Nginx + PHP-FPM + Yii = why is there a 504 error?

Question

PHP

Given:
There is a web server with Nginx, php-fpm and MySQL installed, on it several XML parsers process tens of thousands of files and put them into the database, the average processing time is 3-5 minutes, it's all written in Yii .
The essence of the problem is this:
If you run any parser, then during these 5 minutes while it is working on any calls to the rest of the resource pages, the web server issues 504 Gateway Time-out
At the same time, if on the same server I run the old version of parsers written in pure php, then 504 no errors occur and I manage to run several of them in parallel and open other pages of the resource without difficulty.
Errors in the logs only for Nginx:
2014/07/16 14:25:27 [error] 11665#0: *9 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 37.#.#.#, server: ## ###.ru, request: "GET /index.php?r=loading/parsenotifications HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "#####.ru" , referrer: " http://#####.ru/index.php?r=loading/index "
2014/07/16 14:25:29 [error] 11665#0: *12 upstream timed out (110 : Connection timed out) while reading response header from upstream, client: 37.#.#.#, server: #####.ru, request: "GET /index.php?r=loading/parsecontracts HTTP/1.1" , upstream: "fastcgi://127.0.0.1:9000", host: "#####.ru", referrer: " http://#####.ru/index.php?r=loading/ index "

Answer 1

There is a suspicion that file sessions are being locked. Try not to use them, or use sessions in the database if you need them (just be careful with race conditions). Here is more details. Well, yes, it would be even better to run the parsers through the console, and not through the web server.

Answer 2

There could be a lot here.
1) mysql overload by load, by the number of connections (most likely)
2) parsers if there are a lot of them at once and you start them not from the console, choose nginx workers

Answer 3

take the parser to the CLI daemon and just tie the whole thing together via RabbitMQ for example.

Answer 4

How are parsers launched?

Answer 5

Go to the logs and just look
at the edge enable slolog in php-fpm

Answer 6

Do you happen to have an important plate in the database that is not locked when parsers work?
Maybe the parser is locking it, and all requests to the site are waiting for the blocking to subside?
Have you monitored what happens to queries in the database when the parser is running?