I'm currently running this simple Python CGI script to test rudimentary IPC:
#!/usr/bin/python -u
import cgi, errno, fcntl, os, os.path, sys, time
print("""Content-Type: text/html; charset=utf-8
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>IPC test</title>
</head>
<body>
""")
ftempname = '/tmp/ipc-messages'
master = not os.path.exists(ftempname)
if master:
fmode = 'w'
else:
fmode = 'r'
print('<p>Opening file</p>')
sys.stdout.flush()
ftemp = open(ftempname, fmode)
print('<p>File opened</p>')
if master:
print('<p>Operating as master</p>')
sys.stdout.flush()
for i in range(10):
print('<p>' + str(i) + '</p>')
sys.stdout.flush()
time.sleep(1)
ftemp.close()
os.remove(ftempname)
else:
print('<p>Operating as a slave</p>')
ftemp.close()
print("""
</body>
</html>""")
The 'server-push' portion works; that is, for the first
request, I do see piecewise updates. However, while the first
request is being serviced, subsequent requests are not started, only to be started after the first
request has finished.
Any ideas on why, and how to fix it?
Edit:
I see the same non-concurrent behaviour with vanilla PHP, running this:
<!doctype html>
<html lang="en">
<!-- $Id: $-->
<head>
<meta charset="utf-8" />
<title>IPC test</title>
</head>
<body>
<p>
<?php
function echofl($str)
{
echo $str . "</b>\n";
ob_flush();
flush();
}
define('tempfn', '/tmp/emailsync');
if (file_exists(tempfn))
$perms = 'r+';
else
$perms = 'w';
assert($fsync = fopen(tempfn, $perms));
assert(chmod(tempfn, 0600));
if (!flock($fsync, LOCK_EX | LOCK_NB, $wouldblock))
{
assert($wouldblock);
$master = false;
}
else
$master = true;
if ($master)
{
echofl('Running as master.');
assert(fwrite($fsync, 'content') != false);
assert(sleep(5) == 0);
assert(flock($fsync, LOCK_UN));
}
else
{
echofl('Running as slave.');
echofl(fgets($fsync));
}
assert(fclose($fsync));
echofl('Done.');
?>
</p>
</body>
</html>
