feat: add Redis lock backend

[rustatian]

The lock plugin gains a Redis backend that shares locks between RoadRunner instances through the existing RPC API, and the in-memory backend stays the default.

Changes

• Redis backend on go-redis/v9: Lua scripts check ownership and change lock state atomically, and all waiting calls of one RoadRunner instance share one Pub/Sub connection.
• New lock.config keys for addresses, authentication, database, Sentinel, pool size, timeouts, and TLS. An unknown driver, a negative database number, a non-zero database with a cluster client, a negative timeout, and a failed connection test stop plugin initialization.
• Lock, LockRead, and UpdateTTL reject a ttl outside 0 to 9223372036854775 microseconds. All methods reject a wait outside that range. A rejected request returns an RPC error and changes no lock state.
• ForceRelease now returns Ok: true only if it removed at least one lock on both backends.
• Both backends now refuse a second read lock with the same ID on the same resource.
• Lock and LockRead return Ok: false on contention until the wait expires. On Redis, a failed command or a deadline that occurs during a command returns an RPC error, because the lock state is then unknown.
• New log records: the selected backend at the info level, a failed lock script and a failed Pub/Sub subscribe at the error level, and a Pub/Sub subscription that is established again at the warning level.
• CI starts a Redis 7 service and runs both Go modules.

Configuration

lock:
  driver: redis
  config:
    addrs: ["127.0.0.1:6379"]
    username: ""
    password: ""
    db: 0
    master_name: "" # set to use Redis Sentinel; addrs then holds the Sentinel addresses
    sentinel_password: "" # password of the Sentinel nodes
    pool_size: 0 # 0 selects the go-redis default
    dial_timeout: 5s
    read_timeout: 5s
    write_timeout: 5s
    tls:
      root_ca: "" # empty selects the system root certificates
      cert: ""
      key: ""

A set master_name selects a failover client. Without master_name, one address selects a standalone client and two or more addresses select a cluster client. The db setting applies to a standalone client and to a failover client, and a cluster client uses database 0 only.

Omitted timeouts use the Redis client defaults. Write at least one key in the tls block, because the configuration reader drops an empty block and the connection then stays plaintext. Set cert and key together to send a client certificate.

The backend stores lock state under the fixed rr:lock: prefix, with the resource name as the namespace. Redis 7 or later is required.

closes: roadrunner-server/roadrunner#2070.

[Copilot]

🟡 Changes recommended

There are confirmed correctness issues in the new concurrent writer test and Redis wait-loop timer handling that can cause nondeterministic behavior and busy looping, plus an empty-key cleanup issue in the Lua script that can lead to unbounded key buildup.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds a Redis-backed implementation for the lock plugin so multiple RoadRunner instances can share exclusive/read locks via the existing RPC API, while keeping in-memory locks as the default when no lock config section is provided.

Changes:

• Introduces a Redis backend using go-redis/v9 plus an embedded Lua script for atomic lock state transitions and TTL handling.
• Implements wait/notification behavior using Redis Pub/Sub and client-side timers.
• Expands documentation and adds Redis-focused integration tests; updates CI to run the full ./tests/... module with a Redis service.

File summaries

File	Description
redis.go	Implements Redis backend operations, waiting via Pub/Sub + timers.
redis.lua	Atomic Lua script for lock/read/exists/release/ttl/force operations.
config.go	Adds lock/Redis configuration structs with mapstructure tags.
plugin.go	Selects memory vs Redis backend based on config; wires backend into plugin lifecycle.
memory.go	Wraps existing in-memory locker behind the new backend interface (preserves default behavior).
rpc.go	Routes RPC methods through the backend interface and propagates backend errors.
tests/redis_test.go	Adds Redis integration tests covering exclusivity, readers, waits, expiry, and stop behavior.
tests/go.mod / tests/go.sum	Adds go-redis/v9 and required indirect deps for the test module.
go.mod / go.sum	Adds go-redis/v9 and required indirect deps for the plugin module.
.github/workflows/linux.yml	Adds Redis service and runs go test ./... for the tests module.
README.md	Documents backend selection, Redis config, behavior semantics, and how to run tests locally.

Review details

• Files reviewed: 11/13 changed files
• Comments generated: 3
• Review effort level: Lite

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[codecov]

Codecov Report

❌ Patch coverage is 95.48533% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.18%. Comparing base (d2614fc) to head (bf0a334).

Files with missing lines	Patch %	Lines
tls.go	52.38%	10 Missing ⚠️
redis.go	96.93%	9 Missing ⚠️
config.go	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #101      +/-   ##
==========================================
+ Coverage   78.82%   87.18%   +8.36%     
==========================================
  Files           4        9       +5     
  Lines         595     1007     +412     
==========================================
+ Hits          469      878     +409     
- Misses        126      129       +3     

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