Bug #30932 slave_net_timeout for connect() to master is not optimal.

• Submitted: 10 Sep 2007 14:09
• Modified: 24 Oct 2007 12:46
• Reporter: Domas Mituzas
• Status: Closed
• Category: MySQL Server: Replication
• Severity: S2 (Serious)
• Version: 5.0, 5.1, ..
• OS: Any
• Assigned to: Andrei Elkin
• CPU Architecture: Any
• Tags: replication

[10 Sep 2007 14:09] Domas Mituzas

Description:
Connections to master from slave use slave_net_timeout as connect() timeout. 
There're multiple issues with it:

a) Default value is 3600, so connect() will be terminated by OS rather than MySQL
b) Reducing slave_net_timeout to reasonable amount for connect() (like 10s) would cause disconnects in case of idle replication, as well as log rotation (see Bug#20435)

As there is no way to fail fast with connects (unlike in client library), it seems to be buggy implementation of replication networking. 

How to repeat:
SLAVE START;

Suggested fix:
decouple connect timeout from network timeout, make it settable properly or at least set to reasonable value.

[13 Oct 2007 11:19] Andrei Elkin

With fixes for bug#20435 introducing a new heartbeat feature `slave_net_timeout'
can be set to a small values e.g the same suggested 10 seconds.
The heartbeat replication event - to be sent in master's idling time - resets `slave_net_timeout'. Provided that the heartbeat period would be set to a value
less that `slave_net_timeout' there is a very slim chance for the latter to elapse and force reconnecting.

[16 Oct 2007 20:59] Lars Thalmann

This is fixed by the fix for BUG#20435:

> a) Default value is 3600, so connect() will be terminated by OS
>    rather than MySQL

With heartbeats enabled, there will be no termination of connect().

> b) Reducing slave_net_timeout to reasonable amount for connect()
>    (like 10s) would cause disconnects in case of idle replication, as
>    well as log rotation (see Bug#20435)

With heartbeats enabled, there will be no idle replication.

[24 Oct 2007 9:54] Jon Stephens

Documented fix in mysql-5.1.22-ndb-6.3.4 changelog; closed.

[24 Oct 2007 10:15] Domas Mituzas

This is generic bug, not related to NDB - is it going to be added to mainstream versions?

[8 Nov 2007 14:08] Lars Thalmann

Domas, yes it will appear in 6.0.

[28 Nov 2007 20:21] Jon Stephens

Also documented for 6.0.4 release - see also Bug #20435.

[18 Mar 2019 7:07] WANG GUANGYOU

Still in 5.7.21 in production.