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Message
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| hdjur |
 Posted: Wed Feb 07, 2007 1:00 am Post subject: store variables to LocalEnvironment using mapping node |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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Talking about LocalEnvironment tree structure:
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Variables
This subtree is optional. If you create local environment variables, you are recommended to
store them in a subtree called Variables. It provides a work area that you can use to pass
information between nodes. This subtree is never inspected or modified by any supplied node.
Variables in the local environment can be changed by any subsequent message processing node...
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I would like to store MQMD.MsgId to this tree using mapping node. Is it possible?
I have changed Mapping mode to LocalEnvironment And Message, using Add or Remove Headers and Folders... dialogue box in target pane I have chosen LocalEnvironment (and in source pane I have chosen MQMD), but the only LocalEnvironment subtree I see is Destination (MQ,HTTP,RouterList). Can I use some of these, or do I have to use compute nodes instead? I would like to access this variable the same way in a subsequent mapping node. Thank you. |
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| hdjur |
| Posted: Wed Feb 07, 2007 9:34 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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Forget about the mapping node. I have a problem with a scope of LocalEnvironment variables. I have compute node immediately after MQInput node, it stores MsgId to LocalEnvironment properly with:
| Code: |
| SET OutputLocalEnvironment.Variables.MsgId = InputRoot.MQMD.MsgId; |
Before MQOutput node, I have another compute node, which tries to access it with:
| Code: |
SET OutputRoot.MQMD.CorrelId = InputLocalEnvironment.Variables.MsgId;
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Both compute nodes have compute mode set to LocalEnvironment and Message. Trace node which precedes second compute node shows correctly preserved LocalEnvironment variable until that point:
local env: (
(0x01000000):Variables = (
(0x03000000):MsgId = X'414d51205742524b5f544553545f514d458974692006820b'
)
(0x01000000):LOCAL_STACK = (
. . .
Trace node which follows second compute node shows that CorrelId was not properly set:
(0x01000000):MQMD = (
(0x03000000):StrucId = 'MD '
(0x03000000):Version = 2
(0x03000000):Encoding = 546
(0x03000000):CodedCharSetId = 819
(0x03000000):CorrelId = X'000000000000000000000000000000000000000000000000'
(0x03000000):Format = ''
(0x03000000):Transactional = FALSE
(0x03000000):Persistence = 0
(0x03000000):PutDate = DATE '2007-02-07'
(0x03000000):PutTime = GMTTIME '17:03:55.212683'
(0x03000000):Expiry = -1
(0x03000000):Priority = 0
)
and that LocalEnvironment is lost.
| Quote: |
Variables in the local environment can be changed by any subsequent message processing node, and persist until the message flow goes out of scope and the node that created it has completed its work and returns control to the previous node. |
I don't understand that. Variable persists throughout the flow, but when I try to access it, it disappears. Thanks in advance. |
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| jefflowrey |
| Posted: Wed Feb 07, 2007 9:54 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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You have to not only set the compute mode, you have to copy InputLocalEnvironment to OutputLocalEnvironment.
_________________
I am *not* the model of the modern major general. |
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| hdjur |
| Posted: Thu Feb 08, 2007 1:12 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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You are right about preserving LocalEnvironment after the second compute node, which I shouldn't probably mention at all.
Any comments on posted ESQL? Because I still have null CorrelId.
(0x03000000):CorrelId = X'000000000000000000000000000000000000000000000000'
The reason I'm doing this, is because I remove MQMD header before issuing HTTP request, and when I restore it, to return response to a queue I have to set CorrelId to the MsgId of the request. Is there a better practice to do it besides using LocalEnvironment? I have read some suggestions to copy data to an intermediate queue. |
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| hdjur |
| Posted: Thu Feb 08, 2007 1:59 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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| Quote: |
| but the only LocalEnvironment subtree I see is Destination (MQ,HTTP,RouterList). Can I use some of these, or do I have to use compute nodes instead? |
According to data type xsd:hexBinary, none of them might be suitable? |
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| fjb_saper |
| Posted: Thu Feb 08, 2007 4:19 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Have you tried using the Environment tree instead of LocalEnvironment? 
_________________
MQ & Broker admin |
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| hdjur |
| Posted: Thu Feb 08, 2007 8:22 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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I just did, didn't solve the problem. I have replaced in the first compute node:
| Code: |
SET Environment.Variables.MsgId = InputRoot.MQMD.MsgId;
-- SET OutputLocalEnvironment.Variables.MsgId = InputRoot.MQMD.MsgId;
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and in the second
| Code: |
SET OutputRoot.MQMD.CorrelId = Environment.Variables.MsgId;
-- SET OutputRoot.MQMD.CorrelId = InputLocalEnvironment.Variables.MsgId;
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set on both nodes compute mode="All".
The only difference I see is that Environment persists after the second compute node without being explicitly copied from input to output in that node. |
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| hdjur |
| Posted: Thu Feb 08, 2007 9:10 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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I have tried also in the second compute node (I don't know why, I just did):
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SET OutputRoot.MQMD.CorrelId = CAST(Environment.Variables.MsgId AS BLOB);
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Useless. |
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| hdjur |
| Posted: Thu Feb 08, 2007 9:31 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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| Do I have to emphasize somehow that InputRoot.MQMD.MsgId is of REFERENCE data type before storing it to Environment? Or while accessing it from Environment? Any example please? |
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| hdjur |
| Posted: Thu Feb 22, 2007 7:20 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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| I have solved my problem of correlating response (output) mq message and request (input) mq message in the same flow, by changing Advanced Properties of HTTP Request node, so that input mq message (especially important is its MQMD) is passed on together with http response, on the output of HTTP Request node. So that I am able now to map in the mapping node source MQMD to target MQMD (MsgId to CorrelId). I have eliminated the need for compute node, since the only reason for introducing it was to restore MQMD, which was lost with previous HTTP Request node settings. The interesting part here is the secret link between MQMD.CorrelId element and Properties.ReplyIdentifier element. Namely, the reason why the posted esql didn't work was because I have mapped Properties.ReplyIdentifier, setting it this way to null in a mapping node, and I couldn't fix it in subsequent compute node (set MQMD.CorrelId), although MsgId value was stored correctly in Environment.Variables. Anyone, please feel free to add any comment. |
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| fjb_saper |
| Posted: Thu Feb 22, 2007 1:36 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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Depending on how you create the correlation id...
If created in preceding MQOutput node you need to get it from
| Code: |
| set OutputRoot.MQMD.correlid = InputLocalEnvironment.WrittenDestination.MQ.DestinationData.correlId; |
as this is where the output value of the node gets written AND NOT to the message's MQMD.
Enjoy
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| hdjur |
| Posted: Thu Feb 22, 2007 2:52 pm Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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I'm sorry for not explaining clearly what does the flow look like. I have MQInput node, Mapping node#1, HTTP Request node, Mapping node#2, and MQOutput node. The flow works as a web service client. Web service call is issued via http. Request arrives as mq message, gets transformed to http request, and http response gets transformed to response mq message. MQOutput node is not preceding to any other node in this flow. Does that change anything, or the suggestion still stands?
Thanks. |
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| fjb_saper |
| Posted: Thu Feb 22, 2007 8:32 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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No but you need to preserve the input message or at least the MQMD for the MQReply node.
Best way is to create the adequate parser in the Environment and park it there until you need it again....
Enjoy
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| hdjur |
| Posted: Thu Feb 22, 2007 11:55 pm Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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I have preserved input message by using Advanced Properties settings of HTTP Request node, that is :
"Replace input message with web-service response"
and
"Response message location in tree"
From input MQMD I have used not only MsgId for correlation purposes,
but also for example Persistence and Expiry, and every other attribute which makes sense to be the same or similar to request message attributes. Is there anything wrong with this logic? |
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| hdjur |
| Posted: Fri Feb 23, 2007 1:00 am Post subject: |
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Centurion
Joined: 16 Sep 2004
Posts: 116
Location: Zagreb
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When I said:
| Quote: |
| and I couldn't fix it in subsequent compute node (set MQMD.CorrelId), although MsgId value was stored correctly in Environment.Variables |
I meant until I didn't remove Properties mapping, so that it works now this way too (using compute node). But I still wonder why this was a neccessary step? |
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