Updating the main globaltag

13.2. Updating the main globaltag#

Tip

Please have a look to this page for a broader overview about the Conditions Database.

basf2 needs payloads to work so we need a special globaltag (usually called “main” globaltag) for software development. The main globaltag is also used as baseline for our run-independent MC productions. Due to the development model there are a few requirements for this globaltag:

  • The contents of the database should work correctly for any commit on the main basf2 branch. We have to be sure that updates to the globaltag do not affect existing development on other branches. As such every change to the code which requires changes to the payloads to work needs to be coordinated and result in a new globaltag.

  • The globaltag should not contain run-dependent calibrations for data.

  • The globaltag should clearly fail when running on data. Running with wrong calibrations is worse than not running at all. The main globaltag only contains payloads for experiment 0 (nominal Phase 3), 1003 (early Phase 3, pre LS1) and 1004 (early Phase 3, post LS1).

Tip

If you want to know who is the manager of the main globaltag, please browse the relevant file in the versioning repository, go down to the jira_global_tag_v2 function and look for the assignee of the task labelled as main.

13.2.1. Preparation of payloads#

Before requesting any changes of payloads, or introduction of new payloads, the payload code needs to be prepared. Please create a merge request which contains the changes to the code which are required. In all cases you should create a local database containing the new payload versions. This is one text file containing a description of which payload is valid for which experiment and run range and the payloads themselves as root files named dbstore_${payloadName}_rev_${revision}.root where the revision number is just an alphanumeric string (the first few characters of the MD5 checksum of the payload file) to distinguish different versions. A local database file might look something like this:

dbstore/KLMStripEfficiency b82d5b 0,0,0,-1
dbstore/KLMStripEfficiency b82d5b 1003,0,1003,-1
dbstore/KLMStripEfficiency b82d5b 1004,0,1004,-1
dbstore/ECLLeakageCorrections a211cd3 0,0,-1,-1

Each line describes one interval of validity for one payload and consists of:

  1. A dbstore/ prefix. This one is always the same and is there for historical reasons.

  2. The payload name. This is usually the class name of your payload.

  3. The revision code. Note that the revision code is not the final revision in the Conditions Database, that is instead a number and it is unique

  4. The Interval of Validity (IoV) for which the payload is valid, see the Conditions Database overview.

Warning

The payload name should start with the package name and should clearly indicate somehow what this payload is for (no MyPayload or similar).

Valid values for IoVs to be included in the main globaltag are listed in the following table:

IoV

Valid for

0,0,0,-1

Valid only for nominal Phase 3

1003,0,1003,-1

Valid only for early Phase 3, pre LS1

1004,0,1004,-1

Valid only for early Phase 3, post LS1

0,0,-1,-1

Valid for all the phases

Mostly the database.txt file should be generated automatically if you use the DBImport interface but please review it and make sure all payloads have the correct IoV and make sure it contains all the payloads you want to add and nothing else. The database.txt and the corresponding payload files should then be provided to the globaltag manager (using the b2conditionsdb-request tool) for each of the three following use cases:

Warning

The IoV (1002,0,1002,-1), covering Phase 2, was supported until the globaltag main_2023-06-29.

Create a new payload#

If you create new payloads it is advisable to split the creation of the payloads and the usage of the payloads in separate merge requests:

  1. Create, review and merge a merge request to create the payload definition without using it.

  2. Request payloads to be added to the globaltag by just providing the payloads.

  3. Create, review and merge a merge request to actually use the payload already in the globaltag.

This allows to merge the actual code changes without any coordination with the globaltag manager and greatly speeds up and simplifies the globaltag update procedure.

Tip

To create new payload, please check the corresponding documentation.

Warning

If you cannot manage to split the merge requests please create a merge request with the code changes and make sure that, apart from the missing payload, it is approved by all necessary people and can be merged on short notice. Only then should you ask for an update of the globaltag by providing the merge request number and the new payloads to the globaltag manager.

Update a payload to contain new contents without changing its definition#

This is the simplest type of operation: just provide new payloads to the globaltag manager for inclusion in the globaltag.

Modify an existing payload definition#

This is the most tricky one as changes in payload definitions often lead to problems: globaltags might contain older versions of the payload and cannot be read correctly.

Warning

If you change the member definition of a payload class:

  • you must make sure you increase the ClassDef version number correctly;

  • you run the tool b2code-classversion-update over the corresponding linkdef.h file;

  • you should provide schema evolution rules or otherwise make sure the code still works if an older version of the payload is found in a globaltag.

If you manage to make sure that the code also works with the old payload you can just review and test the changes as usual and don’t need to coordinate with the globaltag manager. Once your new payload definition is merged you can just provide the new payloads to the globaltag manager.

Warning

If you cannot ensure backwards compatibility, you should discuss about this with the globaltag manager or during a Software Developers meeting. Then, after having found a proper solution, please create a merge request with the code changes and make sure that, apart from the missing payload, it is approved by all necessary people and can be merged on short notice. Only then you should ask for an update of the globaltag by providing the merge request number and the new payloads to the globaltag manager.

13.2.2. Testing of all changes#

Please make sure the payloads contain the contents you expect them to have. You can easily inspect a payload file using the tool b2conditionsdb-dump (see the full documentation here).

Warning

It’s not recommended to inspect very large payloads like the magnetic field as this can take up to half an hour and \(\mathcal{O}(10)\) GB of RAM.

Tip

You can also pipe the output of this command into a file to compare different revisions with diff.

All merge requests and payload requests must be tested. Once you have prepared your local database file please run the following snippet:

# include your local database in the fallbacks
export BELLE2_CONDB_FALLBACK="/cvmfs/belle.cern.ch/conditions /full/path/to/your/database.txt"
# disable access to central database to make your local database the most important one
export BELLE2_CONDB_GLOBALTAG=""
# run the tests
b2test-units
b2test-scripts
# don't forget to unset the environment variables afterwards
unset BELLE2_CONDB_FALLBACK
unset BELLE2_CONDB_GLOBALTAG

and make sure there are no failing tests. You might want to run b2test-scripts -j N to execute N tests in parallel.

13.2.3. Update procedure#

Once you have prepared all the payloads, and the merge request if one is required, you need to notify the globaltag manager that you need a change to payloads on main using the b2conditionsdb-request tool by calling

b2condtionsdb-request /path/to/database.txt

and following the instructions (select main as target of your request).

You need to provide appropriate information so that the other groups know how to handle this payload in other globaltags:

  1. The new payloads.

  2. Is a merge request needed (see above)?

  3. Does a previous version of this payload exist? If so, is the new code compatible or will it crash if the old version is found?

  4. Is this payload required when processing existing data? If so, can a common payload be prepared for existing data processing or is a dedicated calibration needed?

The globaltag manager for software development will create a new main globaltag and a merge request to change the software to use this globaltag, the “Tag Update Procedure Pull Request” (TUPPR). This merge request is like a box to contain a set of changes to the globaltag in an airtight way to make sure they all stay fresh and don’t break other branches until the change to the globaltag is actually added to main.

Additional changes to the main globaltag by other developers can thus join in on this update.

Tip

All the TUPPRs names start with the tag TUPPR for clearly distinguishing them from the other merge requests.

Warning

All merge requests to join into this globaltag update will be modified to not merge against main but against the TUPPR branch. After these changes the merge requests should be able to see any payloads uploaded to the new globaltag.

Warning

Review of the separate merge requests can then proceed as usual: once all reviewers have approved the merge request can be merged as usual. However this will not directly make these changes available on main. Instead the changes will be aggregated into TUPPR first.

Once all merge requests requiring changes are approved and merged, the globaltag manager for software development will review the changes in the globaltag.

  1. IoVs for common payloads will be split into separate Phase 2 and Phase 3 IoVs.

  2. All duplicate payloads will be removed (for example older revisions).

  3. The remaining changes to the main globaltag will be posted on the TUPPR description

Finally, once these changes are reviewed the globaltag will be published and the TUPPR will be merged which makes the changes available on the main branch.

../../../_images/tuppr.png

Fig. 13.2 Workflow for updating the main globaltag via TUPPR.#

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