Buffered Streams

Buffered streams improve the efficiency of network I/O (for example, the exchange of HTTP requests and responses), especially for dynamic content generation. Buffered streams are implemented as transparent NSPR I/O layers, which means even existing NSAPI modules can use them without any change.

The buffered streams layer adds the following features to the Sun Java System Web Proxy Server:

• Enhanced keep-alive support: When the response is smaller than the buffer size, the buffering layer generates the Content-Length header so that the client can detect the end of the response and reuse the connection for subsequent requests.

• Response length determination: If the buffering layer cannot determine the length of the response, it uses HTTP/1.1 chunked encoding instead of the Content-Length header to convey the delineation information. If the client only understands HTTP/1.0, the server must close the connection to indicate the end of the response.

• Deferred header writing: Response headers are written out as late as possible to give the servlets a chance to generate their own headers (for example, the session management header set-cookie).

• Ability to understand request entity bodies with chunked encoding: Though popular clients do not use chunked encoding for sending POST request data, this feature is mandatory for HTTP/1.1 compliance.

The improved connection handling and response length header generation provided by buffered streams also addresses the HTTP/1.1 protocol compliance issues, where absence of the response length headers is regarded as a category 1 failure. In previous Enterprise Server versions, it was the responsibility of the dynamic content generation programs to send the length headers. If a CGI script did not generate the Content-Length header, the server had to close the connection to indicate the end of the response, breaking the keep-alive mechanism. However, it is often very inconvenient to keep track of response length in CGI scripts or servlets, and as an application platform provider, the web server is expected to handle such low-level protocol issues.

Output buffering has been built in to the functions that transmit data, such as net_write (see Chapter 4, NSAPI Function Reference). You can specify the following Service SAF parameters that affect stream buffering, which are described in detail in the chapter “Syntax and Use of magnus.conf” in the Sun Java System Web Proxy Server 4.0.2 Configuration File Reference.

• UseOutputStreamSize

• ChunkedRequestBufferSize

• ChunkedRequestTimeout

The UseOutputStreamSize, ChunkedRequestBufferSize, and ChunkedRequestTimeout parameters also have equivalent magnus.conf directives; see “Chunked Encoding” in the chapter “Syntax and Use of magnus.conf” in the Sun Java System Web Proxy Server 4.0.2 Configuration File Reference. The obj.conf parameters override the magnus.conf directives.

The UseOutputStreamSize parameter can be set to zero (0) in the obj.conf file to disable output stream buffering. For the magnus.conf file, setting UseOutputStreamSize to zero has no effect.

To override the default behavior when invoking an SAF that uses one of the functions net_read or netbuf_grab, you can specify the value of the parameter in obj.conf, for example:

Service fn="my-service-saf" type=perf UseOutputStreamSize=8192