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From Vladimir Ozerov <voze...@gridgain.com>
Subject Re: Thin client: transactions support
Date Wed, 27 Mar 2019 08:49:55 GMT
Hi Alex,

My comments was only about the protocol. Getting current info about
transaction should be handled by the client itself. It is not protocl's
concern. Same about other APIs and behavior in case another transaction is
attempted from the same thread.

Putting protocol aside, transaction support is complicated matter. I would
propose to route through IEP and wide community discussion. We need to
review API and semantics very carefully, taking SUSPEND/RESUME in count.
Also I do not see how we support client transactions efficiently without
decoupling transactions from threads on the server side first. Because
without it you will need a dedicated server thread for every client's
transaction which is slow and may even crash the server.

Vladimir.

On Wed, Mar 27, 2019 at 11:44 AM Alex Plehanov <plehanov.alex@gmail.com>
wrote:

> Vladimir, what if we want to get current transaction info (tx() method)?
>
> Does close() method mapped to TX_END(rollback)?
>
> For example, this code:
>
> try(tx = txStart()) {
>     tx.commit();
> }
>
> Will produce:
> TX_START
> TX_END(commit)
> TX_END(rollback)
>
> Am I understand you right?
>
> About xid. There is yet another proposal. Use some unique per connection id
> (integer, simple counter) for identifying the transaction on
> commit/rollback message. The client gets this id from the server with
> transaction info and sends it back to the server when trying to
> commit/rollback transaction. This id is not shown to users. But also we can
> pass from server to client real transaction id (xid) with transaction info
> for diagnostic purposes.
>
> And one more question: what should we do if the client starts a new
> transaction without ending the old one? Should we end the old transaction
> implicitly (rollback) or throw an exception to the client? In my opinion,
> the first option is better. For example, if we got a previously used
> connection from the connection pool, we should not worry about any
> uncompleted transaction started by the previous user of this connection.
>
> ср, 27 мар. 2019 г. в 11:02, Vladimir Ozerov <vozerov@gridgain.com>:
>
> > As far as SUSPEND/RESUME/SAVEPOINT - we do not support them yet, and
> adding
> > them in future should not conflict with simple START/END infrastructure.
> >
> > On Wed, Mar 27, 2019 at 11:00 AM Vladimir Ozerov <vozerov@gridgain.com>
> > wrote:
> >
> > > Hi Alex,
> > >
> > > I am not sure we need 5 commands. Wouldn't it be enough to have only
> two?
> > >
> > > START - accepts optional parameters, returns transaction info
> > > END - provides commit flag, returns void
> > >
> > > Vladimir.
> > >
> > > On Wed, Mar 27, 2019 at 8:26 AM Alex Plehanov <plehanov.alex@gmail.com
> >
> > > wrote:
> > >
> > >> Sergey, yes, the close is something like silent rollback. But we can
> > >> also implement this on the client side, just using rollback and
> ignoring
> > >> errors in the response.
> > >>
> > >> ср, 27 мар. 2019 г. в 00:04, Sergey Kozlov <skozlov@gridgain.com>:
> > >>
> > >> > Nikolay
> > >> >
> > >> > Am I correctly understand you points:
> > >> >
> > >> >    - close: rollback
> > >> >    - commit, close: do nothing
> > >> >    - rollback, close: do what? (I suppose nothing)
> > >> >
> > >> > Also you assume that after commit/rollback we may need to free some
> > >> > resources on server node(s)or just do on client started TX?
> > >> >
> > >> >
> > >> >
> > >> > On Tue, Mar 26, 2019 at 10:41 PM Alex Plehanov <
> > plehanov.alex@gmail.com
> > >> >
> > >> > wrote:
> > >> >
> > >> > > Sergey, we have the close() method in the thick client, it's
> > behavior
> > >> is
> > >> > > slightly different than rollback() method (it should rollback
if
> the
> > >> > > transaction is not committed and do nothing if the transaction
is
> > >> already
> > >> > > committed). I think we should support try-with-resource semantics
> in
> > >> the
> > >> > > thin client and OP_TX_CLOSE will be useful here.
> > >> > >
> > >> > > Nikolay, suspend/resume didn't work yet for pessimistic
> > transactions.
> > >> > Also,
> > >> > > the main goal of suspend/resume operations is to support
> transaction
> > >> > > passing between threads. In the thin client, the transaction
is
> > bound
> > >> to
> > >> > > the client connection, not client thread. I think passing a
> > >> transaction
> > >> > > between different client connections is not a very useful case.
> > >> > >
> > >> > > вт, 26 мар. 2019 г. в 22:17, Nikolay Izhikov <nizhikov@apache.org
> >:
> > >> > >
> > >> > > > Hello, Alex.
> > >> > > >
> > >> > > > We also have suspend and resume operations.
> > >> > > > I think we should support them
> > >> > > >
> > >> > > > вт, 26 марта 2019 г., 22:07 Sergey Kozlov <skozlov@gridgain.com
> >:
> > >> > > >
> > >> > > > > Hi
> > >> > > > >
> > >> > > > > Looks like I missed something but why we need OP_TX_CLOSE
> > >> operation?
> > >> > > > >
> > >> > > > > Also I suggest to reserve a code for SAVEPOINT operation
which
> > >> very
> > >> > > > useful
> > >> > > > > to understand where transaction has been rolled back
> > >> > > > >
> > >> > > > > On Tue, Mar 26, 2019 at 6:07 PM Alex Plehanov <
> > >> > plehanov.alex@gmail.com
> > >> > > >
> > >> > > > > wrote:
> > >> > > > >
> > >> > > > > > Hello Igniters!
> > >> > > > > >
> > >> > > > > > I want to pick up the ticket IGNITE-7369 and add
> transactions
> > >> > support
> > >> > > > to
> > >> > > > > > our thin client implementation.
> > >> > > > > > I've looked at our current implementation and
have some
> > >> proposals
> > >> > to
> > >> > > > > > support transactions:
> > >> > > > > >
> > >> > > > > > Add new operations to thin client protocol:
> > >> > > > > >
> > >> > > > > >     OP_TX_GET, 4000, Get current transaction for
client
> > >> connection
> > >> > > > > >     OP_TX_START, 4001, Start a new transaction
> > >> > > > > >     OP_TX_COMMIT, 4002, Commit transaction
> > >> > > > > >     OP_TX_ROLLBACK, 4003, Rollback transaction
> > >> > > > > >     OP_TX_CLOSE, 4004, Close transaction
> > >> > > > > >
> > >> > > > > > From the client side (java) new interfaces will
be added:
> > >> > > > > >
> > >> > > > > > public interface ClientTransactions {
> > >> > > > > >     public ClientTransaction txStart();
> > >> > > > > >     public ClientTransaction txStart(TransactionConcurrency
> > >> > > > concurrency,
> > >> > > > > > TransactionIsolation isolation);
> > >> > > > > >     public ClientTransaction txStart(TransactionConcurrency
> > >> > > > concurrency,
> > >> > > > > > TransactionIsolation isolation, long timeout,
int txSize);
> > >> > > > > >     public ClientTransaction tx(); // Get current
connection
> > >> > > > transaction
> > >> > > > > >     public ClientTransactions withLabel(String
lb);
> > >> > > > > > }
> > >> > > > > >
> > >> > > > > > public interface ClientTransaction extends AutoCloseable
{
> > >> > > > > >     public IgniteUuid xid(); // Do we need it?
> > >> > > > > >     public TransactionIsolation isolation();
> > >> > > > > >     public TransactionConcurrency concurrency();
> > >> > > > > >     public long timeout();
> > >> > > > > >     public String label();
> > >> > > > > >
> > >> > > > > >     public void commit();
> > >> > > > > >     public void rollback();
> > >> > > > > >     public void close();
> > >> > > > > > }
> > >> > > > > >
> > >> > > > > > From the server side, I think as a first step
(while
> > >> transactions
> > >> > > > > > suspend/resume is not fully implemented) we can
use the same
> > >> > approach
> > >> > > > as
> > >> > > > > > for JDBC: add a new worker to each ClientRequestHandler
and
> > >> process
> > >> > > > > > requests by this worker if the transaction is
started
> > >> explicitly.
> > >> > > > > > ClientRequestHandler is bound to client connection,
so there
> > >> will
> > >> > be
> > >> > > > 1:1
> > >> > > > > > relation between client connection and thread,
which process
> > >> > > operations
> > >> > > > > in
> > >> > > > > > a transaction.
> > >> > > > > >
> > >> > > > > > Also, there is a couple of issues I want to discuss:
> > >> > > > > >
> > >> > > > > > We have overloaded method txStart with a different
set of
> > >> > arguments.
> > >> > > > Some
> > >> > > > > > of the arguments may be missing. To pass arguments
with
> > >> OP_TX_START
> > >> > > > > > operation we have the next options:
> > >> > > > > >  * Serialize full set of arguments and use some
value for
> > >> missing
> > >> > > > > > arguments. For example -1 for int/long types and
null for
> > string
> > >> > > type.
> > >> > > > We
> > >> > > > > > can't use 0 for int/long types since 0 it's a
valid value
> for
> > >> > > > > concurrency,
> > >> > > > > > isolation and timeout arguments.
> > >> > > > > >  * Serialize arguments as a collection of property-value
> pairs
> > >> > (like
> > >> > > > it's
> > >> > > > > > implemented now for CacheConfiguration). In this
case only
> > >> > explicitly
> > >> > > > > > provided arguments will be serialized.
> > >> > > > > > Which way is better? The simplest solution is
to use the
> first
> > >> > option
> > >> > > > > and I
> > >> > > > > > want to use it if there were no objections.
> > >> > > > > >
> > >> > > > > > Do we need transaction id (xid) on the client
side?
> > >> > > > > > If yes, we can pass xid along with OP_TX_COMMIT,
> > OP_TX_ROLLBACK,
> > >> > > > > > OP_TX_CLOSE operations back to the server and
do additional
> > >> check
> > >> > on
> > >> > > > the
> > >> > > > > > server side (current transaction id for connection
==
> > >> transaction
> > >> > id
> > >> > > > > passed
> > >> > > > > > from client side). This, perhaps, will protect
clients
> against
> > >> some
> > >> > > > > errors
> > >> > > > > > (for example when client try to commit outdated
> transaction).
> > >> But
> > >> > > > > > currently, we don't have data type IgniteUuid
in thin client
> > >> > > protocol.
> > >> > > > Do
> > >> > > > > > we need to add it too?
> > >> > > > > > Also, we can pass xid as a string just to inform
the client
> > and
> > >> do
> > >> > > not
> > >> > > > > pass
> > >> > > > > > it back to the server with commit/rollback operation.
> > >> > > > > > Or not to pass xid at all (.NET thick client works
this way
> as
> > >> far
> > >> > > as I
> > >> > > > > > know).
> > >> > > > > >
> > >> > > > > > What do you think?
> > >> > > > > >
> > >> > > > > > ср, 7 мар. 2018 г. в 16:22, Vladimir Ozerov
<
> > >> vozerov@gridgain.com
> > >> > >:
> > >> > > > > >
> > >> > > > > > > We already have transactions support in JDBC
driver in TX
> > SQL
> > >> > > branch
> > >> > > > > > > (ignite-4191). Currently it is implemented
through
> separate
> > >> > thread,
> > >> > > > > which
> > >> > > > > > > is not that efficient. Ideally we need to
finish
> decoupling
> > >> > > > > transactions
> > >> > > > > > > from threads. But alternatively we can change
the logic on
> > >> how we
> > >> > > > > assign
> > >> > > > > > > thread ID to specific transaction and "impersonate"
thin
> > >> client
> > >> > > > worker
> > >> > > > > > > threads when serving requests from multiple
users.
> > >> > > > > > >
> > >> > > > > > >
> > >> > > > > > >
> > >> > > > > > > On Tue, Mar 6, 2018 at 10:01 PM, Denis Magda
<
> > >> dmagda@apache.org>
> > >> > > > > wrote:
> > >> > > > > > >
> > >> > > > > > > > Here is an original discussion with
a reference to the
> > JIRA
> > >> > > ticket:
> > >> > > > > > > > http://apache-ignite-developers.2346864.n4.nabble.
> > >> > > > > > > >
> > com/Re-Transaction-operations-using-the-Ignite-Thin-Client-
> > >> > > > > > > > Protocol-td25914.html
> > >> > > > > > > >
> > >> > > > > > > > --
> > >> > > > > > > > Denis
> > >> > > > > > > >
> > >> > > > > > > > On Tue, Mar 6, 2018 at 9:18 AM, Dmitriy
Setrakyan <
> > >> > > > > > dsetrakyan@apache.org
> > >> > > > > > > >
> > >> > > > > > > > wrote:
> > >> > > > > > > >
> > >> > > > > > > > > Hi Dmitriy. I don't think we have
a design proposal
> for
> > >> > > > transaction
> > >> > > > > > > > support
> > >> > > > > > > > > in thin clients. Do you mind taking
this initiative
> and
> > >> > > creating
> > >> > > > an
> > >> > > > > > IEP
> > >> > > > > > > > on
> > >> > > > > > > > > Wiki?
> > >> > > > > > > > >
> > >> > > > > > > > > D.
> > >> > > > > > > > >
> > >> > > > > > > > > On Tue, Mar 6, 2018 at 8:46 AM,
Dmitriy Govorukhin <
> > >> > > > > > > > > dmitriy.govorukhin@gmail.com>
wrote:
> > >> > > > > > > > >
> > >> > > > > > > > > > Hi, Igniters.
> > >> > > > > > > > > >
> > >> > > > > > > > > > I've seen a lot of discussions
about thin client and
> > >> binary
> > >> > > > > > protocol,
> > >> > > > > > > > > but I
> > >> > > > > > > > > > did not hear anything about
transactions support. Do
> > we
> > >> > have
> > >> > > > some
> > >> > > > > > > draft
> > >> > > > > > > > > for
> > >> > > > > > > > > > this purpose?
> > >> > > > > > > > > >
> > >> > > > > > > > > > As I understand we have several
problems:
> > >> > > > > > > > > >
> > >> > > > > > > > > >    - thread and transaction
have hard related (we
> use
> > >> > > > > thread-local
> > >> > > > > > > > > variable
> > >> > > > > > > > > >    and thread name)
> > >> > > > > > > > > >    - we can process only one
transaction at the same
> > >> time
> > >> > in
> > >> > > > one
> > >> > > > > > > thread
> > >> > > > > > > > > (it
> > >> > > > > > > > > >    mean we need hold thread
per client. If connect
> 100
> > >> thin
> > >> > > > > clients
> > >> > > > > > > to
> > >> > > > > > > > 1
> > >> > > > > > > > > >    server node, then need
to hold 100 thread on the
> > >> server
> > >> > > > side)
> > >> > > > > > > > > >
> > >> > > > > > > > > > Let's discuss how we can implement
transactions for
> > the
> > >> > thin
> > >> > > > > > client.
> > >> > > > > > > > > >
> > >> > > > > > > > >
> > >> > > > > > > >
> > >> > > > > > >
> > >> > > > > >
> > >> > > > >
> > >> > > > >
> > >> > > > > --
> > >> > > > > Sergey Kozlov
> > >> > > > > GridGain Systems
> > >> > > > > www.gridgain.com
> > >> > > > >
> > >> > > >
> > >> > >
> > >> >
> > >> >
> > >> > --
> > >> > Sergey Kozlov
> > >> > GridGain Systems
> > >> > www.gridgain.com
> > >> >
> > >>
> > >
> >
>

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