Lost connection to Sentinel

Error message

Lost connection to Sentinel {}. Sleeping {}ms and retrying.

What it means

This warning is logged by the Sentinel master/replica subscription task in SentineledConnectionProvider when the pub/sub connection to a Sentinel node is lost. Rather than failing the client, the provider logs the node and a computed backoff delay, sleeps, and retries resubscribing to that Sentinel. It is a recovery-path log, not an exception thrown to the caller; the underlying JedisException is attached to the log record.

Solutions

No code change needed if clients recover — this is expected resilience logging; verify the retry succeeds in subsequent logs.
Check connectivity/latency to the Sentinel nodes (host/port list, firewall, DNS).
Increase Sentinel's client-output-buffer-limit for pubsub if subscribers are being dropped.
Verify the sleeper/resubscribeDelay settings so retries back off appropriately for your environment.
Inspect the attached JedisException in the log for the root cause (connection refused vs reset vs timeout).

Example fix

// before: assuming any Sentinel log means an outage
// after: correlate with node identity and check subsequent successful resubscription
LOG.warn("Lost connection to Sentinel {}. Sleeping {}ms and retrying.", node,
  subscribeRetryWaitTimeMillis, e); // library-side; users should monitor, not fix

Defensive patterns

Strategy: retry

Validate before calling

// check Sentinel reachability before building the client
for (HostAndPort hp : sentinels) {
  try (Jedis s = new Jedis(hp)) { s.ping(); } // throws if node unreachable
}

Try / catch

// library retries internally; for your own sentinel lookups:
try {
  hostPort = client.sentinelResolve(...);
} catch (JedisConnectionException e) {
  sleep(exponentialBackoff(attempt)); // then retry
}

Prevention

Monitor Sentinel node health and quorum independently of the app
Set generous pubsub client-output-buffer limits on Sentinel
Ensure all listed Sentinel nodes are reachable (firewall/DNS checks)
Alert on repeated 'Lost connection to Sentinel' warnings rather than ignoring them

When it happens

Trigger: A Sentinel node drops the pub/sub subscription: Sentinel restart, network interruption, Sentinel-side client-output-buffer limit exceeded, Sentinel failover/switchover, or idle connection timeout while the resubscribe thread is running.

Common situations: Flaky network between client and Sentinel quorum; Sentinel instances restarted by ops; long-running services that survive transient Sentinel outages; misconfigured Sentinel output-buffer limits (client-output-buffer-limit pubsub) killing slow subscribers.

Understand the failure class

Background: ECONNREFUSED and "connection refused" / "could not connect to server" errors: what they mean and how to fix them — this error's family across 44 libraries.

Related errors

AI-assisted analysis of redis/jedis@6dac31d4c2 (2026-09-08). Data as JSON: /api/errors/725d56910e8da880. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/redis/clients/jedis/providers/SentineledConnectionProvider.java:386

                  initMaster(toHostAndPort(switchMasterMsg[3], switchMasterMsg[4]));
                } else {
                  LOG.debug("Ignoring message on +switch-master for master {}. Our master is {}.",
                    switchMasterMsg[0], masterName);
                }

              } else {
                LOG.error("Invalid message received on sentinel {} on channel +switch-master: {}.",
                  node, message);
              }
            }
          }, "+switch-master");

        } catch (JedisException e) {

          if (running.get()) {
            long subscribeRetryWaitTimeMillis = resubscribeDelay.delay(subscribeAttempt).toMillis();
            subscribeAttempt++;
            LOG.warn("Lost connection to Sentinel {}. Sleeping {}ms and retrying.", node,
              subscribeRetryWaitTimeMillis, e);
            try {
              sleeper.sleep(subscribeRetryWaitTimeMillis);
            } catch (InterruptedException se) {
              LOG.error("Sleep interrupted.", se);
            }
          } else {
            LOG.debug("Unsubscribing from sentinel {}.", node);
          }
        } finally {
          IOUtils.closeQuietly(sentinelJedis);
        }
      }
    }

    // must not throw exception
    public void shutdown() {
      try {

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