feat(M6): token-ring incremental log sync — append-only op log, delta rides token round-2, nodes converge on identical history (e2e verified join events)

internal/cluster/token_join.go

@@ -0,0 +1,47 @@
+// Join helper: a newcomer POSTs its JoinInfo to a target node's join endpoint
+// and adopts the returned ring state (leader preserved, newcomer inserted as
+// the target's successor).
+package cluster
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+)
+
+// JoinRing asks target to add us to its ring and returns the adopted state.
+func (e *Engine) JoinRing(ctx context.Context, targetAddr string, ji JoinInfo) error {
+	url := fmt.Sprintf("http://%s/api/manager/cluster/join", targetAddr)
+	body, err := json.Marshal(ji)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	if e.User != "" || e.Pass != "" {
+		req.SetBasicAuth(e.User, e.Pass)
+	}
+	cli := &http.Client{Timeout: 8 * time.Second}
+	resp, err := cli.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("join %s -> HTTP %d", targetAddr, resp.StatusCode)
+	}
+	var out struct {
+		State State `json:"state"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
+		return err
+	}
+	e.AdoptState(out.State)
+	return nil
+}