Perl Issue with concurrent requests with IO::Async and Future::Utils - perl

Question

I'm trying to use an IO loop to send concurrent requests (5) to a pool of hosts (3), but the code stops after 3 requests. I've had help to kickstart this code, but I certainly understand most of it now. What I don't get is why the number of processed requests is linked to the number of hosts in my pool of hosts. The objective of the code is to determine routing information from a given IP.
use strict;
use warnings;
use Net::OpenSSH;
use IO::Async::Loop;
use Future::Utils 'fmap_concat';
my #hosts = qw(host1 host2 host3);
my #ssh;
my $user = 'myuser';
my $pass = 'mypassword';
foreach my $host (#hosts) {
my $ssh = Net::OpenSSH->new(host => $host, user => $user, password => $pass, master_opts => [-o => "StrictHostKeyChecking=no"]);
die "Failed to connect to $host: " . $ssh->error if $ssh->error;
push #ssh, $ssh;
}
my #ipv4 = (
'ip1','ip2','ip3','ip4','ip5'
);
my $loop = IO::Async::Loop->new;
my $future = fmap_concat {
my $ip = shift;
my $ssh = shift #ssh;
my $cmd = 'show ip route '.$ip.' | i \*';
my #remote_cmd = $ssh->make_remote_command($cmd);
return $loop->run_process(command => \#remote_cmd)
->transform(done => sub { [#_] })
->on_ready(sub { push #ssh, $ssh });
} generate => sub { return () unless #ssh and #ipv4; shift #ipv4 }, concurrent => scalar #ssh;
my #results = $future->get;
foreach my $result (#results) {
my ($exit, $stdout) = #$result;
print $stdout, "\n";
}
Here are the results
Connection to host1 closed by remote host.
Connection to host2 closed by remote host.
Connection to host3 closed by remote host.
* ip1, from host1, 3w0d ago, via GigabitEthernet0/0/0
* ip2, from host2, 7w0d ago, via GigabitEthernet0/0/0
* ip3, from host3, 3w0d ago, via GigabitEthernet0/0/1

Answer 1

After researching on the problem, I found out that network devices such as Cisco might have an issue handling several requests over the same connection. So the code changed a bit in a way where a new connection is opened everytime the future is called instead of using a pool of pre-opened connections.
use strict;
use warnings;
use Net::OpenSSH;
use IO::Async::Loop;
use Future::Utils 'fmap_concat';
my #hosts = qw(host1 host2 host3);
my #ssh;
my $user = 'myuser';
my $pass = 'mypassword';
my #ipv4 = (
'ip1','ip2','ip3','ip4','ip5'
);
my $loop = IO::Async::Loop->new;
my $future = fmap_concat {
my $ip = shift;
my $host = shift #hosts;
my $ssh = Net::OpenSSH->new(host => $host, user => $user, password => $pass, master_opts => [-o => "StrictHostKeyChecking=no"]);
die "Failed to connect to $host: " . $ssh->error if $ssh->error;
my $cmd = 'show ip route '.$ip.' | i \*|^Routing entry';
my #remote_cmd = $ssh->make_remote_command($cmd);
return $loop->run_process(command => \#remote_cmd)
->transform(done => sub { [#_] })
->on_ready(sub { push #hosts, $host ; });
} generate => sub { return () unless #hosts and #ipv4; shift #ipv4 }, concurrent => scalar #hosts;
my #results = $future->get;
foreach my $result (#results) {
my ($exit, $stdout) = #$result;
print $stdout, "\n";
}
But this has leaded to other problems with underlying openssh library.
It looks like there was a race condition with the ssh connection not being released properly when the future was being invoked on the $host again.
undef $ssh fixed it
->on_ready(sub { undef $ssh; push #hosts, $host ; });