# SENTINEL: arbiter node unreachable, failover delayed for 30000ms

- **ID:** `redis/sentinel-arbiter-down-failover-delay`
- **Domain:** redis
- **Category:** network_error
- **Error Code:** `SENTINEL`
- **Verification:** ai_generated
- **Fix Rate:** 77%

## Root Cause

Sentinel's arbiter node is not reachable, preventing the quorum from being reached for failover, causing a delay.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 6.2.0 | active | — | — |
| 7.0.0 | active | — | — |
| 7.2.0 | active | — | — |

## Workarounds

1. **Check network connectivity from sentinel to arbiter: 'telnet <arbiter-ip> 26379' and ensure firewall rules allow traffic. If the arbiter is down, restart it and verify it rejoins the quorum: 'redis-cli -p 26379 SENTINEL CKQUORUM <mymaster>'** (80% success)
   ```
   Check network connectivity from sentinel to arbiter: 'telnet <arbiter-ip> 26379' and ensure firewall rules allow traffic. If the arbiter is down, restart it and verify it rejoins the quorum: 'redis-cli -p 26379 SENTINEL CKQUORUM <mymaster>'
   ```
2. **Temporarily reconfigure sentinel to use a different arbiter or increase the down-after-milliseconds to allow more time for arbiter recovery before failover is triggered** (70% success)
   ```
   Temporarily reconfigure sentinel to use a different arbiter or increase the down-after-milliseconds to allow more time for arbiter recovery before failover is triggered
   ```

## Dead Ends

- **Increasing sentinel quorum to 2 to bypass arbiter requirement** — This reduces fault tolerance; if the arbiter is down but other nodes are up, failover may still be blocked if quorum is not met. (70% fail)
- **Restarting the arbiter node without checking network connectivity** — If the network between Sentinel and arbiter is partitioned, restarting alone won't fix the connectivity issue. (85% fail)
- **Removing the arbiter from the sentinel configuration** — This changes the quorum requirement and can lead to split-brain scenarios if the arbiter was intentionally placed there. (80% fail)