another. Note also that the entire 32 bytes of the message identifier value are significant, so the value identified by MSGID
must be completely initialized (for example, padded with spaces).
TPQGETBYCORRID
CORRID
be dequeued. The correlation identifier is specified by the application when enqueuing the message with TPENQUEUE()
. Note that the entire 32 bytes of the correlation identifier value are significant, so the value identified by CORRID
must be completely initialized (for example, padded with spaces).
TPQWAIT
TPQNOWAIT
to not wait until a message is available. If TPQWAIT
is set in conjunction with TPQGETBYMSGID
or TPQGETBYCORRID
, it indicates that an error should not be returned if no message with the specified message identifier or correlation identifier is present in the queue. Instead, the process should wait until a message meeting the criteria is available. The process is still subject to the caller's transaction timeout, or, when not in transaction mode, the process is still subject to the timeout specified on the TMQUEUE
process by the -t
option.
TPDEQUEUE
fails, TP-STATUS
is set to TPEDIAGNOSTIC
, and DIAGNOSTIC
is set to QMESYSTEM
.
Note that each TPDEQUEUE()
request specifying the TPQWAIT
control parameter requires that a queue manager (TMQUEUE
) action object be available if a message satisfying the condition is not immediately available. If one is not available, the TPDEQUEUE()
request fails. The number of available queue manager actions are specified when a queue space is created or modified. When a waiting dequeue request completes, the associated action object associated is made available for another request.
TPQPEEK
TPQPEEK
is set, the specified message is read but not removed from the queue. The TPNOTRAN
flag must be set. It is not possible to read messages enqueued or dequeued within a transaction before the transaction completes.
TPQPEEK
, the message may not be seen by other non-blocking dequeuers for the brief time the system is processing the non-destructive dequeue request. This includes dequeuers using specific selection criteria (such as message identifier and correlation identifier) that are looking for the message currently being non-destructively dequeued.
On output from TPDEQUEUE()
, the following elements may be set in TPQUEDEF-REC
:
05 PRIORITY PIC S9(9) COMP-5.
05 MSGID PIC X(32).
05 CORRID PIC X(32).
05 TPQUEQOS-DELIVERY-FLAG PIC S9(9) COMP-5.
05 TPQUEQOS-REPLY-FLAG PIC S9(9) COMP-5.
05 REPLYQUEUE PIC X(15).
05 FAILUREQUEUE PIC X(15).
05 DIAGNOSTIC PIC S9(9) COMP-5.
05 CLIENTID OCCURS 4 TIMES PIC S9(9) COMP-5
05 APPL-RETURN-CODE PIC S9(9) COMP-5.
05 APPKEY PIC S9(9) COMP-5.
The following is a list of valid settings in TPQUEDEF-REC
controlling output information from TPDEQUEUE()
. For any of these settings, if the setting is true when TPDEQUEUE()
is called, the associated element in the record is populated with the value provided when the message was queued, and the setting remains true. If the value is not available (that is, no value was provided when the message was queued) or the setting is not true when TPDEQUEUE()
is called, TPDEQUEUE()
completes with the setting not true.
TPQPRIORITY
TPDEQUEUE()
is successful, and the message was queued with an explicit priority, then the priority is stored in PRIORITY
. The priority is in the range 1 to 100, inclusive, and the higher the number, the higher the priority (that is, a message with a higher number is dequeued before a message with a lower number). If TPQNOPRIORITY
is set, the priority is not available.
TPQMSGID
TPDEQUEUE()
is successful, the message identifier is stored in MSGID
. The entire 32 bytes of the message identifier value are significant. If TPQNOMSGID
is set, the message identifier is not available.
TPQCORRID
TPDEQUEUE()
is successful, and the message was queued with a correlation identifier, then the correlation identifier is stored in CORRID
. The entire 32 bytes of the correlation identifier value are significant. Any BEA Tuxedo /Q provided reply to a message has the correlation identifier of the original message. If TPQNOCORRID
is set, the correlation identifier is not available.
TPQDELIVERYQOS
TPDEQUEUE()
is successful, and the message was queued with a delivery quality of service, then the flag—TPQQOSDELIVERYDEFAULTPERSIST
, TPQQOSDELIVERYPERSISTENT
, or TPQQOSDELIVERYNONPERSISTENT
—specified by TPQUEQOS-DELIVERY-FLAG
indicates the delivery quality of service. If TPQNODELIVERYQOS
is set, the delivery quality of service is not available.
TPQREPLYQOS
TPDEQUEUE()
is successful, and the message was queued with a reply quality of service, then the flag—TPQQOSREPLYDEFAULTPERSIST
, TPQQOSREPLYPERSISTENT
, or TPQQOSREPLYNONPERSISTENT
—specified by TPQUEQOS-REPLY-FLAG
indicates the reply quality of service. If TPQNOREPLYQOS
is set, the reply quality of service is not available.
REPLYQUEUE
queue dictates the delivery quality of service for any reply. The default delivery policy is determined when the reply to a message is enqueued. That is, if the default delivery policy of the reply queue is modified between the time that the original message is enqueued and the reply to the message is enqueued, the policy used is the one in effect when the reply is finally enqueued.
TPQREPLYQ
TPDEQUEUE()
is successful, and the message was queued with a reply queue, then the name of the reply queue is stored in REPLYQUEUE
. Any reply to the message should go to the named reply queue within the same queue space as the request message. If TPQNOREPLYQ
is set, the reply queue is not available.
TPQFAILUREQ
TPDEQUEUE()
is successful, and the message was queued with a failure queue, then the name of the failure queue is stored in FAILUREQUEUE
. Any failure message should go to the named failure queue within the same queue space as the request message. If TPQNOFAILUREQ
is set, the failure queue is not available.
The remaining settings in TPQUEDEF-REC
are set to the following values when TPDEQUEUE()
is called: TPQNOTOP
, TPQNOBEFOREMSGID
, TPQNOTIME_ABS
, TPQNOTIME_REL
, TPQNOEXPTIME_ABS
, TPQNOEXPTIME_REL
, and TPQNOEXPTIME_NONE
.
If the call to TPDEQUEUE()
fails and TP-STATUS
is set to TPEDIAGNOSTIC
, a value indicating the reason for failure is returned in DIAGNOSTIC
. The valid settings for DIAGNOSTIC
include those for TPENQUEUE()
described in TPQUEDEF-REC Structure (except for QMENOSPACE
and QMERELEASE
) and the following additional codes.
QMENOMSG
]
QMEINUSE
]
When TPDEQUEUE()
is called with flags set to include TPQWAIT
, if a message is not immediately available, the TMQUEUE
server waits for the arrival, on the queue, of a message that matches the TPDEQUEUE()
request before TPDEQUEUE()
returns control to the caller. The TMQUEUE
process sets the waiting request aside and processes requests from other processes while waiting to satisfy the first request. If TPQGETBYMSGID
and/or TPQGETBYCORRID
are also specified, the server waits until a message with the indicated message identifier and/or correlation identifier becomes available on the queue. If neither of these flags is set, the server waits until any message is put onto the queue. The amount of time it waits is controlled by the caller's transaction timeout, if the call is in transaction mode, or by the -t
option in the CLOPT
parameter of the TMQUEUE
server, if the call is not in transaction mode.
The TMQUEUE
server can handle a number of waiting TPDEQUEUE()
requests at the same time, as long as action resources are available to handle the request. If there are not enough action resources configured for the queue space, TPDEQUEUE()
fails. If this happens on your system, increase the number of action resources for the queue space.
In considering how best to handle errors when dequeuing it is helpful to differentiate between two types of errors:
By default, if a message is dequeued within a transaction and the transaction is rolled back, then the message ends up back on the queue and can be dequeued and executed again. It may be desirable to delay for a short period before retrying to dequeue and execute the message, allowing the transient problem to clear (for example, allowing for locks in a database to be released by another transaction). Normally, a limit on the number of retries is also useful to ensure that an application flaw doesn't cause significant waste of resources. When a queue is configured by the administrator, both a retry count and a delay period (in seconds) can be specified. A retry count of 0 implies that no retries are done. After the retry count is reached, the message is moved to an error queue that is configured by the administrator for the queue space. If the error queue is not configured, then messages that have reached the retry count are simply deleted. Messages on the error queue must be handled by the administrator who must work out a way of notifying the originator that meets the requirements of the application. The message handling method chosen should be mostly transparent to the originating program that put the message on the queue. There is a virtual guarantee that once a message is successfully enqueued it will be processed according to the parameters of TPENQUEUE()
and the attributes of the queue. Notification that a message has been moved to the error queue should be a rare occurrence in a system that has properly tuned its queue parameters.
A failure queue (normally, different from the queue space error queue) may be associated with each queued message. This queue is specified on the enqueuing call as the place to put any failure messages. The failure message for a particular request can be identified by an application-generated correlation identifier that is associated with the message when it is enqueued.
The default behavior of retrying until success (or a predefined limit) is quite appropriate when the failure is caused by a transient problem that is later resolved, allowing the message to be handled appropriately.
There are cases where the problem is not transient. For example, the queued message may request operating on an account that does not exist (and the application is such that it won't come into existence within a reasonable time period if at all). In this case, it is desirable not to waste any resources by trying again. If the application programmer or administrator determines that failures for a particular operation are never transient, then it is simply a matter of setting the retry count to zero, although this will require a mechanism to constantly clear the queue space error queue of these messages (for example, a background client that reads the queue periodically). More likely, it is the case that some problems will be transient (for example, database lock contention) and some problems will be permanent (for example, the account doesn't exist) for the same service.
In the case that the message is processed (dequeued and passed to the application via a TPCALL
) by TMQFORWARD
, there is no mechanism in the information returned by TPCALL
to indicate whether a TPESVCFAIL
error is caused by a transient or permanent problem.
As in the case where the application is handling the dequeuing, a simple solution is to return success for the service, that is, TPRETURN
with TPSUCCESS
, even though the operation failed. This allows the transaction to be committed and the message removed from the queue. If reply messages are being used, the information in the buffer returned from the service can indicate that the operation failed and the message will be enqueued on the reply queue. The APPL-CODE
in the TPSVCRET-REC
argument of TPRETURN
can also be used to return application specific information.
In the case where the service fails and the transaction must be rolled back, it is not clear whether or not TMQFORWARD
should execute a second transaction to remove the message from the queue without further processing. By default, TMQFORWARD
will not delete a message for a service that fails. TMQFORWARD
's transaction is rolled back and the message is restored to the queue. A command-line option may be specified for TMQFORWARD
that indicates that a message should be deleted from the queue if the service fails and a reply message is sent back with length greater than 0. The message is deleted in a second transaction. The queue must be configured with a delay time and retry count for this to work. If the message is associated with a failure queue, the reply data is enqueued to the failure queue in the same transaction as the one in which the message is deleted from the queue.
If your application expects to receive replies to queued messages, the following is a procedure you may want to follow:
TPSUCCESS
on a logical failure and return an explanatory code in the APPL-CODE
in the TPSVCRET-REC
argument of TPRETURN
. TPENQUEUE()
to put the message on the queue, set the following: TPQCORRID TPQREPLYQ
TPQFAILUREQ TPQMSGID
(Fill in the values for CORRID
, REPLYQUEUE
and FAILUREQUEUE
before issuing the call. On return from the call, save CORRID
.)
TPDEQUEUE()
to check for a reply, specify the reply queue in QNAME
and set the following: TPQCORRID TPQREPLYQ
TPQFAILUREQ TPQMSGID
TPQGETBYCORRID
(Use the saved correlation identifier to populate CORRID
before issuing the call. If the call to TPDEQUEUE()
fails and sets TP-STATUS
to TPEDIAGNOSTIC
, then further information is available in the DIAGNOSTIC
settings. If you receive the error code QMENOMSG
, it means that no message was available for dequeuing.)
TPDEQUEUE()
. This time have QNAME
point to the name of the failure queue and set the following: TPQCORRID TPQREPLYQ
TPQFAILUREQ TPQMSGID
TPQGETBYCORRID
Populate TPQCORRID
with the correlation identifier. When the call returns, check LEN
to see if data has been received and check APPL-RETURN-CODE
to see if the service has returned a user return code.
Sequential processing of messages can be achieved by having one service enqueue a message for the next service in the chain before its transaction is committed. The originating process can track the progress of the sequence with a series of TPDEQUEUE()
calls to the reply_queue
, if each member uses the same correlation-ID and returns a 0 length reply.
Alternatively, word of the successful completion of the entire sequence can be returned to the originator by using unsolicited notification. To make sure that the last transaction in the sequence ended with a TPCOMMIT
, a job step can be added that calls TPNOTIFY
using the client identifier that is carried in the TPQUEDEF-REC
structure. The originating client must have called TPSETUNSOL
to name the unsolicited message handler being used.
In all of the foregoing discussion of enqueuing and dequeuing messages there has been an implicit assumption that queues were being used as an alternative form of request/response processing. A message does not have to be a service request. The queued message facility can transfer data from one process to another as effectively as a service request. This style of communication between applications or clients is called peer-to-peer communication.
If it suits your application to use BEA Tuxedo /Q for this purpose, have the administrator create a separate queue and code your own receiving program for dequeuing messages from that queue.