31.07.2018 20:30, Vladimir Sementsov-Ogievskiy wrote:
> Implement reconnect. To achieve this:
>
> 1. add new modes:
> connecting-wait: means, that reconnecting is in progress, and there
> were small number of reconnect attempts, so all requests are
> waiting for the connection.
> connecting-nowait: reconnecting is in progress, there were a lot of
> attempts of reconnect, all requests will return errors.
>
> two old modes are used too:
> connected: normal state
> quit: exiting after fatal error or on close
>
> Possible transitions are:
>
> * -> quit
> connecting-* -> connected
> connecting-wait -> connecting-nowait (transition is done after
> reconnect-delay seconds in connecting-wait mode)
> connected -> connecting-wait
>
> 2. Implement reconnect in connection_co. So, in connecting-* mode,
> connection_co, tries to reconnect unlimited times.
>
> 3. Retry nbd queries on channel error, if we are in connecting-wait
> state.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> block/nbd-client.h | 4 +
> block/nbd-client.c | 304
> +++++++++++++++++++++++++++++++++++++++++++----------
> 2 files changed, 255 insertions(+), 53 deletions(-)
>
> diff --git a/block/nbd-client.h b/block/nbd-client.h
> index ef8a6a9239..52e4ec66be 100644
> --- a/block/nbd-client.h
> +++ b/block/nbd-client.h
> @@ -40,6 +40,10 @@ typedef struct NBDClientSession {
> Coroutine *connection_co;
> int in_flight;
> NBDClientState state;
> + bool receiving;
> + int connect_status;
> + Error *connect_err;
> + bool wait_in_flight;
>
> NBDClientRequest requests[MAX_NBD_REQUESTS];
> NBDReply reply;
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index 41e6e6e702..b09907096d 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -34,10 +34,26 @@
> #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ (uint64_t)(intptr_t)(bs))
> #define INDEX_TO_HANDLE(bs, index) ((index) ^ (uint64_t)(intptr_t)(bs))
[...]
> +static coroutine_fn void nbd_reconnect_attempt(NBDConnection *con)
> +{
> + NBDClientSession *s = nbd_get_client_session(con->bs);
> + Error *local_err = NULL;
> +
> + assert(nbd_client_connecting(s));
> +
> + /* Wait completion of all in-flight requests */
> +
> + qemu_co_mutex_lock(&s->send_mutex);
> +
> + while (s->in_flight > 0) {
> + qemu_co_mutex_unlock(&s->send_mutex);
> + nbd_recv_coroutines_wake_all(s);
> + s->wait_in_flight = true;
> + qemu_coroutine_yield();
> + s->wait_in_flight = false;
> + qemu_co_mutex_lock(&s->send_mutex);
> + }
> +
> + qemu_co_mutex_unlock(&s->send_mutex);
> +
> + /* Now we are sure, that nobody accessing the channel now and nobody
> + * will try to access the channel, until we set state to CONNECTED
> + */
> +
> + /* Finalize previous connection if any */
> + if (s->ioc) {
> + nbd_client_detach_aio_context(con->bs);
> + object_unref(OBJECT(s->sioc));
> + s->sioc = NULL;
> + object_unref(OBJECT(s->ioc));
> + s->ioc = NULL;
> + }
> +
> + s->connect_status = nbd_client_connect(con->bs, con->saddr,
> + con->export, con->tlscreds,
> + con->hostname,
> con->x_dirty_bitmap,
> + &local_err);
> + error_free(s->connect_err);
> + s->connect_err = NULL;
> + error_propagate(&s->connect_err, local_err);
> + local_err = NULL;
>
> - nbd_client_detach_aio_context(bs);
> - object_unref(OBJECT(client->sioc));
> - client->sioc = NULL;
> - object_unref(OBJECT(client->ioc));
> - client->ioc = NULL;
> + if (s->connect_status == -EINVAL) {
> + /* Protocol error or something like this, go to NBD_CLIENT_QUIT */
> + nbd_channel_error(s, s->connect_status);
> + return;
Unfortunately, nbd_client_connect returns -EINVAL for io errors instead
of -EIO. And it is not trivial to fix it. So, this if{} should be removed.
> + }
> +
> + if (s->connect_status < 0) {
> + /* failed attempt */
> + return;
> + }
> +
> + /* successfully connected */
> + s->state = NBD_CLIENT_CONNECTED;
> + qemu_co_queue_restart_all(&s->free_sema);
> +}
> +
--
Best regards,
Vladimir
