CSC/ECE 517 Fall 2015/oss/M1502/AAAASS

M1502: Improve HTTP monitoring devtool support

Firefox supports remote developer tools - ie. communicating with an arbitrary server that implements a protocol for exposing information about web content. Servo implements a very basic developer tools server that currently supports executing JS remotely and investigating the DOM tree in the document inspector. We want to expand these capabilities by exposing further information about HTTP requests and responses that web content initiates. <ref>https://github.com/servo/servo/wiki/Expand-HTTP-request-response-monitoring</ref>.

Github Location

https://github.com/akumar21NCSU/servo

Build Process

git clone https://github.com/servo/servo cd servo ./mach build --dev ./mach run tests/html/about-mozilla.html

Forked Branch

A branch was forked from https://github.com/servo/servo and placed at the following location: https://github.com/akumar21NCSU/servo

Development

The primary goal of the development effort is to support the presence of a pipeline id. The goal is to pass values to send_request_to_devtools derived from the actual request. The request containing the new pipeline id. The development command is: ./mach build --dev

Code Changes

Adding pipeline Id

Pipeline id was added in http_loader.rs file for request and response messages.

fn send_request_to_devtools(devtools_chan: Option<Sender<DevtoolsControlMsg>>,
                            request_id: String,
                            url: Url,
                            method: Method,
                            headers: Headers,
                            body: Option<Vec<u8>>,
                            pipeline_id: PipelineId) {

    if let Some(ref chan) = devtools_chan {
        let request = DevtoolsHttpRequest {
            url: url, method: method, headers: headers, body: body, pipeline_id: pipeline_id };
        let net_event = NetworkEvent::HttpRequest(request);

        let msg = ChromeToDevtoolsControlMsg::NetworkEvent(request_id, net_event);
        chan.send(DevtoolsControlMsg::FromChrome(msg)).unwrap();
    }
}

fn send_response_to_devtools(devtools_chan: Option<Sender<DevtoolsControlMsg>>,
                             request_id: String,
                             headers: Option<Headers>,
                             status: Option<RawStatus>,
                             pipeline_id: PipelineId) {
    if let Some(ref chan) = devtools_chan {
        let response = DevtoolsHttpResponse { headers: headers, status: status, body: None, pipeline_id: pipeline_id };
        let net_event_response = NetworkEvent::HttpResponse(response);

        let msg = ChromeToDevtoolsControlMsg::NetworkEvent(request_id, net_event_response);
        chan.send(DevtoolsControlMsg::FromChrome(msg)).unwrap();
    }
}

This required us to change HttpRequest and HttpResponse structs in lib.rs file inside devtool_traits.

pub struct HttpRequest {
    pub url: Url,
    pub method: Method,
    pub headers: Headers,
    pub body: Option<Vec<u8>>,
    pub pipeline_id: PipelineId,
}

pub struct HttpResponse {
    pub headers: Option<Headers>,
    pub status: Option<RawStatus>,
    pub body: Option<Vec<u8>>,
    pub pipeline_id: PipelineId,
} 

Changes were also made to the load_whole_resource function inside lib.rs for adding pipeline id

pub fn load_whole_resource(resource_task: &ResourceTask, url: Url, pipeline_id: Option<PipelineId>)
        -> Result<(Metadata, Vec<u8>), String> {
    let (start_chan, start_port) = ipc::channel().unwrap();
    resource_task.send(ControlMsg::Load(LoadData::new(url, pipeline_id),
                       LoadConsumer::Channel(start_chan))).unwrap();
    let response = start_port.recv().unwrap();

    let mut buf = vec!();
    loop {
        match response.progress_port.recv().unwrap() {
            ProgressMsg::Payload(data) => buf.push_all(&data),
            ProgressMsg::Done(Ok(())) => return Ok((response.metadata, buf)),
            ProgressMsg::Done(Err(e)) => return Err(e)
        }
    }
}

Test

A unit test is added to test the new functionality of the pipeline id. The testing is run by performing the following command in the command line: ./mach test-wpt

Implementation

Servo implements a very basic developer tools server that currently supports executing JS remotely and investigating the DOM tree in the document inspector. We want to expand these capabilities by exposing further information about HTTP requests and responses that web content initiates. <ref>https://github.com/servo/servo/wiki/Expand-HTTP-request-response-monitoring</ref>

Project Benefits & Challenges

Benefits:

1. Helps add additional debug to the HTTP monitoring in Servo

2. Provides developers capability of monitoring the data traffic

3. Mozilla messages are clearly analyzed using Servo

Challenges:

Rust code development presents a challenge as the build environment takes time to build. Adding additional filters to the Servo causes failures initially as development tends to be a hit or miss. Communicating with both the TA and the Mozilla team members is critical. It is generally expected that new changes should not introduce new crashes in the testsuite however this was not the case. The team did encounter crashes when unit tests were carried out.

Design Pattern

The requirements did not require us to implement any design pattern.

External Links

Also see:

Development

Attaching Developer Tools

References

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