redis/jedis · critical · JedisException

Can connect to sentinel, but

Error message

Can connect to sentinel, but ${masterName} seems to be not monitored.

What it means

SentineledConnectionProvider.initSentinels() reached and communicated with at least one sentinel, but none of them know a master with the configured masterName, so it throws JedisException. This means the sentinel quorum is monitoring different masters than the client expects.

Solutions

1. Run SENTINEL masters (or redis-cli -p 26379 sentinel get-master-addr-by-name <name>) to list monitored masters and use the exact configured name.
2. Correct the masterName in your client configuration to match what the sentinels monitor.
3. Add the master to sentinel monitoring (SENTINEL MONITOR <name> <ip> <port> <quorum>) if it is genuinely unmonitored.
4. Verify you are connecting to the sentinel set belonging to your environment.

Example fix

// before
new JedisSentinelPool("mymaster", sentinels);
// after
new JedisSentinelPool("prod-master", sentinels); // name confirmed via SENTINEL masters

try (Jedis s = new Jedis(sentinelHost, 26379)) {
  List<String> m = s.sentinelGetMasterAddrByName(masterName);
  if (m == null || m.isEmpty()) throw new IllegalStateException("Sentinel does not monitor master '" + masterName + "'");
}

try {
  pool = new JedisSentinelPool(masterName, sentinels, clientConfig);
} catch (JedisException e) {
  if (e.getMessage().contains("seems to be not monitored")) {
    throw new IllegalStateException("masterName '" + masterName + "' is not monitored by the sentinels — check SENTINEL masters", e);
  }
  throw e;
}

When it happens

Trigger: Building JedisSentinelPool / RedisSentinelClient / SentineledConnectionProvider with a masterName that no monitored master matches, e.g. masterName("mymaster") while sentinels monitor "prod-master".

Common situations: Typos in the master name; pointing the client at a sentinel cluster from a different deployment/environment (staging sentinels vs prod master name); sentinel was reconfigured (SENTINEL REMOVE) so the name no longer exists; copy-paste of sentinel endpoints without updating the master name.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Can connect to sentinel, but
• Master name is required for Sentinel mode
• At least one sentinel must be specified for Sentinel mode
• No nodes to initialize cluster slots cache.
• All sentinels down, cannot determine where

AI-assisted analysis of redis/jedis@6dac31d4c2 (2026-09-08). Data as JSON: /api/errors/fb562b73753bd969. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/redis/clients/jedis/providers/SentineledConnectionProvider.java:283

        if (masterAddr == null || masterAddr.size() != 2) {
          LOG.warn("Sentinel {} is not monitoring master {}.", sentinel, masterName);
          continue;
        }

        master = toHostAndPort(masterAddr);
        LOG.debug("Redis master reported at {}.", master);
        break;
      } catch (JedisException e) {
        // resolves #1036, it should handle JedisException there's another chance
        // of raising JedisDataException
        LOG.warn("Could not get master address from {}.", sentinel, e);
      }
    }

    if (master == null) {
      if (sentinelAvailable) {
        // can connect to sentinel, but master name seems to not monitored
        throw new JedisException(
            "Can connect to sentinel, but " + masterName + " seems to be not monitored.");
      } else {
        throw new JedisConnectionException(
            "All sentinels down, cannot determine where " + masterName + " is running.");
      }
    }

    LOG.info("Redis master running at {}. Starting sentinel listeners...", master);

    for (HostAndPort sentinel : sentinels) {

      SentinelListener listener = new SentinelListener(sentinel);
      // whether SentinelListener threads are alive or not, process can be stopped
      listener.setDaemon(true);
      sentinelListeners.add(listener);
      listener.start();
    }

View on GitHub (pinned to 6dac31d4c2)