Preliminary analysis of Docker Registry service start-up process

When we pull a registry image or make a mirror ourselves, using the command Docker run-d-P 5000:5000 Registry, you can start a private container service, so how exactly does it work?

First, Docker PS shows that cmd is "docker-registry", but it is not entered when it is started.
[Email protected]:/home/opuser# Docker PS
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ffca4ca34c3f registry "Docker-registry" , hours ago up, hours 0.0.0.0:5000->5000/tcp desperate_lumiere

Remember that you can specify a command to execute after starting Docker in Dockerfile, and see the Dockerfile to create a registry image
[Email protected]:/# Cat Docker-registry/dockerfile
# VERSION 0.1
# docker-version 0.7.3
# Author:sam Alba <[email protected]>
# Description:image with Docker-registry project and Dependecies
# To_build:docker Build-rm-t registry.
# To_run:docker Run-p 5000:5000 Registry

# Latest Ubuntu LTS
From ubuntu:14.04

# Update
RUN apt-get update \
# Install Pip
&& apt-get install-y \
Swig \
python-pip \
# Install Deps for Backports.lzma (python2 requires it)
python-dev \
python-mysqldb \
python-rsa \
libssl-dev \
liblzma-dev \
libevent1-dev \
# Install Deps for building gevent
Curl \
cython \
&& rm-rf/var/lib/apt/lists/*

COPY. /docker-registry
COPY./config/boto.cfg/etc/boto.cfg

# Install Core
RUN Pip Install/docker-registry/depends/docker-registry-core

# Install Gevent 1.0.1 using updated config.guess and Config.sub
RUN Curl https://pypi.python.org/packages/source/g/gevent/gevent-1.0.1.tar.gz | tar-xzf-c/\
&& Curl-o/gevent-1.0.1/libev/config.guess \
' Http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD ' \
&& Curl-o/gevent-1.0.1/libev/config.sub \
' Http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD ' \
&& cp-pf/gevent-1.0.1/libev/config.guess/gevent-1.0.1/c-ares/config.guess \
&& cp-pf/gevent-1.0.1/libev/config.sub/gevent-1.0.1/c-ares/config.sub \
&& pip install/gevent-1.0.1

# Install Registry
RUN pip Install file:///docker-registry#egg=docker-registry[bugsnag,newrelic,cors]

RUN patch \
$ (python-c ' import boto; import os; print Os.path.dirname (boto.__file__) ')/connection.py \
</docker-registry/contrib/boto_header_patch.diff

ENV docker_registry_config/docker-registry/config/config_sample.yml
ENV Settings_flavor Dev

EXPOSE 5000

CMD ["Docker-registry"]

You can see the last sentence of Cmd ["Docker-registry"], here it is.

So how does this command start the registry service? into the registry container.
[Email protected]:/# which docker-registry
/usr/local/bin/docker-registry

[Email protected]:/# cat/usr/local/bin/docker-registry
#!/usr/bin/python
# easy-install-entry-script: ' Docker-registry==1.0.0-dev ', ' console_scripts ', ' docker-registry '
__requires__ = ' Docker-registry==1.0.0-dev '
Import Sys
From pkg_resources import Load_entry_point

if __name__ = = ' __main__ ':
Sys.exit (
Load_entry_point (' Docker-registry==1.0.0-dev ', ' console_scripts ', ' Docker-registry ') ()
)
Here is a Python method, not very clear, you can refer to the article
Http://blog.sina.com.cn/s/blog_85998e380101bojs.html
Http://www.cnblogs.com/babykick/archive/2012/03/09/2387808.html
Keep looking down.

[Email protected]:/# cat/usr/local/lib/python2.7/dist-packages/docker_registry-1.0.0_dev-py2.7.egg-info/ Entry_points.txt
[Console_scripts]
Docker-registry = Docker_registry.run:run_gunicorn
In this case, we probably know what's going on, and it's actually called the Run_gunicorn method of run.py.

[email protected]:/# cat/usr/local/lib/python2.7/dist-packages /docker_registry/run.py
def Run_gunicorn ():

args = [

'--access-logfile ', Env.source (' Gunicorn_access_log_file '),
"-- Error-logfile ', Env.source (' Gunicorn_error_log_file '),
'--max-requests ', ' n ',

'--graceful-timeout ', Env.source (' Gunicorn_graceful_timeout '),
'-T ', Env.source (' Gunicorn_silent_timeout '),
'-W ', Env.source (' gunicorn_workers '),
'-B ', address,
"

......

args + = Env.source (' gunicorn_opts ')
Args.append (' docker_registry.wsgi:application ')
# stringify all args and call
Os.execl (*[str (v) for V in Args])

Run_gunicorn () called the Gunicorn program, the host on the PS when you can see that the registry container launched 5 Gunicorn process.
Root 17466 0.0 0.9 21504 19264? Ss Dec09 0:00/usr/bin/python/usr/local/bin/gunicorn--access-logfile---error-logfil
Root 17480 1.2 2.2 48896 45888? S Dec09 15:37/usr/bin/python/usr/local/bin/gunicorn--access-logfile---error-logfil
Root 17481 1.2 2.2 48960 46080? S Dec09 15:34/usr/bin/python/usr/local/bin/gunicorn--access-logfile---error-logfil
Root 17482 1.2 2.2 49088 46080? S Dec09 15:35/usr/bin/python/usr/local/bin/gunicorn--access-logfile---error-logfil
Root 17483 1.2 2.2 49664 46720? S Dec09 15:34/usr/bin/python/usr/local/bin/gunicorn--access-logfile---error-logfil

Resources
Gunicorn-python WSGI HTTP Server for UNIX
www.gunicorn.org

Preliminary analysis of Docker Registry service start-up process