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Some talks and tutorials

Most of the slides can be found on my slideshare account and more recently on my SpeakerDeck page. 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2005

nolinger option for Galera Load Balancer (glb)

If you test Galera synchronous replication with Percona XtraDB Cluster or MariaDB Galera Cluster you must have tried to use a load balancer like HA Proxy or Galera Load Balancer. On very heavy load, you may have issue with a large amount of TCP in TIME_WAIT like this one:
tcp        0      0          TIME_WAIT
This can lead to a TCP port exhaustion as explained on this post. On HA proxy since version 1.4.19, you can use the nolinger option also on TCP backends. This terminate the connection (TCP RST) as soon as the loadbalancer finished the communication. The counter part is that Aborted_clients status counter in MySQL increases with each connections' end. This counter becomes then useless. This option is not available on glb (with -l parameter) if you apply the patch attached to this post. I provide also rpm package with the patch applied :
Name        : glb
Version     : 0.9.2
Release     : 2
Architecture: x86_64
Install Date: (not installed)
Group       : Productivity/Networking/Routing
Size        : 208489
License     : GNU General Public License version 2 or later (GPL v2 or later)
Signature   : (none)
Source RPM  : glb-0.9.2-2.src.rpm
Build Date  : mer 27 fév 2013 17:15:54 CET
Build Host  : percona1
Relocations : (not relocatable)
URL         :
Summary     : TCP Connection Balancer
Description :
glb is a simple user-space TCP connection balancer made with scalability and
performance in mind. It was inspired by pen, but unlike pen its functionality
is limited only to balancing generic TCP connections.

* list of backend servers is configurable in runtime.
* supports server "draining", i.e. does not allocate new connections to server,
  but does not kill existing ones, waiting for them to end gracefully.
* on Linux 2.6 and higher glb uses epoll API for ultimate performance.
* glb is multithreaded, so it can utilize multiple CPU cores. In fact even on a
  single core CPU using several threads can significantly improve performance
  when using poll()-based IO.
* connections are distributed proportionally to weights assigned to backend
* this is a patched version providing SO_LINGER
[root@macbookair ~]# glbd -K -l --threads 6 --control
glb v0.9.2 (epoll)
Incoming address: , control FIFO: /tmp/glbd.fifo
Control  address: 
Number of threads: 6, max conn: 493, policy: 'least connected', top: NO, nodelay:
 ON, keepalive: OFF, defer accept: OFF, verbose: OFF, linger: ON, daemon: NO
Destinations: 1
   0: , w: 1.000
        Address       :   weight   usage    map  conns  :    1.000   0.000    N/A      0
Destinations: 1, total connections: 0 of 493 max

Pool: connections per thread:     0     0     0     0     0     0
If you test it please post a comment.

As MySQL Community Manager, I am an employee of Oracle and the views expressed on this blog are my own and do not necessarily reflect the views of Oracle.

You can find articles I wrote on Oracle’s blog.