[pve-devel] [PATCH storage v2] iscsi: disable Open-iSCSI login retries

[pve-devel] [PATCH storage v2] iscsi: disable Open-iSCSI login retries

[Friedrich Weber]

Since 90c1b10 ("fix #254: iscsi: add support for multipath targets"),
iSCSI storage activation checks whether a session exists for each
discovered portal. If there is a discovered portal without a session,
it performs a discovery and login in the hope of establishing a
session to the portal. If the portal is unreachable when trying to log
in, Open-iSCSI's default behavior is to retry for up to 2 minutes, as
explained in /etc/iscsi/iscid.conf:

> # The default node.session.initial_login_retry_max is 8 and
> # node.conn[0].timeo.login_timeout is 15 so we have:
> #
> # node.conn[0].timeo.login_timeout * \
> node.session.initial_login_retry_max = 120s

If pvestatd is activating the storage, it will be blocked during that
time, which is undesirable. This is particularly unfortunate if the
target announces portals that the host permanently cannot reach. In
that case, every pvestatd iteration will take 2 minutes. While it can
be argued that such setups are misconfigured, it is still desirable to
keep the fallout of that misconfiguration as low as possible.

In order to reduce the time Open-iSCSI tries to log in, instruct
Open-ISCSI to not perform login retries for that target. For this, set
node.session.initial_login_retry_max for the target to 0. This setting
is stored in Open-iSCSI's records under /etc/iscsi/nodes. As these
records are overwritten with the defaults from /etc/iscsi/iscsid.conf
on discovery, the setting needs to be applied after discovery.

With this setting, one login attempt should take at most 15 seconds.
This is still higher than pvestatd's iteration time of 10 seconds, but
more tolerable. Logins will still be continuously retried by pvestatd
in every iteration until there is a session to each discovered portal.

Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
Tested-by: Mira Limbeck <m.limbeck@proxmox.com>
Reviewed-by: Mira Limbeck <m.limbeck@proxmox.com>
---

Notes:
    changes since v1:
    - dropped "to avoid blocking pvestatd" from commit title, as pvestatd
      will still be blocked, just for a shorter time
    - changed formatting
    - added Mira's R-b and T-b (thx!). Took the liberty to include them
      although the code, strictly speaking, changed
    
    v1: https://lore.proxmox.com/pve-devel/20241011093744.25545-1-f.weber@proxmox.com/

 src/PVE/Storage/ISCSIPlugin.pm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/PVE/Storage/ISCSIPlugin.pm b/src/PVE/Storage/ISCSIPlugin.pm
index 2bdd9a2..2e3d6ee 100644
--- a/src/PVE/Storage/ISCSIPlugin.pm
+++ b/src/PVE/Storage/ISCSIPlugin.pm
@@ -132,6 +132,20 @@ sub iscsi_login {
     eval { iscsi_discovery($portals); };
     warn $@ if $@;
 
+    # Disable retries to avoid blocking pvestatd for too long, next iteration will retry anyway
+    eval {
+	my $cmd = [
+	    $ISCSIADM,
+	    '--mode', 'node',
+	    '--targetname', $target,
+	    '--op', 'update',
+	    '--name', 'node.session.initial_login_retry_max',
+	    '--value', '0',
+	];
+	run_command($cmd);
+    };
+    warn $@ if $@;
+
     run_command([$ISCSIADM, '--mode', 'node', '--targetname',  $target, '--login']);
 }
 
-- 
2.39.5



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Re: [pve-devel] [PATCH storage v2] iscsi: disable Open-iSCSI login retries

[Mira Limbeck]

On 10/11/24 14:58, Friedrich Weber wrote:
> Since 90c1b10 ("fix #254: iscsi: add support for multipath targets"),
> iSCSI storage activation checks whether a session exists for each
> discovered portal. If there is a discovered portal without a session,
> it performs a discovery and login in the hope of establishing a
> session to the portal. If the portal is unreachable when trying to log
> in, Open-iSCSI's default behavior is to retry for up to 2 minutes, as
> explained in /etc/iscsi/iscid.conf:
> 
>> # The default node.session.initial_login_retry_max is 8 and
>> # node.conn[0].timeo.login_timeout is 15 so we have:
>> #
>> # node.conn[0].timeo.login_timeout * \
>> node.session.initial_login_retry_max = 120s
> 
> If pvestatd is activating the storage, it will be blocked during that
> time, which is undesirable. This is particularly unfortunate if the
> target announces portals that the host permanently cannot reach. In
> that case, every pvestatd iteration will take 2 minutes. While it can
> be argued that such setups are misconfigured, it is still desirable to
> keep the fallout of that misconfiguration as low as possible.
> 
> In order to reduce the time Open-iSCSI tries to log in, instruct
> Open-ISCSI to not perform login retries for that target. For this, set
> node.session.initial_login_retry_max for the target to 0. This setting
> is stored in Open-iSCSI's records under /etc/iscsi/nodes. As these
> records are overwritten with the defaults from /etc/iscsi/iscsid.conf
> on discovery, the setting needs to be applied after discovery.
> 
> With this setting, one login attempt should take at most 15 seconds.
> This is still higher than pvestatd's iteration time of 10 seconds, but
> more tolerable. Logins will still be continuously retried by pvestatd
> in every iteration until there is a session to each discovered portal.
> 
> Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
> Tested-by: Mira Limbeck <m.limbeck@proxmox.com>
> Reviewed-by: Mira Limbeck <m.limbeck@proxmox.com>
> ---
> 
> Notes:
>     changes since v1:
>     - dropped "to avoid blocking pvestatd" from commit title, as pvestatd
>       will still be blocked, just for a shorter time
>     - changed formatting
>     - added Mira's R-b and T-b (thx!). Took the liberty to include them
>       although the code, strictly speaking, changed
>     
>     v1: https://lore.proxmox.com/pve-devel/20241011093744.25545-1-f.weber@proxmox.com/
> 
>  src/PVE/Storage/ISCSIPlugin.pm | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/src/PVE/Storage/ISCSIPlugin.pm b/src/PVE/Storage/ISCSIPlugin.pm
> index 2bdd9a2..2e3d6ee 100644
> --- a/src/PVE/Storage/ISCSIPlugin.pm
> +++ b/src/PVE/Storage/ISCSIPlugin.pm
> @@ -132,6 +132,20 @@ sub iscsi_login {
>      eval { iscsi_discovery($portals); };
>      warn $@ if $@;
>  
> +    # Disable retries to avoid blocking pvestatd for too long, next iteration will retry anyway
> +    eval {
> +	my $cmd = [
> +	    $ISCSIADM,
> +	    '--mode', 'node',
> +	    '--targetname', $target,
> +	    '--op', 'update',
> +	    '--name', 'node.session.initial_login_retry_max',
> +	    '--value', '0',
> +	];
> +	run_command($cmd);
> +    };
> +    warn $@ if $@;
> +
>      run_command([$ISCSIADM, '--mode', 'node', '--targetname',  $target, '--login']);
>  }
>  
I tested the v2 again with the same setup, so my `Tested-by` is now true
for this one as well. The commit message and the array formatting are
now clearer.
So the `Tested-by` and `Reviewed-by` included are fine from my side.


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[pve-devel] applied: [PATCH storage v2] iscsi: disable Open-iSCSI login retries

[Thomas Lamprecht]

 Am 11/10/2024 um 14:58 schrieb Friedrich Weber:
> Since 90c1b10 ("fix #254: iscsi: add support for multipath targets"),
> iSCSI storage activation checks whether a session exists for each
> discovered portal. If there is a discovered portal without a session,
> it performs a discovery and login in the hope of establishing a
> session to the portal. If the portal is unreachable when trying to log
> in, Open-iSCSI's default behavior is to retry for up to 2 minutes, as
> explained in /etc/iscsi/iscid.conf:
> 
>> # The default node.session.initial_login_retry_max is 8 and
>> # node.conn[0].timeo.login_timeout is 15 so we have:
>> #
>> # node.conn[0].timeo.login_timeout * \
>> node.session.initial_login_retry_max = 120s
> 
> If pvestatd is activating the storage, it will be blocked during that
> time, which is undesirable. This is particularly unfortunate if the
> target announces portals that the host permanently cannot reach. In
> that case, every pvestatd iteration will take 2 minutes. While it can
> be argued that such setups are misconfigured, it is still desirable to
> keep the fallout of that misconfiguration as low as possible.
> 
> In order to reduce the time Open-iSCSI tries to log in, instruct
> Open-ISCSI to not perform login retries for that target. For this, set
> node.session.initial_login_retry_max for the target to 0. This setting
> is stored in Open-iSCSI's records under /etc/iscsi/nodes. As these
> records are overwritten with the defaults from /etc/iscsi/iscsid.conf
> on discovery, the setting needs to be applied after discovery.
> 
> With this setting, one login attempt should take at most 15 seconds.
> This is still higher than pvestatd's iteration time of 10 seconds, but
> more tolerable. Logins will still be continuously retried by pvestatd
> in every iteration until there is a session to each discovered portal.
> 
> Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
> Tested-by: Mira Limbeck <m.limbeck@proxmox.com>
> Reviewed-by: Mira Limbeck <m.limbeck@proxmox.com>
> ---
> 
> Notes:
>     changes since v1:
>     - dropped "to avoid blocking pvestatd" from commit title, as pvestatd
>       will still be blocked, just for a shorter time
>     - changed formatting
>     - added Mira's R-b and T-b (thx!). Took the liberty to include them
>       although the code, strictly speaking, changed
>     
>     v1: https://lore.proxmox.com/pve-devel/20241011093744.25545-1-f.weber@proxmox.com/
> 
>  src/PVE/Storage/ISCSIPlugin.pm | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
>

applied, thanks!

FWIW, for such run command call where the CMD does not need to get arguments
added on some conditional check you could avoid the intermediate variable, i.e.:

run_command([
    $ISCSIADM,
    ...,
]);

but no hard feelings, I kept it as is, this just stuck out to me.


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