Merge branch 'main' of github.com:jepsen-io/maelstrom

demo/go/README.md

@@ -0,0 +1,20 @@
+maelstrom-go
+============
+
+This is a Go implementation of the Maelstrom Node. This provides basic message
+handling, an event loop, & a client interface to the key/value store. It's a
+good starting point for implementing a Maelstrom node as it helps to avoid a
+lot of boilerplate.
+
+## Usage
+
+Binaries run by `maelstrom` need to be referenced by absolute or relative path.
+The easiest way to use Go with Maelstrom is to `go install` and then specify
+the relative path to the `--bin` flag:
+
+```sh
+$ cd /path/to/maelstrom-echo
+$ go install .
+$ maelstrom test --bin ~/go/bin/maelstrom-echo ...
+```
+

demo/go/kv.go

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+package maelstrom
+
+import (
+	"context"
+	"encoding/json"
+)
+
+// Types of key/value stores.
+const (
+	LinKV = "lin-kv"
+	SeqKV = "seq-kv"
+	LWWKV = "lww-kv"
+)
+
+// KV represents a client to the key/value store service.
+type KV struct {
+	typ  string
+	node *Node
+}
+
+// NewKV returns a new instance a KV client for a node.
+func NewKV(typ string, node *Node) *KV {
+	return &KV{
+		typ:  typ,
+		node: node,
+	}
+}
+
+// NewLinKV returns a client to the linearizable key/value store.
+func NewLinKV(node *Node) *KV { return NewKV(LinKV, node) }
+
+// NewSeqKV returns a client to the sequential key/value store.
+func NewSeqKV(node *Node) *KV { return NewKV(SeqKV, node) }
+
+// NewLWWKV returns a client to the last-write-wins key/value store.
+func NewLWWKV(node *Node) *KV { return NewKV(LWWKV, node) }
+
+// Read returns the value for a given key in the key/value store.
+// Returns an *RPCError error with a KeyDoesNotExist code if the key does not exist.
+func (kv *KV) Read(ctx context.Context, key string) (any, error) {
+	resp, err := kv.node.SyncRPC(ctx, kv.typ, kvReadMessageBody{
+		MessageBody: MessageBody{Type: "read"},
+		Key:         key,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Parse read_ok specific data in response message.
+	var body kvReadOKMessageBody
+	if err := json.Unmarshal(resp.Body, &body); err != nil {
+		return nil, err
+	}
+
+	// Convert numbers to integers since that's what maelstrom workloads use.
+	switch v := body.Value.(type) {
+	case float64:
+		return int(v), nil
+	default:
+		return v, nil
+	}
+}
+
+// ReadInt reads the value of a key in the key/value store as an int.
+func (kv *KV) ReadInt(ctx context.Context, key string) (int, error) {
+	v, err := kv.Read(ctx, key)
+	i, _ := v.(int)
+	return i, err
+}
+
+// Write overwrites the value for a given key in the key/value store.
+func (kv *KV) Write(ctx context.Context, key string, value any) error {
+	_, err := kv.node.SyncRPC(ctx, kv.typ, kvWriteMessageBody{
+		MessageBody: MessageBody{Type: "write"},
+		Key:         key,
+		Value:       value,
+	})
+	return err
+}
+
+// CompareAndSwap updates the value for a key if its current value matches the
+// previous value. Creates the key if createIfNotExists is true.
+//
+// Returns an *RPCError with a code of PreconditionFailed if the previous value
+// does not match. Return a code of KeyDoesNotExist if the key did not exist.
+func (kv *KV) CompareAndSwap(ctx context.Context, key string, from, to any, createIfNotExists bool) error {
+	_, err := kv.node.SyncRPC(ctx, kv.typ, kvCASMessageBody{
+		MessageBody:       MessageBody{Type: "cas"},
+		Key:               key,
+		From:              from,
+		To:                to,
+		CreateIfNotExists: createIfNotExists,
+	})
+	return err
+}
+
+// kvReadMessageBody represents the body for the KV "read" message.
+type kvReadMessageBody struct {
+	MessageBody
+	Key string `json:"key"`
+}
+
+// kvReadOKMessageBody represents the response body for the KV "read_ok" message.
+type kvReadOKMessageBody struct {
+	MessageBody
+	Value any `json:"value"`
+}
+
+// kvWriteMessageBody represents the body for the KV "cas" message.
+type kvWriteMessageBody struct {
+	MessageBody
+	Key   string `json:"key"`
+	Value any    `json:"value"`
+}
+
+// kvCASMessageBody represents the body for the KV "cas" message.
+type kvCASMessageBody struct {
+	MessageBody
+	Key               string `json:"key"`
+	From              any    `json:"from"`
+	To                any    `json:"to"`
+	CreateIfNotExists bool   `json:"create_if_not_exists,omitempty"`
+}