Stories from life: "The site is slow"
15:06
Dima, please help us move to a new server. How can we do this with minimal disruption? Our small Intel Atom server is already dying.
15:08
hello
15:08
Good afternoon! Can we clone it somehow?
15:09
is it virtual?
15:09
No, physical.
15:10
and where are we moving to?
15:10
We are preparing a clean Intel Pentium G6950/4GB/1TB server + UNLIM 100 Mbit/s. Please request IP-KVM separately once you are ready to work with the equipment. Please wait for a notification from our technical-service colleagues.
15:10
Yes, there. We simply had the most basic configuration at the Romashka data center for (0000) UAH. Now we are taking this one.
(discussion of server migration approaches and methods omitted)
15:34
question: why did you decide that your server cannot cope?
15:35
the site is very slow. When there were 30 people on the site, everything was very slow.
15:36
and CPU load jumped to 90%. More than 3,100 users have registered already. It is an Intel Atom.
15:36
and how long did it stay at 90%? So what if it is an Atom...
15:37
It remained high until people left because of the slowness. It is quite seriously slow.
15:39
(once again, for myself) how do you substantiate the term "slow"?
15:40
The site takes a very long time to open. Everything used to be instant, and now we wait 3–4 seconds. It kind of lags. People say the same thing.
15:41
OK, let us look at this differently. You currently have 4 CPU/4 GB and will have 4 CPU/4 GB. Where is the difference?
15:43
For example, what process is this?
15:44
No idea. Something related to Perl.
15:44
Second example:
15:45
it is clearly visible that MySQL consumed the lion's share. The question is WHY? Does it have 1,000,000 queries? How many? Or is the disk subsystem slow? What kind do you have, and what kind are you getting? Will there be a difference?
15:46
It currently has a 250 GB hard drive; we are getting a 1 TB one.
15:46
or perhaps unindexed queries are pouring in? Have you checked how many? Disk size is NOT related to its speed.
15:47
Intel Atom D510/4GB/250GB -> Intel Pentium G6950/4GB/1TB. I understand.
15:47
And judging by the amount used, you are far from the limit!
15:47
Our database is causing lag. Yes.
15:49
I cannot answer your question with this amount of information. I will say this: I believe you have not named factors that require replacing this hardware.
15:50
I understand. The factors are as follows: the site was fast, but when we reached 3,000 users, it became very slow. When 30 people were online, working with the site was practically impossible. I watched CPU load—it was at its maximum.
15:51
Those are not facts; they are external symptoms.
15:51
I understand that we need to optimize the code, specifically database operation. Apparently, we have a huge number of queries.
15:51
first we need to understand the cause of the CPU load. No, not "apparently"... where is the evidence?
15:52
Then I give up.)
15:56
"bang-bang... dead" :)
15:56
Dima, do you have advice for identifying the problem? Working with the site is already uncomfortable. When 30 people are on the site, it is practically impossible. Connect an SSD? Add RAM?
15:57
Advice: find the cause of the "slowness."
16:26
mysql 85.3 % /usr/sbin/mysqld. Our database really is consuming all resources of the weak Atom.
16:28
yes, that is clear, but with what?
16:29
An example that also began with the words "The site is slow": https://note.wdm.net.ua/fromLife/dovecot-gruzit-cpu/
16:31
I am sure this is our case. Is the MySQL cache enabled?
16:32
nothing is a fact until you check and see it.
16:33
Dima, where do they view database record statistics? There are such nice graphs there. Top shows MySQL took all the resources. We see queries with colossal execution times. How and where can we view all this?
16:34
Zabbix generates the graphs.
16:38
in that case, 90% of the slowness was caused by "idiotic" database queries.
16:40
Use the mytop utility or run SHOW PROCESSLIST in the MySQL client.
17:00
I read your conversation, reviewed my new queries, and optimized them a little—please check whether the slowness and load have gone away. It seems to work faster visually.
17:00
It has become much faster!
17:01
and what did you do?
17:01
the queries were not optimal—several were made instead of one. This happened every time a page was generated for a user. That caused the slowness, and now it is gone.
17:02
The site is flying like Schumacher! We no longer knew what to do. Dima, thank you so much for a sober assessment of the situation. The problem truly was not the configuration.
21:32
Ivan Vasilyevich, what would you call your role in this project?
21:55
Startup manager.)