Exposed backend core

Library module

Problem

Defines the shared SQL schema, table mappings, retry policy, history codec, and migrations used by JDBC and R2DBC electors. Applications normally select an adapter instead.

When to use it

Use it directly when your team owns schema migration or builds a custom SQL adapter.

Coordinates

Artifact: io.github.bluetape4k.leader:bluetape4k-leader-exposed-core

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

Core concepts

Lock, group-slot, and history tables share keys and expiry rules. Conditional SQL transactions provide ownership; retry handles transient conflicts.

Quick start

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

API by task

ExposedLeaderSchema, table objects, and RetryStrategy are the main support APIs. Adapter initializers are the normal application entry point.

Recommended patterns

Give schema creation to one deployment step, keep a dedicated namespace, preserve unique keys, and apply migrations before application rollout.

Integrations

JDBC and R2DBC share these tables and metadata formats; consistent configuration lets both observe the same logical namespace.

Configuration

Adapters own schema names and retry settings. Database clock, isolation, timeout, and pool sizing remain application responsibilities.

Failure modes

Missing tables and permission errors are deployment failures, not contention. Serialization conflicts may retry; malformed migration state must surface.

Operations

Monitor table growth, history retention, dead tuples, and database latency. Never delete a row from application-local time alone.

Testing

Run schema tests per dialect and verify JDBC/R2DBC agree on keys, expiry units, and metadata.

Workshops and learning path

Read this before JDBC/R2DBC when migration ownership is separate. The migration-gate example shows election around deployment work.

Limitations

This is not a complete elector and selects no driver, pool, or transaction manager.

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.

leader exposed core ERD diagram

Release README: leader-exposed-core/README.md

Sources

Schema · Lock table · Stable guide