MySQL Bugs: #76611: ndb_restore doesn't handle SIGHUP

Bug #76611	ndb_restore doesn't handle SIGHUP
Submitted:	7 Apr 2015 13:41	Modified:	8 Apr 2015 11:57
Reporter:	Edward Mackenzie	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Cluster: Cluster (NDB) storage engine	Severity:	S4 (Feature request)
Version:	mysql-5.6.23 ndb-7.4.5	OS:	Linux (Discovered on Oracle Linux)
Assigned to:		CPU Architecture:	Any
Tags:	ndb_restore

Description:
ndb_restore does not seem to catch the SIGHUP signal (not obviously at least).

This was noticed when trying to restore a database backup on a remote system via ssh. All backup files were local to the database cluster, but the ndb_restore command was called remotely.

When the ssh session either timed out or was closed (VPN connection timeout) after backgrounding the ndb_restore process the ndb_restore process just stops - albeit not immediately.

After some extensive searching, I found that this was being caused by SIGHUP. While there are ways around this - I am reporting it as a bug because there is no logging to indicate that this is what has happened.

This can be avoided by executing the ndb_restore command using nohup, or by using disown on an existing process.

How to repeat:
Open an ssh connection to the database cluster.

Start restoring a large database, background the ndb_restore process.

Disconnect the ssh session.

Expected behavior would be for the process to continue running in the background. However, the process just stops with no log message.

Suggested fix:
Either catch and ignore the SIGHUP signal, or catch it, log that it has been caught then stop.

I would recommend that SIGHUP should be ignored.

Hi Eduard,

This is designed behavior so not a bug, but is a feature request worth working on :)

all best
Bogdan Kecman

Workaround: use screen
http://www.manpagez.com/man/1/screen/