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## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
Noticed a few leftover places where we were referencing the assets by
their version instead of using latest.
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
## Breaking Changes
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## Types of changes
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the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
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that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
## Additional context
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Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>
## Summary
Fixes race conditions in concurrent server publishing that could result
in data integrity violations:
- Multiple versions marked as `isLatest=true` for the same server
- Duplicate (serverId, version) combinations
- Same server name assigned different serverIDs
## Solution
Uses two complementary approaches for correctness:
### 1. PostgreSQL Advisory Locks
- Serializes concurrent publishes per server name using
`pg_advisory_xact_lock`
- Uses FNV-1a hash to convert server name to lock ID
- Transaction-scoped locks auto-release on commit/rollback
- **Required after #465**: The serverId introduction means concurrent
publishes must atomically coordinate whether to reuse an existing
serverId (for additional versions) or generate a new one (for first
version). Without locks, race conditions would assign different
serverIDs to versions of the same server.
### 2. Unique Constraints (Migration 007)
Two new indexes provide data integrity guarantees:
- **idx_unique_server_version**: Ensures (serverId, version) is unique
across all versions
- **idx_unique_latest_version**: Partial index ensuring only one version
per serverId has `isLatest=true`
These constraints serve as defense-in-depth safety nets. Even if lock
logic had a bug, the database would reject integrity violations.
Also drops redundant `idx_servers_version_id` since `version_id` is
already the primary key.
## Why WithPublishLock validation is needed after #465
The `ctx.Err()` check at the start of `WithPublishLock` is critical
because:
1. After #465 introduced serverId, the publish flow must atomically
check existing versions and assign/reuse serverId
2. If the context is cancelled during lock acquisition, we could
deadlock
3. Checking ctx validity before acquiring locks prevents these deadlocks
## Testing
Added `TestPublishConcurrentVersionsNoRace` with 100 concurrent
goroutines publishing different versions of the same server. All succeed
with:
- Exactly one version marked as latest
- All versions sharing the same serverId
- No duplicate (serverId, version) combinations
NB: this only covers the in memory db, not the postgres db. It'd be nice
to write tests for this one as well, but our current setup is a bit
annoying for this. Separately looking into ways to easily run all our
tests with real postgres and ideally scrap memory.go completely.
