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http: remove excess calls to removeSocket
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socket.destroy() triggers a 'close' event from the socket which triggers
the onClose handler of HTTPAgent which calls self.removeSocket(). So by
calling self.removeSocket() prior to socket.destroy() we end up with two
calls to self.removeSocket().

If there are pending requests, removeSocket ends up creating a new socket.
So if there are pending requests, each time a request completes, we tear
down one socket and create two more. So the total number of sockets grows
exponentially and without regard for any maxSockets settings. This was
noticed in #4050. Let's get rid of
the extra calls to removeSocket so we only call it once per completed
request.

PR-URL: #4172
Reviewed-By: Brian White <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Fedor Indutny <[email protected]>
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Dave authored and Myles Borins committed Jan 19, 2016
1 parent d19da66 commit 39dc054
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Showing 2 changed files with 43 additions and 2 deletions.
2 changes: 0 additions & 2 deletions lib/_http_agent.js
Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,6 @@ function Agent(options) {
count += self.sockets[name].length;

if (count > self.maxSockets || freeLen >= self.maxFreeSockets) {
self.removeSocket(socket, options);
socket.destroy();
} else {
freeSockets = freeSockets || [];
Expand All @@ -78,7 +77,6 @@ function Agent(options) {
freeSockets.push(socket);
}
} else {
self.removeSocket(socket, options);
socket.destroy();
}
}
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43 changes: 43 additions & 0 deletions test/parallel/test-http-agent-maxsockets-regress-4050.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const http = require('http');

const MAX_SOCKETS = 2;

const agent = new http.Agent({
keepAlive: true,
keepAliveMsecs: 1000,
maxSockets: MAX_SOCKETS,
maxFreeSockets: 2
});

const server = http.createServer(function(req, res) {
res.end('hello world');
});

function get(path, callback) {
return http.get({
host: 'localhost',
port: common.PORT,
agent: agent,
path: path
}, callback);
}

server.listen(common.PORT, function() {
var finished = 0;
const num_requests = 6;
for (var i = 0; i < num_requests; i++) {
const request = get('/1', function() {
});
request.on('response', function() {
request.abort();
const sockets = agent.sockets[Object.keys(agent.sockets)[0]];
assert(sockets.length <= MAX_SOCKETS);
if (++finished === num_requests) {
server.close();
}
});
}
});

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