Kotlin/Native Multiplatform Target

Diagram

The shared protocol and booblik-protocol

The Kotlin/Native client is not a reimplementation of the protocol but a target of the shared protocol. The codec, the IDs, and the partitioner are all sourced from :booblik-protocol, which compiles for the JVM and both native targets from a single source (build.gradle.kts:37-38). This ensures that the native client is a true target of the shared protocol rather than a fifth implementation.

Blocking POSIX sockets and the absence of Dispatchers.IO

The client uses blocking POSIX sockets and does not utilize coroutines for the core connection logic. Because Dispatchers.IO is internal in the Kotlin/Native runtime (build.gradle.kts:18-19), there is no standard IO pool to offload blocking socket calls onto. Consequently, the client remains synchronous, and the Sequence used in the consumer is chosen specifically because there is nothing to suspend on when the socket is a blocking POSIX one (README.md:54-56).

The Producer accumulator and newSingleThreadContext

While the Connection remains blocking, the Producer acts as an accumulator. Because the standard IO dispatcher is unavailable, the concurrency model requires a dedicated thread; specifically, newSingleThreadContext is used so that the producer owns a thread where both the loop and the socket reside (build.gradle.kts:20-22).

CRC32C checksum and the reflected polynomial trap

Verifying a record's checksum is the responsibility of the client. This is implemented via expect/actual to allow the JVM to use its intrinsic CRC32C while Kotlin/Native uses a 256-entry table (README.md:72-78). A significant edge case occurred during development where a hand-derived negative literal -0x7D644AC8 was used, which actually represents 0x829BB538, resulting in a stable but incorrect sum (README.md:82-84).

The gate.sh and conformance-client.sh validation

Validation is performed through two distinct scripts. gate.sh is used for local checks, selecting a target that the host can actually execute, such as linuxX64 or macosArm64 (README.md:100-104). The conformance-client.sh script handles the heavy lifting of building the binary if necessary and then executing it against a real broker (conformance-client.sh:37-38).

Key files

Behaviour that surprise

• produce returns null when AckPolicy.NONE is used, because no offset exists until the writer reaches the batch (README.md:89-90).
• partitionFor(null) is not a static lookup but advances a round-robin counter (README.md:95).
• The position in a consumer is managed by the client and must be persisted after records are dealt with to ensure restart reliability (README.md:62-63).