Shared concourse RFC

Signed-off-by: Derek Richard <[email protected]>

Author: drich10

toc/rfc/rfc-0040-shared-concourse.md

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+# Meta
+[meta]: #meta
+- Name: Shared Concourse Instance
+- Start Date: 2025-07-07
+- Author(s): @drich10
+- Status: Draft
+- RFC Pull Request: (fill in with PR link after you submit it)
+
+## Summary
+
+Provide a shared Concourse instance for CI/CD workloads within the CFF.
+
+## Problem
+
+Currently, _most_ teams using Concourse are deploying and managing their own instance. This creates overhead in both engineering time and cloud costs.
+
+## Proposal
+
+The Concourse WG MUST host a shared Concourse for working groups to leverage for CI/CD. This MUST reduce both engineering and cloud expenses. Consolidating Concourse spend into a singular account MAY make it easier to manage the spend and usage. Additionally centralizing management of CI maintenance, MAY remove load on members/leads of working groups managing their own instance(s). Working groups MAY use this instance if they choose to.
+
+### Access
+Concourse can use Github teams to manage access control within pipelines and credential systems. As such, working group areas and membership MUST determine roles within the system:
+* New role in the Concourse WG to administrate.
+* WG execution leads that are onboarded are given adminstration permissions.
+* WGs must identify area(s) to give access to.
+
+### Credential Management
+Credential access and management MUST be segmented so that WGs cannot access one another's secrets.
+  * Vault MAY be the secret manager to allow consistent management and separation of secrets between teams on the shared instance.
+  * We believe most teams currently use Credhub which does not easily allow us to implement the separation that MUST exist between teams.
+
+### Cost Reduction
+* Removes the overhead from additional Web and DB instances that come from running multiple instances of Concourse.
+* Enables sharing of lesser used worker types such like Windows Workers. Reducing the number of these workers that MUST exist.
+
+### Expectations and Agreements
+* Concourse WG leads will be primarily responsible for system availability during the business hours for each individual.
+* Concourse WG leads will be responsible for system upgrades.
+* WGs onboarded to the shared instance MUST be given sufficient access to operate the system. This includes, but is not limited to:
+  * IaaS access
+  * Runbooks and tooling for Concourse deployment
+* Support Issues MUST be shared between the Concourse working group maintainers and the concourse supporters
+
+### Timeline
+* Concourse team creates the new, shared, instance and migrates itself (2-3 weeks from acceptance of this proposal)
+* Onboard 1 working group to the new instance and refine deployment and operational strategies from initial learnings (2-3 weeks). Shut down the concourse owned by the working group.
+* Open onboarding to the rest of the working groups and migrate their pipelines. Shut down the concourse owned by the working group(s).
+* Success criteria:
+  * 2 or more teams leveraging this instance.
+  * Each team onboarding MUST either reduce or maintain the current level of infrastructure costs.