Re: transaction: getting hooks and synchronizers to work

2013-03-03 Thread Laurence Rowe 
On Sunday, 17 February 2013 22:54:30 UTC-8, cguardia wrote:

 Hi, 

 there were some problems with the code snippets in the book. I updated 
 them here: 

 http://zodb.readthedocs.org/en/latest/transactions.html#before-commit-hooks 

 For some reason I could only get synch to work using classmethod. 


Pass an instance of the MySynch class rather than the class itself, e.g:

class MySynch(object):
def beforeCompletion(self, transaction):
print Commit started

def afterCompletion(self, transaction):
print Commit finished
import transactionsynch = MySynch()transaction.manager.registerSynch(synch)

Laurence

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Re: transaction: getting hooks and synchronizers to work

2013-03-03 Thread Carlos de la Guardia 
Laurence, did you get it to work like that? I tried before using
classmethod and wasn't able to make it work.

Carlos de la Guardia


 Pass an instance of the MySynch class rather than the class itself, e.g:

 class MySynch(object):
 def beforeCompletion(self, transaction):
 print Commit started

 def afterCompletion(self, transaction):
 print Commit finished

 import transaction
 synch = MySynch()
 transaction.manager.registerSynch(synch)

 Laurence

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Re: transaction: getting hooks and synchronizers to work

2013-03-03 Thread Siddhartha Kasivajhula 
Ok, it looks like the synchronizer instance needs to remain in the calling
scope for the synchronizer to work. This code (Laurence) works:

synch = MySynch()
transaction.manager.registerSynch(synch)

while this code (what we were doing earlier) doesn't:

transaction.manager.registerSynch(MySynch())

Is this a bug or is it supposed to work this way?

Now, regarding the newTransaction() interface method -- this actually looks
very handy and may be just what I need for a mongodb data manager that I'm
writing. But it looks like it's only called when there is an explicit call
to transaction.begin(), which apparently isn't necessary to use the
transaction machinery as it happens implicitly by just using
transaction.get() and then commit()ing. These implicitly begun transactions
don't appear trigger the newTransaction() method in the synchronizer. Is
there any way to make it trigger without an explicit begin()? (this should
probably be the default behavior?)

btw I'm not able to find any of these interface methods by using help() or
dir() on the interfaces in transaction.interfaces. All of the interfaces
appear to show exactly the same set of properties and methods... though I
do see them if I look directly in the transaction/interfaces.py source. is
there another way to introspect these?

Thanks, -Sid


On Sun, Mar 3, 2013 at 10:28 AM, Laurence Rowe laurencer...@gmail.comwrote:

 On 3 March 2013 08:37, Carlos de la Guardia
 carlos.delaguar...@gmail.com wrote:
  Laurence, did you get it to work like that? I tried before using
  classmethod and wasn't able to make it work.

 Ah, you need to implement all methods on ISynchronizer:

  class MySynch(object):
 ... def newTransaction(self, transaction):
 ... pass
 ...
 KeyboardInterrupt
  class MySynch(object):
 ... def newTransaction(self, transaction):
 ... print New transaction
 ... def beforeCompletion(self, transaction):
 ... print Commit started
 ... def afterCompletion(self, transaction):
 ... print Commit finished
 ...
  import transaction
  synch = MySynch()
  transaction.manager.registerSynch(synch)
  tx = transaction.begin()
 New transaction
  tx.commit()
 Commit started
 Commit finished

 If you want a singleton synchronizer then you can use classmethods
 everywhere, but you'll still need to implement them all.

 Laurence

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Re: transaction: getting hooks and synchronizers to work

2013-03-03 Thread Laurence Rowe 


On Sunday, March 3, 2013 4:59:58 PM UTC-8, Sid K wrote:

 Ok, it looks like the synchronizer instance needs to remain in the calling 
 scope for the synchronizer to work. This code (Laurence) works:

 synch = MySynch()
 transaction.manager.registerSynch(synch)

 while this code (what we were doing earlier) doesn't:

 transaction.manager.registerSynch(MySynch())

 Is this a bug or is it supposed to work this way?


The TransactionManager keeps the reference to the synchronizer in a 
WeakSet, so you will need to keep a reference to the synchronizer around 
some other way in order to avoid it being garbage collected.
 

 Now, regarding the newTransaction() interface method -- this actually 
 looks very handy and may be just what I need for a mongodb data manager 
 that I'm writing. But it looks like it's only called when there is an 
 explicit call to transaction.begin(), which apparently isn't necessary to 
 use the transaction machinery as it happens implicitly by just using 
 transaction.get() and then commit()ing. These implicitly begun transactions 
 don't appear trigger the newTransaction() method in the synchronizer. Is 
 there any way to make it trigger without an explicit begin()? (this should 
 probably be the default behavior?)


I think this might be worth bringing up on zodb-dev, I'm not sure why the 
distinction exists. In Pyramid and Zope the transaction will always be 
begun explicitly at the start of a request. 

btw I'm not able to find any of these interface methods by using help() or 
 dir() on the interfaces in transaction.interfaces. All of the interfaces 
 appear to show exactly the same set of properties and methods... though I 
 do see them if I look directly in the transaction/interfaces.py source. is 
 there another way to introspect these?


An interface object is not a class, to access the methods and attributes 
defined in an Interface you can use iface.names() and iface[name'].

I've not used MongoDB myself, but what are you hoping to gain from the 
Synchronizer? A DataManager sounds more appropriate. You'll only be able to 
handle a single document update atomically with MongoDB, but that case 
should be able to integrate safely with the two phase commit protocol by 
committing during tpc_vote while ensuring the data manager sort key sorts 
last (take a look at one phase variant of zope.sqlalchemy's DataManager.) 
For multi-document updates you probably want to treat them more like 
zope.sendmail does and add them to a queue which then processes them 
asynchronously.

Laurence

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Re: transaction: getting hooks and synchronizers to work

2013-02-19 Thread Siddhartha Kasivajhula 
Carlos, great, thanks for the corrections. They appear to be working now :)


On Sun, Feb 17, 2013 at 10:54 PM, Carlos de la Guardia 
carlos.delaguar...@gmail.com wrote:

 Hi,

 there were some problems with the code snippets in the book. I updated
 them here:

 http://zodb.readthedocs.org/en/latest/transactions.html#before-commit-hooks

 For some reason I could only get synch to work using classmethod.

 Carlos de la Guardia

 On Sat, Feb 16, 2013 at 3:56 AM, Siddhartha Kasivajhula
 countvajh...@gmail.com wrote:
  Hi there,
  I'm not able to get before/after commit hooks or synchronizers to work,
 hope
  someone here can explain what I'm doing wrong (or please point me at the
  relevant list). I'm following the tutorial here:
 
  http://www.zodb.org/zodbbook/transactions.html
 
  .. and got the PickleDataManager working. But when I add the before- and
  after-commit hooks verbatim from the tutorial, I get the following error:
 
  Traceback (most recent call last):
File pickledm.py, line 145, in module
  transaction.commit()
File
 
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_manager.py,
  line 107, in commit
  return self.get().commit()
File
 
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_transaction.py,
  line 339, in commit
  self._callBeforeCommitHooks()
File
 
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_transaction.py,
  line 413, in _callBeforeCommitHooks
  hook(*args, **kws)
  TypeError: before_commit() got an unexpected keyword argument 'a'
 
  When I pass in a blank dict instead of the {'a':1} from the tutorial, I
 get
  this error:
 
File pickledm.py, line 17, in before_commit
  for arg in args:
  TypeError: 'int' object is not iterable
 
  ... and I find that, in fact, printing 'args' inside the hook function
 shows
  that it is equal to 1, and not the tuple (1,2) that was passed.
 
  I also tried adding a synchronizer, and initially got this error:
 
  TypeError: unbound method beforeCompletion() must be called with synch
  instance as first argument (got Transaction instance instead)
 
  It looked like this may have been due to a typo in the tutorial, I
 changed:
 
  transaction.manager.registerSynch(sync)
 
  to:
 
  transaction.manager.registerSynch(sync())
 
  ...to pass an instance instead of a class and the error goes away.
  Unfortunately the synchronizer methods don't seem to be called when the
  transaction is executed, and I don't see the output from those functions.
 
  Could someone point me in the right direction here on how to get these to
  work? Here is my full code if anyone wants to take a look:
  https://gist.github.com/countvajhula/4966286
 
  Thanks,
  -Sid
 
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Re: transaction: getting hooks and synchronizers to work

2013-02-17 Thread Carlos de la Guardia 
Hi,

there were some problems with the code snippets in the book. I updated
them here:

http://zodb.readthedocs.org/en/latest/transactions.html#before-commit-hooks

For some reason I could only get synch to work using classmethod.

Carlos de la Guardia

On Sat, Feb 16, 2013 at 3:56 AM, Siddhartha Kasivajhula
countvajh...@gmail.com wrote:
 Hi there,
 I'm not able to get before/after commit hooks or synchronizers to work, hope
 someone here can explain what I'm doing wrong (or please point me at the
 relevant list). I'm following the tutorial here:

 http://www.zodb.org/zodbbook/transactions.html

 .. and got the PickleDataManager working. But when I add the before- and
 after-commit hooks verbatim from the tutorial, I get the following error:

 Traceback (most recent call last):
   File pickledm.py, line 145, in module
 transaction.commit()
   File
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_manager.py,
 line 107, in commit
 return self.get().commit()
   File
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_transaction.py,
 line 339, in commit
 self._callBeforeCommitHooks()
   File
 /Users/siddhartha/.virtualenvs/pyramid/lib/python2.7/site-packages/transaction/_transaction.py,
 line 413, in _callBeforeCommitHooks
 hook(*args, **kws)
 TypeError: before_commit() got an unexpected keyword argument 'a'

 When I pass in a blank dict instead of the {'a':1} from the tutorial, I get
 this error:

   File pickledm.py, line 17, in before_commit
 for arg in args:
 TypeError: 'int' object is not iterable

 ... and I find that, in fact, printing 'args' inside the hook function shows
 that it is equal to 1, and not the tuple (1,2) that was passed.

 I also tried adding a synchronizer, and initially got this error:

 TypeError: unbound method beforeCompletion() must be called with synch
 instance as first argument (got Transaction instance instead)

 It looked like this may have been due to a typo in the tutorial, I changed:

 transaction.manager.registerSynch(sync)

 to:

 transaction.manager.registerSynch(sync())

 ...to pass an instance instead of a class and the error goes away.
 Unfortunately the synchronizer methods don't seem to be called when the
 transaction is executed, and I don't see the output from those functions.

 Could someone point me in the right direction here on how to get these to
 work? Here is my full code if anyone wants to take a look:
 https://gist.github.com/countvajhula/4966286

 Thanks,
 -Sid

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