Perlbal is a Perl-based reverse-proxying load balancer and web server. It helps distribute site load over a number of servers. A backend can instruct Perlbal to fetch the user's data from a completely separate server and port and URL, 100% transparent to the user. You might use this to serve images elsewhere (like an image caching service, as part of a content delivery network).
One way LiveJournal can use this is with “
Palimg files can be used in user styles to
dynamically alter the palette of a
GIF image, according to user
customizations. Doing this through the Perlbal plugin instead of using
mod_perl is more efficient.
You will need the Perlbal server code from SVN
http://code.sixapart.com/svn/perlbal/trunk/). It is is
automatically checked out into your cvs subdirectory then
for you. To set it up, build and install the code as before:
You will need to create a directory for your configuration file. If you know
what you are doing, you may find it useful to combine the contents of the
a single file, and place that under
Alternatively, an example
Now, edit the configuration file.
EXAMPLEHOSTNAME.lj with the full hostname of your domain, or
virtual machine if you are using one (and verify all hostname configurations).
If you will not be using SSL, comment out all SSL lines.
Similarly, if you are not storing static files (like site images and stylesheets) under
their own subdomain, you can amend or comment out all 'stat' lines.
load palimg load Vhosts load AccessControl SERVER aio_mode = ioaio CREATE SERVICE uptrack SET role = upload_tracker SET listen = 127.0.0.1:7002 ENABLE uptrack CREATE SERVICE ss SET listen = 0.0.0.0:80 SET role = selector SET plugins = vhosts VHOST *.EXAMPLEHOSTNAME.lj = web_proxy VHOST stat.EXAMPLEHOSTNAME.lj = web_stat ENABLE ss CREATE POOL web_proxy_pool POOL web_proxy_pool ADD 127.0.0.1:8081 CREATE SERVICE web_proxy SET role = reverse_proxy SET pool = web_proxy_pool SET persist_backend = on SET max_backend_uses = 10 SET backend_persist_cache = 2 SET verify_backend = on SET balance_method = random SET enable_reproxy = on SET upload_status_listeners = 127.0.0.1:7002 SET buffer_uploads = off ENABLE web_proxy CREATE SERVICE ssl_proxy SET role = reverse_proxy SET pool = web_proxy_pool SET listen = 0.0.0.0:443 SET enable_ssl = on SET persist_backend = on SET max_backend_uses = 10 SET backend_persist_cache = 2 SET verify_backend = on SET balance_method = random SET enable_reproxy = on SET ssl_key_file = /etc/perlbal/certs/server-key.pem SET ssl_cert_file = /etc/perlbal/certs/server-cert.pem ENABLE ssl_proxy CREATE SERVICE web_stat SET role = web_server SET docroot = /home/lj/htdocs/stc SET dirindexing = on ENABLE web_stat CREATE SERVICE mgmt SET role = management SET listen = 127.0.0.1:8065 ENABLE mgmt
Create a self-signed certificate and key for SSL next. You only need to add this if you are using SSL. If you have already purchased a signed certificate and have a key, then of course you can use that instead.
sudo openssl req -x509 -newkey rsa:1024 -keyout server-key.pem -out server-cert.pem -days 365 -nodes
Last, start the Perlbal daemon:
If it reports the listening socket is already in use, edit your Apache
Port 80 with
126.96.36.199:8081 for LiveJournal
188.8.131.52:80> with <