zookeeper-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Alexander Shraer <shra...@gmail.com>
Subject Re: RE: Question about the two-phrase commit
Date Wed, 07 Jan 2015 05:57:47 GMT
This is one of the differences of consensus from two phase commit - there
is no "nack" in consensus. Followers ack every proposal.


On Tue, Jan 6, 2015 at 9:44 PM, bit1129@163.com <bit1129@163.com> wrote:

> Hi,Alex,
>
> I still have following questions.
> 1. When the leader asks the followers to ack the proposal, what are the
> common cases that the follower  would not ack the proposal. If the follower
> can't ack the proposal, will the follower explicitly tell the leader that
> it can't ack?
> 2. If follower A acks, while the others don't. A will wait for the commit
> request from the leader?  What if the leader never sends out the commit
> request? How does A know that the write fail?
> 3. If follower A doesn't receive the commit request, then A can't tell the
> client that the write has successfully done. what will A tell the client?
>
> Thanks !!
>
>
>
>
> bit1129@163.com
>
> From: Ibrahim
> Date: 2015-01-07 08:38
> To: zookeeper-user
> Subject: RE: Question about the two-phrase commit
> Thank you Alexander. I get it
>
> Ibrahim
>
> From: Alexander Shraer-2 [via zookeeper-user] [mailto:
> ml-node+s578899n7580745h19@n2.nabble.com]
> Sent: Wednesday, January 07, 2015 12:29 ص
> To: Ibrahim El-sanosi (PGR)
> Subject: Re: Question about the two-phrase commit
>
> Edward is totally right - if the operation hasn't been acked by a quorum
> then whether or not it is lost depends on failures (both server failures
> and network failures) as well as latencies.
>
> The leader doesn't have to re-broadcast everything - when a follower
> connects to a leader it tells him whats the last operation in its log and
> the leader only needs to send the missing log suffix or a snapshot + suffix
> if the follower is really behind.
>
> The leader indeed doesn't know which operations were acked by a quorum. The
> operations that weren't acked are always some suffix of the log
> (potentially empty).
>
> On Tue, Jan 6, 2015 at 4:19 PM, Ibrahim <[hidden
> email]</user/SendEmail.jtp?type=node&node=7580745&i=0>>
> wrote:
>
> > Thank you Edward for replaying.
> >
> > In my opinion, your first case can’t happen, because the election
> > mechanism will elect the node that has the latest transaction  (zxid)
> seen.
> > In this case, it will be only your second case is correct, unless the
> node
> > that has latest transaction crashes forever.
> >
> > Ibrahim
> > From: Edward Carter [via zookeeper-user] [mailto:
> > [hidden email]</user/SendEmail.jtp?type=node&node=7580745&i=1>]
> > Sent: Tuesday, January 06, 2015 11:53 م
> > To: Ibrahim El-sanosi (PGR)
> > Subject: Re: Question about the two-phrase commit
> >
> > If an operation is logged to disk on a minority of servers, then what
> > happens on restart depends on which server wins the leader election.
> Since
> > the new operation is on a minority, depending on network conditions, a
> > server that did *not* log the operation might win the leader election.
> In
> > this case, the operation will be discarded.  If a server that *did* log
> the
> > operation wins the leader election (as would be the case in the absence
> of
> > network or latency issues), then the operation will be propagated to the
> > remaining servers in the ensemble.
> >
> > Edward
> >
> > On Jan 6, 2015, at 3:42 PM, Ibrahim <[hidden
> > email]</user/SendEmail.jtp?type=node&node=7580741&i=0>> wrote:
> >
> > > Hi Alexander,
> > >
> > > So, you meant that if there is operation loged to the disk but it
> hasn't
> > got
> > > enough majority, then if the zookeeper servers restart, the new leader
> > will
> > > re-broadcast the loged operation again to the followers to commit that
> > > operation.
> > >
> > > Does above what you meant by (NEWLEADER message acts as the accept and
> > > UPTODATE message acts as commit).
> > >
> > > Am I right?
> > >
> > > Thank you
> > >
> > > Ibrahim
> > >
> > >
> > >
> > > --
> > > View this message in context:
> >
> https://urldefense.proofpoint.com/v1/url?u=http://zookeeper-user.578899.n2.nabble.com/Question-about-the-two-phrase-commit-tp7580725p7580739.html&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=09h%2FR60Z1NzKuJcTv9DkEw%3D%3D%0A&m=T7mEM8unY7tsVTbHXoSOqvwXEZEBCs8%2BRWl0cT03ruo%3D%0A&s=bcce5c88300c51126777473143b3f560542cf1c5699b33283f888e27ed41529f
> > > Sent from the zookeeper-user mailing list archive at Nabble.com.
> >
> >
> > ________________________________
> > If you reply to this email, your message will be added to the discussion
> > below:
> >
> >
> http://zookeeper-user.578899.n2.nabble.com/Question-about-the-two-phrase-commit-tp7580725p7580741.html
> > To unsubscribe from Question about the two-phrase commit, click here<
> > >.
> > NAML<
> >
> http://zookeeper-user.578899.n2.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml
> > >
> >
> >
> >
> >
> > --
> > View this message in context:
> >
> http://zookeeper-user.578899.n2.nabble.com/Question-about-the-two-phrase-commit-tp7580725p7580743.html
> > Sent from the zookeeper-user mailing list archive at Nabble.com.
> >
>
> ________________________________
> If you reply to this email, your message will be added to the discussion
> below:
>
> http://zookeeper-user.578899.n2.nabble.com/Question-about-the-two-phrase-commit-tp7580725p7580745.html
> To unsubscribe from Question about the two-phrase commit, click here<
> http://zookeeper-user.578899.n2.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=7580725&code=aS5zLmVsLXNhbm9zaUBuZXdjYXN0bGUuYWMudWt8NzU4MDcyNXw1NTE4MjI0Njk=
> >.
> NAML<
> http://zookeeper-user.578899.n2.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml
> >
>
>
>
>
> --
> View this message in context:
> http://zookeeper-user.578899.n2.nabble.com/Question-about-the-two-phrase-commit-tp7580725p7580746.html
> Sent from the zookeeper-user mailing list archive at Nabble.com.
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message