Perlbal::FAQ(3) User Contributed Perl Documentation Perlbal::FAQ(3)NAMEPerlbal::FAQ - Frequently Asked Questions about Perlbal
VERSION
Perlbal 1.78.
DESCRIPTION
This document aims at listing several Frequently Asked Questions
regarding Perlbal.
Configuring Perlbal
Is there a sample "perlbal.*" I can use for my "init.d"?
Yes, you can find one under "debian/perlbal.init". It implements
"start", "stop" and "restart/force-reload". Make sure you adjust it to
your particular taste and/or needs.
Is there a way to make perlbal re-read the config file without shuting
it down?
No, there is not. But typically, if you're making changes, you can just
make them on the management console, which doesn't require any restart
whatsoever.
Still, restarting is probably easy. The trick to it is to simulate a
graceful restart.
How can I implement a graceful restart?
Here's a sample script that will allow you to perform a graceful
restart:
$ cat restart-perlbal.sh
echo "shutdown graceful" | nc localhost 60000
/usr/local/bin/perlbal --conf=/etc/perlbal.conf
The idea is that you tell the old Perlbal to do a graceful shutdown;
that immediately closes all of the listening sockets, so new
connections are not accepted. As soon as that's done (which is instant)
you can start up a new Perlbal.
This gives you a minimum of downtime that can be measured on the order
of milliseconds (the time it takes for the new Perlbal to start up).
Remember that you need to have a "management" service listening on port
60000 for this example to work. See Perlbal::Manual::Management.
Load Balancing
What balancing algorithm does Perlbal use?
Currently, Perlbal supports only one balancing method: "random".
SET pool balance_method = 'random'
With this mode, Perlbal selects one of the nodes within the pool
randomly for each request received. It prefers reusing existing idle
backend connections if backend_persist is enabled, which is faster than
waiting for a new connection to open each time.
Plugins
Can I influence the order plugins are used?
Yes. When you set the plugins for your service they get to register
their hooks in order.
SET plugins = AccessControl HighPri
These hooks are pushed into an array, which means that they preserve
the order of the plugins.
HTTP, SSL
Does perlbal support HTTP 1.1?
Perlbal for the most part only speaks HTTP/1.0 both to clients and to
backend webservers. It happily takes requests advertising HTTP/1.1 and
downgrading them to HTTP/1.0 when speaking to backend serves.
It knows all about persistent connections (in both 1.0 and 1.1) and
will reply with HTTP/1.0 Connection: keep-alive the request was only
implicitly keep-alive with HTTP/1.1. etc.
Perlbal is now also starting to speak more of 1.1. For instance,
Perlbal does support receiving transfer-encoding "chunked" requests
from clients (a feature of HTTP/1.1), will send a "100 Continue" in
response to "Expect: 100-continue", and will parse the chunked
requests, writing the request-of-unknown-length to disk (only if
"buffered_uploads" is enabled), and then will send an HTTP/1.0 request
to the backends, with the actual "Content-Length" (now known) filled
in.
When more of 1.1 is supported, it will become an option, and later
become the default. However, after several years of usage, there just
hasn't been that much of a reason. The chunked requests (common from
mobile phones uploading large images) has been the most annoying
shortcoming but now that it's solved, it's questionable whether or not
more of HTTP/1.1 will be supported.
Does perlbal support SSL?
Yes. To use SSL mode you'll need IO::Socket::SSL "v0.98+" installed.
You can do SSL either on "web_server", "reverse_proxy" or "selector"
modes, but not on a vhost-based "selector" service, because SSL and
vhosts aren't compatible.
See the configuration file ssl.conf under conf/ for an example.
SEE ALSO
Perlbal::Manual.
perl v5.14.2 2012-02-20 Perlbal::FAQ(3)
