Guard HMGET against empty payload keys in GetWorkflowInstanceHistory - #487
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cschleiden merged 3 commits intoAug 10, 2026
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Funnily enough this is already fixed in my Valkey PR: https://github.com/cschleiden/go-workflows/pull/460/changes#diff-33c2b06ea8a250f39db361963182b32d9f40e48dc055d65daa85e0e4597df261R103 @cschleiden let me know if you need more information, this is a bug I found in production, if you need specific logs or failure conditions, hit me up. :) |
When an instance's history stream is empty, payloadKeys is empty and HMGET is called with no fields, which Redis rejects with 'ERR wrong number of arguments for hmget'. Guard the payload fetch with len(payloadKeys) > 0, mirroring the existing guard in workflow.go.
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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
cschleiden
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Problem
(*redisBackend).GetWorkflowInstanceHistorycallsHMGET key <fields...>with an empty field list when an instance's history stream has no events, which Redis rejects:This surfaces as
reading payloads: ...fromGetWorkflowInstanceHistoryfor instances whose history stream is empty (e.g. an orphaned/pruned instance, or a read wherelastSequenceIDis at/after the newest event soXRANGEreturns nothing).Fix
getWorkflowInstanceStateinbackend/redis/workflow.goalready guards the identical payload fetch withif len(payloadKeys) > 0. This applies the same guard inbackend/redis/instance.go. When there are no events there are no payloads to fetch, so the block is simply skipped and an empty history is returned.