Filter Declarations, Providers and Chains

Filter Declarations, Providers and Chains -

+
+Figure 1: The traditional filter model

In the traditional model, output filters are a simple chain from the content generator (handler) to the client. This works well provided the filter chain can be correctly configured, but presents problems when the filters need to be configured dynamically based on the outcome of the handler.

+
+Figure 2: The mod_filter model

mod_filter works by introducing indirection into the filter chain. Instead of inserting filters in the chain, we insert a filter harness which in turn dispatches conditionally 1.3 +1 -1 httpd-2.0/docs/manual/mod/mod_isapi.xml.ko Index: mod_isapi.xml.ko =================================================================== RCS file: /home/cvs/httpd-2.0/docs/manual/mod/mod_isapi.xml.ko,v retrieving revision 1.2 retrieving revision 1.3 diff -u -u -r1.2 -r1.3 --- mod_isapi.xml.ko 22 Sep 2004 09:39:35 -0000 1.2 +++ mod_isapi.xml.ko 15 Oct 2004 21:16:25 -0000 1.3 @@ -105,7 +105,7 @@

HSE_REQ_SEND_URL_REDIRECT_RESP

��ڸ� �ٸ� ��ġ�� ̷��Ѵ�.
�� URL�� ؾ� �Ѵ� (�� , - http://server/location).

. + http://server/location).

HSE_REQ_SEND_URL

��ڸ� �ٸ� ��ġ�� ̷��Ѵ�.
1.4 +24 -22 httpd-2.0/docs/manual/mod/mod_proxy_ajp.xml Index: mod_proxy_ajp.xml =================================================================== RCS file: /home/cvs/httpd-2.0/docs/manual/mod/mod_proxy_ajp.xml,v retrieving revision 1.3 retrieving revision 1.4 diff -u -u -r1.3 -r1.4 --- mod_proxy_ajp.xml 6 Oct 2004 06:35:15 -0000 1.3 +++ mod_proxy_ajp.xml 15 Oct 2004 21:16:25 -0000 1.4 @@ -47,6 +47,8 @@ +mod_proxy +

Overview of the protocol

The AJP13 protocol is packet-oriented. A binary format was presumably chosen over the more readable plain text for reasons of @@ -62,10 +64,10 @@ cause more connections to be open at once.

Once the web server has opened a connection to the servlet container, the connection can be in one of the following states:

Idle
No request is being handled over this connection.
Assigned
The connecton is handling a specific request.

Once a connection is assigned to handle a particular request, the basic request informaton (e.g. HTTP headers, etc) is sent over the connection in a highly condensed form (e.g. common strings are encoded as integers). @@ -74,7 +76,7 @@ separate packet immediately after.

At this point, the servlet container is presumably ready to start processing the request. As it does so, it can send the - following messages back to the web server: + following messages back to the web server:

SEND_HEADERS
Send a set of headers back to the browser.
SEND_BODY_CHUNK
Send a chunk of body data back to the browser. @@ -85,7 +87,7 @@ request (for uploaded files, for example). (Note: this is unrelated to HTTP chunked tranfer).
END_RESPONSE
Finish the request-handling cycle.

Each message is accompanied by a differently formatted packet of data. See Response Packet Structures below for details.

@@ -99,7 +101,7 @@ making that so (on the C side). If anyone with a better knowledge of socket calls can step in, that would be great.

There are four data types in the protocol: bytes, booleans, - integers and strings. + integers and strings.

Byte: A single byte.
Boolean

Packet Size

According to much of the code, the max packet size is @@ -136,7 +138,7 @@ ASCII code for B). After those first two bytes, there is an integer (encoded as above) with the length of the payload. Although this might suggest that the maximum payload could be as large as 2^16, in fact, the - code sets the maximum to be 8K. + code sets the maximum to be 8K.


       
  @@ -176,13 +178,14 @@
           
  -    
         
           Packet Format (Server->Container) Data Length (n)
           Data
         

  +    
       For most packets, the first byte of the payload encodes the type of
        message.  The exception is for request body packets sent from the server to
        the container -- they are sent with a standard packet header (
        0x1234 and then length of the packet), but without any prefix code
        after that.
  -     The web server can send the following messages to the servlet container:
  +     
The web server can send the following messages to the servlet
  +     container:
       
  @@ -216,14 +219,14 @@
           
  -    
         
           Code Data
           Size (2 bytes) and corresponding body data.
         

  +    
       To ensure some basic security, the container will only actually do the
       Shutdown if the request comes from the same machine on which
       it's hosted.
       The first Data packet is send immediatly after the
       Forward Request by the web server.
       The servlet container can send the following types of messages to the
  -    webserver:
  +    webserver:
       
  @@ -259,7 +262,7 @@
           
  -    
         
           Code CPong Reply
           The reply to a CPing request
         

  +    
       Each of the above messages has a different internal structure, detailed
       below.


  @@ -311,7 +314,7 @@

Command Name	Code
OPTIONS	1
GET	2
MERGE	25
BASELINE_CONTROL	26
MKACTIVITY	27

Name	Code value	Code name
accept	0xA001	SC_REQ_ACCEPT
accept-charset	0xA002	SC_REQ_ACCEPT_CHARSET @@ -381,7 +384,7 @@
pragma	0xA00C	SC_REQ_PRAGMA
referer	0xA00D	SC_REQ_REFERER
user-agent	0xA00E	SC_REQ_USER_AGENT

Information	Code Value	Note
?context	0x01	Not currently implemented
?ssl_key_size	0x0B
are_done	0xFF	request_terminator

Name	Code value
Content-Type	0xA001
Content-Language	0xA002
Servlet-Engine	0xA009
Status	0xA00A
WWW-Authenticate	0xA00B