Site Refresh 10 seconds is 502 What is the problem, the server configuration is very high

Cpu:2 Core, Memory: 8192 MB, Bandwidth 10Mbps
Open the website home page hold F5, always refresh and then 502. MySQL is using the extranet, MySQL is not hanging.
The other one is 2 cores, the memory is 2048, the bandwidth is 2m. has not used Lnmp, refresh on the brush does not die.
Do you have a friend who has the same problem, ask for advice?

PS: A refresh of the dead environment with the LNMP installation package

Reply content:

Cpu:2 Core, Memory: 8192 MB, Bandwidth 10Mbps
Open the website home page hold F5, always refresh and then 502. MySQL is using the extranet, MySQL is not hanging.
The other one is 2 cores, the memory is 2048, the bandwidth is 2m. has not used Lnmp, refresh on the brush does not die.
Do you have a friend who has the same problem, ask for advice?

PS: A refresh of the dead environment with the LNMP installation package

HTTP Status 502 (Error Gateway)
The server received an invalid response from the upstream server as a gateway or proxy.
Workaround:

1. Improve the response speed of the Web server, that is, reduce the internal call relationship, you can put the required pages, footage or data, in memory, can be a dedicated cache server, or the WEB server itself cache, to improve response speed;

2. The network bandwidth problem, the transmission of the packet compression processing, or to IDC application to increase the bandwidth;

3. The internal network is a fault or setup problem, that is, internal network congestion, there may be a large number of internal data calls or interactions caused by the need to optimize the internal network transmission or protocol;

4. Database data read caused by the front-end server, in response to the user's request is slow, you must improve the database processing capacity, if the read-only business can increase the data cache mode or increase the database standby machine, decentralized reading pressure

• Look at Nginx error.log log, there is no error message

• Nginx limit maximum number of connections

• is not php-fpm the number of connections exhausted, optimize the PHP-FPM parameter

is not your code is a problem ah, if the code there is a dead loop, or a very late memory operation, there is a possibility that this problem

Elimination Method Analysis steps:
1. Test with Static page
2, with pure PHP script test, not even cache, non-connected DB
3, each analysis of the backend used to the DB, cache, call the third-party service is normal
4, 502 is usually due to the fastcgi process for some reason hanging off, you can look at the PHP-FPM log

