[PATCH 1/3] standardize timer-related event-loop code

[Eric Wong <e@80x24.org>]

Standardize the code we have in place to avoid creating too many
timer objects.  We do not need exact timers for things that don't
need to be run ASAP, so we can play things fast and loose to avoid
wasting power with unnecessary wakeups.

We only need two classes of timers:

* asap - run this on the next loop tick, after operating on
  @Danga::Socket::ToClose to close remaining sockets

* later - run at some point in the future.  It could be as
  soon as immediately (like "asap"), and as late as 60s into
  the future.

In the future, we support an "emergency" switch to fire "later"
timers immediately.
---
 lib/PublicInbox/EvCleanup.pm   | 41 +++++++++++++++++++++++++++++++++++++++++
 lib/PublicInbox/HTTP.pm        | 26 +++++++++++++-------------
 lib/PublicInbox/HTTPD/Async.pm |  3 ++-
 lib/PublicInbox/NNTP.pm        | 30 +++++++++++++-----------------
 4 files changed, 69 insertions(+), 31 deletions(-)
 create mode 100644 lib/PublicInbox/EvCleanup.pm

diff --git a/lib/PublicInbox/EvCleanup.pm b/lib/PublicInbox/EvCleanup.pm
new file mode 100644
index 0000000..5efb093
--- /dev/null
+++ b/lib/PublicInbox/EvCleanup.pm
@@ -0,0 +1,41 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# event cleanups (currently for Danga::Socket)
+package PublicInbox::EvCleanup;
+use strict;
+use warnings;
+
+my $asapq = { queue => [], timer => undef };
+my $laterq = { queue => [], timer => undef };
+
+sub _run_all ($) {
+	my ($q) = @_;
+
+	my $run = $q->{queue};
+	$q->{queue} = [];
+	$q->{timer} = undef;
+	$_->() foreach @$run;
+}
+
+sub _run_asap () { _run_all($asapq) }
+sub _run_later () { _run_all($laterq) }
+
+sub asap ($) {
+	my ($cb) = @_;
+	push @{$asapq->{queue}}, $cb;
+	$asapq->{timer} ||= Danga::Socket->AddTimer(0, *_run_asap);
+}
+
+sub later ($) {
+	my ($cb) = @_;
+	push @{$laterq->{queue}}, $cb;
+	$laterq->{timer} ||= Danga::Socket->AddTimer(60, *_run_later);
+}
+
+END {
+	_run_asap();
+	_run_later();
+}
+
+1;
diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 104a213..00c9a04 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -26,13 +26,22 @@ use constant {
 
 # FIXME: duplicated code with NNTP.pm
 my $WEAKEN = {}; # string(inbox) -> inbox
-my $WEAKTIMER;
+my $weakt;
 sub weaken_task () {
-	$WEAKTIMER = undef;
+	$weakt = undef;
 	$_->weaken_all for values %$WEAKEN;
 	$WEAKEN = {};
 }
 
+my $pipelineq = [];
+my $pipet;
+sub process_pipelineq () {
+	my $q = $pipelineq;
+	$pipet = undef;
+	$pipelineq = [];
+	rbuf_process($_) foreach @$q;
+}
+
 # Use the same configuration parameter as git since this is primarily
 # a slow-client sponge for git-http-backend
 # TODO: support per-respository http.maxRequestBuffer somehow...
@@ -234,7 +243,7 @@ sub response_write {
 		if (my $obj = $env->{'pi-httpd.inbox'}) {
 			# grace period for reaping resources
 			$WEAKEN->{"$obj"} = $obj;
-			$WEAKTIMER ||= Danga::Socket->AddTimer(60, *weaken_task);
+			$weakt ||= PublicInbox::EvCleanup::later(*weaken_task);
 		}
 		$self->{env} = undef;
 	};
@@ -281,15 +290,6 @@ sub more ($$) {
 	$self->write($_[1]);
 }
 
-my $pipelineq = [];
-my $next_tick;
-sub process_pipelineq () {
-	$next_tick = undef;
-	my $q = $pipelineq;
-	$pipelineq = [];
-	rbuf_process($_) foreach @$q;
-}
-
 # overrides existing Danga::Socket method
 sub event_write {
 	my ($self) = @_;
@@ -300,7 +300,7 @@ sub event_write {
 		$self->watch_read(1);
 	} else { # avoid recursion for pipelined requests
 		push @$pipelineq, $self;
-		$next_tick ||= Danga::Socket->AddTimer(0, *process_pipelineq);
+		$pipet ||= PublicInbox::EvCleanup::asap(*process_pipelineq);
 	}
 }
 
diff --git a/lib/PublicInbox/HTTPD/Async.pm b/lib/PublicInbox/HTTPD/Async.pm
index bd2eacb..47ba27d 100644
--- a/lib/PublicInbox/HTTPD/Async.pm
+++ b/lib/PublicInbox/HTTPD/Async.pm
@@ -10,6 +10,7 @@ use strict;
 use warnings;
 use base qw(Danga::Socket);
 use fields qw(cb cleanup);
+require PublicInbox::EvCleanup;
 
 sub new {
 	my ($class, $io, $cb, $cleanup) = @_;
@@ -61,7 +62,7 @@ sub close {
 	$self->SUPER::close(@_);
 
 	# we defer this to the next timer loop since close is deferred
-	Danga::Socket->AddTimer(0, $cleanup) if $cleanup;
+	PublicInbox::EvCleanup::asap($cleanup) if $cleanup;
 }
 
 # do not let ourselves be closed during graceful termination
diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index ac536f7..f3de4b1 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -11,6 +11,7 @@ use PublicInbox::Search;
 use PublicInbox::Msgmap;
 use PublicInbox::Git;
 use PublicInbox::MID qw(mid2path);
+require PublicInbox::EvCleanup;
 use Email::Simple;
 use POSIX qw(strftime);
 use Time::HiRes qw(clock_gettime CLOCK_MONOTONIC);
@@ -38,15 +39,15 @@ my $LIST_HEADERS = join("\r\n", @OVERVIEW,
 my %DISABLED; # = map { $_ => 1 } qw(xover list_overview_fmt newnews xhdr);
 
 my $EXPMAP; # fd -> [ idle_time, $self ]
-my $EXPTIMER;
+my $expt;
 our $EXPTIME = 180; # 3 minutes
 my $WEAKEN = {}; # string(nntpd) -> nntpd
-my $WEAKTIMER;
+my $weakt;
+my $nextt;
 
-my $next_tick;
 my $nextq = [];
 sub next_tick () {
-	$next_tick = undef;
+	$nextt = undef;
 	my $q = $nextq;
 	$nextq = [];
 	foreach my $nntp (@$q) {
@@ -70,7 +71,7 @@ sub update_idle_time ($) {
 # reduce FD pressure by closing some "git cat-file --batch" processes
 # and unused FDs for msgmap and Xapian indices
 sub weaken_groups () {
-	$WEAKTIMER = undef;
+	$weakt = undef;
 	foreach my $nntpd (values %$WEAKEN) {
 		$_->weaken_all foreach (@{$nntpd->{grouplist}});
 	}
@@ -81,7 +82,6 @@ sub expire_old () {
 	my $now = now();
 	my $exp = $EXPTIME;
 	my $old = $now - $exp;
-	my $next = $now + $exp;
 	my $nr = 0;
 	my %new;
 	while (my ($fd, $v) = each %$EXPMAP) {
@@ -89,26 +89,22 @@ sub expire_old () {
 		if ($idle_time < $old) {
 			$nntp->close; # idempotent
 		} else {
-			my $nexp = $idle_time + $exp;
-			$next = $nexp if ($nexp < $next);
 			++$nr;
 			$new{$fd} = $v;
 		}
 	}
 	$EXPMAP = \%new;
 	if ($nr) {
-		$next -= $now;
-		$next = 0 if $next < 0;
-		$EXPTIMER = Danga::Socket->AddTimer($next, *expire_old);
+		$expt = PublicInbox::EvCleanup::later(*expire_old);
 		weaken_groups();
 	} else {
-		$EXPTIMER = undef;
+		$expt = undef;
 		# noop to kick outselves out of the loop ASAP so descriptors
 		# really get closed
-		Danga::Socket->AddTimer(0, sub {});
+		PublicInbox::EvCleanup::asap(sub {});
 
 		# grace period for reaping resources
-		$WEAKTIMER ||= Danga::Socket->AddTimer(30, *weaken_groups);
+		$weakt ||= PublicInbox::EvCleanup::later(*weaken_groups);
 	}
 }
 
@@ -122,7 +118,7 @@ sub new ($$$) {
 	$self->watch_read(1);
 	update_idle_time($self);
 	$WEAKEN->{"$nntpd"} = $nntpd;
-	$EXPTIMER ||= Danga::Socket->AddTimer($EXPTIME, *expire_old);
+	$expt ||= PublicInbox::EvCleanup::later(*expire_old);
 	$self;
 }
 
@@ -633,7 +629,7 @@ sub long_response ($$$$) {
 			update_idle_time($self);
 
 			push @$nextq, $self;
-			$next_tick ||= Danga::Socket->AddTimer(0, *next_tick);
+			$nextt ||= PublicInbox::EvCleanup::asap(*next_tick);
 		} else { # all done!
 			$self->{long_res} = undef;
 			$self->watch_read(1);
@@ -996,7 +992,7 @@ sub watch_read {
 		# in case we really did dispatch a read event and started
 		# another long response.
 		push @$nextq, $self;
-		$next_tick ||= Danga::Socket->AddTimer(0, *next_tick);
+		$nextt ||= PublicInbox::EvCleanup::asap(*next_tick);
 	}
 	$rv;
 }