env-04-kv-quorum

# Quorum-replicated key-value store

Three replica nodes (`peer0`, `peer1`, `peer2`) form a key-value store with **N=3, W=2, R=2**
(W+R>N, so a quorum read always observes the latest quorum write). A separate `client` drives it.

Implement the replica program (`peer.go`) and the `client.go` so that:

- A **PUT** to any replica (the coordinator) stores the value and replicates it to a **write quorum
  of W=2** replicas (itself + one peer), then acknowledges. It must NOT assume every replica gets a
  copy.
- A **GET** from any replica performs a **quorum read (R=2)** across replicas and returns the value
  with the highest version — so a replica that did not receive a particular write still returns the
  correct value.
- The client must: PUT `k1=alpha` via `peer0`, PUT `k2=beta` via `peer1`, then GET both `k1` and
  `k2` **from `peer2`**, and write them to `result.txt` as:

  ```
  k1=alpha
  k2=beta
  ```

`peer2` will be the replica left without those keys, so reading them back from `peer2` only succeeds
with a working quorum read. Use only the Go standard library (`net/http`).

Discovery contract: `PORT` (your listen port) and `PEER_<NAME>_HOST` / `PEER_<NAME>_PORT` for peers.

[turn 1] list_nodes({}) -> {"nodes": [{"name": "peer0", "provides": "go run .", "ports": [7000], "needs": ["peer1", "peer2"]}, {"name": "peer1", "provides": "go run .", "ports": [7000], "needs": ["peer0", "peer2"]}, {"name": "p
[turn 2] run({"node": "peer0", "cmd": "env | grep -E '^(PORT|PEER)'"}) -> {"rc": 0, "output": "PORT=60685\nPORTS=60685\nPEER_PEER1_HOST=127.0.0.1\nPEER_PEER2_HOST=127.0.0.1\nPEER_PEER1_PORT=36509\nPEER_PEER2_PORT=34019\n"}
[turn 3] run({"node": "peer1", "cmd": "env | grep -E '^(PORT|PEER)'"}) -> {"rc": 0, "output": "PORT=36509\nPORTS=36509\nPEER_PEER0_HOST=127.0.0.1\nPEER_PEER2_HOST=127.0.0.1\nPEER_PEER0_PORT=60685\nPEER_PEER2_PORT=34019\n"}
[turn 4] run({"node": "peer2", "cmd": "env | grep -E '^(PORT|PEER)'"}) -> {"rc": 0, "output": "PORT=34019\nPORTS=34019\nPEER_PEER0_HOST=127.0.0.1\nPEER_PEER1_HOST=127.0.0.1\nPEER_PEER0_PORT=60685\nPEER_PEER1_PORT=36509\n"}
[turn 5] run({"node": "client", "cmd": "env | grep -E '^(PORT|PEER)'"}) -> {"rc": 0, "output": "PEER_PEER0_HOST=127.0.0.1\nPEER_PEER1_HOST=127.0.0.1\nPEER_PEER2_HOST=127.0.0.1\nPEER_PEER0_PORT=60685\nPEER_PEER1_PORT=36509\nPEER_PEER2_PORT=34019\n"}
[turn 6] write_file({"node": "peer0", "path": "peer.go", "content": "package main\n\nimport (\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"strconv\"\n\t\"strings\"\n\t\"sync\"\n\t\"time\"\n)\) -> {"ok": true, "node": "peer0", "path": "peer.go"}
[turn 7] write_file({"node": "peer1", "path": "peer.go", "content": "package main\n\nimport (\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"strconv\"\n\t\"strings\"\n\t\"sync\"\n\t\"time\"\n)\) -> {"ok": true, "node": "peer1", "path": "peer.go"}
[turn 8] write_file({"node": "peer2", "path": "peer.go", "content": "package main\n\nimport (\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"strconv\"\n\t\"strings\"\n\t\"sync\"\n\t\"time\"\n)\) -> {"ok": true, "node": "peer2", "path": "peer.go"}
[turn 9] write_file({"node": "client", "path": "client.go", "content": "package main\n\nimport (\n\t\"bytes\"\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"io/ioutil\"\n\t\"net/http\"\n\t\"os\"\n)\n\ntype Value struct {\n\tKey   ) -> {"ok": true, "node": "client", "path": "client.go"}
[turn 10] verify({}) -> {"passed": false, "checks": [{"name": "quorum read on a non-replica node returned both writes", "ok": false, "detail": "client wrote ''; want 'k1=alpha\\nk2=beta'"}], "launch_errors": ["peer0:7000 nev
[turn 11] run({"node": "peer0", "cmd": "go run peer.go &\nsleep 2\ncurl -s http://localhost:$PORT/put -X POST -d '{\"key\":\"test\",\"value\":\"val\"}' || echo \"Failed\""}) -> {"rc": 0, "output": "Failed\n# command-line-arguments\n./peer.go:9:2: \"strconv\" imported and not used\n./peer.go:10:2: \"strings\" imported and not used\n./peer.go:95:4: declared and not used: val\n
[turn 12] write_file({"node": "peer0", "path": "peer.go", "content": "package main\n\nimport (\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"sync\"\n\t\"time\"\n)\n\n// Key-value store with ver) -> {"ok": true, "node": "peer0", "path": "peer.go"}
[turn 13] write_file({"node": "peer0", "path": "peer.go", "content": "package main\n\nimport (\n\t\"bytes\"\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"sync\"\n\t\"time\"\n)\n\n// Key-value s) -> {"ok": true, "node": "peer0", "path": "peer.go"}
[turn 14] write_file({"node": "peer1", "path": "peer.go", "content": "package main\n\nimport (\n\t\"bytes\"\n\t\"encoding/json\"\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\t\"os\"\n\t\"sync\"\n\t\"time\"\n)\n\n// Key-value s) -> {"ok": true, "node": "peer1", "path": "peer.go"}