Perlbal::FAQ - Frequently Asked Questions about Perlbal
Perlbal 1.78.
This document aims at listing several Frequently Asked Questions regarding Perlbal.
perlbal.*
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.
debian/perlbal.init
start
stop
restart/force-reload
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.
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.
management
Currently, Perlbal supports only one balancing method: random.
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.
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.
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.
100 Continue
Expect: 100-continue
buffered_uploads
Content-Length
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.
Yes. To use SSL mode you'll need IO::Socket::SSL v0.98+ installed.
v0.98+
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.
web_server
reverse_proxy
selector
See the configuration file ssl.conf under conf/ for an example.
Perlbal::Manual.
To install Perlbal, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perlbal
CPAN shell
perl -MCPAN -e shell install Perlbal
For more information on module installation, please visit the detailed CPAN module installation guide.