Coalescent Comptuting Prototypes

Inspired by Coalescent Computing.

A high-performance, asynchronous, (soon-to-be) distributed WebAssembly (Wasm) task executor node built in Rust. This platform uses Wasmtime and WASI to securely sandbox, schedule, and execute workloads with (sort of) granular resource tracking and epoch-based deadline guarantees.

Crate structure:

coalescent/
 crates/
 coalescent-interface/ # pure types + traits, no runtime deps
 coalescent-executor/ # wasmtime, tokio, epoch management
 coalescent-node/ # wires everything together, gRPC binary

Some Technical Notes

• Greedily pre-compiles registered binaries to reduce latency
• Caches registered and compiled binaries
• Structured error codes distinguishing between deadline exceeded, execution failure, and missing modules
• Node capability advertisement
• Startup orphan sweep
  • Tasks left in Queued or Running from a crashed process are marked Failed on restart

Getting Started

Prerequisites

• Rust Toolchain
• Clang (supporting target wasm32-wasip1)
• wasi-libc / wasi-sysroot (for c compilation testing)
• grpcurl for testing and interaction
• jq for test scripts

Building

Compile the workspace directly from root directory:

cargo build

Running

RUST_LOG=info cargo run -p coalescent-node

The node will listen on :50051.

RPC API

RegisterModule

Upload a WASM binary. The node computes a SHA256 content hash as the module ID, persists the binary, and eagerly compiles it. Uploading the same binary twice is idempotent.

WASM_B64=$(base64 -w 0 program.wasm 2>/dev/null || base64 program.wasm)
grpcurl -plaintext \
 -import-path ./proto \
 -proto ./proto/coalescent.proto \
 -d "{\"wasm_binary\": \"$WASM_B64\"}" \
 localhost:50051 coalescent.CoalescentExecutor/RegisterModule

Response:

{
 "moduleId": "1f18a4b7341b5cda412b2599c98ec560ef274132a1aee6ba...",
 "alreadyExisted": false
}

alreadyExisted: true means the binary was already cached, so compilation was skipped and the call is a no-op.

ExecuteTask

Enqueue a task and stream status updates. The stream emits one event per status transition and closes when the task reaches a terminal state (completed or failed).

epoch_deadline is optional. The node applies a sensible default if omitted.

grpcurl -plaintext \
 -import-path ./proto \
 -proto ./proto/coalescent.proto \
 -d "{\"module_id\": \"$MODULE_ID\", \"input_data\": \"\"}" \
 localhost:50051 coalescent.CoalescentExecutor/ExecuteTask

Event stream:

{"taskId": "c6a29c4c-...", "status": "TASK_STATUS_QUEUED"}
{"taskId": "c6a29c4c-...", "status": "TASK_STATUS_RUNNING"}
{"taskId": "c6a29c4c-...", "status": "TASK_STATUS_COMPLETED", "output": "SGVsbG8...", "stderr": "", "elapsedMs": "53"}

On failure, a structured error field is included:

{
 "taskId": "c6a29c4c-...",
 "status": "TASK_STATUS_FAILED",
 "error": {
 "code": "TASK_ERROR_DEADLINE_EXCEEDED",
 "message": "epoch deadline exceeded"
 }
}

Error codes:

Decoding output:

echo "$OUTPUT" | jq -r 'select(.output != null) | .output' | base64 -d

GetNodeInfo

Returns the node's stable identity and hardware capabilities.

grpcurl -plaintext \
 -import-path ./proto \
 -proto ./proto/coalescent.proto \
 -d '{}' \
 localhost:50051 coalescent.CoalescentExecutor/GetNodeInfo

Response:

{
 "nodeId": "e3b0c442-...",
 "queueDepth": 2,
 "caps": {
 "cpuCores": 8,
 "memoryBytes": "16424108032",
 "arch": "x86_64"
 }
}

Task Lifecycle

Submitted -> Queued -> Running -> Completed -> Failed

Tasks communicate via stdin/stdout. A WASM module reads its input from stdin and writes results to stdout. stderr is captured separately and included in the final status event.

Compiling a C Task

clang --target=wasm32-wasip1 \
 --sysroot=/usr/share/wasi-sysroot \
 program.c -o program.wasm \
 -nodefaultlibs -lc

See the tasks/ directory for examples.