Hi Honza,
On Aug 7, 2014 2:55 PM, "Jan Friesse" <jfriesse@xxxxxxxxxx> wrote:
>
> Jason
>
>
>
>> Hi Honza,
>>
>> I think I am clear with this patch after your explanation, thanks!
>>
>> But if there is a very simple qdevice implementation which voting is
>> not based on changed membership,but based on the current voting
>> result, can it simply ignore the feature of this patch by setting
>
>
> I'm not exactly sure what is such qdevice then good for...
>
>
>> timeout to 0 to keep on the old behavior? I'm afraid it can't any
>
>
> That's why I wrote *almost* same behavior
>
>
>> more. Because if set timeout to 0, qdevice_timer_fn() will be called
>> immediately, which result in us->flags being erased, thus, votequorum
>> lost the current voting result. Right?
>
>
> Right.
>
> But IF you want to use old result for some reason, you can keep default config as it is and in your qdevice just call poll with new ring id and old result right after receiving votequorum change. Timeout there should be almost minimal (from my test with testvotequorum2, it's really few milliseconds).
I agree with you. This should be the way that my use case adaptes to this patch to omit the waiting in sync process. So for my case, thers is no need for you to make patch to reverts new functionality by setting sync_timeout to 0.
>
> Anyway. I can make patch which reverts new functionality completely if sync_timeout is set to 0 (that's easy). But can you please explain me a little more your use case (at least to have something for commit message)?
My use case is a qdevice running in master_win mode. Normally, all qdevices always poll to votequorum in a constant time cycle(for example, 1sec), but only one master do cast vote. So after network partition or node down occured, votequorum can immediately find out the primary component by seeing which component includes the master. So now I mainly wonder what and how a qdevice can benifit from deciding to vote or not vote based on changed membership with the cost of letting sync process to wait the decision? Althrough it looks my use case is not a good qdevice implemented, but at least, it can totally omit the waiting in sync process.
>
> Honza
>
>
>>
>> On Wed, Aug 6, 2014 at 5:58 PM, Jan Friesse <jfriesse@xxxxxxxxxx> wrote:
>>>
>>> Jason,
>>>
>>>> Hi Honza,
>>>> Could you please explain this more detaily ? Why should corosync block
>>>> until it got poll from qdevice(or timeout)? Why not simply using the
>>>> information provided by the latest poll? For example, in master win mode,
>>>
>>>
>>> Because qdevice may decide to not vote based on changed membership. I
>>> will give you example:
>>>
>>> - Qdevice votes
>>> - membership change
>>> - sync
>>> - sync completed
>>> - Qdevice decides to not vote
>>>
>>> Now, between membership change and qdevice decision may be quite a long
>>> time when votequorum uses incorrect information. Patch simply prevents
>>> this race condition.
>>>
>>>> infomation about who is master is already on hand when network split
>>>> happen. So it can be used immediately to choose the primary component
>>>> without any delay. But the blocking method in this patch will introduce
>>>
>>>
>>> It has not too much to do with master...
>>>
>>>> delay on deciding primay component, which may cause upper level application
>>>> stop providing service in a longer time, doesn't it?
>>>
>>>
>>> It has again nothing to do with primary component. But yes, patch can
>>> cause upper level application to stop providing service for quite a long
>>> time (max 30 sec by default). That's why sync timeout is configurable
>>> (you can set 0 and you have almost old behavior) and why qdevice must be
>>> developed with this problem in mind. Meaning, qdevice must be as fast as
>>> possible.
>>>
>>> Did it explained your questions?
>>>
>>> Regards,
>>> Honza
>>>
>>>> On Aug 5, 2014 6:10 PM, "Jan Friesse" <jfriesse@xxxxxxxxxx> wrote:
>>>>
>>>>> If qdevice is registered a alive, corosync waits in sync phase until
>>>>> timeout expires or qdevice votes with correct nodeid parameter.
>>>>>
>>>>> This gives qdevice time to decide to vote or not undisturbed and without
>>>>> time hazard.
>>>>>
>>>>> Signed-off-by: Jan Friesse <jfriesse@xxxxxxxxxx>
>>>>> ---
>>>>> exec/votequorum.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
>>>>> 1 files changed, 43 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/exec/votequorum.c b/exec/votequorum.c
>>>>> index dd5bea7..7781077 100644
>>>>> --- a/exec/votequorum.c
>>>>> +++ b/exec/votequorum.c
>>>>> @@ -234,6 +234,8 @@ static corosync_timer_handle_t qdevice_timer;
>>>>> static int qdevice_timer_set = 0;
>>>>> static corosync_timer_handle_t last_man_standing_timer;
>>>>> static int last_man_standing_timer_set = 0;
>>>>> +static int sync_nodeinfo_sent = 0;
>>>>> +static int sync_wait_for_poll_or_timeout = 0;
>>>>>
>>>>> /*
>>>>> * Service Interfaces required by service_message_handler struct
>>>>> @@ -310,6 +312,8 @@ static int quorum_lib_init_fn (void *conn);
>>>>>
>>>>> static int quorum_lib_exit_fn (void *conn);
>>>>>
>>>>> +static void qdevice_timer_fn(void *arg);
>>>>> +
>>>>> static void message_handler_req_lib_votequorum_getinfo (void *conn,
>>>>> const void
>>>>> *message);
>>>>>
>>>>> @@ -2182,6 +2186,8 @@ static void votequorum_sync_init (
>>>>> ENTER();
>>>>>
>>>>> sync_in_progress = 1;
>>>>> + sync_nodeinfo_sent = 0;
>>>>> + sync_wait_for_poll_or_timeout = 0;
>>>>>
>>>>> if (member_list_entries > 1) {
>>>>> us->flags &= ~NODE_FLAGS_FIRST;
>>>>> @@ -2231,17 +2237,46 @@ static void votequorum_sync_init (
>>>>> quorum_members_entries = member_list_entries;
>>>>> memcpy(&quorum_ringid, ring_id, sizeof(*ring_id));
>>>>>
>>>>> + if (us->flags & NODE_FLAGS_QDEVICE_REGISTERED && us->flags &
>>>>> NODE_FLAGS_QDEVICE_ALIVE) {
>>>>> + /*
>>>>> + * Reset poll timer. Sync waiting is interrupted on valid
>>>>> qdevice poll or after timeout
>>>>> + */
>>>>> + if (qdevice_timer_set) {
>>>>> + corosync_api->timer_delete(qdevice_timer);
>>>>> + }
>>>>> + corosync_api->timer_add_duration((unsigned long
>>>>> long)qdevice_timeout*1000000, qdevice,
>>>>> + qdevice_timer_fn,
>>>>> &qdevice_timer);
>>>>> + qdevice_timer_set = 1;
>>>>> + sync_wait_for_poll_or_timeout = 1;
>>>>> +
>>>>> + log_printf(LOGSYS_LEVEL_INFO, "waiting for quorum device
>>>>> %s poll (but maximum for %u ms)",
>>>>> + qdevice_name, qdevice_timeout);
>>>>> + }
>>>>> +
>>>>> LEAVE();
>>>>> }
>>>>>
>>>>> static int votequorum_sync_process (void)
>>>>> {
>>>>> - votequorum_exec_send_nodeinfo(us->node_id);
>>>>> - votequorum_exec_send_nodeinfo(VOTEQUORUM_QDEVICE_NODEID);
>>>>> - if (strlen(qdevice_name)) {
>>>>> -
>>>>> votequorum_exec_send_qdevice_reg(VOTEQUORUM_QDEVICE_OPERATION_REGISTER,
>>>>> - qdevice_name);
>>>>> +
>>>>> + if (!sync_nodeinfo_sent) {
>>>>> + votequorum_exec_send_nodeinfo(us->node_id);
>>>>> + votequorum_exec_send_nodeinfo(VOTEQUORUM_QDEVICE_NODEID);
>>>>> + if (strlen(qdevice_name)) {
>>>>> +
>>>>> votequorum_exec_send_qdevice_reg(VOTEQUORUM_QDEVICE_OPERATION_REGISTER,
>>>>> + qdevice_name);
>>>>> + }
>>>>> + sync_nodeinfo_sent = 1;
>>>>> }
>>>>> +
>>>>> + if (us->flags & NODE_FLAGS_QDEVICE_REGISTERED &&
>>>>> sync_wait_for_poll_or_timeout) {
>>>>> + /*
>>>>> + * Waiting for qdevice to poll with new ringid or timeout
>>>>> + */
>>>>> +
>>>>> + return (-1);
>>>>> + }
>>>>> +
>>>>> return 0;
>>>>> }
>>>>>
>>>>> @@ -2336,6 +2371,7 @@ static void qdevice_timer_fn(void *arg)
>>>>> votequorum_exec_send_nodeinfo(us->node_id);
>>>>>
>>>>> qdevice_timer_set = 0;
>>>>> + sync_wait_for_poll_or_timeout = 0;
>>>>>
>>>>> LEAVE();
>>>>> }
>>>>> @@ -2675,6 +2711,7 @@ static void
>>>>> message_handler_req_lib_votequorum_qdevice_unregister (void *conn,
>>>>> if (qdevice_timer_set) {
>>>>> corosync_api->timer_delete(qdevice_timer);
>>>>> qdevice_timer_set = 0;
>>>>> + sync_wait_for_poll_or_timeout = 0;
>>>>> }
>>>>> us->flags &= ~NODE_FLAGS_QDEVICE_REGISTERED;
>>>>> us->flags &= ~NODE_FLAGS_QDEVICE_ALIVE;
>>>>> @@ -2777,6 +2814,7 @@ static void
>>>>> message_handler_req_lib_votequorum_qdevice_poll (void *conn,
>>>>> corosync_api->timer_add_duration((unsigned long
>>>>> long)qdevice_timeout*1000000, qdevice,
>>>>> qdevice_timer_fn,
>>>>> &qdevice_timer);
>>>>> qdevice_timer_set = 1;
>>>>> + sync_wait_for_poll_or_timeout = 0;
>>>>> } else {
>>>>> error = CS_ERR_NOT_EXIST;
>>>>> }
>>>>> --
>>>>> 1.7.1
>>>>>
>>>>> _______________________________________________
>>>>> discuss mailing list
>>>>> discuss@xxxxxxxxxxxx
>>>>> http://lists.corosync.org/mailman/listinfo/discuss
>>>>>
>>>>
>>>
>>
>>
>>
>
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