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lib/Algorithm/ToNumberMunger.pm  view on Meta::CPAN

Unlike every other munger this one consults external state -- but the state
lives in the daemon, not here, so the munger itself remains a stateless client
and rows stay reproducible I<given> the daemon. Because the daemon is shared,
multiple writer processes marking the same keys see one B<global> rate, which an
in-process meter could never give.

Spec keys:

=over 4

=item * C<socket> - unix socket path of the daemon. Defaults to
C<$Algorithm::ToNumberMunger::EPS_SOCKET>
(C</var/run/iqbi-damiq.sock>).

=item * C<prefix> - string prepended to the input to form the key, namespacing
this column's meters (two columns keyed on the same field need different
prefixes or they share meters). No whitespace/control characters. Default C<''>.

=item * C<mark> - whether to mark the key (default C<1>). Marking rides
C<MARKRATE>: with C<< read => 'rate' >> that one command is the whole exchange;
with C<count>/C<total> the read is pipelined after it (the C<MARKRATE> rate

lib/Algorithm/ToNumberMunger.pm  view on Meta::CPAN

best-effort via C<SO_RCVTIMEO>/C<SO_SNDTIMEO>), so a wedged daemon cannot hang a
writer forever.

=back

Semantics worth knowing: a marked read B<includes the event just marked>; keys
have whitespace/control bytes replaced with C<_> to satisfy the daemon's key
rules; connections are made lazily on first use and kept open (reconnecting
transparently after a fork or an error), so compiling a plan -- including the
eager validation in C<write_info> -- needs no running daemon. Each eps column
costs one unix-socket round trip per row; the multi-output form exists so
rate+count of the same key costs one round trip, not two.

=cut

# Default socket path of the iqbi-damiq daemon.
our $EPS_SOCKET = '/var/run/iqbi-damiq.sock';

# Persistent daemon connections, keyed by socket path, shared by every eps
# munger in the process. Entries record the pid that opened them so a forked
# writer transparently reopens instead of sharing a socket with its parent.