MySQL error 2013 (CR_SERVER_LOST) means the client lost its connection to the MySQL server while a query was running.
MySQL Error 2013: CR_SERVER_LOST occurs when the client loses its network or socket connection to the MySQL server during a query. Check network stability, increase timeout variables, and optimize long-running queries to resolve the issue.
Lost connection to MySQL server during query
MySQL throws error 2013 with the condition name CR_SERVER_LOST when the client unexpectedly loses its connection to the server in the middle of a query. The message usually reads: “Lost connection to MySQL server during query.”
The disconnect can originate from network glitches, server restarts, timeouts, or resource exhaustion.
Because the query never completes, the client must decide whether to retry or fail gracefully.
Network interruptions are the most frequent cause. Packet loss, VPN drops, or unstable Wi-Fi can sever the TCP connection before the server finishes sending results.
Server-side timeouts such as wait_timeout, interactive_timeout, or net_read_timeout can close idle or slow connections.
Large result sets that exceed max_allowed_packet can also trigger disconnects.
Resource constraints like high CPU, low RAM, or an abrupt mysqld restart will end active sessions and propagate error 2013 to clients.
Begin by confirming that the MySQL service is up and reachable on its host and port. Use ping and telnet or nc to rule out basic connectivity issues.
Increase client-side and server-side timeout variables to accommodate slow networks or heavy queries.
On the server, adjust wait_timeout, interactive_timeout, net_read_timeout, net_write_timeout, and max_allowed_packet. On the client, tweak --connect_timeout and --net_buffer_length.
Optimize long-running queries by adding indexes, splitting huge SELECTs, and paginating results.
Galaxy’s AI copilot can refactor complex joins and flag missing indexes quickly.
Large BLOB exports: raise max_allowed_packet and use --quick with mysqldump to stream rows.
Slow report queries: add covering indexes or materialize intermediate results in temp tables.
Unstable VPN: enable TCP keep-alive and raise net_read_timeout to keep the socket open longer.
Monitor network latency and packet loss with tools like mtr.
Set dashboard alerts for sudden spikes.
Keep server OS and MySQL versions current to benefit from improved timeout handling and bug fixes.
Document and reuse optimized queries in Galaxy Collections so teams avoid running unindexed, 10-minute reports in production.
Error 2006 (MySQL server has gone away) signals a disconnect before the query starts; check server crashes or max_allowed_packet.
Error 2055 (Lost connection to MySQL server at '%s', system error: %d) points to SSL or handshake problems; verify certificates and ssl_cipher.
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Run mtr or traceroute while the query runs. Packet loss spikes usually correlate with CR_SERVER_LOST events.
Yes. If the server must send or receive a packet larger than the configured size, it terminates the connection, throwing error 2013.
Retrying a SELECT is generally safe. For INSERT, UPDATE, or DELETE use idempotent design or transactions to avoid duplicate changes.
Galaxy flags long-running queries, suggests indexes, and lets teams share optimized versions, reducing the chance of timeouts that cause error 2013.
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