alibaba/arthas · error · McpError

-32602

-32602

Error message

Task not found (may have expired after TTL): {}

What it means

Thrown by InMemoryTaskStore during result storage (the storeResult/update path) when the target taskId is not present in the tasks map (taskFound.get() is false after the compute-if-present block). It builds a McpError with ErrorCodes.INVALID_PARAMS (-32602). The message notes the task may have expired after its TTL, distinguishing a 'never existed or evicted' case from a session-mismatch case.

Source

Thrown at arthas-mcp-server/src/main/java/com/taobao/arthas/mcp/server/task/InMemoryTaskStore.java:275

                    wasTerminal.set(true);
                    return entry;
                }
                results.put(taskId, result);
                String now = Instant.now().toString();
                McpSchema.Task newTask = McpSchema.Task.builder()
                    .taskId(oldTask.getTaskId())
                    .status(status)
                    .createdAt(oldTask.getCreatedAt())
                    .lastUpdatedAt(now)
                    .ttl(oldTask.getTtl())
                    .pollInterval(oldTask.getPollInterval())
                    .build();
                logger.debug("Stored result for task: {}", taskId);
                return new TaskEntry(newTask, entry.originatingRequest(), entry.context(), entry.sessionId());
            });

            if (!taskFound.get()) {
                throw new CompletionException(
                    McpError.builder(McpSchema.ErrorCodes.INVALID_PARAMS)
                        .message("Task not found (may have expired after TTL): " + taskId)
                        .build()
                );
            }
            if (!sessionValid.get()) {
                throw new CompletionException(
                    McpError.builder(McpSchema.ErrorCodes.INVALID_PARAMS)
                        .message("Task not found (may have expired after TTL): " + taskId)
                        .build()
                );
            }
            if (wasTerminal.get()) {
                logger.debug("Skipped storing result for task {} - already in terminal state", taskId);
            }
        });
    }

View on GitHub (pinned to 21cf2e9ba5)

Solutions

  1. Ensure task completion stores results well within the configured TTL window.
  2. Increase the task TTL to exceed the handler's realistic completion time.
  3. Confirm the result is stored against the same TaskStore instance and taskId used at creation.
  4. For durability across restarts, use a persistent TaskStore instead of the in-memory one.

Example fix

// before
Long ttl = Duration.ofSeconds(10).toMillis(); // shorter than task runtime
store.createTask(opts.withRequestedTtl(ttl));
// ... later, after expiry
store.storeResult(taskId, result); // INVALID_PARAMS

// after
Long ttl = Duration.ofMinutes(10).toMillis(); // exceeds runtime
store.createTask(opts.withRequestedTtl(ttl));
store.storeResult(taskId, result); // ok
Defensive patterns

Strategy: validation

Validate before calling

// Ensure TTL exceeds the handler's realistic completion time
long ttl = Math.max(defaultTtl, estimatedMaxRuntimeMillis * 3);
options = options.withRequestedTtl(ttl);
store.createTask(options);

Try / catch

try {
    store.storeResult(taskId, result).join();
} catch (CompletionException e) {
    Throwable c = e.getCause();
    if (c instanceof McpError me && me.getMessage().contains("expired after TTL")) {
        // task was evicted; recreate or report stale, do not loop
        logger.warn("Task {} expired before result stored", taskId);
        return;
    }
    throw e;
}

Prevention

When it happens

Trigger: A task handler tries to store a result for a taskId that was evicted by TTL before completion, or for a taskId that was never created in this store; late result delivery after expiry.

Common situations: Long-running task whose result arrives after TTL eviction; result posted to the wrong store instance; store restart losing in-memory state; handler holding a stale taskId.

Related errors

AI-assisted analysis of alibaba/arthas@21cf2e9ba5 (2026-08-14). Data as JSON: /api/errors/b07d7bf57bbc029a. Report an issue: GitHub.