Phase 5 Batch 2: 4 RM Tool + rm 客户端 + 日志降级链

- internal/rm/client.go: YARN RM 客户端
  - ListApps / GetApp / KillApp / GetLogs
  - GetLogs 降级链数据驱动 (amContainerLogs → aggregated-logs → logs)
  - 跨主机 redirect 保留 Authorization (URLAllowlist 兜底)
- 4 Tool: list_applications / get_application_status /
  get_application_logs / kill_application
  - mcp.WithEnum(state) 约束 YARN app 状态
  - tool handler 永远 (result, nil), 业务错误用 NewToolResultError
- deps.go: +HTTPClient + MaxResponseBytes
- main.go: 注入 httpclient.Client
- 端到端实测: mock RM 验证 4 Tool + 降级链 + 错误路径

Co-Authored-By: Claude <noreply@anthropic.com>

internal/rm/client.go

@@ -0,0 +1,131 @@
+package rm
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"spark-mcp-go/internal/cluster"
+	"spark-mcp-go/internal/httpclient"
+)
+
+// Client is a YARN ResourceManager REST API client bound to a single cluster.
+type Client struct {
+	hc      *httpclient.Client
+	cluster *cluster.Cluster
+}
+
+// New creates a ResourceManager client bound to c.
+func New(hc *httpclient.Client, c *cluster.Cluster) *Client {
+	return &Client{hc: hc, cluster: c}
+}
+
+// ListApps returns raw JSON from GET /ws/v1/cluster/apps[?state=&user=].
+func (r *Client) ListApps(ctx context.Context, state, user string) (json.RawMessage, error) {
+	base := r.cluster.RMURL + "/ws/v1/cluster/apps"
+	u, err := url.Parse(base)
+	if err != nil {
+		return nil, err
+	}
+	q := u.Query()
+	if state != "" {
+		q.Set("state", state)
+	}
+	if user != "" {
+		q.Set("user", user)
+	}
+	u.RawQuery = q.Encode()
+	return r.do(ctx, http.MethodGet, u.String(), nil)
+}
+
+// GetApp returns raw JSON from GET /ws/v1/cluster/apps/{id}.
+func (r *Client) GetApp(ctx context.Context, appID string) (json.RawMessage, error) {
+	return r.do(ctx, http.MethodGet, r.cluster.RMURL+"/ws/v1/cluster/apps/"+appID, nil)
+}
+
+// KillApp PUT {"state":"KILLED"} to /ws/v1/cluster/apps/{id}/state.
+func (r *Client) KillApp(ctx context.Context, appID string) (json.RawMessage, error) {
+	body := `{"state":"KILLED"}`
+	return r.do(ctx, http.MethodPut, r.cluster.RMURL+"/ws/v1/cluster/apps/"+appID+"/state",
+		strings.NewReader(body))
+}
+
+// GetLogs walks a fallback chain to retrieve YARN application logs:
+//  1. GET /ws/v1/cluster/apps/{id}/amContainerLogs (RM often 307 to a NodeManager)
+//  2. GET /ws/v1/cluster/apps/{id}/aggregated-logs?container=...
+//  3. GET /ws/v1/cluster/apps/{id}/logs
+//
+// The first successful endpoint wins.  The returned source names the endpoint
+// that produced the body.
+func (r *Client) GetLogs(ctx context.Context, appID, container string) (body []byte, source string, err error) {
+	endpoints := []struct{ path, name string }{
+		{fmt.Sprintf("/ws/v1/cluster/apps/%s/amContainerLogs", appID), "amContainerLogs"},
+		{fmt.Sprintf("/ws/v1/cluster/apps/%s/aggregated-logs?container=%s", appID, url.QueryEscape(container)), "aggregated-logs"},
+		{fmt.Sprintf("/ws/v1/cluster/apps/%s/logs", appID), "logs"},
+	}
+	var lastErr error
+	for _, ep := range endpoints {
+		b, e := r.doBytes(ctx, http.MethodGet, r.cluster.RMURL+ep.path, nil)
+		if e == nil {
+			return b, ep.name, nil
+		}
+		lastErr = e
+	}
+	return nil, "", fmt.Errorf("rm: all log endpoints failed: %w", lastErr)
+}
+
+// do executes a single HTTP request with auth and allowed-host exemptions,
+// returning the validated JSON body.
+func (r *Client) do(ctx context.Context, method, rawURL string, body io.Reader) (json.RawMessage, error) {
+	b, err := r.doBytes(ctx, method, rawURL, body)
+	if err != nil {
+		return nil, err
+	}
+	raw := json.RawMessage(b)
+	if !json.Valid(raw) {
+		return nil, fmt.Errorf("rm: invalid JSON response from %s", rawURL)
+	}
+	return raw, nil
+}
+
+func (r *Client) doBytes(ctx context.Context, method, rawURL string, body io.Reader) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, method, rawURL, body)
+	if err != nil {
+		return nil, err
+	}
+	if err := httpclient.ApplyAuth(req, "", r.cluster); err != nil {
+		return nil, err
+	}
+	resp, err := r.hc.DoWithRedirect(ctx, req, 5, r.allowedHosts()...)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 400 {
+		return nil, fmt.Errorf("rm: %s %s returned %d", method, rawURL, resp.StatusCode)
+	}
+	return io.ReadAll(resp.Body)
+}
+
+func (r *Client) allowedHosts() []string {
+	hosts := []string{extractHost(r.cluster.RMURL)}
+	for _, pat := range r.cluster.URLAllowlist {
+		if pat == "" {
+			continue
+		}
+		hosts = append(hosts, pat)
+	}
+	return hosts
+}
+
+func extractHost(u string) string {
+	parsed, err := url.Parse(u)
+	if err != nil {
+		return ""
+	}
+	return parsed.Hostname()
+}