Re: Procmail locking and timeouts

Philip Guenther caught a bug in my suggestion to Jason Carroll:

| Assuming that $ORGMAIL == $DEFAULT, the above will lead to deadlock
| when procmail tries to do the implicit delivery to $DEFAULT as it'll
| try to lock $DEFAULT$LOCKEXT, and hang on it until it decides the lock
| is stale.

Thanks for spotting that, Philip.  Unfortunately, it looks as though you've
allowed me an opportunity to return the favor.

|       # Try locking $DEFAULT with no retries:
|       :0
|       * ? lockfile -r0 $DEFAULT$LOCKEXT
|       {
|           # Attempt delivery
|           :0 c
|           $DEFAULT
| 
|           # On success, cleanup the lock and exit
|           :0 ai
|           |rm -f $DEFAULT$LOCKEXT
|       }

Unfortunately, nothing removes $DEFAULT$LOCKEXT if the lock was acquired but
the save failed.

|       # Dang, it didn't work.  If $ORGMAIL != $DEFAULT then try ORGMAIL
|       :0
|       * ! ORGMAIL ?? ^^$\DEFAULT^^
|       * ? lockfile -r0 $ORGMAIL$LOCKEXT
|       {
|           # Attempt delivery
|           :0 c
|           $ORGMAIL
| 
|           # On success, cleanup the lock and exit
|           :0 ai
|           |rm -f $ORGMAIL$LOCKEXT
|       }
| 
|       # Okay, we couldn't deliver to either $DEFAULT or $DEFAULT.
|       # Give up and throw EX_TEMPFAIL
|       EXITCODE = 75
|       HOST

And again, if it got that far, nothing removes $ORGMAIL$LOCKEXT if the
lock was acquired but the save failed.

So let's try tweak that in.

        # Try locking $DEFAULT with no retries:
        :0
        * ? lockfile -r0 $DEFAULT$LOCKEXT
        {
            # Attempt delivery
            :0 c
            $DEFAULT

            :0 e # record results of save attempt
            { FAILED=yes }
 
            # On success, clean up the lock and exit
            # On failure, clean up the lock and keep trying
            :0 i${FAILED+c}
            |rm -f $DEFAULT$LOCKEXT
        }

        # Dang, it didn't work.  If $ORGMAIL != $DEFAULT then try ORGMAIL
        :0
        * ! ORGMAIL ?? ^^$\DEFAULT^^
        * ? lockfile -r0 $ORGMAIL$LOCKEXT
        {
            # Attempt delivery
            :0 c
            $ORGMAIL
 
            :0 e # record result of desperation attempt
            { FAILED_AGAIN=yes }

            # On success, clean up the lock and exit
            # On failure, clean up the lock, requeue, and bail
            :0 i${FAILED_AGAIN:+c}
            |rm -f $ORGMAIL$LOCKEXT
        }
 
        # Okay, we couldn't deliver to either $DEFAULT or $DEFAULT.
        # Give up and throw EX_TEMPFAIL
        EXITCODE = 75
        HOST

Some of you may prefer the perkier approach of recording successes rather
than failures.  OK then ...

        # Try locking $DEFAULT with no retries:
        :0
        * ? lockfile -r0 $DEFAULT$LOCKEXT
        {
            # Attempt delivery
            :0 c
            $DEFAULT

            :0 a # record results of save attempt
            { SUCCEEDED=H } # H, B, or D would be non-null and harmless
 
            # On success, clean up the lock and exit
            # On failure, clean up the lock and keep trying
            :0 i${SUCCEEDED:-c}
            |rm -f $DEFAULT$LOCKEXT
        }

        # Dang, it didn't work.  If $ORGMAIL != $DEFAULT then try ORGMAIL
        :0
        * ! ORGMAIL ?? ^^$\DEFAULT^^
        * ? lockfile -r0 $ORGMAIL$LOCKEXT
        {
            # Attempt delivery
            :0 c
            $ORGMAIL
 
            :0 e # record result of desperation attempt
            { SUCCESS_AT_LAST=B }

            # On success, clean up the lock and exit
            # On failure, clean up the lock, requeue, and bail
            :0 i${SUCCESS_AT_LAST:-c}
            |rm -f $ORGMAIL$LOCKEXT
        }
 
        # Okay, we couldn't deliver to either $DEFAULT or $DEFAULT.
        # Give up and throw EX_TEMPFAIL
        EXITCODE = 75
        HOST