WSGI学习系列eventlet.wsgi
WSGI是Web Service Gateway Interface的缩写。
WSGI标准在PEP(Python Enhancement Proposal)中定义并被许多框架实现，其中包括现广泛使用的django框架。
PythonWeb服务器接口（Python Web Server Gateway Interface，缩写为WSGI)是Python应用程序或框架和Web服务器之间的一种接口，已经被广泛接受, 它已基本达成它的可移植性方面的目标。
Nova使用了eventlet.wsgi接口。
"""This is a simple example of running a wsgi application with eventlet. For a more fully-featured server which supports multiple processes, multiple threads, and graceful code reloading, see: http://pypi.python.org/pypi/Spawning/ """ import eventlet from eventlet import wsgi def hello_world(env, start_response): if env['PATH_INFO'] != '/': start_response('404 Not Found', [('Content-Type', 'text/plain')]) return ['Not Found\r\n'] start_response('200 OK', [('Content-Type', 'text/plain')]) return ['Hello, World!\r\n'] wsgi.server(eventlet.listen(('', 8090)), hello_world)
SSL方式(Secure Socket Layer)
wsgi.server(eventlet.wrap_ssl(eventlet.listen(('', 8090)), certfile='cert.crt', keyfile='private.key', server_side=True), hello_world)
流程描述：
服务器开一个socket等待客户端连接；请求来了，服务器会读出传来的数据，然后根据HTTP协议做一些初步的封装，
接着就可以调用事先注册的应用程序了，并将请求的数据塞进去；等响应处理完毕了再把数据通过socket发出去
server参数介绍：
def server(sock, # Server socket, must be already bound to a port and listening(IP和端口并开启监听).
site, # WSGI application function(事件处理函数，发送start_response响应头然后返回响应内容)
log=None, # File-like object that logs should be written to.If not specified, sys.stderr is used.(日志处理，默认为sys.stderr用来重定向标准错误信息的)
environ=None, # Additional parameters that go into the environ dictionary of every request(每次请求的参数，写入一个字典中)
max_size=None, #Maximum number of client connections opened at any time by this server.(默认为1024)
max_http_version=DEFAULT_MAX_HTTP_VERSION, # Set to "HTTP/1.0" to make the server pretend it only supports HTTP 1.0.
# This can help with applications or clients that don't behave properly using HTTP 1.1.(HTTP协议版本,默认为HTTP/1.1)
protocol=HttpProtocol, # Protocol class.（协议类，默认为HttpProtocol）
server_event=None, # Used to collect the Server object(搜集服务器对象信息)
minimum_chunk_size=None, # Minimum size in bytes for http chunks. This can be used to improve performance of applications which yield many small strings, though
# using it technically violates the WSGI spec. This can be overridden on a per request basis by setting environ['eventlet.minimum_write_chunk_size'].
# 设置最小的Chunk大小，可以通过设置environ['eventlet.minimum_write_chunk_size']来覆盖.Chunk表示服务器发送给客户端的分块传输编码（Chunked transfer encoding）
log_x_forwarded_for=True, # If True (the default), logs the contents of the x-forwarded-for header in addition to the actual client ip address in the 'client_ip' field of the log line.
# 默认为True,记录客户端IP日志,X-Forwarded-For(XFF)是用来识别通过HTTP代理或负载均衡方式连接到Web服务器的客户端最原始的IP地址的HTTP请求头字段。
custom_pool=None, # A custom GreenPool instance which is used to spawn client green threads.If this is supplied, max_size is ignored.(协程池，如果启用则可以忽略前面的max_size参数)
keepalive=True, # If set to False, disables keepalives on the server; all connections will be closed after serving one request.（控制客户端连接数是否保持alive）
log_output=True, # A Boolean indicating if the server will log data or not.(确定服务端是否输出日志)
log_format=DEFAULT_LOG_FORMAT, # A python format string that is used as the template to generate log lines.(日志输出格式)
url_length_limit=MAX_REQUEST_LINE, # A maximum allowed length of the request url. If exceeded, 414 error is returned.（最大的url长度限制，默认为8192）
debug=True, # True if the server should send exception tracebacks to the clients on 500 errors.If False, the server will respond with empty bodies.(是否发送调式信息给客户端)
socket_timeout=None, # Timeout for client connections' socket operations. Default None means wait forever.(Socket超时时间设置，单位是秒)
capitalize_response_headers=True) # Normalize response headers' names to Foo-Bar(是否标准化相应头)
