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ReserveCacheError: Unable to reserve cache with key <cache-key> #722
Description
When using a reusable build inside a matrix workflow, only one of the jobs is able to write its cache.
example:
# .github/workflows/main.yaml
on:
push: [main]
jobs:
build-android:
strategy:
matrix:
app-name:
- app1
- app2
uses: ./.github/workflows/reusable-build.yaml
with:
app-name: ${{ matrix.app-name }}# .github/workflows/reusable-build.yaml
on:
workflow_call:
inputs:
app-name:
required: true
type: string
jobs:
build:
steps:
# ...
- uses: gradle/actions/setup-gradle@v4
# ... build <app-name>In the example above, one of the gradle steps will successfully write its cache, but the other fails with error
Failed to save cache entry with path '<path>' and key: <key>: ReserveCacheError: Unable to reserve cache with key <key>, another job may be creating this cache.
Both jobs have the same key. Edit: the cache key doesn't include anything for the matrix context (eg gradle-home-v1|Linux-X64|build[ef6094c74d56794d327380021ca7a151]-2baefdce1c4b89355ff1a945a35e960b6289568f)
Activity
bennettp123 commentedon Sep 4, 2025
Assuming this is caused by colliding cache keys. Looking at the cache-key.ts, it already attempts to include the matrix context in the cache key.
I'm guessing it's because the matrix context is only defined at the top level, and it doesn't propagate into the reusable workflow.
Possible workarounds:
workflow-job-contextGRADLE_BUILD_ACTION_CACHE_KEY_JOB_INSTANCEbigdaz commentedon Sep 4, 2025
This is an issue specific to reusable workflows, and is discussed extensively in this issue: #316 (comment)
Unfortunately, we haven't been able to find a way to differentiate between different instances of the same reusable workflow: these jobs share the same name, matrix and everything else that goes into the cache key.
Setting
workflow-job-contextis likely the best workaround.