validator: validate host constraints against instance hostlist #7203
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Problem: In test t2260-job-list.t, a fake resource set forces the nodelist to `node[0-3]`, but this fake hostlist does not also apply to the `hostlist` broker attribute. Since the jobspec validator will soon check for valid hostlist constraints using the `hostlist` attribute, this may cause job submissions using `--requires=host:nodeX` to fail. Use the `--test-hosts` option of `flux start` to ensure the `hostlist` attribute matches the hostlist in the resource set.
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Problem: Hostlist constraints set in jobspec are currently validated only to determine if they conform to RFC 29 Hostlist format. Invalid hosts required in a constraint currently result in an empty set of potential resources in the scheduler and thereby an "unsatisfiable" error, and invalid excluded hosts are silently ignored. Neither of these are helpful to users who may have mistyped the intended hosts. When possible, fetch the enclosing hostlist and ensure all hosts in a constraint are contained within it, and raise an exception calling out any invalid hostnames. Add a function to create an on-demand, per-thread Flux handle in the Jobspec module for use by the validation functions. Use this to fetch the local hostlist attribute (if there is one) and cache it, and validate any hosts in constraints using that hostlist. Fixes flux-framework#7200
Problem: No tests in the testsuite ensure that the job validator catches invalid hosts in a hostlist constraint. Add a couple tests to t2110-job-ingest-validator.t.
garlick
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Nov 14, 2025
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LGTM! That worked out nicely.
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #7203 +/- ##
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- Coverage 83.70% 83.70% -0.01%
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Files 553 553
Lines 92350 92370 +20
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+ Hits 77304 77320 +16
- Misses 15046 15050 +4
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Currently invalid hostnames in a jobspec hostlist constraint either result in mysterious unsatisfiable errors or are silently ignored. The jobspec validator only ensures the hostlist can be decoded, but does no further validation.
This PR adds support for validating constraint hosts against the instance hostlist (if it is available), and gives users a more meaningful error:
This approach will not detect excluded hosts, nor if hosts are requested that are not also currently in the selected queue, etc. However, this ensures the hosts are at least valid hostnames for the current instance, and the implementation is very lightweight. Further validation would be much more heavyweight, but could potentially be done in the future in a separate validator plugin.