spark-mcp/internal/mcp/tools/spark_submit.go

package tools

import (
	"context"
	"fmt"
	"sort"
	"strconv"

	"github.com/mark3labs/mcp-go/mcp"

	"spark-mcp-go/internal/executor"
)

const SparkSubmitName = "spark_submit"

// NewSparkSubmitTool returns the schema for the spark_submit MCP Tool.
func NewSparkSubmitTool() mcp.Tool {
	return mcp.NewTool(SparkSubmitName,
		mcp.WithDescription("Submit a Spark application to a configured cluster. The command is built in this order: --master, --queue, --executor-memory, --executor-cores, --num-executors, then --conf per spark_conf entry, then --flag value per extra_args entry, then script_path last. For script_path, pass the `path` field returned by upload_file (do not construct your own path). Returns {app_id, exit_code, stdout_tail, stderr_tail, duration_ms}. Binary is invoked as a child process — no shell, no command injection."),
		mcp.WithString("cluster_id",
			mcp.Required(),
			mcp.Description("ID of the configured cluster (from list_clusters)"),
		),
		mcp.WithString("master",
			mcp.Required(),
			mcp.Description("Spark master URL, e.g. yarn, k8s://https://..."),
		),
		mcp.WithString("deploy_mode",
			mcp.Required(),
			mcp.Description("Required for forward compatibility; not currently emitted in the command by the builder (matches Python reference)."),
			mcp.Enum("client", "cluster"),
		),
		mcp.WithString("script_path",
			mcp.Required(),
			mcp.Description("Absolute path to the script. Pass the `path` field returned by upload_file — do not construct your own path. The script is always the last argv element. Paths not minted by upload_file on this server are rejected."),
		),
		mcp.WithString("queue",
			mcp.Required(),
			mcp.Description("YARN queue name"),
		),
		mcp.WithString("executor_memory",
			mcp.Required(),
			mcp.Description("e.g. 4G"),
		),
		mcp.WithNumber("executor_cores",
			mcp.Required(),
			mcp.Description("Cores per executor (integer)"),
		),
		mcp.WithNumber("num_executors",
			mcp.Required(),
			mcp.Description("Static executor count (integer)"),
		),
		mcp.WithObject("spark_conf",
			mcp.Description("Map of key=value pairs, each emitted as --conf key=value"),
			mcp.AdditionalProperties(map[string]any{"type": "string"}),
		),
		mcp.WithObject("extra_args",
			mcp.Description("Map of flag -> value, each emitted as --flag value"),
			mcp.AdditionalProperties(map[string]any{"type": "string"}),
		),
	)
}

// SparkSubmitHandler runs spark-submit against the requested cluster.
func (d *Deps) SparkSubmitHandler(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
	clusterID, err := req.RequireString("cluster_id")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	master, err := req.RequireString("master")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	deployMode, err := req.RequireString("deploy_mode")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	scriptPath, err := req.RequireString("script_path")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}

	// Reject paths that didn't come through upload_file on this server.
	// Cluster-local paths and arbitrary host paths are unreachable from the MCP
	// server's spark-submit, so we fail fast with a clear message rather than
	// letting spark-submit produce a confusing FileNotFoundException later.
	if d.UploadStore != nil {
		if _, err := d.UploadStore.Validate(scriptPath); err != nil {
			return errResult(fmt.Errorf("spark_submit: script_path %q is not from upload_file on this server; upload the file first via upload_file and pass back the path field: %w", scriptPath, err).Error()), nil
		}
	}
	queue, err := req.RequireString("queue")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	executorMemory, err := req.RequireString("executor_memory")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}

	args := req.GetArguments()

	// deploy_mode is required for forward compatibility but the builder does not
	// emit --deploy-mode, matching the Python reference's actual behavior. If the
	// Go side needs --deploy-mode later, add it here and document the divergence.
	if deployMode != "client" && deployMode != "cluster" {
		return errResult("spark_submit: deploy_mode must be client or cluster"), nil
	}

	sparkConf, err := parseStringMap(args, "spark_conf")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	extraArgs, err := parseStringMap(args, "extra_args")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}

	executorCores, err := requireNonNegativeInt(args, "executor_cores")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}
	numExecutors, err := requireNonNegativeInt(args, "num_executors")
	if err != nil {
		return errResult("spark_submit: " + err.Error()), nil
	}

	callLog := startToolCall(ctx, d.Logger, SparkSubmitName, map[string]any{
		"cluster_id":      clusterID,
		"master":          master,
		"deploy_mode":     deployMode,
		"script_path":     scriptPath,
		"queue":           queue,
		"executor_memory": executorMemory,
		"executor_cores":  executorCores,
		"num_executors":   numExecutors,
		"spark_conf":      sparkConf,
		"extra_args":      extraArgs,
	})
	defer callLog.End()

	cl, err := d.ClusterRepo.Get(ctx, clusterID)
	if err != nil {
		callLog.WithError(err)
		return errResult("spark_submit: cluster " + clusterID + ": " + err.Error()), nil
	}

	binary := cl.SparkSubmitExecuteBin

	// Build argv inline, mirroring the Python reference's output order exactly.
	// DefaultSubmitArgs is no longer prepended; the field is currently unused at
	// runtime but kept for backward compatibility with the admin API. Removal is
	// a separate follow-up.
	cmd := []string{binary}
	cmd = append(cmd, "--master", master)
	cmd = append(cmd, "--queue", queue)
	cmd = append(cmd, "--executor-memory", executorMemory)
	cmd = append(cmd, "--executor-cores", strconv.Itoa(executorCores))
	cmd = append(cmd, "--num-executors", strconv.Itoa(numExecutors))

	for _, k := range sortedStringKeys(sparkConf) {
		cmd = append(cmd, "--conf", k+"="+sparkConf[k])
	}
	for _, k := range sortedStringKeys(extraArgs) {
		cmd = append(cmd, "--"+k, extraArgs[k])
	}
	cmd = append(cmd, scriptPath)

	if d.Logger != nil {
		d.Logger.Debug("spark_submit.built", "cluster_id", clusterID, "argv", cmd)
	}

	result, err := executor.Run(ctx, executor.SparkSubmitOpts{
		Binary:  binary,
		Args:    cmd,
		Timeout: d.SparkSubmitTimeout,
	})
	if err != nil {
		callLog.WithError(err)
		// Even on error, result carries ExitCode/Stderr for the LLM.
		if result != nil {
			callLog.WithResult(map[string]any{
				"app_id":      result.AppID,
				"exit_code":   result.ExitCode,
				"duration_ms": result.DurationMS,
			})
			return textResult(encodeJSON(map[string]any{
				"app_id":      result.AppID,
				"exit_code":   result.ExitCode,
				"stdout_tail": result.StdoutTail,
				"stderr_tail": result.StderrTail,
				"duration_ms": result.DurationMS,
				"error":       err.Error(),
			})), nil
		}
		return errResult("spark_submit: " + err.Error()), nil
	}

	callLog.WithResult(map[string]any{
		"app_id":      result.AppID,
		"exit_code":   result.ExitCode,
		"duration_ms": result.DurationMS,
	})
	return textResult(encodeJSON(result)), nil
}

// requireNonNegativeInt extracts an integer parameter from the request and
// rejects negative or non-integer values.
func requireNonNegativeInt(args map[string]any, key string) (int, error) {
	v, ok := args[key]
	if !ok || v == nil {
		return 0, fmt.Errorf("%s is required", key)
	}
	switch n := v.(type) {
	case int:
		if n < 0 {
			return 0, fmt.Errorf("%s must be a non-negative integer", key)
		}
		return n, nil
	case float64:
		ni := int(n)
		if n < 0 || float64(ni) != n {
			return 0, fmt.Errorf("%s must be a non-negative integer", key)
		}
		return ni, nil
	default:
		return 0, fmt.Errorf("%s must be a number", key)
	}
}

// parseStringMap extracts an optional object whose values are strings.
func parseStringMap(args map[string]any, key string) (map[string]string, error) {
	out := make(map[string]string)
	v, ok := args[key]
	if !ok || v == nil {
		return out, nil
	}
	m, ok := v.(map[string]any)
	if !ok {
		return nil, fmt.Errorf("%s must be an object", key)
	}
	for k, val := range m {
		s, ok := val.(string)
		if !ok {
			return nil, fmt.Errorf("%s[%q] must be a string", key, k)
		}
		out[k] = s
	}
	return out, nil
}

// sortedStringKeys returns the keys of m in deterministic order.
func sortedStringKeys(m map[string]string) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}