cachecm-redissessionmagento-1.7varnish
Right now I am using Magento 1.7.0.2 with Redis Session Storage. I am looking forward to adding additional frontend server behind a load balancer. Can I use the same Redis server for sessions for both frontend servers?
Idea:
Server1 = Apache + PHP + Redis Server2 = Apache + PHP + Database
Varnish listens for connections and uses Server1 or Server2 to handle misses and esi stuff
Thanks!
There are two difficult things in computer science:
Hole punching falls into category #2 :)
General
The best approach is to start at the lower points of the stack and optimize up to the frontend of Magento.
Database and Filesystem
Should always be the first areas to focus on. Because. I/O.
MyTop is a handy Linux based perl script that will mimic the Linux 'top' command and give you insight on the state of your MySQL instance(s).
Htop is a more robust top, The strace feature can help determine ins/outs of a process to find potential bottlenecks.
Iotop is another tool to consider for monitoring I/O.
Other handy utility scripts like mysqltuner.pl and mysql tunning primer can offer insight into your MySQL runtime variables and offer advice to help. Keep in mind these are meant to be guides as the best approach is always an evaluation of requirements and tuning based on known data gathered. Blindly doing so can cause more damage at times than good. And prematurely running these without at least 24 hours of mysql runtime variables may offer bad advice.
Keep in mind Percona, MariaDB and standard MySQL should work with all of the above. Favoring Percona as a MySQL fork, since Magento is so heavy on InnoDB and XtraDB offers many tools and enhancements to the db engine.
Apache or Nginx
Still using Apache as it has served many others well, myself included. I have used and configured Nginx as well. While it does offer some advantages there is a learning curve. While the two are both popular options, it does offer some advantages over Apache, one would be a smaller memory footprint. However a slim downed Apache running PHP-FPM will have a similar memory footprint.
Case in point:
Since this article was about performance, I should point out that one of the easiest ways to help apache get out of its own way is to not use .htaccess files. Put what you'd put there in your Directory stanzas, set AllowOverride to "None" and you end up not asking apache to traverse the whole document path to figure out if it needs to pay attention to .htaccess or not. This is a basic, simple tuning hint that many people seem to miss.
To help facilitate this check out:
Utilizing a CDN to help take the ease off of either will help obviously but will have added benefit on frontend optimization since most end users browsers will be able to connect to both servers with the same number of connection limits. This also frees up Apache from not having to jump through checks and such just to serve up a simple static image. Lighthttpd is an option if you want to run a static web server just for content besides a CDN.
PHP
PHP-FPM and APC. Use them, strip out any unneeded or unrequired PHP modules not needed for Magento.
Magento codebase
AOE_TemplateHints is great to determine if your blocks are caching properly:
AOE_Profiler is good for profiling, be sure and enable its DB layer profiling (in a local/dev environment obviously). This in conjunction with the mytop tool mentioned previously makes finding bad behaving SQL an easier task.
3rd Party modules & Custom code
Some very good best practices for optimization from Magento themselves is a good read, and to keep in mind when reviewing 3rd party modules before using them. (there are lots of bad behaving ones IMO).
A tool Magniffer from Magento ECG will help easily identify bad behaving code based on the PDF provided above. It is symfony/php-parser based however but installable via composer.
Varnish
As an advocate of Varnish being the author was a FreeBSD kernel dev, it offers some crazy sub second load times. However if you even have some of the slightest differences in your templates that isn't out of box, you will spend time configuring varnish / magento to holepunch the content you need. Most I've seen will simply AJAX'ify the needed items uncached from Varnish.
There are a number of Magento modules to help facilitate this hole punching and caching:
Ultimately this should be at the last end of your optimization journey, and MAY require some customization to get things right.
Magento CE FPC
So far the best CE FPC I have found is: Lesti::FPC
it is a very well put together (all observer based) open-source and free FPC for Community.
At the end of the day use your own testing and judgement.
Some further reading:
It could be a dozen different things, and without a full overview of your entire server at that point in time, it isn't going to be possible to give a definitive answer.
It could be,
redis-server process at 100% CPU
The list could go on and on. What you need is full and proper monitoring of your entire server, so that you can see exactly what is happening to make a diagnosis.
That includes graphing every application with Munin, historical logging with the Atop daemon, logging and centralisation of log data into a single dashboard.
New Relic is a nice tool, whilst useful for some identification of issues, its not necessarily the best tool to try and have full visibility of the cause of issues.
Easiest place to start would be to check if Redis needs more memory,
redis-cli
> info
Compare the peak memory with the limit you have defined.
NB. Your hosting provider should be able to answer this question in an instant, I would definitely suggest asking for their input.
Best Answer
You can provided you are using Redis over TCP and not via a local socket.