--- cvsroot/AnyEvent-SNMP/SNMP.pm 2009/03/31 21:55:18 1.1 +++ cvsroot/AnyEvent-SNMP/SNMP.pm 2009/04/19 11:06:21 1.4 @@ -45,6 +45,77 @@ requests with Net::SNMP>. It is recommended but not required to load this module before C. +=head1 GLOBAL VARIABLES + +=over 4 + +=item $AnyEvent::SNMP::MAX_OUTSTANDING (default: C<50>, dynamic) + +Use this package variable to restrict the number of outstanding SNMP +requests at any point in time. + +Net::SNMP is very fast at creating and sending SNMP requests, but much +slower at parsing (big, bulk) responses. This makes it easy to request a +lot of data that can take many seconds to parse. + +In the best case, this can lead to unnecessary delays (and even time-outs, +as the data has been received but not yet processed) and in the worst +case, this can lead to packet loss, when the receive queue overflows and +the kernel can no longer accept new packets. + +To avoid this, you can (and should) limit the number of outstanding requests +to a number low enough so that parsing time doesn't introduce noticable delays. + +Unfortunately, this number depends not only on processing speed and load +of the machine running Net::SNMP, but also on the network latency and the +speed of your SNMP agents. + +AnyEvent::SNMP tries to dynamically adjust this number dynamically upwards +and downwards. + +Note that you can use L to speed up parsing of responses +considerably. + +=item $AnyEvent::SNMP::MIN_RECVQUEUE (default: C<4>) + +=item $AnyEvent::SNMP::MAX_RECVQUEUE (default: C<64>) + +These values specify the minimum and maximum receive queue length (in +units of one response packet). + +When AnyEvent::SNMP handles $MAX_RECVQUEUE or more packets per iteration +it will reduce $MAX_OUTSTANDING. If it handles less than $MIN_RECVQUEUE, +it increases $MAX_OUTSTANDING. + +This has the result of adjusting the number of outstanding requests so that +the recv queue is between the minimum and maximu, usually. + +This algorithm works reasonably well as long as the responses, response +latencies and processing times are the same size per packet on average. + +=back + +=head1 COMPATIBILITY + +This module may be used as a drop in replacement for the +Net::SNMP::Dispatcher in existing programs. You can still call +C to start the event-loop, but then you loose the benefit +of mixing Net::SNMP events with other events. + + use AnyEvent::SNMP; + use Net::SNMP; + + # just use Net::SNMP as before + + # ... start non-blocking snmp request(s)... + Net::SNMP->session ( + -hostname => "127.0.0.1", + -community => "public", + -nonblocking => 1, + )->get_request (-callback => sub { ... }); + + snmp_dispatcher; + =cut package AnyEvent::SNMP; @@ -63,7 +134,7 @@ use Net::SNMP (); use AnyEvent (); -our $VERSION = '0.1'; +our $VERSION = '0.2'; $Net::SNMP::DISPATCHER = instance Net::SNMP::Dispatcher; @@ -75,6 +146,12 @@ our $BUSY; our %TRANSPORT; # address => [count, watcher] +our @QUEUE; +our $MAX_OUTSTANDING = 50; +our $MIN_RECVQUEUE = 4; +our $MAX_RECVQUEUE = 64; + +sub kick_job; sub _send_pdu { my ($pdu, $retries) = @_; @@ -87,6 +164,7 @@ if (!defined $msg) { --$BUSY; + kick_job; # Inform the command generator about the Message Processing error. $pdu->status_information ($MESSAGE_PROCESSING->error); return; @@ -105,6 +183,7 @@ }); } else { --$BUSY; + kick_job; } # Inform the command generator about the send() error. @@ -119,56 +198,73 @@ # register the transport unless ($TRANSPORT{$transport+0}[0]++) { $TRANSPORT{$transport+0}[1] = AnyEvent->io (fh => $transport->socket, poll => 'r', cb => sub { - # Create a new Message object to receive the response - my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport); - - if (!defined $msg) { - die sprintf 'Failed to create Message object [%s]', $error; - } + for my $count (1..$MAX_RECVQUEUE) { # handle up to this many requests in one go + # Create a new Message object to receive the response + my ($msg, $error) = Net::SNMP::Message->new (-transport => $transport); - # Read the message from the Transport Layer - if (!defined $msg->recv) { - # for some reason, connected-oriented transports seem to need this - unless ($transport->connectionless) { - delete $TRANSPORT{$transport+0} - unless --$TRANSPORT{$transport+0}[0]; + if (!defined $msg) { + die sprintf 'Failed to create Message object [%s]', $error; } - $msg->error; - return; - } + # Read the message from the Transport Layer + if (!defined $msg->recv) { + if ($transport->connectionless) { + # if we handled very few replies and we have queued work, try + # to increase the parallelity as we probably can handle more. + if ($count < $MIN_RECVQUEUE && @QUEUE) { + ++$MAX_OUTSTANDING; + kick_job; + } + } else { + # for some reason, connected-oriented transports seem to need this + delete $TRANSPORT{$transport+0} + unless --$TRANSPORT{$transport+0}[0]; + } - # For connection-oriented Transport Domains, it is possible to - # "recv" an empty buffer if reassembly is required. - if (!$msg->length) { - return; - } + $msg->error; + return; + } - # Hand the message over to Message Processing. - if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) { - $MESSAGE_PROCESSING->error; - return; - } + # For connection-oriented Transport Domains, it is possible to + # "recv" an empty buffer if reassembly is required. + if (!$msg->length) { + return; + } - # Set the error if applicable. - $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error; + # Hand the message over to Message Processing. + if (!defined $MESSAGE_PROCESSING->prepare_data_elements ($msg)) { + $MESSAGE_PROCESSING->error; + return; + } - # Cancel the timeout. - my $rtimeout_w = $msg->timeout_id; - if ($$rtimeout_w) { - undef $$rtimeout_w; - delete $TRANSPORT{$transport+0} - unless --$TRANSPORT{$transport+0}[0]; + # Set the error if applicable. + $msg->error ($MESSAGE_PROCESSING->error) if $MESSAGE_PROCESSING->error; - --$BUSY; + # Notify the command generator to process the response. + $msg->process_response_pdu; + + # Cancel the timeout. + my $rtimeout_w = $msg->timeout_id; + if ($$rtimeout_w) { + undef $$rtimeout_w; + + --$BUSY; + kick_job; + + unless (--$TRANSPORT{$transport+0}[0]) { + delete $TRANSPORT{$transport+0}; + return; + } + } } - # Notify the command generator to process the response. - $msg->process_response_pdu; + # when we end up here, we successfully handled $MAX_RECVQUEUE + # replies in one iteration, so assume we are overloaded + # and reduce the amount of parallelity. + $MAX_OUTSTANDING = (int $MAX_OUTSTANDING * 0.9) || 1; }); } - #####d# timeout_id, wtf? $msg->timeout_id (\(my $rtimeout_w = AnyEvent->$timer (after => $pdu->timeout, cb => sub { my $rtimeout_w = $msg->timeout_id; @@ -181,31 +277,49 @@ if ($retries--) { _send_pdu ($pdu, $retries); } else { - --$BUSY; $MESSAGE_PROCESSING->msg_handle_delete ($pdu->msg_id); $pdu->status_information ("No response from remote host '%s'", $pdu->hostname); + + --$BUSY; + kick_job; } }) )); } else { --$BUSY; + kick_job; } } +sub kick_job { + while ($BUSY < $MAX_OUTSTANDING) { + my $pdu = shift @QUEUE + or last; + + ++$BUSY; + + _send_pdu $pdu, $pdu->retries; + } +} sub send_pdu($$$) { my (undef, $pdu, $delay) = @_; - ++$BUSY; - + # $delay is not very sensibly implemented by AnyEvent::SNMP, + # but apparently it is not a very sensible feature. if ($delay > 0) { + ++$BUSY; my $delay_w; $delay_w = AnyEvent->$timer (after => $delay, cb => sub { undef $delay_w; - _send_pdu ($pdu, $pdu->retries); + --$BUSY; + push @QUEUE, $pdu; + kick_job; }); return 1; } - _send_pdu $pdu, $pdu->retries; + push @QUEUE, $pdu; + kick_job; + 1 } @@ -214,12 +328,12 @@ } sub one_event($) { - die; + AnyEvent->one_event; } =head1 SEE ALSO -L, L, L. +L, L, L, L. =head1 AUTHOR