CentOS上でFlaskをpython3.4、Gunicorn + Nginxで動かす。


実際に動かすファイルは下記

```Python:app.py
from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"
```

## install
* pyenv(anyenv) + virualenvをインストール

```bash
$ git clone https://github.com/riywo/anyenv ~/.anyenv
$ echo 'export PATH="$HOME/.anyenv/bin:$PATH"' >> ~/.bashrc
$ echo 'eval "$(anyenv init -)"' >> ~/.bashrc
$ exec $SHELL -l

$ pyenv install 3.4.1
$ cd ~/.anyenv/envs/pyenv/plugins
$ git clone git://github.com/yyuu/pyenv-virtualenv.git
$ pyenv virtualenv flask-3.4.1
$ pyenv rehash
```


```bash
$ sudo yum install -y nginx
```

環境を汚さないように、virtualenv環境を作成。
アプリを保存するディレクトリを作成し、アプリを持ってきて、libraryをインストール

```bash
$ mkdir -p /path/to/flask
$ cd /path/to/flask
$ pyenv local flask-3.4.1
$ python --version
Python 3.4.1

$ cp -r /path/to/flask/app ./
$ pip install gunicorn
$ pip install -r requirements.txt
or 
$ pip install hoge fuga...
```

## gunicornを動かす

実際にgunicornを動かす。

```bash
$ ~/.anyenv/envs/pyenv/shims/gunicorn app:app &
```

### 確認
プロセスが正常に立ち上がっているか確認

```
$ ps ax | grep gunicorn

 2234 pts/0    S      0:00 /home/vagrant/.anyenv/envs/pyenv/versions/flask-3.4.1/bin/python3.4 /home/vagrant/.anyenv/envs/pyenv/versions/flask-3.4.1/bin/gunicorn app:app
 2241 pts/0    S      0:00 /home/vagrant/.anyenv/envs/pyenv/versions/flask-3.4.1/bin/python3.4 /home/vagrant/.anyenv/envs/pyenv/versions/flask-3.4.1/bin/gunicorn app:app
 2265 pts/0    S+     0:00 grep gunicorn
```


### 設定ファイルを作成

テストで立ち上げたgunicornプロセスを一旦落とす。

```bash
$ ps ax | grep gunicorn | awk '{print $1}' | xargs kill
```

nginxの設定ファイルを作成
<code>$ vim example.conf</code>

```example.conf
upstream app_server {
    server unix:/tmp/gunicorn.sock fail_timeout=0;
    # For a TCP configuration:
}

server {
    listen 80 default;
    client_max_body_size 4G;
    server_name _;

    keepalive_timeout 5;

    # path for static files
    root /path/to/flask/public;

    location / {
        # checks for static file, if not found proxy to app
        try_files $uri @proxy_to_app;
		break;
    }

    location @proxy_to_app {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;

        proxy_pass   http://app_server;
    }
}

```

copy

```bash
$ sudo cp example.conf /etc/nginx/conf.d/
```


gunicornの設定ファイルを作成。
<code>$ vim gunicorn.conf.py</code>

```Python:gunicorn.conf.py
# Sample Gunicorn configuration file.

#
# Process naming
#
#   proc_name - A base to use with setproctitle to change the way
#       that Gunicorn processes are reported in the system process
#       table. This affects things like 'ps' and 'top'. If you're
#       going to be running more than one instance of Gunicorn you'll
#       probably want to set a name to tell them apart. This requires
#       that you install the setproctitle module.
#
#       A string or None to choose a default of something like 'gunicorn'.
#
proc_name = "gunicorn"

#
# Server socket
#
#   bind - The socket to bind.
#
#       A string of the form: 'HOST', 'HOST:PORT', 'unix:PATH'.
#       An IP is a valid HOST.
#
#   backlog - The number of pending connections. This refers
#       to the number of clients that can be waiting to be
#       served. Exceeding this number results in the client
#       getting an error when attempting to connect. It should
#       only affect servers under significant load.
#
#       Must be a positive integer. Generally set in the 64-2048
#       range.
#
bind = 'unix:/tmp/{0}.sock'.format(proc_name)
backlog = 2048

#
# Worker processes
#
#   workers - The number of worker processes that this server
#       should keep alive for handling requests.
#
#       A positive integer generally in the 2-4 x $(NUM_CORES)
#       range. You'll want to vary this a bit to find the best
#       for your particular application's work load.
#
#   worker_class - The type of workers to use. The default
#       async class should handle most 'normal' types of work
#       loads. You'll want to read http://gunicorn/deployment.hml
#       for information on when you might want to choose one
#       of the other worker classes.
#
#       An string referring to a 'gunicorn.workers' entry point
#       or a python path to a subclass of
#       gunicorn.workers.base.Worker. The default provided values
#       are:
#
#           egg:gunicorn#sync
#           egg:gunicorn#eventlet   - Requires eventlet >= 0.9.7
#           egg:gunicorn#gevent     - Requires gevent >= 0.12.2 (?)
#           egg:gunicorn#tornado    - Requires tornado >= 0.2
#
#   worker_connections - For the eventlet and gevent worker classes
#       this limits the maximum number of simultaneous clients that
#       a single process can handle.
#
#       A positive integer generally set to around 1000.
#
#   timeout - If a worker does not notify the master process in this
#       number of seconds it is killed and a new worker is spawned
#       to replace it.
#
#       Generally set to thirty seconds. Only set this noticeably
#       higher if you're sure of the repercussions for sync workers.
#       For the non sync workers it just means that the worker
#       process is still communicating and is not tied to the length
#       of time required to handle a single request.
#
#   keepalive - The number of seconds to wait for the next request
#       on a Keep-Alive HTTP connection.
#
#       A positive integer. Generally set in the 1-5 seconds range.
#

workers = 1
worker_class = 'sync'
worker_connections = 1000
timeout = 30
keepalive = 2

#
# Debugging
#
#   debug - Turn on debugging in the server. This limits the number of
#       worker processes to 1 and changes some error handling that's
#       sent to clients.
#
#       True or False
#
#   spew - Install a trace function that spews every line of Python
#       that is executed when running the server. This is the
#       nuclear option.
#
#       True or False
#

debug = False
spew = False

#
# Server mechanics
#
#   daemon - Detach the main Gunicorn process from the controlling
#       terminal with a standard fork/fork sequence.
#
#       True or False
#
#   pidfile - The path to a pid file to write
#
#       A path string or None to not write a pid file.
#
#   user - Switch worker processes to run as this user.
#
#       A valid user id (as an integer) or the name of a user that
#       can be retrieved with a call to pwd.getpwnam(value) or None
#       to not change the worker process user.
#
#   group - Switch worker process to run as this group.
#
#       A valid group id (as an integer) or the name of a user that
#       can be retrieved with a call to pwd.getgrnam(value) or None
#       to change the worker processes group.
#
#   umask - A mask for file permissions written by Gunicorn. Note that
#       this affects unix socket permissions.
#
#       A valid value for the os.umask(mode) call or a string
#       compatible with int(value, 0) (0 means Python guesses
#       the base, so values like "0", "0xFF", "0022" are valid
#       for decimal, hex, and octal representations)
#
#   tmp_upload_dir - A directory to store temporary request data when
#       requests are read. This will most likely be disappearing soon.
#
#       A path to a directory where the process owner can write. Or
#       None to signal that Python should choose one on its own.
#
daemon = True
pidfile = "/tmp/gunicorn.pid"
umask = 0
user = None
group = None
tmp_upload_dir = None

#
#   Logging
#
#   logfile - The path to a log file to write to.
#
#       A path string. "-" means log to stdout.
#
#   loglevel - The granularity of log output
#
#       A string of "debug", "info", "warning", "error", "critical"
#
errorlog = '/var/log/gunicorn/error.log'
loglevel = 'debug'
accesslog = '/var/log/gunicorn/access.log'

#
# Server hooks
#
#   post_fork - Called just after a worker has been forked.
#
#       A callable that takes a server and worker instance
#       as arguments.
#
#   pre_fork - Called just prior to forking the worker subprocess.
#
#       A callable that accepts the same arguments as after_fork
#
#   pre_exec - Called just prior to forking off a secondary
#       master process during things like config reloading.
#
#       A callable that takes a server instance as the sole argument.
#

def post_fork(server, worker):
    server.log.info("Worker spawned (pid: %s)", worker.pid)

def pre_fork(server, worker):
    pass

def pre_exec(server):
    server.log.info("Forked child, re-executing.")

def when_ready(server):
    server.log.info("Server is ready. Spawning workers")

def worker_int(worker):
    worker.log.info("worker received INT or QUIT signal")

    ## get traceback info
    import threading, sys, traceback
    id2name = dict([(th.ident, th.name) for th in threading.enumerate()])
    code = []
    for threadId, stack in sys._current_frames().items():
        code.append("\n# Thread: %s(%d)" % (id2name.get(threadId,""),
            threadId))
        for filename, lineno, name, line in traceback.extract_stack(stack):
            code.append('File: "%s", line %d, in %s' % (filename,
                lineno, name))
            if line:
                code.append("  %s" % (line.strip()))
    worker.log.debug("\n".join(code))

def worker_abort(worker):
    worker.log.info("worker received SIGABRT signal")
```

毎回コマンドを打つのは面倒なので、scriptを作成する。
<code>$ vim production_server_rc</code>

```production_server_rc
#!/bin/sh

GUNICORN=$HOME/.anyenv/envs/pyenv/shims/gunicorn
PROJECT_ROOT=/path/to/flask

APP=app:app

cd $PROJECT_ROOT
exec $GUNICORN -c $PROJECT_ROOT/gunicorn.conf.py $APP
```

nginxを立ち上げる。

```bash
$ sudo /etc/init.d/nginx start
```

gunicornを立ち上げる。

```bash
$ ./production_server.sh
```


### 参考
[pyenvとvirtualenvのインストールと使い方](http://qiita.com/la_luna_azul/items/3f64016feaad1722805c)
[gunicorn / examples / gunicorn_rc](https://github.com/benoitc/gunicorn/blob/master/examples/gunicorn_rc)
[gunicorn / examples / example_config.py](https://github.com/benoitc/gunicorn/blob/master/examples/)