This is an interview question brought back by a reader
Nginx How to achieve concurrency ？ Why? Nginx No multithreading ？Nginx What are the common optimization methods ？502 What are the possible causes of the error ？
Psychological analysis of interviewers
Mainly depends on the candidate's right NGINX Are you familiar with the basic principles of , Because most people know more or less NGINX, But few of them really understand the principle . Understand its principle , To optimize , Otherwise, we can only copy the same , If something goes wrong, there is no way to start .
Interview questions ：Nginx How to achieve high concurrency ？ What are the common optimization methods ？
People who know fur , I usually do Web Server, Building a Web Site ; Primary operation and maintenance may be HTTPS 、 Configure a reverse proxy ; Intermediate operation and maintenance defines a upstream、 Write a regular judgment ; Old bird, do a performance optimization 、 Write a ACL, It is also possible to change the source code （ Xiaobian said he had no ability to change the source code ）.
Analysis of interview questions
Nginx How to achieve high concurrency ？
asynchronous , Non blocking , Used epoll And a lot of underlying code optimization .
If one server Use one process to be responsible for one request The way , So the number of processes is the number of concurrent . Under normal circumstances , There will be many processes waiting .
and nginx Use a master process , Multiple woker The pattern of the process .
- master The process is mainly responsible for collecting 、 Distribute the requests . Every time a request comes ,master Just pick up one worker The process is responsible for processing the request .
- meanwhile master The process is also responsible for monitoring woker The state of , High reliability
- woker The process is generally set to follow cpu The number of cores is the same .nginx Of woker The number of requests a process can process at the same time is limited by memory , Can handle multiple requests .
- Nginx The asynchronous non blocking working mode of is taking advantage of the waiting time . When it's time to wait , These processes are idle and on standby , So a few processes solve a lot of concurrency problems .
Every time I come in request, There will be one. worker Process to deal with . But not the whole process , To what extent ？ Deal with where there might be a blockage , Like upstream （ Back end ） Server forwarding request, And wait for the request to return . that , This one deals with worker Very clever , He will send the request after , Register an event ：“ If upstream Back to , Tell me , I'll go on with it ”. So he went to rest .
here , If there is more request Come in , He can deal with it this way soon . And once the upstream server returns , Will trigger this event ,worker To take over , This request And then I'll go down .
Why? Nginx No multithreading ？
Apache: Create multiple processes or threads , And each process or thread allocates cpu And memory （ Threads are much smaller than processes , therefore worker Support than perfork High concurrency ）, Concurrent conferences consume server resources .
Nginx: Using a single thread to process requests asynchronously and non blocking （ Administrators can configure Nginx The number of worker processes in the main process ）(epoll), No... Is assigned to each request cpu And memory resources , It saves a lot of resources , It also reduces a lot of CPU Context switch of . That's why Nginx Support for higher concurrency .
Nginx What are the common optimized configurations ？
1） adjustment worker_processes
finger Nginx To generate the worker Number , The best practice is every CPU function 1 Working process .
Understand... In the system CPU The core number , Input
$ grep processor / proc / cpuinfo | wc -l2) Maximize worker_connections
Nginx Web The number of clients that the server can serve at the same time . And worker_processes When used in combination , Get the maximum number of clients that can be served per second
Maximum number of clients / second = Working process * Number of worker connections
To maximize Nginx The full potential of , The worker connection should be set to the maximum number of processes allowed for the core to run at one time 1024.
3) Enable Gzip Compress
Compressed file size , Reduce the number of clients http The transmission bandwidth of , So it improves the page loading speed
Suggested gzip An example configuration is as follows :( stay http In part ）
4) Enable caching for static files
Enable caching for static files , To reduce bandwidth and improve performance , You can add the following command , Limit the static file of the computer cache web page ：
location ~* .(jpg|jpeg|png|gif|ico|css|js)$ {
expires 365d;
}5）Timeouts
keepalive Connections reduce the time required to open and close connections CPU And network overhead , For the variables that need to be adjusted to obtain the best performance, refer to ：
6) Ban access_logs
Access logging , It records every nginx request , So it consumes a lot of CPU resources , So it reduces nginx performance .
Completely disable access logging
access_log off;If you must have access logging , Enable access log buffering
access_log /var/log/nginx/access.log The main buffer = 16k502 What are the possible reasons for the error report ？
- 1）FastCGI Is the process started
- 2）FastCGI worker Whether the number of processes is not enough
- 3）FastCGI Execution time is too long
- 4）FastCGI Buffer Not enough
nginx and apache equally , There is a front-end buffer limit , Buffer parameters can be adjusted
fastcgi_buffer_size 32k;
fastcgi_buffers 8 32k;- 5）Proxy Buffer Not enough
If you use Proxying, adjustment
proxy_buffer_size 16k;
proxy_buffers 4 16k;- 6）php Script takes too long to execute
take php-fpm.conf Of <value name="request_terminate_timeout">0s</value> Of 0s Change to a time
source ：toutiao.com/i6698255904053133827/
