http: make http.ServerResponse emit 'end'

This used to be the internal 'finish' event. Make it public so API users will
know when the response has been sent completely.

Fixes #3855.

doc/api/http.markdown

@@ -312,6 +312,17 @@ passed as the second parameter to the `'request'` event.
 The response implements the [Writable Stream][] interface. This is an
 [EventEmitter][] with the following events:
 
+### Event: 'end'
+
+`function () { }`
+
+Emitted when the response has been sent. More specifically, this event is
+emitted when the last segment of the response headers and body have been
+handed off to the operating system for transmission over the network. It
+does not imply that the client has received anything yet.
+
+After this event, no more events will be emitted on the response object.
+
 ### Event: 'close'
 
 `function () { }`

lib/http.js

@@ -833,7 +833,7 @@ OutgoingMessage.prototype._finish = function() {
     assert(this instanceof ClientRequest);
     DTRACE_HTTP_CLIENT_REQUEST(this, this.connection);
   }
-  this.emit('finish');
+  this.emit('end');
 };
 
 
@@ -1760,7 +1760,7 @@ function connectionListener(socket) {
 
     // When we're finished writing the response, check if this is the last
     // respose, if so destroy the socket.
-    res.on('finish', function() {
+    res.on('end', function() {
       // Usually the first incoming element should be our request.  it may
       // be that in the case abortIncoming() was called that the incoming
       // array will be empty.

test/simple/test-http-response-end.js

@@ -0,0 +1,59 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var http = require('http');
+
+http.createServer(onRequest).listen(common.PORT, onListen);
+
+function onRequest(req, res) {
+  var gotEnd = 0;
+
+  res.on('close', assert.fail);
+
+  res.on('end', function() {
+    gotEnd++;
+  });
+
+  process.on('exit', function() {
+    assert.equal(gotEnd, 1);
+  });
+
+  res.writeHead(200);
+  res.end();
+  this.close();
+}
+
+function onListen() {
+  var req = http.get('http://127.0.0.1:' + common.PORT);
+  var gotEnd = 0;
+
+  req.on('close', assert.fail);
+
+  req.on('end', function() {
+    gotEnd++;
+  });
+
+  process.on('exit', function() {
+    assert.equal(gotEnd, 1);
+  });
+}