<p>The replica received malformed or unexpected heartbeat information from the primary server, breaking replication.</p>
<p>MySQL Error 1623: ER_SLAVE_HEARTBEAT_FAILURE occurs when a replica cannot parse the masters heartbeat packet, halting replication. Check network latency, version mismatch, and heartbeat period, then restart replication with corrected settings.</p>
Unexpected master's heartbeat data: %s
Error 1623 signals that the replica thread received unexpected heartbeat data from its master while running in row or statement replication mode. MySQL aborts the io_thread to prevent data divergence, printing the message Unexpected master's heartbeat data: %s.
The heartbeat mechanism is a lightweight ping used to detect lags and network issues. When the packet structure or timing is off, MySQL assumes corruption or version mismatch and stops replication.
The error surfaces immediately after a START SLAVE or CHANGE MASTER command, during long running transactions, or after network hiccups. High latency WAN links, SSL renegotiations, or upgrading only one side of the replication pair often trigger it.
Because replication stops, downstream applications may read stale data. Fixing the issue quickly avoids data loss and service disruption.
The master runs a newer MySQL version that sends heartbeat fields the older replica cannot parse.
Setting a heartbeat period lower than 1 millisecond or higher than the default 60 seconds can create malformed frames.
Unstable VPN links, packet filtering, or TCP offload bugs can mangle the heartbeat packet in transit.
Expired certificates or improper ciphersuites disrupt the encrypted channel, corrupting heartbeat content.
Corrupted relay logs stop the SQL thread, but the heartbeat packet is intact.
Replication fails to start because master.info is unreadable.
Long running queries on the replica are killed, sometimes preceding a heartbeat failure.
Data on the replica freezes but is not lost. Once replication restarts, missing events apply automatically.
No. You must issue CHANGE MASTER followed by STOP SLAVE and START SLAVE for the setting to take effect.
SSL is optional. However, if enabled, ensure certificates are valid and identical cipher suites are supported.
Galaxy's version-controlled queries let teams document the correct CHANGE MASTER commands, ensuring consistent fixes across environments.
.avif)
.avif){kind=logo}
