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feat: add gha
Signed-off-by: Matthias Riegler <[email protected]>
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‎README.md

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# mq-lease-service
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> A priority mutex with stabilisation window and TTLs, designed to work with the Github MergeQueue accessing a shared resource.
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> Add a funnel for shared resources on the Github Merge Queue.
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If you want to use the github merge-queue feature and have a shared resource that can only be accessed by one process at a time (e.g. deploying a staging environment and running tests), this service/action is for you.
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It allows actions running as part of a merge group to get a mutex/lease on a shared resource, ensuring that only one action can access the resource at a time. Here, it takes in the priority of the action based on the number of commits ahead of the base branch and ensures that the highest priority action gets the lease.
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After releasign the mutex/lease (and by the nature of the merge queue combining commits), a positive outcome is propagated forward to action runs with a lower priority, or, on a failure, the lease is released and the next action with the highest priority gets the lease.
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## Contributing
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@@ -23,6 +27,53 @@ make run-server # to run the server
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## Components
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### Github Action
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The Github Action component of this repo interacts with the LeaseProvider and determines the priority of each run based on the commits ahead of the base.
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It has two stages:
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1. Acquiring a lease
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2. Releasing a lease when (1) has been successful, reporting the Github action job status
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An example workflow can look like this:
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```yaml
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on:
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# Trigger on PRs; here we just skip
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pull_request:
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branches: [ main ]
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# Trigger on the merge group event
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merge_group:
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branches: [ main ]
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types: [ checks_requested ]
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jobs:
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access-shared-resource:
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runs-on: ubuntu-latest
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if: ${{ github.event_name == 'merge_group' }}
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steps:
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- name: Checkout Plugin Repository
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uses: actions/checkout@v3
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- name: acquire lease
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id: acquire_lease
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uses: ankorstore/mq-lease-service@main
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with:
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endpoint: https://your.lease.service.com
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# auth: "" Optional: Authorization header value
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- name: sleep
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# Only perform github actions when this run acquired the lease
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if: ${{ steps.acquire_lease.outputs.result == 'acquired' }}
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run: |
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echo "Do some stuff"
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- name: release lease
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id: release
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uses: ankorstore/mq-lease-service@main
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if: always() # always run this step to ensure we don't leave the lease-service in a dirty state
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with:
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endpoint: https://your.lease.service.com
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release_with_status: ${{ job.status }}
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# auth: "" Optional: Authorization header value
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```
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### LeaseProvider
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The LeaseProvider is a server that provides the ability to manage distributed leases among multiple github action runs, letting the highest priority run _win_ the lease. This process is helpful when there are multiple runs running that need access to a shared resource. It allows them to agree on the _winner_ of a race for the resource, and subsequently provide the _winner_ with a lease until it is released.
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Depending on the release status (success/failure), the lease is completed and confirmation is awaited or the request from the failing lease is discarded and the process restarts.
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- GET `/healthz` Kubernetes health endpoint
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- GET `/readyz` Kubernetes readiness endpoint
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- GET `/metrics` Prometheus metric endpoint
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- POST `/:owner/:repo/:baseRef/aquire` for aquiring a lease (poll until status is acquired or completed)
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- POST `/:owner/:repo/:baseRef/acquire` for aquiring a lease (poll until status is acquired or completed)
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- POST `/:owner/:repo/:baseRef/release` for releasing a lease (the winnder informs the LeaseProvider with the end result)
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The payload and response (_LeaseRequest_) is encoded as JSON and follows this scheme:
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Configuration options:
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- `--port` (8080)
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- `--stabilisation-window` (5m) - time to wait before giving out a lease without all expected PRs being in the merge queue
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- `--ttl` (30s) - time to wait before considering an aquire interest being stale
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- `--ttl` (30s) - time to wait before considering an acquire interest being stale
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- `--expected-build-count` (4) - number of parallel builds to be expected for a given merge group
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#### STM of status transformations
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```
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### GithubAction
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The GithubAction component of this repo interacts with the LeaseProvider and determines the priority of each run based on the commits ahead of the base.
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It has two stages:
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1. Acquiring a lease
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2. Releasing a lease when (1) has been successful, reporting the Github action job status
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An example workflow can look like this:
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```yaml
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on:
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# Trigger on PRs; here we just skip
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pull_request:
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branches: [ main ]
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# Trigger on the merge group event
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merge_group:
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branches: [ main ]
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types: [ checks_requested ]
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jobs:
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access-shared-resource:
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runs-on: ubuntu-latest
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if: ${{ github.event_name == 'merge_group' }}
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steps:
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- name: Checkout Plugin Repository
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uses: actions/checkout@v3
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- name: Aquire lease
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id: acquire_lease
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uses: ankorstore/mq-lease-service@main
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with:
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# Endpoint to connect to
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endpoint: https://your.lease.service.com
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# **IMPORTANT** the job-status always has to be defined like this
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job_status: ${{ job.status }}
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# Optional: timeout_seconds (how long to wait before something is considered going wrong)
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# timeout_seconds: 7200
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# Optional: interval_seconds (the polling interval)
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# timeout_seconds: 15
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- name: sleep
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# Only perform github actions when this run acquired the lease
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if: ${{ steps.acquire_lease.outputs.result == 'acquired' }}
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run: |
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sleep 30
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# Note: there is no further action required, the lease will be released in a post hook of the `Aquire lease` action.
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```

‎action.yaml

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name: MQ Lease Service
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description: "Interact with the mq-lease-service to have a priority-mutex/deduplication mechanism"
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inputs:
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lease_service_url:
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description: "URL of the lease service"
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required: true
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release_with_status:
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description: "If set, release a previously acquired lease with the given status"
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required: false
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default: ""
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auth:
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description: "Authorization header to use for the lease service"
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required: false
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default: ""
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outputs:
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status:
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value: "${{ steps.acquire.outputs.status }}"
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description: "Lease Status"
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stacked_pull_requests:
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value: "${{ steps.acquire.outputs.stacked_pull_requests }}"
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description: "Stacked Pull Requests"
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runs:
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using: "composite"
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steps:
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- name: retrieve status for merge group
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shell: bash
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id: status
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env:
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MERGE_GROUP_BASE_SHA: "${{ github.event.merge_group.base_sha }}"
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MERGE_GROUP_HEAD_SHA: "${{ github.event.merge_group.head_sha }}"
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MERGE_GROUP_BASE_REF: "${{ github.event.merge_group.base_ref }}"
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MERGE_GROUP_HEAD_REF: "${{ github.event.merge_group.head_ref }}"
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GH_TOKEN: ${{ github.token }}
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run: |
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set -eux
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# Determine merge group priority
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echo "merge_group_priority=$(
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gh api "/repos/${{ github.repository_owner }}/${{ github.event.repository.name }}/compare/${MERGE_GROUP_BASE_SHA}...${MERGE_GROUP_HEAD_SHA}" \
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| jq -r '.ahead_by'
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)" >> "$GITHUB_OUTPUT"
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echo "merge_group_base_branch=${MERGE_GROUP_BASE_REF#refs/heads/}" >> "$GITHUB_OUTPUT"
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echo "merge_group_head_branch=${MERGE_GROUP_HEAD_REF#refs/heads/}" >> "$GITHUB_OUTPUT"
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# Try to acquire the lease
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- name: acquire
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id: acquire
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if: ${{ inputs.release_with_status == '' }}
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shell: bash
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env:
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LEASE_API_ENDPOINT: "${{ inputs.lease_service_url }}/${{ github.repository }}/${{ steps.status.outputs.merge_group_base_branch }}"
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AUTH_HEADER_VALUE: "${{ inputs.auth }}"
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HEAD_SHA: "${{ github.event.merge_group.head_sha }}"
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BASE_BRANCH: "${{ steps.status.outputs.merge_group_base_branch }}"
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HEAD_BRANCH: "${{ steps.status.outputs.merge_group_head_branch }}"
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PRIORITY: "${{ steps.status.outputs.merge_group_priority }}"
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run: |
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while true; do
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echo "[ ] Trying to acquire lease"
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resp=$(curl -H"Content-Type: json" -H"Authorization: ${AUTH_HEADER_VALUE}" -X POST -d "{\"head_sha\": \"${HEAD_SHA}\", \"head_ref\": \"${HEAD_BRANCH}\", \"priority\": ${PRIORITY}}" "{$LEASE_API_ENDPOINT}/acquire")
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if [[ $? -ne 0 ]]; then
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echo "[-] Failed to contact lease service (${resp}), retrying"
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sleep 5
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continue
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fi
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status=$(echo "$resp" | jq -r '.request.status')
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error=$(echo "$resp" | jq -r '.error')
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if [[ "$error" != "null" ]]; then
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echo "[-] Unable to aquire lease: $error, retrying"
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sleep 15
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continue
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fi
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if [[ "$status" == "pending" ]]; then
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echo "[+] Lease pending, retrying"
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sleep 15
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continue
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fi
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echo "[+] Lease status: $status"
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# Retrieve stacked pullrequest for better communication at later stages
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stacked_pull_requests=$(echo "$resp" | jq -c '.stacked_pull_requests')
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# Report to output
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echo "status=$status" >> "${GITHUB_OUTPUT}"
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echo "stacked_pull_requests=$stacked_pull_requests" >> "${GITHUB_OUTPUT}"
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break
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done
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- name: release
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id: release
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if: ${{ inputs.release_with_status != '' }}
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shell: bash
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env:
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LEASE_API_ENDPOINT: "${{ inputs.lease_service_url }}/${{ github.repository }}/${{ steps.status.outputs.merge_group_base_branch }}"
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AUTH_HEADER_VALUE: "${{ inputs.auth }}"
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HEAD_SHA: "${{ github.event.merge_group.head_sha }}"
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BASE_BRANCH: "${{ steps.status.outputs.merge_group_base_branch }}"
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HEAD_BRANCH: "${{ steps.status.outputs.merge_group_head_branch }}"
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PRIORITY: "${{ steps.status.outputs.merge_group_priority }}"
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STATUS: "${{ inputs.release_with_status }}"
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run: |
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resp=$(curl -H"Content-Type: json" --fail-with-body -H"Authorization: ${AUTH_HEADER_VALUE}" -X POST -d "{\"head_sha\": \"${HEAD_SHA}\", \"head_ref\": \"${HEAD_BRANCH}\", \"priority\": ${PRIORITY}, \"status\": \"${STATUS}\"}" "${LEASE_API_ENDPOINT}/release")
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if [ $? -eq 0 ]; then
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echo "[+] Updated lease status: $RELEASE_WITH_STATUS"
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else
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echo "[!] Failed to update lease status - merge queue may be stuck"
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echo "$resp"
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fi

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