Re: [Qemu-devel] [PATCH v3 00/11] NBD reconnect

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Hi all.

before v4 realization, I'd like to discuss some questions.

Our proposal for v4 is the following:

1. don't reconnect on nbd_open. So, on open we do only one connect 
attempt, and if it fails, open fails.
2. don't configure timeout between attempts. instead do the following:
     1s timeout, then 2s, then 4, 8, 16, and then always 16 until success
3. configure only time, after disconnect, during which requests are 
paused (and after this time, if not connected, they will return EIO). Or 
not configure it for now, make a default of 5 minutes.

Any ideas?


09.06.2018 18:32, Vladimir Sementsov-Ogievskiy wrote:
> Hi all.
>
> Here is NBD reconnect.
> The feature realized inside nbd-client driver and works as follows:
>
> There are two parameters: reconnect-attempts and reconnect-timeout.
> So, we will try to reconnect in case of initial connection failed or
> in case of connection lost. All current and new io operations will wait
> until we make reconnect-attempts tries to reconnect. After this, all
> requests will fail with EIO, but we will continue trying to reconnect.
>
> v3:
> 06: fix build error in function 'nbd_co_send_request':
>       error: 'i' may be used uninitialized in this function
>
> v2 notes:
> Here is v2 of NBD reconnect, but it is very very different from v1, so,
> forget about v1.
> The series includes my "NBD reconnect: preliminary refactoring", with
> changes in 05: leave asserts (Eric).
>
> Vladimir Sementsov-Ogievskiy (11):
>    block/nbd-client: split channel errors from export errors
>    block/nbd: move connection code from block/nbd to block/nbd-client
>    block/nbd-client: split connection from initialization
>    block/nbd-client: fix nbd_reply_chunk_iter_receive
>    block/nbd-client: don't check ioc
>    block/nbd-client: move from quit to state
>    block/nbd-client: rename read_reply_co to connection_co
>    block/nbd-client: move connecting to connection_co
>    block/nbd: add cmdline and qapi parameters for nbd reconnect
>    block/nbd-client: nbd reconnect
>    iotests: test nbd reconnect
>
>   qapi/block-core.json          |  12 +-
>   block/nbd-client.h            |  23 ++-
>   block/nbd-client.c            | 429 ++++++++++++++++++++++++++++++------------
>   block/nbd.c                   |  61 +++---
>   tests/qemu-iotests/220        |  68 +++++++
>   tests/qemu-iotests/220.out    |   7 +
>   tests/qemu-iotests/group      |   1 +
>   tests/qemu-iotests/iotests.py |   4 +
>   8 files changed, 445 insertions(+), 160 deletions(-)
>   create mode 100755 tests/qemu-iotests/220
>   create mode 100644 tests/qemu-iotests/220.out
>


-- 
Best regards,
Vladimir