{"id":17841,"date":"2026-01-23T09:06:56","date_gmt":"2026-01-23T17:06:56","guid":{"rendered":"https:\/\/www.couchbase.com\/blog\/?p=17841"},"modified":"2026-01-28T08:32:42","modified_gmt":"2026-01-28T16:32:42","slug":"using-ondeploy-in-couchbase-eventing-to-gate-mutations-with-pre-flight-setup","status":"publish","type":"post","link":"https:\/\/www.couchbase.com\/blog\/ko\/using-ondeploy-in-couchbase-eventing-to-gate-mutations-with-pre-flight-setup\/","title":{"rendered":"\uce74\uc6b0\uce58\ubca0\uc774\uc2a4 \uc774\ubca4\ud2b8\uc5d0\uc11c \uc628\ub514\ud50c\ub85c\uc774\ub97c \uc0ac\uc6a9\ud558\uc5ec \ube44\ud589 \uc804 \uc124\uc815\uc73c\ub85c \ub3cc\uc5f0\ubcc0\uc774\ub97c \uac8c\uc774\ud2b8\ud558\uae30"},"content":{"rendered":"

The problem: \u201cStateless\u201d doesn\u2019t mean \u201csetup-free\u201d<\/b><\/h2>\n

Couchbase Eventing is intentionally built like a short-running, stateless lambda: react to a mutation, do some work, exit. That model is clean \u2013 until your eventing function needs <\/span>one-time<\/span><\/i> housekeeping before it can safely process the first mutation.<\/span><\/p>\n

Historically, developers worked around this by doing a \u201cfirst mutation warmup\u201d inside OnUpdate, often with CAS-safe writes or counters so only one thread would load a shared state. That approach can work, but it forces you to depend on a mutation just to establish prerequisites, and it pushes setup concerns into the hottest part of your code path: mutation processing.<\/span>
\n<\/span>
\n<\/span>This is exactly why there was a need for a mutationless initialization concept in Eventing \u2013 an explicit setup phase that can run without an initial mutation and make the function ready before any real work begins.<\/span><\/p>\n

The idea: a pre-flight checklist<\/b><\/h2>\n

OnDeploy<\/b> is a new Eventing handler that runs <\/span>once<\/b> when an Eventing function is:<\/span><\/p>\n