Gossip Glomers

Solutions to the Gossip Glomers distributed systems challenges by fly.io, implemented in Rust.

The challenges use Maelstrom, a workbench for writing toy distributed systems and testing them against a suite of consistency models.

Challenges

#	Challenge	Status
1	Echo	Done
2	Unique ID Generation	Done
3a	Single-Node Broadcast	-
3b	Multi-Node Broadcast	-
3c	Fault Tolerant Broadcast	-
3d	Efficient Broadcast (Part I)	-
3e	Efficient Broadcast (Part II)	-
4	Grow-Only Counter	-
5a	Single-Node Kafka-Style Log	-
5b	Multi-Node Kafka-Style Log	-
5c	Efficient Kafka-Style Log	-
6a	Single-Node, Totally-Available Transactions	-
6b	Totally-Available, Read Uncommitted Transactions	-
6c	Totally-Available, Read Committed Transactions	-

Project Structure

Each challenge lives in its own crate under src/. The maelstrom crate provides the shared node infrastructure (stdin/stdout message loop, serialization, etc.).

Prerequisites

• Docker with Compose

No local Rust or Java installation required — everything runs inside the container.

Running a Challenge

Build and start the container:

docker compose up -d --build

Open a shell inside the container:

docker compose exec maelstrom bash

Inside the container, build and test a challenge:

cargo build --bin echo
maelstrom test -w echo \
  --bin ./target/debug/echo \
  --node-count 1 \
  --time-limit 10

Replace echo and the -w workload flag with the appropriate challenge binary and workload. Your source is mounted into the container, so edits on the host are picked up immediately, just rebuild and re-test.

Stop the container when done:

docker compose down

Viewing Test Results

After running a test, start the Maelstrom web UI from inside the container:

maelstrom serve

Then open http://localhost:8080 in your browser. Port 8080 is already exposed by the Docker Compose setup.

How Maelstrom Works

Maelstrom spawns one or more node processes and communicates with them over stdin/stdout using a line-delimited JSON protocol. Each message has the shape:

{
  "src": "c1",
  "dest": "n1",
  "body": {
    "type": "echo",
    "msg_id": 1,
    "echo": "hello"
  }
}

Nodes read from stdin, process the message, and write replies to stdout. Maelstrom then checks whether the system's behavior satisfies the required consistency guarantees.