Nginx Source Analysis: 3 images to understand the start and process of working principle

diagram One: Nginx startup and memory application process Analysis

No program can be separated from start-up and configuration parsing. NGX's code is inseparable from the two core data structures of ngx_cycle_s and ngx_pool_s, so let's analyze it before starting.

The memory application process is divided into 3 steps

If the requested memory is less than the space remaining in the current block, it is allocated directly in the current block.

If the current block space is insufficient, call Ngx_palloc_block to assign a new block and then link the new block to D.next, and then assign the data.

If the size of the request is greater than the maximum value of the current block, then call Ngx_palloc_large directly to allocate a chunk, and link to the Pool→large linked list

The memory allocation process is illustrated below

(Image from Network)

In order to better understand the above diagram, you can refer to the 2 data structures at the end of the text: ngx_pool_s and ngx_cycle_s.

Knowing the two core data structures, we formally enter the main function, and the main function executes as follows

Call Ngx_get_options () to parse the command parameters;

Call Ngx_time_init () to initialize and update time, such as global variable ngx_cached_time;

Call Ngx_log_init () to initialize the log, such as initializing the global variable Ngx_prefix, to open the log file ngx_log_file.fd;

Clear 0 global variable ngx_cycle, and create a memory pool of size 1024B for Ngx_cycle.pool;

Call NGX_SAVE_ARGV () to save the command-line arguments to global variables ngx_os_argv, NGX_ARGC, NGX_ARGV;

Call Ngx_process_options () to initialize the ngx_cycle prefix, Conf_prefix, Conf_file, conf_param fields;

Call Ngx_os_init () to initialize system related variables, such as memory page size ngx_pagesize, ngx_cacheline_size, maximum number of connections ngx_max_sockets, etc.;

Call Ngx_crc32_table_init () to initialize the CRC table (the subsequent CRC check is done by checking the table, high efficiency);

Call Ngx_add_inherited_sockets () to inherit sockets:

Parse environment variable Nginx_var = "NGINX" in sockets, and save to ngx_cycle.listening array;

Set ngx_inherited = 1;

Call Ngx_set_inherited_sockets () to set the sockets in the ngx_cycle.listening array;

Initializes the index of each module and calculates the Ngx_max_module;

Call Ngx_init_cycle () to initialize;

The initialization is mainly carried out on the ngx_cycle structure;

If there is a signal, enter the ngx_signal_process () processing;

Call Ngx_init_signals () to initialize the signal, mainly to complete the signal processing program registration;

If there is no inheritance sockets, and the daemon identity is set, call Ngx_daemon () to create the daemon;

Call Ngx_create_pidfile () to create the process record file; (non-ngx_process_master = 1 process, do not create the file)

Enter the process main loop;

In the case of ngx_process_single=1 mode, call Ngx_single_process_cycle () into the process loop;

Otherwise, the Master-worker mode calls Ngx_master_process_cycle () into the process loop;

In the main function execution, there is a very important function ngx_init_cycle, what does this phase do? The following analysis Ngx_init_cycle, the initialization process:

Update timezone and Time

Create a memory pool

allocating memory to cycle pointers

Save installation path, configuration file, startup parameters, etc.

Initialize Open file handle

Initializing shared memory

Initializing the connection queue

Save hostname

Call the Create_conf method of each Ngx_core_module

Parsing the configuration file

Call the Init_conf method of each Ngx_core_module

Open a new file handle

Create shared memory

Processing a listening socket

Creating a socket for listening

Call the Init_module of each module

Figure Two: Master process working principle and work Engineering

The following procedures are performed in the Ngx_master_process_cycle function, starting the process:

Temporarily block all signals that NGX need to process

Set process Name

Start a worker process

Start the cache management process

Enter the loop to start processing the relevant signal

Master Process Work process

Set the work process exit wait time

Hang up and wait for the new signal to come

Update Time

Restart worker Process If there is a worker process because the SIGCHLD signal is exited

The master process exits. If all worker processes are exited and receive a SIGTERM signal or SIGINT signal or sigquit signal, etc., the master process begins processing the exit

Handling Sigterm Signals

Process the sigquit signal and close the socket

Handling Sighup Signals

Smooth upgrade, restart worker process

Not a smooth upgrade, requires a re-read configuration

Process Restart 10 process SIGUSR1 signal reopen all Files 11 process SIGUSR2 signal Hot code replacement, execute new program 12 process sigwinch signal, no longer process any request

Figure three: How Worker processes work

Start by executing the ngx_start_worker_processes function:

Find the pit bit in the ngx_processes array first if (Ngx_processes[s].pid = =-1) {break;}

Process-related structure initialization work

Create Pipeline (Socketpair)

Set the pipeline to non-blocking mode

Set the pipeline to asynchronous mode

To set the owner of an asynchronous I/O

If exec executes, this FD is not passed to the process created by exec

Fork to create the child process. After a successful creation, the child process executes the relevant logic: proc (cycle, data).

Set Ngx_processes[s] Related properties

Notifies the child process that a new process has been created Ngx_pass_open_channel (cycle, &ch);

Next is the Ngx_worker_process_cycle worker process logic

Ngx_worker_process_init

Initializing environment variables

Set process priority

Set the limit on the number of file handles

Setting up the Core_file file

User group settings

CPU Affinity Settings

Set working directory

Set Random seed number

Initializing the Listening state

The Init_process method of each module is called to initialize

Close others ' fd[1] and keep others ' fd[1] used to communicate with each other. Own fd[1] receives the message of the master process.

Monitor Channel Read Events

Process mode

Process the piping signal. This process is done by Ngx_channel_handler, which is specifically explained in the pipeline event.

Threading mode

Ngx_worker_thread_cycle is a thread loop: In addition to processing the exit signal in the dead loop. The main work of the ngx_event_thread_process_posted, this piece of concrete content in the later talk about the event model, and then expand.

Processing of related signals

The master and Worker communication Principles are: