[Libguestfs] [PATCH nbdkit 0/2] Add new retry filter.

[Martin Kletzander]

On Thu, Sep 19, 2019 at 01:47:45PM +0200, Nenad Peric wrote:
>A theoretical way to test this against any other protocol is to have a
>firewall rule which can be triggered locally which just drops the traffic
>and then re-enables the traffic in a while (short or long, can be
>decided/tweaked).
>This way, there is no need to think about which protocol is used, when we
>kill the connectivity.
>The only consideration could probably be that the dropped connections would
>cover only the ports we need.
>To reduce the size of the hammer :)
>

Good idea, you just need to keep in mind that the underlying protocols might
have their own keep-alive methods, which should be removed or at least minimised
when testing this.

>
>*Nenad Perić*
>
>PRINCIPAL SOFTWARE ENGINEER
>
>Red Hat - Migration Engineering
>
>nenad at redhat.com
>
><http://redhat.com>
>
>
>On Thu, Sep 19, 2019 at 1:34 PM Richard W.M. Jones <rjones at redhat.com>
>wrote:
>
>> This is a retry filter implementation as outlined here:
>> https://www.redhat.com/archives/libguestfs/2019-September/msg00167.html
>>
>> It is only lightly tested.  One way to test it is to try an SSH copy
>> (see the commit message for patch 2/2), and in the middle of the copy
>> kill the per-connection sshd on the remote machine.  You will see that
>> the copy recovers after a few seconds.  Add the nbdkit -v option to
>> see some useful messages from the filter:
>>
>>   ...
>>   nbdkit: ssh[1]: debug: ssh: pread count=2097152 offset=216006656
>>   nbdkit: ssh[1]: error: read failed: Socket error: Connection reset by
>> peer (-1)
>>   nbdkit: ssh[1]: debug: retry 1: original errno = 5
>>   nbdkit: ssh[1]: debug: waiting 2 seconds before retrying
>>   nbdkit: ssh[1]: debug: ssh: reopen
>>   nbdkit: ssh[1]: debug: close
>>   nbdkit: ssh[1]: error: cannot close file: Socket error: Connection reset
>> by peer
>>   nbdkit: ssh[1]: debug: ssh: open readonly=0
>>   nbdkit: ssh[1]: debug: opened libssh handle
>>   nbdkit: ssh[1]: debug: ssh: pread count=2097152 offset=216006656
>>   ...
>>
>> It really needs an actual test, which is tricky to implement.  My
>> thinking currently is that a custom (sh) plugin is the way to go, but
>> it would also be nice to test curl/ssh/vddk with this filter -- if
>> anyone has any suggestions on how to do that ...
>>
>> This patch will probably conflict with Eric's series here:
>> https://www.redhat.com/archives/libguestfs/2019-September/msg00180.html
>> but that shouldn't be too hard to fix up.
>>
>> Rich.
>>
>>
>>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libguestfs/attachments/20190919/6ccefff1/attachment.sig>