[질문] apache에서 content-length...

Chunked Transfers

Normally, when sending back a response the sever has to know everything about the response it is about to send before it sends it. For instance, servers should set the Content-Length header on each response to the length of the response itself. This can be difficult for the server to do if the content is dynamically created (e.g. if it is the output of a CGI script). So in practice servers (including Apache) often do not send a Content-Length with dynamic documents. This has not been a problem with HTTP/1.0, but for persistent connections to work in HTTP/1.1, the Content-Length must be known in advance.

The server could find out the length of the output of a CGI script by reading it into memory until the script has finished, then setting the Content-Length and returning the stored content. This might be acceptable for small content, but could be a problem if the CGI produces a lot of output. One possible way around this is to use the new chunked encoding method. This lets the server send output a bit at a time. Each bit (or chunk) is small enough for its content-length to be known before it is sent. Using chunked encoding will let servers send out dynamic content that is either large or produced slowly without having to disable persistent connections.

In addition, after a chunked-encoded document has been completely sent, additional response headers can be transmitted. This could allow dynamically produced headers to be associated with the document, even if they are not available until after the script (or whatever produced the document) has finished.