IIS Handlers responseBufferLimit="0"

Eric offered a reply a couple days later, appearing within a thread above, here. 

Thanks. I was facing IIS CPU spikes. I was exploring this buffer setting to know if it could be a source of my issue. The response was no in my case. I was excpecting more documentation on this setting that is not a small one and I was questionning it in regard of Coldfusion application that is running on our servers.

For my understanding
responseBufferLimit="0" disables IIS buffering — data is flushed immediately to Coldfusion.

Concerning <cfcontent>, I changed it and it did not affected files delivered with <cfcontent>. I will put it back to 0 because content could be stream to client.

If we take <cfcontent> as an example. When you serve a file with <cfcontent> or via Java I/O streaming:

1. The request is received by IIS.
2. The ISAPI connector (via isapi_redirect.dll) sends it to the ColdFusion servlet (Tomcat).
3. ColdFusion generates the response (possibly buffering it itself).
4. The response goes back through the ISAPI connector to IIS.
5. IIS can then buffer or stream the response to the client depending on responseBufferLimit.

So:

• ColdFusion’s buffering happens first (especially if you use <cfcontent file="...">).

• IIS buffering is after ColdFusion, which can help smooth delivery to clients, or reduce TCP fragmentation, but won’t reduce ColdFusion memory usage.

For cfcontent there are many discussions over the years. Asking an AI about cfcontent and buffering today I have this answer. 

By default, when you use <cfcontent> to serve a file:

• ColdFusion reads the entire file into memory.

• Then it writes it to the output buffer, which is eventually flushed to the client.

• This can be inefficient or problematic for large files (e.g., videos, high-res images, large PDFs).

it proposes this solution that I will certainly implement soon.

<cfscript>
    filePath = expandPath("./largefile.mp4");
    response = getPageContext().getResponse();
    response.setContentType("video/mp4");

    file = createObject("java", "java.io.File").init(filePath);
    inputStream = createObject("java", "java.io.FileInputStream").init(file);
    outputStream = response.getOutputStream();

    buffer = createObject("java", "java.lang.reflect.Array").newInstance("byte", 8192);

    while ((len = inputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, len);
    }

    inputStream.close();
    outputStream.flush();
    outputStream.close();
    abort;
</cfscript>