INTRODUCTION

hapolicy enables high availability, weighted loadbalancing and a fallback action for postfix policy delegation services. Invoked via postfix spawn it acts as a wrapper that queries other policy servers via tcp connection. The order of the service queries can be influenced by assigning a specific priority and weight to each service. A service is considered 'failing', if the connection is refused or the specified service timeout is reached. If all of the configured policy services were failing, hapolicy returns a default action (e.g. dunno) to postfix.

With version 1.00 hapolicy has less than 200 lines of perl code using only standard perl modules. It does not require any disk access nor configuration files and runs under an unpriviledged user account. This should allow fast and reliable operation.

CONFIGURATION

A service has the following attributes

    "servicename"           => {
               ip              => '127.0.0.1',         # ip address
               port            => '10040',             # tcp port
               prio            => '10',                # optional, lower wins
               weight          => '1',                 # optional, for items with same prio (weighted round-robin), higher is better
               timeout         => '30',                # optional, query timeout in seconds
    },

You may define multiple services at the command line. Which means that

        hapolicy -s "grey1=10.0.0.1:10031:10" -s "grey2=10.0.0.2:10031:20"

will always try first service grey1 at ip 10.0.0.1 port 10031 and if that service is not available or does not answer within the default of 30 seconds the next service grey2 at ip 10.0.0.2 port 10031 will be queried.

If you want to load balance connections you may define

        hapolicy -s "polw1=10.0.0.1:12525:10:2" -s "polw2=10.0.0.2:12525:10:1"

which queries service polw1 at ip 10.0.0.1 twice as much as service polw2 at ip 10.0.0.2. Note that this setup also ensures high availability for both services. If polw1 is not available or does not answer within the default of 30 seconds polw2 will be queried and vice versa. There is no reason to define a service twice.

INTEGRATION

Enter the following at the bottom of your postfix master.cf (usually located at /etc/postfix):

        # service description, note the leading blanks at the second line
        127.0.0.1:10060 inet    n       n       n       -       0       spawn
          user=nobody argv=/usr/local/bin/hapolicy -l -s GREY1=10.0.0.1:10031:10 -s GREY2=10.0.0.2:10031:10

save the file and open postfix main.cf. Modify it as follows:

        127.0.0.1:10060_time_limit   = 3600
        smtpd_recipient_restrictions =
            permit_mynetworks,
            ... other authed permits ...
            reject_unauth_destination,
            ... other restrictions ...
            check_policy_service inet:127.0.0.1:10060   # <- hapolicy query

Now issue 'postfix reload' at the command line. Of course you can have more enhanced setups using postfix restriction classes. Please see "LINKS" for further options.