asyncTransactionChain right way to create a new Entity

[lbedu...@gmail.com]

Hello, 

I am new to Activate framework and I am testing Activate async support.

It seems to work great except that I had a hard time making an async transaction

I lost 1 hour fighting with a net.fwbrasil.radon.RequiredTransactionException

  asyncTransactionalChain { implicit context =>

    .... more work inside the transaction ...

    new MyEntity("Pierre")

    .... more work inside the transaction ...

  }

Turned out I had to delimit the Entity creation with a future :

import scala.concurrent._

  asyncTransactionalChain { implicit context =>

    .... more work inside the transaction ...

    future { new MyEntity("Pierre") }

    .... more work inside the transaction ...

  } 

I don't know if it's really that OK nor if a rollback would work (have to test it) but it's the only solution I found to create a new Entity inside the asyncTransaction.

Maybe the doc should explain this (maybe I am tired and missed the example too:)

Regards

Laurent

[Flavio W. Brasil]

Hi Laurent,

The asyncTransactionalChain is designed to be used when using queries that produce other futures.

If the transaction doesn’t have a query the method to be used is asyncTransactional, so your code would be:

  asyncTransactional {

new MyEntity("Pierre")

  } 

Let me know if the explanation clarifies. :)

Cheers,

-- 

Flavio W. Brasil

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[Laurent Bedubourg]

The asyncTransactionalChain is designed to be used when using queries that produce other futures.

If the transaction doesn’t have a query the method to be used is asyncTransactional, so your code would be:

  asyncTransactional {

new MyEntity("Pierre")

  } 

Let me know if the explanation clarifies. :)

Hi Flavio,

I just tested Entity creation inside asyncTransactionalChain and the rollback works perfectly with future.

asyncTransactionalChain { implicit context => 

   ... some queries necessary to create my Entity here ...

   future { new MyEntity("aaa") }

   ... more queries ...

   throw new Exception("Rollback please")

   ... dummy ...

}

Because I am curious I tried to replace, in the above code,

future { new MyEntity("aaa') }

with

asyncTransactional { new MyEntity("aaa") }

The MyEntity aaa appeared in mongo, I don't know if it's the same for the regular transactional feature but is it possible to reuse the current transaction or at least to throw some error when a sub transaction is started ?  (I am using activate v 1.7)

Best regards and thank you Flavio

Laurent

Cheers,

-- 

Flavio W. Brasil

On Friday, December 12, 2014 at 12:41 PM, lbedu...@gmail.com wrote:

Hello, 

I am new to Activate framework and I am testing Activate async support.

It seems to work great except that I had a hard time making an async transaction

I lost 1 hour fighting with a net.fwbrasil.radon.RequiredTransactionException

  asyncTransactionalChain { implicit context =>

    .... more work inside the transaction ...

    new MyEntity("Pierre")

    .... more work inside the transaction ...

  }

Turned out I had to delimit the Entity creation with a future :

import scala.concurrent._

  asyncTransactionalChain { implicit context =>

    .... more work inside the transaction ...

    future { new MyEntity("Pierre") }

    .... more work inside the transaction ...

  } 

I don't know if it's really that OK nor if a rollback would work (have to test it) but it's the only solution I found to create a new Entity inside the asyncTransaction.

Maybe the doc should explain this (maybe I am tired and missed the example too:)

Regards

Laurent

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[Laurent Bedubourg]

Hello,

I did a few more tests (playing with undertow) and it occurred to me that there's another thread which calls the future onResult callback.

In fact it looks like the API / driver use the scala future API on top of the java nio Future api. 

If I understood correctly the former uses threads to handle concurrency whereas the later only works with Listeners which are invoked by one nio thread when some data is ready to process.

1/ I am a little bit afraid of the extra complexity of creating threads for each SQL(or other) request/transaction whereas NIO is designed to avoid that. Am I too paranoid ? :)

2/ when I create a new Entity, I imagine that there are database queries triggered by the constructor? Hence the thread is probably locked to await replies. I understood that async API should never lock the current thread. Maybe an Entity factory should be used instead of direct constructor call?

Thank you for your insight.

Best regards

Laurent

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[Flavio W. Brasil]

Hey Laurent,

On Saturday, December 13, 2014 at 9:32 AM, Laurent Bedubourg wrote:

Hello,

I did a few more tests (playing with undertow) and it occurred to me that there's another thread which calls the future onResult callback.

In fact it looks like the API / driver use the scala future API on top of the java nio Future api. 

If I understood correctly the former uses threads to handle concurrency whereas the later only works with Listeners which are invoked by one nio thread when some data is ready to process.

1/ I am a little bit afraid of the extra complexity of creating threads for each SQL(or other) request/transaction whereas NIO is designed to avoid that. Am I too paranoid ? :)

It is possible to reuse threads with a thread pool. Activate uses the scala’s default pool, but it is possible to override in you storage definition:

https://github.com/fwbrasil/activate/blob/a29e704a06b7f8dbba0aba7b6dd014c155b5d95f/activate-jdbc-async/src/main/scala/net/fwbrasil/activate/storage/relational/async/AsyncSQLStorage.scala#L38

2/ when I create a new Entity, I imagine that there are database queries triggered by the constructor? Hence the thread is probably locked to await replies. I understood that async API should never lock the current thread. Maybe an Entity factory should be used instead of direct constructor call?

Activate runs the entire transaction in-memory, relying on the STM’s transactional guarantees. It goes to the database only if you use an explicit query. If you use the async* methods that Activate provides, there aren’t blocking operations being done.