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Add proxy support for global fetch #696

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Add proxy support for global fetch #696

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24 changes: 24 additions & 0 deletions package-lock.json
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1 change: 1 addition & 0 deletions package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@
"sinon-chai": "^3.5.0",
"tsd": "^0.25.0",
"typescript": "^4.4.4",
"undici": "^6.21.0",
"upath": "^1.2.0"
},
"engines": {
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3 changes: 2 additions & 1 deletion sdk_contrib/fetch/lib/fetch_p.js
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Expand Up @@ -77,6 +77,7 @@ function enableCapture(baseFetchFunction, requestClass, downstreamXRayEnabled, s

// Facilitate the addition of Segment information via the request arguments
const params = args.length > 1 ? args[1] : {};
const fetchOptions = 'dispatcher' in params ? {dispatcher: params.dispatcher} : undefined;

// Short circuit if the HTTP is already being captured
if (request.headers.has('X-Amzn-Trace-Id')) {
Expand Down Expand Up @@ -127,7 +128,7 @@ function enableCapture(baseFetchFunction, requestClass, downstreamXRayEnabled, s
const requestClone = request.clone();
let response;
try {
response = await baseFetchFunction(requestClone);
response = await baseFetchFunction(requestClone, fetchOptions);
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My first idea was to pass down the entire args again but this would overwrite the changes we do to the request like adding the trace header as the headers from the options take priority over the headers that are already set for a request.

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Consider this code:

const agent = new Agent({maxSockets: 1234});
const request = new Request('someurl', { dispatcher: agent });
fetch(request);

Here, fetch is only called with one parameter. The dispatcher is "baked in" into the request. For undici, it's actually a symbol property. When you call baseFetchFunction(requestClone, fetchOptions), requestClone doesn't contain that property, So that per-request-setting wouldn't be passed on.

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Made an attempt to fix this. Sorry for the complexity, but it should work more reliably for you.
#698

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#698 fixes a different issue that is there so I would open another issue to point to your PR to.


if (thisSubsegmentCallback) {
thisSubsegmentCallback(subsegment, requestClone, response);
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46 changes: 46 additions & 0 deletions sdk_contrib/fetch/test/integration/fetch_p.test.js
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Expand Up @@ -3,6 +3,9 @@ let listener;
let server;
let goodUrl;
let receivedHeaders;
let proxyServer;
let proxyUrl;
let proxyListener;


before(() => {
Expand All @@ -19,11 +22,37 @@ before(() => {
const address = server.address();
const host = address.family === 'IPv6' ? `[${address.address}]` : address.address;
goodUrl = `http://${host}:${address.port}/test`;

proxyServer = http.createServer();
proxyServer.on('connect', (req, socket) => {
const res = new http.ServerResponse(req);
res.assignSocket(socket);

const lastColon = req.url.lastIndexOf(':');
const host = req.url.substring(0, lastColon);
const port = parseInt(req.url.substring(lastColon + 1), 10);
const opts = {host: host.replace(/^\[|\]$/g, ''), port};

const net = require('net');
const target = net.connect(opts, () => {
res.writeHead(200);
res.flushHeaders();
res.detachSocket(socket);

socket.pipe(target);
target.pipe(socket);
});
});
proxyListener = proxyServer.listen();
const proxyAddress = proxyServer.address();
const proxyHost = proxyAddress.family === 'IPv6' ? `[${proxyAddress.address}]` : proxyAddress.address;
proxyUrl = `http://${proxyHost}:${proxyAddress.port}`;
});

after(() => {
// close http server
listener.close();
proxyListener.close();
});

describe('Integration tests', function () {
Expand Down Expand Up @@ -111,6 +140,23 @@ describe('Integration tests', function () {
stubClose.should.have.been.calledOnce;
});

it('adds headers when called with fetchOptions', async function () {
const spyCallback = sandbox.spy();
const fetch = captureFetchGlobal(true, spyCallback);
const undici = require('undici');
const response = await fetch(goodUrl, {dispatcher: new undici.ProxyAgent(proxyUrl), headers: {'foo': 'bar'}});
response.status.should.equal(200);
receivedHeaders.should.to.have.property('x-amzn-trace-id');
receivedHeaders.should.to.have.property('foo', 'bar');
(await response.text()).should.contain('Example');
stubIsAutomaticMode.should.have.been.called;
stubAddNewSubsegment.should.have.been.calledOnce;
stubResolveSegment.should.have.been.calledOnce;
stubAddFetchRequestData.should.have.been.calledOnce;
stubAddErrorFlag.should.not.have.been.calledOnce;
stubClose.should.have.been.calledOnce;
});

it('sets error flag on failed fetch when global fetch exists', async function () {
const spyCallback = sandbox.spy();
const fetch = captureFetchGlobal(true, spyCallback);
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14 changes: 14 additions & 0 deletions sdk_contrib/fetch/test/unit/fetch_p.test.js
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Expand Up @@ -339,6 +339,20 @@ describe('Unit tests', function () {
response.should.equal(stubValidResponse);
});

it('resolves to response through proxy when fetch options are supplied', async function () {
const activeFetch = captureFetch(true);
const proxyStub = sinon.stub();
const request = new FetchRequest('https://www.foo.com/test');
const response = await activeFetch(request, {
dispatcher: proxyStub
});
stubFetch.should.have.been.calledOnce;
const callArgs = stubFetch.firstCall.args;
callArgs[0].should.contain(request);
callArgs[1].dispatcher.should.equal(proxyStub);
response.should.equal(stubValidResponse);
});

it('calls subsegmentCallback with error upon fetch throwing', async function () {
const spyCallback = sandbox.spy();
const activeFetch = captureFetch(true, spyCallback);
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