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async_hooks: don't reuse resource in HttpAgent
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As discussed in nodejs/diagnostics#248,
#21313 and
https://docs.google.com/document/d/1g8OrG5lMIUhRn1zbkutgY83MiTSMx-0NHDs8Bf-nXxM/preview
reusing the resource object is a blocker for landing a resource based
async hooks API and get rid of the promise destroy hook.

This PR ensures that HttpAgent uses the a new resource object in case
the socket handle gets reused.

PR-URL: #27581
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
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Flarna authored and targos committed May 20, 2019
1 parent f872210 commit 6070e88
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Showing 5 changed files with 141 additions and 7 deletions.
14 changes: 11 additions & 3 deletions lib/_http_agent.js
Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,13 @@ const { async_id_symbol } = require('internal/async_hooks').symbols;
// ClientRequest.onSocket(). The Agent is now *strictly*
// concerned with managing a connection pool.

class ReusedHandle {
constructor(type, handle) {
this.type = type;
this.handle = handle;
}
}

function Agent(options) {
if (!(this instanceof Agent))
return new Agent(options);
Expand Down Expand Up @@ -166,10 +173,11 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
// We have a free socket, so use that.
var socket = this.freeSockets[name].shift();
// Guard against an uninitialized or user supplied Socket.
if (socket._handle && typeof socket._handle.asyncReset === 'function') {
const handle = socket._handle;
if (handle && typeof handle.asyncReset === 'function') {
// Assign the handle a new asyncId and run any destroy()/init() hooks.
socket._handle.asyncReset();
socket[async_id_symbol] = socket._handle.getAsyncId();
handle.asyncReset(new ReusedHandle(handle.getProviderType(), handle));
socket[async_id_symbol] = handle.getAsyncId();
}

// don't leak
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18 changes: 16 additions & 2 deletions src/async_wrap.cc
Original file line number Diff line number Diff line change
Expand Up @@ -410,13 +410,26 @@ void AsyncWrap::PopAsyncIds(const FunctionCallbackInfo<Value>& args) {


void AsyncWrap::AsyncReset(const FunctionCallbackInfo<Value>& args) {
CHECK(args[0]->IsObject());

AsyncWrap* wrap;
ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());

Local<Object> resource = args[0].As<Object>();
double execution_async_id =
args[0]->IsNumber() ? args[0].As<Number>()->Value() : kInvalidAsyncId;
wrap->AsyncReset(execution_async_id);
args[1]->IsNumber() ? args[1].As<Number>()->Value() : kInvalidAsyncId;
wrap->AsyncReset(resource, execution_async_id);
}


void AsyncWrap::GetProviderType(const FunctionCallbackInfo<Value>& args) {
AsyncWrap* wrap;
args.GetReturnValue().Set(AsyncWrap::PROVIDER_NONE);
ASSIGN_OR_RETURN_UNWRAP(&wrap, args.Holder());
args.GetReturnValue().Set(wrap->provider_type());
}


void AsyncWrap::EmitDestroy() {
AsyncWrap::EmitDestroy(env(), async_id_);
// Ensure no double destroy is emitted via AsyncReset().
Expand All @@ -437,6 +450,7 @@ Local<FunctionTemplate> AsyncWrap::GetConstructorTemplate(Environment* env) {
tmpl->SetClassName(FIXED_ONE_BYTE_STRING(env->isolate(), "AsyncWrap"));
env->SetProtoMethod(tmpl, "getAsyncId", AsyncWrap::GetAsyncId);
env->SetProtoMethod(tmpl, "asyncReset", AsyncWrap::AsyncReset);
env->SetProtoMethod(tmpl, "getProviderType", AsyncWrap::GetProviderType);
env->set_async_wrap_ctor_template(tmpl);
}
return tmpl;
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1 change: 1 addition & 0 deletions src/async_wrap.h
Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,7 @@ class AsyncWrap : public BaseObject {
static void PushAsyncIds(const v8::FunctionCallbackInfo<v8::Value>& args);
static void PopAsyncIds(const v8::FunctionCallbackInfo<v8::Value>& args);
static void AsyncReset(const v8::FunctionCallbackInfo<v8::Value>& args);
static void GetProviderType(const v8::FunctionCallbackInfo<v8::Value>& args);
static void QueueDestroyAsyncId(
const v8::FunctionCallbackInfo<v8::Value>& args);

Expand Down
5 changes: 3 additions & 2 deletions test/async-hooks/init-hooks.js
Original file line number Diff line number Diff line change
Expand Up @@ -158,7 +158,7 @@ class ActivityCollector {
// events this makes sense for a few tests in which we enable some hooks
// later
if (this._allowNoInit) {
const stub = { uid, type: 'Unknown', handleIsObject: true };
const stub = { uid, type: 'Unknown', handleIsObject: true, handle: {} };
this._activities.set(uid, stub);
return stub;
} else if (!common.isMainThread) {
Expand All @@ -184,7 +184,8 @@ class ActivityCollector {
triggerAsyncId,
// In some cases (e.g. Timeout) the handle is a function, thus the usual
// `typeof handle === 'object' && handle !== null` check can't be used.
handleIsObject: handle instanceof Object
handleIsObject: handle instanceof Object,
handle
};
this._stamp(activity, 'init');
this._activities.set(uid, activity);
Expand Down
110 changes: 110 additions & 0 deletions test/async-hooks/test-http-agent-handle-reuse.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,110 @@
'use strict';
// Flags: --expose-internals
const common = require('../common');
const initHooks = require('./init-hooks');
const { checkInvocations } = require('./hook-checks');
const assert = require('assert');
const { async_id_symbol } = require('internal/async_hooks').symbols;
const http = require('http');

// Checks that the async resource used in init in case of a resused handle
// is not reused. Test is based on parallel\test-async-hooks-http-agent.js.

const hooks = initHooks();
hooks.enable();

let asyncIdAtFirstReq;
let asyncIdAtSecondReq;

// Make sure a single socket is transparently reused for 2 requests.
const agent = new http.Agent({
keepAlive: true,
keepAliveMsecs: Infinity,
maxSockets: 1
});

const server = http.createServer(common.mustCall((req, res) => {
req.once('data', common.mustCallAtLeast(() => {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.write('foo');
}));
req.on('end', common.mustCall(() => {
res.end('bar');
}));
}, 2)).listen(0, common.mustCall(() => {
const port = server.address().port;
const payload = 'hello world';

// First request. This is useless except for adding a socket to the
// agent’s pool for reuse.
const r1 = http.request({
agent, port, method: 'POST'
}, common.mustCall((res) => {
// Remember which socket we used.
const socket = res.socket;
asyncIdAtFirstReq = socket[async_id_symbol];
assert.ok(asyncIdAtFirstReq > 0, `${asyncIdAtFirstReq} > 0`);
// Check that request and response share their socket.
assert.strictEqual(r1.socket, socket);

res.on('data', common.mustCallAtLeast(() => {}));
res.on('end', common.mustCall(() => {
// setImmediate() to give the agent time to register the freed socket.
setImmediate(common.mustCall(() => {
// The socket is free for reuse now.
assert.strictEqual(socket[async_id_symbol], -1);

// Second request. To re-create the exact conditions from the
// referenced issue, we use a POST request without chunked encoding
// (hence the Content-Length header) and call .end() after the
// response header has already been received.
const r2 = http.request({
agent, port, method: 'POST', headers: {
'Content-Length': payload.length
}
}, common.mustCall((res) => {
asyncIdAtSecondReq = res.socket[async_id_symbol];
assert.ok(asyncIdAtSecondReq > 0, `${asyncIdAtSecondReq} > 0`);
assert.strictEqual(r2.socket, socket);

// Empty payload, to hit the “right” code path.
r2.end('');

res.on('data', common.mustCallAtLeast(() => {}));
res.on('end', common.mustCall(() => {
// Clean up to let the event loop stop.
server.close();
agent.destroy();
}));
}));

// Schedule a payload to be written immediately, but do not end the
// request just yet.
r2.write(payload);
}));
}));
}));
r1.end(payload);
}));


process.on('exit', onExit);

function onExit() {
hooks.disable();
hooks.sanityCheck();
const activities = hooks.activities;

// Verify both invocations
const first = activities.filter((x) => x.uid === asyncIdAtFirstReq)[0];
checkInvocations(first, { init: 1, destroy: 1 }, 'when process exits');

const second = activities.filter((x) => x.uid === asyncIdAtSecondReq)[0];
checkInvocations(second, { init: 1, destroy: 1 }, 'when process exits');

// Verify reuse handle has been wrapped
assert.strictEqual(first.type, second.type);
assert.ok(first.handle !== second.handle, 'Resource reused');
assert.ok(first.handle === second.handle.handle,
'Resource not wrapped correctly');
}

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