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This page is an opinion on DataStage solution design practices and doesn’t affect MettleCI support for the functionality discussed. |
There are two types of Message Handlers in DataStage.
Project Level Message Handlers: These are installed in an application directory per Engine and and aren't supported by MettleCI so should be migrated manually.
Job Level Message Handlers: There is a MettleCI plugin functionality to support their deployment only. While MettleCI deploys Job Level Message Handler files from a Project's Git repository, it doesn't offer native check-in and deletion functions for them so they must be managed via command line Git.
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The following observations about Message Handlers, based on Data Migrators' decades of field experience, suggest DataStage developers and architects should reconsider their use.
Message Handlers are not DataStage assets
Message Handlers are not an asset of DataStage. See Note below for an explanation whyIBM documentation notes that they cannot be managed the same way as jobs, sequences, parameter set definitions, etc., are managed. They cannot be placed in an ISX export of their own, they have to be associated with a Job.
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"You can use the IBM® InfoSphere® Information Server Manager (the deployment tool) to move, deploy, and control your IBM InfoSphere DataStage® and QualityStage® assets." However, message handlers cannot be managed individually using the IS Manager or |
MettleCI can’t handle them in the conventional way for the reasons above. Project-Level Message Handlers can’t be handled at all, while special provisions must be made for Job-Level Message Handlers. Refer to this page to understand the complicated manual process that is required to obtain and on-board Job-Level Message Handlers as you apply devops to your DataStage solution. These considerations mean extra work during all migrations and deployments.
Message Handlers may disguise poor development practices
High-performing DataStage development teams rightly view message handlers as something that disguises risks disguising poor coding or job Job design decisions. They are most often found in organizations that mandate that Jobs should run without warnings but with little else to encourage their developers to remediate the root cause. As a resultUnder this design standard, Jobs are often set to Abort (e.g. via an After Routine) if they generate warning messages. Unfortunately, this oftem often leads to developers - especially those under pressure - applying message handlers Message Handlers to quickly get compliant and move on.Organizations should refrain from using
Message Handlers
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Message Handler Deployment Plug-In
There is a Bamboo Plugin to support deployment of Job-Level Message Handlers: dm-dsmsgh-plugin.
The Plugin includes a task that will read all Message Handlers that follow the "<Job Name>.msh" naming convention and "inject" them into the ISX file of the corresponding Job during deployment. The updated ISX file can then be deployed like normal, resulting in both the Job design and Job-Level Message Handler ending up in the target DataStage instance.
In order to use this MettleCI feature:
All Job-Level Message Handlers in a particular DataStage Project will need to be added to the corresponding Git repository, alongside the existing ISX files. These files need to be named following the "<Job Name>.msh" convention.
Continuous Integration Build Plans and Deployment Environments in Bamboo will need to be updated to execute the new "DataStage Message Handlers Task" immediately before the "DataStage Incremental Deployment Task".
For each Message Handler added to Git, the corresponding <Job Name>.isx jobs need to be checked in to Git again. This is necessary to ensure that the subsequent CI Build Plan deployment (triggered by the check-in) will process the Message Handler as necessary.
No changes to Bamboo Deployment Environment configuration is required.
How to Find the relevant Local.msh in the Information Server File System.
For example: There is a Job called “GR_ACCOUNTS_LOCAL"
Within the relevant Project filesystem, find the RT_SC<Job Number> directory that corresponds to the Job. The simplest method is to use Director to open up a log entry for the Job then get the "Job No." entry from that dialog box.
Within the RT_SC<Job Number> directory, find the Job-Level Message Handler config file (Local.msh)
Once found, copy and rename that file to GR_ACCOUNTS_LOCAL.msh and check it into Git alongside the existing ISX file
Once this file has been checked in, re-check in the corresponding Job. This ensures that automated deployments pick it up.
The (updated) Continuous Integration Bamboo Plan for the corresponding DataStage Project will be auto-triggered and must complete successfully. This will ensure that subsequent deployments to other environments (Test, QA, Production) will include Job-Level Message Handlers.
Changes to CI Plans
Continuous Integration Build Plans in Bamboo will need to be updated to execute the "DataStage Message Handlers" Task.
Once you have deployed the dm-dsmsgh-plugin plugin .jar to Bamboo, you will be able to add a 'DataStage Message Handlers' Task to an existing Continuous Integration Build Plan.
Ensure the new Task is immediately before the "Incremental DataStage Deployment" Task.
Both the 'Root ISX directory' and 'Root message handler directory' fields must contain: datastage.
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are subject to regression
As previously highlighted, the very nature of IBM’s tools for managing Job Level Message Handlers in Information Server means any automation solution for them will be at risk of permanent regression with future IBM Fix Packs and Releases
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. Since they are not “assets”, they may be regarded as “second class citizens” when breaking changes are introduced.
Conclusion
In view of the above drawbacks, it’s recommended that organizations reconsider the wisdom of using Message Handlers and, instead, focus on refactoring Jobs to eliminate (or at least minimise) warnings or errors. MettleCI features like Unit Testing and Compliance are a great way to increase the safety and speed of such refactoring efforts for developers. In conjunction, Job Schedulers can be reconfigured to be able to allow Warnings in exceptional circumstances. In this way, development standards improve but in the unlikely situation that there is no alternative, Job Warnings can be applied consciously, instead of by default.