Connection: keep-alive

[thekid]

Improves performance of peer.http.SocketHttpTransport by implementing keep-alive semantics.

Performance

Same script as in #21, 100 queries using the Neo4J REST API:

Master	Master with keep-alive	This branch	With keep-alive
0.561 seconds	🔴 (hangs)	0.518 seconds	0.185 seconds

Usage

Users need to pass the keep-alive header explicitely, for example as follows:

index 8aff954..bc132fa 100755
--- a/src/main/php/com/neo4j/HttpProtocol.class.php
+++ b/src/main/php/com/neo4j/HttpProtocol.class.php
@@ -38,6 +38,7 @@ class HttpProtocol extends Protocol {
     $req->setMethod('POST');
     $req->setTarget($this->base.'/transaction/commit');
     $req->setHeader('X-Stream', 'true');
+    $req->setHeader('Connection', 'keep-alive');
     $req->setHeader('Content-Type', 'application/json');
     $req->setParameters(new RequestData(Json::of($payload, $this->json)));

[thekid]

Saw this today in a header enumeration:

"Keep-Alive": "timeout=5, max=99"

https://tools.ietf.org/id/draft-thomson-hybi-http-timeout-01.html#rfc.section.2
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Keep-Alive

Non-standard, but seems to have widespread support; we should consider this in the future.

[thekid]

Is this check enough? If the server closes the connection (e.g. because of a timeout on a reused connection), we would probably receive an EOF here, but isConnected() would still be true,

[thekid]

Yes, this actually is a problem; and it seems eof() could help here. In need of some more real-life testing!

[thekid]

This class needs some tests!

[thekid]

Script used for integration testing timeouts and reconnection behaviors:

<?php namespace keep_alive;

use peer\http\HttpConnection;
use util\cmd\Console;
use io\streams\Streams;
use lang\Throwable;

$c= new HttpConnection($argv[1]);

for ($i= 0; $i < 10; $i++) {
  try {
    $r= $c->get([], ['Connection' => 'keep-alive']);
    Console::writeLine(date('r'), ': ', $r);
    Streams::readAll($r->in());
  } catch (Throwable $t) {
    Console::writeLine(date('r'), ': ', $t);
  }

  $delay= rand(100, 6000);
  Console::writeLinef('ZZ %.3f seconds', $delay / 1000);
  usleep($delay * 1000);
}

[thekid]

I think this is ready to get some real-life exposure; this could go into applications as:

"require" : {
  "xp-framework/http": "dev-feature/keep-alive as 9.1.0"
}