* Re: [pve-devel] [PATCH storage v3] fix #957 iscsi: improve check_connection logic
2025-03-11 17:59 [pve-devel] [PATCH storage v3] fix #957 iscsi: improve check_connection logic Victor Seva via pve-devel
@ 2025-03-12 11:45 ` Friedrich Weber
0 siblings, 0 replies; 2+ messages in thread
From: Friedrich Weber @ 2025-03-12 11:45 UTC (permalink / raw)
To: Proxmox VE development discussion
Hi, thanks for the v3! I looked into this together with Mira and we have
some further comments.
Some general comments:
- The indentation settings look off, please have a look at our Perl
style guide [1].
- If you haven't done so yet, please make sure to send a CLA [0].
First, I want to point out that this patch will not completely get rid
of the "TCP ping"s that trigger the messages on the target, because
after booting the PVE node, iscsi_login/iscsi_discovery will do a TCP
ping. You're probably aware of that, I just wanted to mention it.
I was testing this patch and noticed we still get periodic messages on
the target in the following situation:
- configure two portals A and B, B is permanently down
- reboot PVE node
- as there is no session to B, every 10 seconds the iSCSI plugin calls
iscsi_login, then iscsi_discovery, then iscsi_test_portal for portal A:
sub iscsi_discovery {
my ($portals) = @_;
assert_iscsi_support();
my $res = {};
for my $portal ($portals->@*) {
next if !iscsi_test_portal($portal); # fixme: raise exception here?
I guess also here, we don't need to make a TCP ping against portal A if
we already have a LOGGED_IN session with A, similarly to what this patch
does in `check_connection`.
But then we already have this pattern twice, and it might make sense to
instead rewrite `iscsi_test_portal` so that
- it takes a $target, $portal and optionally a $cache
- it calls iscsi_session to get the current list of sessions (passing
$cache to avoid double work)
- it checks whether there is a session to $portal, if yes:
- if it is LOGGED_IN, return 1, otherwise 0
- otherwise, it triggers a tcp_ping against the portal and returns its
result
Then, we could use this new `iscsi_test_portal` as a drop-in replacement
for the current one. To be able to pass the cache in both call sites, we
would need to modify iscsi_discovery to optionally take a cache as
second argument (note that iscsi_discovery has a second call site in
PVE/Storage.pm that wouldn't pass a cache), and modify iscsi_login to
accept and pass down the cache to iscsi_discovery, and finally
activate_storage to pass down the cache to iscsi_login.
What do you think?
> don't check tcp connection directly if there are already
> sessions. Use iscsiadm command to check the sessions
> status instead.
>
> pvestatd is calling check_connection every 10 seconds.
> This check produces a lot of noise at the iscsi server logging.
>
> Signed-off-by: Victor Seva <linuxmaniac@torreviejawireless.org>
> ---
It would be great if you could add a short summary here (under the ---)
of the changes since the last revision. They don't go into the final
commit, but make reviewing easier. See [2] for more details.
> src/PVE/Storage/ISCSIPlugin.pm | 34 +++++++++++++++++++++++++++++++---
> 1 file changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/src/PVE/Storage/ISCSIPlugin.pm b/src/PVE/Storage/ISCSIPlugin.pm
> index eb70453..89fc871 100644
> --- a/src/PVE/Storage/ISCSIPlugin.pm
> +++ b/src/PVE/Storage/ISCSIPlugin.pm
> @@ -66,6 +66,23 @@ sub iscsi_test_portal {
> return PVE::Network::tcp_ping($server, $port || 3260, 2);
> }
>
> +sub iscsi_test_session {
> + my ($sid) = @_;
> + my $cmd = [$ISCSIADM, '--mode', 'session', '--sid', $sid, '-P1'];
Instead of doing a relatively expensive subprocess invocation, we could
try reading the connection state from sysfs. From what I could gather,
`/sys/class/iscsi_session/session$sid/state` should work:
# cat /sys/class/iscsi_session/session1/state
LOGGED_IN
`file_read_firstline` should work for reading this. We should probably
also double-check that $sid is actually just a number, just to be sure
we avoid path traversal.
What do you think?
> +
> + my $res = 0;
> + eval {
> + run_command($cmd, errmsg => 'iscsi session test failed', outfunc => sub {
> + my $line = shift;
> + if ($line =~ m/^\s+iSCSI Session State: LOGGED_IN\s*$/) {
> + $res = 1;
> + }
> + });
> + };
> + die "session check failed: $@\n" if $@;
> + return $res;
> +}
> +
> sub iscsi_portals {
> my ($target, $portal_in) = @_;
>
> @@ -560,11 +577,22 @@ sub activate_volume {
> sub check_connection {
> my ($class, $storeid, $scfg) = @_;
>
> + my $cache = {};
> + my $sessions = iscsi_session($cache, $scfg->{target});
> my $portals = iscsi_portals($scfg->{target}, $scfg->{portal});
>
> - for my $portal (@$portals) {
> - my $result = iscsi_test_portal($portal);
> - return $result if $result;
> + for my $portal ($portals->@*) {
> + my $session_exists = 0;
> + for my $session ($sessions->@*) {
> + next if $session->{portal} ne $portal;
> + $session_exists = 1;
> + my $result = iscsi_test_session($session->{session_id});
> + return $result if $result;
> + }
> + next if $session_exists;
> + # no sessions, check portal via tcp
> + my $result = iscsi_test_portal($portal);
> + return $result if $result;
> }
>
> return 0;
> --
> 2.43.0
>
>
[0]
https://pve.proxmox.com/wiki/Developer_Documentation#Software_License_and_Copyright
[1] https://pve.proxmox.com/wiki/Perl_Style_Guide#Indentation
[2] https://pve.proxmox.com/wiki/Developer_Documentation#Preparing_Patches
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