Runbook: batch high failure rate

Name: MCP Hangar
Author: MCP Hangar

Alert: MCPHangarBatchHighFailureRate (critical) — batch failure ratio exceeds the threshold for 3m.

What it means

rate(mcp_hangar_batch_calls_total{result="failure"}) / rate(mcp_hangar_batch_calls_total) is high — batched multi-tool requests are failing as a whole.

Diagnose

sum by (result) (rate(mcp_hangar_batch_calls_total[5m]))
histogram_quantile(0.95, sum by (le) (rate(mcp_hangar_batch_duration_seconds_bucket[5m])))
sum(rate(mcp_hangar_batch_truncations_total[5m]))         # oversized batches?
sum(rate(mcp_hangar_batch_cancellations_total[5m]))       # cancelled / timed out?

Remediate

Truncations high → clients sending oversized batches (MCPHangarBatchSizeTooLarge); advise smaller batches or raise the limit.
Cancellations high → per-call timeouts or concurrency starvation (MCPHangarConcurrencyQueueBuildup).
Failures concentrated on one server → treat as high-error-rate for that server.

Escalate

If batch failures coincide with a circuit breaker (circuit-breaker), follow that runbook first.