I guess the revert SQL work in just on the roadmap.
But shading-sphere can analyze the SQL do the shading work.
Willem Jiang
Twitter: willemjiang
Weibo: 姜宁willem
On Thu, Jun 7, 2018 at 11:11 AM, Zheng Feng <zh.f...@gmail.com> wrote:
> Can you point out to me the codes related to the SQL convert in the
> sharding-sphere ?
>
> 2018-06-07 8:10 GMT+08:00 Willem Jiang <willem.ji...@gmail.com>:
>
> > Hi，
> >
> > Current Saga implementation cannot guarantee the data isolation. I guess
> > we need to leverage the DB to provide the version of data, and revert it
> > to the states before the transaction.
> >
> > Maybe we need hold T2 before the T1 is finished, otherwise it really hard
> > to tell if the original states is x=1 or x=0.
> >
> > It's kind of trade off, If we want to strong consistent we have to use
> > lock to do it, otherwise we need do introduce the semantic lock from the
> > application such as the credit limits.
> >
> > Let's keep up the discussion and try to find a good way to solve the
> > distribution transaction problems.
> >
> >
> >
> > Willem Jiang
> >
> > Twitter: willemjiang
> > Weibo: 姜宁willem
> >
> > On Thu, Jun 7, 2018 at 12:33 AM, Zheng Feng <zh.f...@gmail.com> wrote:
> >
> > > Hi Zhang Liang,
> > >
> > > It could be great to integrate the saga and the sharding-sphere. I'm
> > trying
> > > to understand the SQL convert and the data snapshot.
> > > So I suppose that we have the simple data set just like {id = 1, x = 0}
> > and
> > > we have the updateX service to update the X
> > >
> > > func updateX ( int x, int i ) {
> > > executeSQL("UPDATE x = $x WHERE id = $i", x, i);
> > > }
> > >
> > > T1: T2:
> > > saga_start(); saga_start();
> > > updateX(1, 1); updateX(2, 1);
> > > call_other_service(); call_other_service();
> > > saga_end(); saga_end();
> > >
> > > So after the T1 runs, the snapshot data should be {id = 1, x = 1} and
> the
> > > convertSQL should be "UPDATE x = 0 WHERE id = 1", is it right ?
> > > Now we have the other T2 to run after T1, the snapshot data should be
> > {id =
> > > 1, x = 2} and convertSQL should be "UPDATE x= 1 WHERE id = 1" ?
> > >
> > > If the Alpha (Saga coordinator) decides to compensate the T1 when the
> > > call_other_service() throws exception, will we call the converSQL to
> set
> > x
> > > = 0 ?
> > >
> > > Thanks,
> > > Zheng Feng
> > >
> > > 2018-06-06 15:51 GMT+08:00 Liang Zhang <zhangli...@apache.org>:
> > >
> > > > Hi Willem Jiang,
> > > >
> > > > I fully agree to keep Omega as simple as possible.
> > > >
> > > > Sharding-Sphere can ask transaction id from Saga, then save SQL and
> > > > snapshot into Sharding-Sphere local db. Saga just as a transaction
> > engine
> > > > to determine and notify Sharding-Sphere when to forward(retry) and
> > > > backward(compensate).
> > > >
> > > > Best regrads,
> > > >
> > > > Zhang Liang
> > > >
> > > >
> > > > On 2018/06/06 06:50:31, Willem Jiang <willem.ji...@gmail.com> wrote:
> > > > > Hi Zhangliang，
> > > > >
> > > > > It's great that you are interesting about the Saga project.
> > > > > Please check out my comments in line.
> > > > >
> > > > >
> > > > > Willem Jiang
> > > > >
> > > > > Twitter: willemjiang
> > > > > Weibo: 姜宁willem
> > > > >
> > > > > On Wed, Jun 6, 2018 at 12:21 PM, zhangli...@apache.org <
> > > > > zhangli...@apache.org> wrote:
> > > > >
> > > > > > Hello servicecomb devs,
> > > > > >
> > > > > > I want discuss for how to integrate with saga and
> sharding-sphere.
> > > > > >
> > > > > > 1. Split saga as service scope and RDB scope. Service scope still
> > use
> > > > > > annotation to associate compensation method, RDB scope can
> generate
> > > > > > reverted SQL and data snapshot automatically. Alpha can use
> revert
> > > SQL
> > > > and
> > > > > > previous data snapshot to compensate automatically, do not need
> end
> > > > users
> > > > > > provide additional cancel method.
> > > > > >
> > > > >
> > > > > Current Saga doesn't touch the DB layer, I think we need to do
> some
> > > work
> > > > > on the Omega.
> > > > > Maybe we need to add a common layer handle the common co-ordinate
> > > events,
> > > > > and sharding-sphere
> > > > > could do some implementation on the data layer. In this way
> > > > > sharding-sphere could reuse the transaction
> > > > > co-ordinate feature here.
> > > > >
> > > > > BTW, for other who don't know sharding-sphere, you may check out
> the
> > > > > github project[1] here.
> > > > >
> > > > > [1] https://github.com/sharding-sphere/sharding-sphere
> > > > >
> > > > > >
> > > > > > 2. Sharding-Sphere can generate reverted SQL and data snapshot:
> > > > > > INSERT SQL will revert to DELETE SQL with primary key and
> sharding
> > > key.
> > > > > > UPDATE/DELETE SQL will generate SELECT SQL and save data snapshot
> > > > first,
> > > > > > and then use UPDATE OR INSERT to compensate data.
> > > > > > Saga may need to change data structure for receive SQL and data
> > > > snapshot,
> > > > > > maybe use json format to save on payload field is a good idea.
> > > > >
> > > > >
> > > > > I think we need to go through the events structure[2], but if the
> > Omega
> > > > > hold the reference,
> > > > > Alpha just need to send the revert command to Omega.
> > > > > If the Sharding-Sphere can store the SQL and revert SQL into the
> DB,
> > > > > I don't think Alpha need to know the SQL information.
> > > > >
> > > > > [2]
> > > > > https://github.com/apache/incubator-servicecomb-saga/blob/
> > > > ce71ab73ae80bc90ba59fe9b038f134fef9426b1/omega/omega-
> > > > transaction/src/main/java/org/apache/servicecomb/saga/omega/
> > > > transaction/TxEvent.java
> > > > >
> > > > >
> > > > > >
> > > > >
> > > > >
> > > > > > 3. Sharding-Sphere use guava's eventBus to post DML event.
> > > > Sharding-Sphere
> > > > > > plan to add 2 listeners, one is just save reverted SQL and
> > snapshot,
> > > > other
> > > > > > is for send correct info to Omega.
> > > > > >
> > > > >
> > > > > I think we can keep Omega as simple as possible, maybe the event
> with
> > > > > transaction id
> > > > > could be enough.
> > > > >
> > > > >
> > > > > >
> > > > > > 4. For version of data modification, just guarantee by end user
> > right
> > > > now,
> > > > > > in future we can consider about use additional version field or
> > > shadow
> > > > > > table to handle it.
> > > > > >
> > > > >
> > > > > This is the hardest part which bother me a lot. For the Saga
> service,
> > > we
> > > > > cannot guarantee
> > > > > the data isolation. The user need to do some addition work on the
> > > > > application layer to
> > > > > minimize the side effect.
> > > > > Maybe we should spend some time to check the project omid[3]
> > > > >
> > > > > [3]https://github.com/apache/incubator-omid/
> > > > >
> > > > >
> > > > >
> > > > > >
> > > > > > Best regards,
> > > > > > Zhang Liang
> > > > > >
> > > > >
> > > >
> > >
> >
>
