sysbench error: failed to connect to mysql during benchmark - how to fix

sysbench error: failed to connect to mysql during benchmark - how to fix

TL;DR

sysbench connects like any MySQL client, so a connection failure is credentials, grants, or network, not a sysbench bug. Test with the mysql CLI using the same parameters first. If the CLI connects and sysbench does not, the difference is in how you passed the options.

sysbench error: failed to connect to mysql

Steps

1. Reproduce with the mysql client: mysql -h [host] -P [port] -u [user] -p'[password]' [db]. Expected: The CLI either connects (sysbench-specific issue) or fails the same way (server-side issue).

2. If the CLI also fails, check the grant: the user needs access from sysbench's host (SHOW GRANTS FOR 'user'@'host'). Expected: You find the missing host grant.

3. Check the network path: port 3306 reachable from the sysbench host, no firewall or security group in the way. Expected: TCP connects.

4. If the CLI works but sysbench fails, compare parameter passing: --mysql-host, --mysql-port, --mysql-user, --mysql-password, --mysql-db must all match what the CLI used. Expected: The option sets are identical.

5. For socket vs TCP confusion, force TCP with --mysql-host set to the server's IP or hostname. MySQL clients treat the default local hostname as a Unix socket, not TCP, so be explicit. Expected: The connection method is explicit and works.

When to use

• sysbench fails to connect to MySQL
• the mysql CLI works but sysbench does not
• setting up a new benchmark host

When not to use

• sysbench connects but the benchmark errors mid-run (different problem)
• the failure is 'access denied' after connecting (grants, step 2)
• MySQL itself is down (check the server first)

Tool compatibility

• sysbench 1.0.x
• MySQL 5.7/8.0, MariaDB

Variant phrasings

• "sysbench failed to connect to mysql"
• "sysbench cannot connect mysql access denied"
• "sysbench mysql connection refused"

Why it happens

sysbench's MySQL driver is a thin client: it does the same handshake as the CLI. Connection failures therefore live in the same three places as any client failure. The sysbench-specific twist is option naming (--mysql-password vs -p) and the local-hostname-means-socket convention, which trips up TCP expectations.

Edge cases

• special characters in passwords need quoting in both the CLI and sysbench; test the exact string
• sysbench --mysql-ssl options must match the server's SSL requirement; a requiresecuretransport server rejects plain connections
• benchmarking through a proxy changes the host the grant must allow; grant for the proxy's egress, not sysbench's host

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_xWDLDPQkBIxQbt-z4d2d5A

Resolved from the public thread: https://vectle.com/posts/pst_xWDLDPQkBIxQbt-z4d2d5A

Thread query: sysbench error: failed to connect to mysql during benchmark - how to fix

TL;DR: sysbench connects like any MySQL client, so a connection failure is credentials, grants, or network, not a sysbench bug. Test with the mysql CLI using the same parameters first. If the CLI connects and sysbench does not, the difference is in how you passed the options.