Redis Lettuce backend

Latest stable Based on Leader release 0.4.0

Library module

Problem

Implements single, fixed-slot group, and strategic election with Lettuce connections, token-owned Redis keys, Lua compare-and-delete/extend, and blocking/coroutine APIs.

When to use it

Choose it when Redis is already operated and the application prefers Lettuce’s connection model and explicit scripting.

Coordinates

Artifact: io.github.bluetape4k.leader:bluetape4k-leader-redis-lettuce

dependencies {
    implementation(platform("io.github.bluetape4k:bluetape4k-dependencies:<version>"))
    implementation("io.github.bluetape4k.leader:bluetape4k-leader-redis-lettuce")
}

Core concepts

A unique token owns a TTL key. Lua scripts make release and extension conditional. Strategic election stores candidate metadata and applies Core strategies.

Quick start

val elector = LettuceLeaderElector(connection)
elector.runIfLeader("daily-report") { generateReport() }

API by task

Use the connection extension/factory, blocking/suspend single/group electors, and strategic electors. The connection is caller-owned.

Recommended patterns

Use a dedicated key prefix, keep Redis client and connection lifecycle explicit, make actions idempotent, and plan behavior during failover.

Integrations

Spring can build factories from Lettuce resources. strategic-election and rate-limiter show candidate and group patterns.

Configuration

Configure wait/lease/minimum lease, auto-extension, key prefix, group size, retry, client timeouts, topology refresh, and Redis durability policy.

Failure modes

Contention returns null. Timeout, MOVED/topology, script, authentication, and extension failures propagate. Expired ownership can overlap an old paused action.

Operations

Monitor command latency, reconnects, topology changes, script failures, keyspace/TTL, extension failure, skip rate, and Redis memory pressure.

Testing

Use Redis integration tests for two connections, token-safe release, expiry, group slots, strategic registry, failover handling, and suspend cancellation.

Workshops and learning path

Run strategic-election for candidate scoring and rate-limiter for group slots; compare Lettuce with Redisson’s higher-level client model.

Limitations

Redis availability and failover semantics are on the job path. A Redis token is not fencing for an external database.

Release diagrams

These diagrams are loaded directly from README assets published with the 0.4.0 release and pinned to its immutable commit. They describe this manual’s released structure and runtime flows, not later Snapshot changes. Select a preview to open the SVG at the same release commit.

Sources

Elector · Lua support · Stable guide