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Name

ngx.process - manage the nginx processes for OpenResty/ngx_lua.

Table of Contents

Status

This Lua module is currently considered experimental. The API is still in flux and may change in the future without notice.

Synopsis

Enables privileged agent process, gets process type, and then gets the master process PID:

# http config
init_by_lua_block {
    local process = require "ngx.process"

    -- enables privileged agent process
    local ok, err = process.enable_privileged_agent()
    if not ok then
        ngx.log(ngx.ERR, "enables privileged agent failed error:", err)
    end

    -- output process type
    ngx.log(ngx.INFO, "process type: ", process.type())
}

init_worker_by_lua_block {
    local process = require "ngx.process"
    ngx.log(ngx.INFO, "process type: ", process.type())
}

server {
    # ...
    location = /t {
        content_by_lua_block {
            local process = require "ngx.process"
            ngx.say("process type: ", process.type())
            ngx.say("master process pid: ", process.get_master_pid() or "-")
        }
    }
}

The example config above produces an output to error.log when server starts:

[lua] init_by_lua:11: process type: master
[lua] init_worker_by_lua:3: process type: privileged agent
[lua] init_worker_by_lua:3: process type: worker

The example location above produces the following response body:

process type: worker
master process pid: 8261

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Functions

type

syntax: type_name = process_module.type()

context: any

Returns the type of the current Nginx process. Depending on the calling context and current process, the type can be one of:

  • master: returned when this function is called from within the master process
  • worker: returned when this function is called from within a worker process
  • single: returned when Nginx is running in the single process mode
  • signaller: returned when Nginx is running as a signaller process
  • privileged agent: returned when this funtion is called from within a privileged agent process

For example:

local process = require "ngx.process"
ngx.say("process type:", process.type())   -- RESPONSE: worker

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enable_privileged_agent

syntax: ok, err = process_module.enable_privileged_agent()

context: init_by_lua*

Enables the privileged agent process in Nginx.

The privileged agent process does not listen on any virtual server ports like those worker processes. And it uses the same system account as the nginx master process, which is usually a privileged account like root.

The init_worker_by_lua* directive handler still runs in the privileged agent process. And one can use the type function provided by this module to check if the current process is a privileged agent.

In case of failures, returns nil and a string describing the error.

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signal_graceful_exit

syntax: process_module.signal_graceful_exit()

context: any

Signals the current nginx (worker) process to quit gracefully, i.e., after all the timers have expired (in time or expired prematurely).

Note that this API function simply sets the nginx global C variable ngx_quit to signal the nginx event loop directly. No UNIX signals or IPC are involved here.

WARNING: the official NGINX core does not perform the graceful exiting procedure when the master_process directive is turned off. The OpenResty's NGINX core has a custom patch applied, which fixes this issue.

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get_master_pid

syntax: pid = process_module.get_master_pid()

context: any

Returns a number value for the nginx master process's process ID (or PID).

This function requires NGINX 1.13.8+ cores to work properly. Otherwise it returns nil.

This feature first appeared in lua-resty-core v0.1.14.

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Community

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English Mailing List

The openresty-en mailing list is for English speakers.

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Chinese Mailing List

The openresty mailing list is for Chinese speakers.

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Bugs and Patches

Please report bugs or submit patches by

  1. creating a ticket on the GitHub Issue Tracker,
  2. or posting to the OpenResty community.

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Author

Yuansheng Wang <membphis@gmail.com> (membphis), OpenResty Inc.

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2017, by Yichun "agentzh" Zhang, OpenResty Inc.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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See Also

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