Core functionality

Core functionality

Example Configuration Directives      accept_mutex      accept_mutex_delay      daemon      debug_connection      debug_points      env      error_log      events      include      load_module      lock_file      master_process      multi_accept      pcre_jit      pid      ssl_engine      thread_pool      timer_resolution      use      user      worker_aio_requests      worker_connections      worker_cpu_affinity      worker_priority      worker_processes      worker_rlimit_core      worker_rlimit_nofile      worker_shutdown_timeout      working_directory

Example Configuration

user www www;worker_processes 2;error_log /var/log/nginx-error.log info;events { use kqueue; worker_connections 2048;}...

Directives

Syntax:	accept_mutex on | off;
Default:	accept_mutex off;
Context:	events

If accept_mutex is enabled,worker processes will accept new connections by turn.Otherwise, all worker processes will be notified about new connections,and if volume of new connections is low, some of the worker processesmay just waste system resources.

There is no need to enable accept_mutexon systems that support theEPOLLEXCLUSIVE flag (1.11.3) orwhen using reuseport.

Prior to version 1.11.3, the default value was on.

Syntax:	accept_mutex_delay time;
Default:	accept_mutex_delay 500ms;
Context:	events

If accept_mutex is enabled, specifies the maximum timeduring which a worker process will try to restart accepting newconnections if another worker process is currently acceptingnew connections.

Syntax:	daemon on | off;
Default:	daemon on;
Context:	main

Determines whether nginx should become a daemon.Mainly used during development.

Syntax:	debug_connection address | CIDR | unix:;
Default:	—
Context:	events

Enables debugging log for selected client connections.Other connections will use logging level set by theerror_log directive.Debugged connections are specified by IPv4 or IPv6 (1.3.0, 1.2.1)address or network.A connection may also be specified using a hostname.For connections using UNIX-domain sockets (1.3.0, 1.2.1),debugging log is enabled by the “unix:” parameter.

events { debug_connection 127.0.0.1; debug_connection localhost; debug_connection 192.0.2.0/24; debug_connection ::1; debug_connection 2001:0db8::/32; debug_connection unix:; ...}

For this directive to work, nginx needs tobe built with --with-debug,see “A debugging log”.

Syntax:	debug_points abort | stop;
Default:	—
Context:	main

This directive is used for debugging.

When internal error is detected, e.g. the leak of sockets onrestart of working processes, enabling debug_pointsleads to a core file creation (abort)or to stopping of a process (stop) for furtheranalysis using a system debugger.

Syntax:	env variable[=value];
Default:	env TZ;
Context:	main

By default, nginx removes all environment variables inheritedfrom its parent process except the TZ variable.This directive allows preserving some of the inherited variables,changing their values, or creating new environment variables.These variables are then:

• inherited during a live upgradeof an executable file;
• used by thengx_http_perl_module module;
• used by worker processes.One should bear in mind that controlling system libraries in this wayis not always possible as it is common for libraries to checkvariables only during initialization, well before they can be setusing this directive.An exception from this is an above mentionedlive upgradeof an executable file.

The TZ variable is always inherited and available to thengx_http_perl_modulemodule, unless it is configured explicitly.

Usage example:

env MALLOC_OPTIONS;env PERL5LIB=/data/site/modules;env OPENSSL_ALLOW_PROXY_CERTS=1;

The NGINX environment variable is used internally by nginxand should not be set directly by the user.

Syntax:	error_log file [level];
Default:	error_log logs/error.log error;
Context:	main, http, mail, stream, server, location

Configures logging.Several logs can be specified on the same configuration level (1.5.2).If on the main configuration level writing a log to a fileis not explicitly defined, the default file will be used.

The first parameter defines a file that will store the log.The special value stderr selects the standard error file.Logging to syslog can be configured by specifyingthe “syslog:” prefix.Logging to acyclic memory buffercan be configured by specifying the “memory:” prefix andbuffer size, and is generally used for debugging (1.7.11).

The second parameter determines the level of logging,and can be one of the following:debug, info, notice,warn, error, crit,alert, or emerg.Log levels above are listed in the order of increasing severity.Setting a certain log level will cause all messages ofthe specified and more severe log levels to be logged.For example, the default level error willcause error, crit,alert, and emerg messagesto be logged.If this parameter is omitted then error is used.

For debug logging to work, nginx needs tobe built with --with-debug,see “A debugging log”.

The directive can be specified on thestream levelstarting from version 1.7.11,and on the mail levelstarting from version 1.9.0.

Syntax:	events { ... }
Default:	—
Context:	main

Provides the configuration file context in which the directives thataffect connection processing are specified.

Syntax:	include file | mask;
Default:	—
Context:	any

Includes another file, or files matching thespecified mask, into configuration.Included files should consist ofsyntactically correct directives and blocks.

Usage example:

include mime.types;include vhosts/*.conf;

Syntax:	load_module file;
Default:	—
Context:	main

This directive appeared in version 1.9.11.

Loads a dynamic module.

Example:

load_module modules/ngx_mail_module.so;

Syntax:	lock_file file;
Default:	lock_file logs/nginx.lock;
Context:	main

nginx uses the locking mechanism to implement accept_mutexand serialize access to shared memory.On most systems the locks are implemented using atomic operations,and this directive is ignored.On other systems the “lock file” mechanism is used.This directive specifies a prefix for the names of lock files.

Syntax:	master_process on | off;
Default:	master_process on;
Context:	main

Determines whether worker processes are started.This directive is intended for nginx developers.

Syntax:	multi_accept on | off;
Default:	multi_accept off;
Context:	events

If multi_accept is disabled, a worker processwill accept one new connection at a time.Otherwise, a worker processwill accept all new connections at a time.

The directive is ignored if kqueueconnection processing method is used, because it reportsthe number of new connections waiting to be accepted.

Syntax:	pcre_jit on | off;
Default:	pcre_jit off;
Context:	main

This directive appeared in version 1.1.12.

Enables or disables the use of “just-in-time compilation” (PCRE JIT)for the regular expressions known by the time of configuration parsing.

PCRE JIT can speed up processing of regular expressions significantly.

The JIT is available in PCRE libraries starting from version 8.20built with the --enable-jit configuration parameter.When the PCRE library is built with nginx (--with-pcre=),the JIT support is enabled via the--with-pcre-jit configuration parameter.

Syntax:	pid file;
Default:	pid logs/nginx.pid;
Context:	main

Defines a file that will store the process ID of the main process.

Syntax:	ssl_engine device;
Default:	—
Context:	main

Defines the name of the hardware SSL accelerator.

Syntax:	thread_pool name threads=number [max_queue=number];
Default:	thread_pool default threads=32 max_queue=65536;
Context:	main

This directive appeared in version 1.7.11.

Defines named thread poolsused for multi-threaded reading and sending of fileswithout blockingworker processes.

The threads parameterdefines the number of threads in the pool.

In the event that all threads in the pool are busy,a new task will wait in the queue.The max_queue parameter limits the numberof tasks allowed to be waiting in the queue.By default, up to 65536 tasks can wait in the queue.When the queue overflows, the task is completed with an error.

Syntax:	timer_resolution interval;
Default:	—
Context:	main

Reduces timer resolution in worker processes, thus reducing thenumber of gettimeofday() system calls made.By default, gettimeofday() is called each timea kernel event is received.With reduced resolution, gettimeofday() is onlycalled once per specified interval.

Example:

timer_resolution 100ms;

Internal implementation of the interval depends on the method used:

• the EVFILT_TIMER filter if kqueue is used;
• timer_create() if eventport is used;
• setitimer() otherwise.

Syntax:	use method;
Default:	—
Context:	events

Specifies the connection processingmethod to use.There is normally no need to specify it explicitly, because nginx willby default use the most efficient method.

Syntax:	user user [group];
Default:	user nobody nobody;
Context:	main

Defines user and groupcredentials used by worker processes.If group is omitted, a group whose name equalsthat of user is used.

Syntax:	worker_aio_requests number;
Default:	worker_aio_requests 32;
Context:	events

This directive appeared in versions 1.1.4 and 1.0.7.

When using aiowith the epollconnection processing method, sets the maximum number ofoutstanding asynchronous I/O operationsfor a single worker process.

Syntax:	worker_connections number;
Default:	worker_connections 512;
Context:	events

Sets the maximum number of simultaneous connections thatcan be opened by a worker process.

It should be kept in mind that this number includes all connections(e.g. connections with proxied servers, among others),not only connections with clients.Another consideration is that the actual number of simultaneousconnections cannot exceed the current limit onthe maximum number of open files, which can be changed byworker_rlimit_nofile.

Syntax:	worker_cpu_affinity cpumask ...; worker_cpu_affinity auto [cpumask];
Default:	—
Context:	main

Binds worker processes to the sets of CPUs.Each CPU set is represented by a bitmask of allowed CPUs.There should be a separate set defined for each of the worker processes.By default, worker processes are not bound to any specific CPUs.

For example,

worker_processes 4;worker_cpu_affinity 0001 0010 0100 1000;

binds each worker process to a separate CPU, while

worker_processes    2;worker_cpu_affinity 0101 1010;

binds the first worker process to CPU0/CPU2,and the second worker process to CPU1/CPU3.The second example is suitable for hyper-threading.

The special value auto (1.9.10) allowsbinding worker processes automatically to available CPUs:

worker_processes auto;worker_cpu_affinity auto;

The optional mask parameter can be used to limit the CPUsavailable for automatic binding:

worker_cpu_affinity auto 01010101;

The directive is only available on FreeBSD and Linux.

Syntax:	worker_priority number;
Default:	worker_priority 0;
Context:	main

Defines the scheduling priority for worker processes like it isdone by the nice command: a negativenumbermeans higher priority.Allowed range normally varies from -20 to 20.

Example:

worker_priority -10;

Syntax:	worker_processes number | auto;
Default:	worker_processes 1;
Context:	main

Defines the number of worker processes.

The optimal value depends on many factors including (but notlimited to) the number of CPU cores, the number of hard diskdrives that store data, and load pattern.When one is in doubt, setting it to the number of available CPU coreswould be a good start (the value “auto”will try to autodetect it).

The auto parameter is supported starting fromversions 1.3.8 and 1.2.5.

Syntax:	worker_rlimit_core size;
Default:	—
Context:	main

Changes the limit on the largest size of a core file(RLIMIT_CORE) for worker processes.Used to increase the limit without restarting the main process.

Syntax:	worker_rlimit_nofile number;
Default:	—
Context:	main

Changes the limit on the maximum number of open files(RLIMIT_NOFILE) for worker processes.Used to increase the limit without restarting the main process.

Syntax:	worker_shutdown_timeout time;
Default:	—
Context:	main

This directive appeared in version 1.11.11.

Configures a timeout for a graceful shutdown of worker processes.When the time expires,nginx will try to close all the connections currently opento facilitate shutdown.

Syntax:	working_directory directory;
Default:	—
Context:	main

Defines the current working directory for a worker process.It is primarily used when writing a core-file, in which casea worker process should have write permission for thespecified directory.