Concurrency Best Practices + Tests
I think the question was if there are any patterns or best practices to identify potential concurrency issues that could be used to build tools... maybe that’s why Complaints occurred...?
Am 07.09.2019 um 10:42 schrieb Andres Valloud avalloud@smalltalk.comcastbiz.net:
On 9/6/19 23:24 , Stéphane Ducasse wrote:
Now it would be nice to read his questions and reply to them and not
just tell him “oh do not use concurrency”
I did not say that at all --- yet you are complaining to me :).
The questions are essentially how do we test? how does concurrent
programming fit in TDD.
A sharper and more open minded question might be "what is the best way
to build reliable programs using concurrency flavor XYZ?".
Andres.
Stef
On 6 Sep 2019, at 02:32, Andres Valloud
<avalloud@smalltalk.comcastbiz.net
mailto:avalloud@smalltalk.comcastbiz.net> wrote:
TL; DR: generally, developing a good sense of what to do before
writing a single line of code works really well.
On 9/4/19 6:32 , N. Bouraqadi wrote:
Hi everyone,
Can I get your input on the following questions :
-
What are your best practices and recommendations for developing and
testing concurrent software? -
How to discover need for synchronization/critical sections/ when
doing TDD? -
How to write code to avoid dead-locks?
Thanks for your help,
Noury
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Assistant: Julie Jonas
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Some random thoughts:
-
model your concurrency problem before you start with TDD, e.g. using
TLA+. This will make clear what you need to implement using TDD. -
once you have a satisfying result from 1, you can start designing your
solution using TDD. Of the tests that you will need to write:
- some will be pure behaviour tests which don’t to worry about concurrency
- some will be coordination tests were you need to worry about concurrency.
The coordination tests can be approached as simulation problems, where you
can manage the choreography of the various concurrent processes. To do this:
A) model your concurrent operation as transactions. Split the transaction
execution into smaller steps, that can be tested separately.
You can then set up a sequence of operations coming from multiple
processes, interleaving ops from one process with those from the others.
This will also make it easier to understand where to use coordination
primitives.
B) Explicitly manage the evaluation of the code in the two processes. You
can do this with a creative use of method wrappers, Delay objects etc., or
by forcing the code to run through a debugger, so that can manage the order
of the message sends between the processes
Please also note that TDD might not be enough and you might need to run
other type of tests than TDD-style unit tests.
Cheers,
Giovanni
Il giorno sab 7 set 2019 alle 03:25 Stéphane Ducasse <
stephane.ducasse@inria.fr> ha scritto:
Hi guys
I imagine that noury knows most of the remarks you sent it.
He is far from dull.
Now it would be nice to read his questions and reply to them and not just
tell him
“oh do not use concurrency”
The questions are essentially how do we test? how does concurrent
programming fit in TDD.
Stef
On 6 Sep 2019, at 02:32, Andres Valloud avalloud@smalltalk.comcastbiz.net
wrote:
TL; DR: generally, developing a good sense of what to do before
writing a single line of code works really well.
On 9/4/19 6:32 , N. Bouraqadi wrote:
Hi everyone,
Can I get your input on the following questions :
-
What are your best practices and recommendations for developing and
testing concurrent software? -
How to discover need for synchronization/critical sections/ when doing
TDD? -
How to write code to avoid dead-locks?
Thanks for your help,
Noury
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.
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Stéphane Ducasse
http://stephane.ducasse.free.fr
http://www.synectique.eu / http://www.pharo.org
03 59 35 87 52
Assistant: Julie Jonas
FAX 03 59 57 78 50
TEL 03 59 35 86 16
S. Ducasse - Inria
40, avenue Halley
https://www.google.com/maps/search/40,+avenue+Halley?entry=gmail&source=g
,
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On 7 Sep 2019, at 10:42, Andres Valloud avalloud@smalltalk.comcastbiz.net wrote:
On 9/6/19 23:24 , Stéphane Ducasse wrote:
Now it would be nice to read his questions and reply to them and not
just tell him “oh do not use concurrency”
I did not say that at all --- yet you are complaining to me :).
Not to you in particular. To everybody :)
The questions are essentially how do we test? how does concurrent
programming fit in TDD.
A sharper and more open minded question might be "what is the best way
to build reliable programs using concurrency flavor XYZ?”.
No you see you are interpreting the questions of Noury.
Again and now this is you: why do you use “sharper” do you imply that the
questions of noury were not sharp. :(
The point of noury is what is the way to approach concurrency when doing TDD.
Now how to build reliable ….
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
Stef
Stef
On 6 Sep 2019, at 02:32, Andres Valloud
<avalloud@smalltalk.comcastbiz.net mailto:avalloud@smalltalk.comcastbiz.net
<mailto:avalloud@smalltalk.comcastbiz.net mailto:avalloud@smalltalk.comcastbiz.net>> wrote:
TL; DR: generally, developing a good sense of what to do before
writing a single line of code works really well.
On 9/4/19 6:32 , N. Bouraqadi wrote:
Hi everyone,
Can I get your input on the following questions :
-
What are your best practices and recommendations for developing and
testing concurrent software? -
How to discover need for synchronization/critical sections/ when
doing TDD? -
How to write code to avoid dead-locks?
Thanks for your help,
Noury
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.
Stéphane Ducasse
http://stephane.ducasse.free.fr
http://www.synectique.eu / http://www.pharo.org
03 59 35 87 52
Assistant: Julie Jonas
FAX 03 59 57 78 50
TEL 03 59 35 86 16
S. Ducasse - Inria
40, avenue Halley,
Parc Scientifique de la Haute Borne, Bât.A, Park Plaza
Villeneuve d'Ascq 59650
France
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Stéphane Ducasse
http://stephane.ducasse.free.fr
http://www.synectique.eu / http://www.pharo.org
03 59 35 87 52
Assistant: Julie Jonas
FAX 03 59 57 78 50
TEL 03 59 35 86 16
S. Ducasse - Inria
40, avenue Halley,
Parc Scientifique de la Haute Borne, Bât.A, Park Plaza
Villeneuve d'Ascq 59650
France
The point of noury is what is the way to approach concurrency when doing TDD.
Now how to build reliable ….
I won’t pretend to answer such a broad question with anything definitive, but I’d start my investigation of concurrency with a look at databases. One of the primary features of any multi-user database (not just GemStone!) is that transactions are in practice concurrent but the system is designed to apply them as if they were serial and in a way where order does not matter. So I would attempt to identify the concurrent tasks and verify that they each got the result that they would have obtained had they been applied in various serial fashions.
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
I would look for a way to pass a set of repeatable tasks to DrTDD and let the testing framework run them in various orders then run them concurrently with interrupts and switching contexts.
James
On 9/7/19 9:03 , Stéphane Ducasse wrote:
Again and now this is you: why do you use “sharper” do you imply that the
questions of noury were not sharp. :(
No, I didn't say that either --- "sharper", not "sharp vs dull".
The point of noury is what is the way to approach concurrency when doing
TDD.
Now how to build reliable ….
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
To me, the interesting part is how to build reliable software, so I'd
prioritize that over choice of tools. Because who knows, maybe you look
at reliability and realize instead of TDD you need XYZ.
Andres.
On 9/7/19 9:03 , Stéphane Ducasse wrote:
Again and now this is you: why do you use “sharper” do you imply that the
questions of noury were not sharp. :(
No, I didn't say that either --- "sharper", not "sharp vs dull”.
At least in french, when we say that "a better/sharper question would
be" it implies that previous question was not sharp/smart.
May be in english this is not the case, I’m sorry my english is rather basic.
I thought that adding “er” at the end of adjective meant more. So by construction
it means that other are less. I do not know I’m not good in logic either.
May be you do see it but I felt that you were saying that
and this is why I reacted because I do not like when people lower other people in this mailing-list.
Of course I could have say using the same pattern, that a nicer/smarter/shaper answer would
have been not to show off and to reply to the question. And when another
person would have mentioned it, I would have decline my intention.
The point of noury is what is the way to approach concurrency when doing
TDD.
Now how to build reliable ….
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
To me, the interesting part is how to build reliable software, so I'd
prioritize that over choice of tools. Because who knows, maybe you look
at reliability and realize instead of TDD you need XYZ.
Again, as professional developers and teachers, I believe that we know all that.
But thanks for your wisdom. It seemed to me that it was quite
a common and basic knowledge.
But again this was not the questions.
Stef
Andres.
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Stéphane Ducasse
http://stephane.ducasse.free.fr
http://www.synectique.eu / http://www.pharo.org
03 59 35 87 52
Assistant: Julie Jonas
FAX 03 59 57 78 50
TEL 03 59 35 86 16
S. Ducasse - Inria
40, avenue Halley,
Parc Scientifique de la Haute Borne, Bât.A, Park Plaza
Villeneuve d'Ascq 59650
France
Thanks you all for your answers.
Best,
Noury
On 7 Sep 2019, at 18:42, James Foster Smalltalk@JGFoster.net wrote:
The point of noury is what is the way to approach concurrency when doing TDD.
Now how to build reliable ….
I won’t pretend to answer such a broad question with anything definitive, but I’d start my investigation of concurrency with a look at databases. One of the primary features of any multi-user database (not just GemStone!) is that transactions are in practice concurrent but the system is designed to apply them as if they were serial and in a way where order does not matter. So I would attempt to identify the concurrent tasks and verify that they each got the result that they would have obtained had they been applied in various serial fashions.
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
I would look for a way to pass a set of repeatable tasks to DrTDD and let the testing framework run them in various orders then run them concurrently with interrupts and switching contexts.
James
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Dear Noury,
I didn’t had the time to do a thorough web search. You certainly did. I found several references that look very promising. Mny of them were concerning Java and OS threads. Othes are about Erlang (https://mariachris.github.io/Pubs/ERLANG-2011.pdf ). I think not only the concurrency problem but also the base technology matters. I couldn’t find anything about Smalltalk yet. So you are probably conquering new land.
Here is a quote from the preface of “Test Driven Development: By Example” from 2003 by Kent Beck: “There certainly are programming tasks that can’t be driven solely by tests (or, at least not yet). Security and concurrency, for example, are two topics where TDD is insufficient to mechanically demonstrate that the goals of the software has been met.” “Subtle concurrency problems can’t be reliably duplicated by running the code.”
Good luck! I am looking forward to your findings.
Helge
Helge Nowak
Cincom Smalltalk Technical Account Manager
[http://internal.cincom.com/signature/logo.png]http://www.cincomsmalltalk.com/
Cincom Systems GmbH & Co. oHG
Humboldtstraße 3
60318 Frankfurt am Main
GERMANY
office
mobile
website
email
+49 89 89 66 44 94
+49 172 74 00 402
http://www.cincomsmalltalk.com
hnowak@cincom.com
A standpoint is an intellectual horizon of radius zero. -- Albert Einstein
Geschäftsführer/Managing Directors: Thomas M. Nies, Donald E. Vick
oHG mit Sitz/based in Frankfurt am Main (Amtsgericht Frankfurt am Main HRA 50297)
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Cincom Systems Verwaltungsgesellschaft mbH (Amtsgericht Königstein/Ts. HRB 5069)
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From: Esug-list esug-list-bounces@lists.esug.org On Behalf Of Noury Bouraqadi
Sent: Tuesday, 10 September 2019 15:12
To: Members ESUG esug-list@lists.esug.org
Subject: Re: [Esug-list] [SPAM] Re: Concurrency Best Practices + Tests
Thanks you all for your answers.
Best,
Noury
On 7 Sep 2019, at 18:42, James Foster <Smalltalk@JGFoster.netmailto:Smalltalk@JGFoster.net> wrote:
The point of noury is what is the way to approach concurrency when doing TDD.
Now how to build reliable ….
I won’t pretend to answer such a broad question with anything definitive, but I’d start my investigation of concurrency with a look at databases. One of the primary features of any multi-user database (not just GemStone!) is that transactions are in practice concurrent but the system is designed to apply them as if they were serial and in a way where order does not matter. So I would attempt to identify the concurrent tasks and verify that they each got the result that they would have obtained had they been applied in various serial fashions.
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
I would look for a way to pass a set of repeatable tasks to DrTDD and let the testing framework run them in various orders then run them concurrently with interrupts and switching contexts.
James
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Hi Noury,
I didn't respond because I really didn't think I had much to add but I've
been thinking about what I would want to have in a concurrent system. This
may be obvious but
Concurrent systems promise either speed or scalability. The goal will
change the requirements. We know that for speed there are two aspects to
consider. You can only go as fast as it takes for your largest component
to process and limited resources means that going really fast on easy to
process components of the problem set will only lead to a large backlog and
coordination issues.
For scalability you need to ensure completeness. You can't just send stuff
off and assume it will get processed. There is a lot to do to ensure that
the everything that fails or is delayed is rescheduled to prevent a major
backup.
Both of these goals, it would seem to me, would be helped considerably by a
system that can explain itself. Depending on the size of the processing
task this could get tricky. Something that processes millions of messages
a second would need to have a much more sophisticated system to gather
information without changing the efficiency of the system itself.
Something that is less time intensive could process and keep this
information with the processed results.
What I would want to know is time to process all of the components compared
to time to process the full solution. I would also want to know about
errors, rescheduling, wait times. Ultimately the best concurrent system
will run at time to run slowest component + coordination time. If the
system is not running at that speed we would like to have information as to
why. Is there a backup, deadlock or other errors, resource issues or
something else that is causing the system to delay. Comparing the
processing time of the full process and the processing time of each
component could tell you a lot about where things are going wrong (maybe
your process tree is wrong, or your scheduling is too aggressive causing
rescheduling on a regular basis or 2 times the processing time of a
component because expected data wasn't available). If this is a huge
system then you can't really keep all that information but you could keep
averages instead.
The idea is probably not that novel but having a system that could explain
itself, what it is doing, and how well it is performing, could be a very
good debugging tool. I would be very careful to build it such that it
doesn't change the processing efficiency of the production system and that
the explanation system is optional (I know they don't really go together
[optional and no effect] which makes this very difficult). That also means
that I wouldn't try to use this reporting system to automatically change
the system itself.
Hope that helps.
All the best,
Ron Teitelbaum
Chief Executive Officer**3D Immersive Collaboration Consulting, LLC
ron@3dicc.com
www.3dicc.com
https://www.facebook.com/3DICC https://twitter.com/RonTeitelbaum
https://www.linkedin.com/in/ronteitelbaum
On Tue, Sep 10, 2019 at 9:52 AM Nowak, Helge HNowak@cincom.com wrote:
Dear Noury,
I didn’t had the time to do a thorough web search. You certainly did. I
found several references that look very promising. Mny of them were
concerning Java and OS threads. Othes are about Erlang (
https://mariachris.github.io/Pubs/ERLANG-2011.pdf ). I think not only the
concurrency problem but also the base technology matters. I couldn’t find
anything about Smalltalk yet. So you are probably conquering new land.
Here is a quote from the preface of “Test Driven Development: By Example”
from 2003 by Kent Beck: “There certainly are programming tasks that can’t
be driven solely by tests (or, at least not yet). Security and concurrency,
for example, are two topics where TDD is insufficient to mechanically
demonstrate that the goals of the software has been met.” “Subtle
concurrency problems can’t be reliably duplicated by running the code.”
Good luck! I am looking forward to your findings.
Helge
*Helge Nowak *Cincom Smalltalk Technical Account Manager
[image: http://internal.cincom.com/signature/logo.png]
http://www.cincomsmalltalk.com/
Cincom Systems GmbH & Co. oHG
Humboldtstraße 3
60318 Frankfurt am Main
GERMANY
office
mobile
website
email
+49 89 89 66 44 94
+49 172 74 00 402
http://www.cincomsmalltalk.com
hnowak@cincom.com
*A standpoint is an intellectual horizon of radius zero. -- Albert
Einstein *
Geschäftsführer/Managing Directors: Thomas M. Nies, Donald E. Vick
oHG mit Sitz/based in Frankfurt am Main (Amtsgericht Frankfurt am Main HRA
50297)
Pers. haftender Gesellschafter/Partner liable to unlimited extent:
Cincom Systems Verwaltungsgesellschaft mbH (Amtsgericht Königstein/Ts. HRB
5069)
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above. If you receive this e-mail in error, please do not read, copy or
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From: Esug-list esug-list-bounces@lists.esug.org *On Behalf Of *Noury
Bouraqadi
Sent: Tuesday, 10 September 2019 15:12
To: Members ESUG esug-list@lists.esug.org
Subject: Re: [Esug-list] [SPAM] Re: Concurrency Best Practices + Tests
Thanks you all for your answers.
Best,
Noury
On 7 Sep 2019, at 18:42, James Foster Smalltalk@JGFoster.net wrote:
The point of noury is what is the way to approach concurrency when doing
TDD.
Now how to build reliable ….
I won’t pretend to answer such a broad question with anything definitive,
but I’d start my investigation of concurrency with a look at databases. One
of the primary features of any multi-user database (not just GemStone!) is
that transactions are in practice concurrent but the system is designed to
apply them as if they were serial and in a way where order does not matter.
So I would attempt to identify the concurrent tasks and verify that they
each got the result that they would have obtained had they been applied in
various serial fashions.
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
I would look for a way to pass a set of repeatable tasks to DrTDD and let
the testing framework run them in various orders then run them concurrently
with interrupts and switching contexts.
James
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Hey Ron,
Part of what you’ve expressed has been distilled into a ‘law’. Amdahl’s law describes the theoretical speedup in execution latency.
https://en.wikipedia.org/wiki/Amdahl%27s_law https://en.wikipedia.org/wiki/Amdahl's_law
Note, concurrency alone would not offer this speedup. This requires parallel execution. Without parallelism, you would still need to wait the aggregate computation time for all concurrent components. The latency of the longest computation is not enough.
Kurt
On Sep 10, 2019, at 9:41 AM, Ron Teitelbaum ron@3dicc.com wrote:
Hi Noury,
I didn't respond because I really didn't think I had much to add but I've been thinking about what I would want to have in a concurrent system. This may be obvious but
Concurrent systems promise either speed or scalability. The goal will change the requirements. We know that for speed there are two aspects to consider. You can only go as fast as it takes for your largest component to process and limited resources means that going really fast on easy to process components of the problem set will only lead to a large backlog and coordination issues.
For scalability you need to ensure completeness. You can't just send stuff off and assume it will get processed. There is a lot to do to ensure that the everything that fails or is delayed is rescheduled to prevent a major backup.
Both of these goals, it would seem to me, would be helped considerably by a system that can explain itself. Depending on the size of the processing task this could get tricky. Something that processes millions of messages a second would need to have a much more sophisticated system to gather information without changing the efficiency of the system itself. Something that is less time intensive could process and keep this information with the processed results.
What I would want to know is time to process all of the components compared to time to process the full solution. I would also want to know about errors, rescheduling, wait times. Ultimately the best concurrent system will run at time to run slowest component + coordination time. If the system is not running at that speed we would like to have information as to why. Is there a backup, deadlock or other errors, resource issues or something else that is causing the system to delay. Comparing the processing time of the full process and the processing time of each component could tell you a lot about where things are going wrong (maybe your process tree is wrong, or your scheduling is too aggressive causing rescheduling on a regular basis or 2 times the processing time of a component because expected data wasn't available). If this is a huge system then you can't really keep all that information but you could keep averages instead.
The idea is probably not that novel but having a system that could explain itself, what it is doing, and how well it is performing, could be a very good debugging tool. I would be very careful to build it such that it doesn't change the processing efficiency of the production system and that the explanation system is optional (I know they don't really go together [optional and no effect] which makes this very difficult). That also means that I wouldn't try to use this reporting system to automatically change the system itself.
Hope that helps.
All the best,
Ron Teitelbaum
Chief Executive Officer
3D Immersive Collaboration Consulting, LLC
ron@3dicc.com mailto:ron@3dicc.com
www.3dicc.com http://www.3dicc.com/
https://www.facebook.com/3DICC https://twitter.com/RonTeitelbaum https://www.linkedin.com/in/ronteitelbaum
On Tue, Sep 10, 2019 at 9:52 AM Nowak, Helge <HNowak@cincom.com mailto:HNowak@cincom.com> wrote:
Dear Noury,
I didn’t had the time to do a thorough web search. You certainly did. I found several references that look very promising. Mny of them were concerning Java and OS threads. Othes are about Erlang (https://mariachris.github.io/Pubs/ERLANG-2011.pdf https://mariachris.github.io/Pubs/ERLANG-2011.pdf ). I think not only the concurrency problem but also the base technology matters. I couldn’t find anything about Smalltalk yet. So you are probably conquering new land.
Here is a quote from the preface of “Test Driven Development: By Example” from 2003 by Kent Beck: “There certainly are programming tasks that can’t be driven solely by tests (or, at least not yet). Security and concurrency, for example, are two topics where TDD is insufficient to mechanically demonstrate that the goals of the software has been met.” “Subtle concurrency problems can’t be reliably duplicated by running the code.”
Good luck! I am looking forward to your findings.
Helge
Helge Nowak
Cincom Smalltalk Technical Account Manager
<image001.png> http://www.cincomsmalltalk.com/
Cincom Systems GmbH & Co. oHG
Humboldtstraße 3
60318 Frankfurt am Main
GERMANY
office
mobile
website
email
+49 89 89 66 44 94
+49 172 74 00 402
http://www.cincomsmalltalk.com http://www.cincomsmalltalk.com/
hnowak@cincom.com mailto:hnowak@cincom.com
A standpoint is an intellectual horizon of radius zero. -- Albert Einstein
Geschäftsführer/Managing Directors: Thomas M. Nies, Donald E. Vick
oHG mit Sitz/based in Frankfurt am Main (Amtsgericht Frankfurt am Main HRA 50297)
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From: Esug-list <esug-list-bounces@lists.esug.org mailto:esug-list-bounces@lists.esug.org> On Behalf Of Noury Bouraqadi
Sent: Tuesday, 10 September 2019 15:12
To: Members ESUG <esug-list@lists.esug.org mailto:esug-list@lists.esug.org>
Subject: Re: [Esug-list] [SPAM] Re: Concurrency Best Practices + Tests
Thanks you all for your answers.
Best,
Noury
On 7 Sep 2019, at 18:42, James Foster <Smalltalk@JGFoster.net mailto:Smalltalk@JGFoster.net> wrote:
The point of noury is what is the way to approach concurrency when doing TDD.
Now how to build reliable ….
I won’t pretend to answer such a broad question with anything definitive, but I’d start my investigation of concurrency with a look at databases. One of the primary features of any multi-user database (not just GemStone!) is that transactions are in practice concurrent but the system is designed to apply them as if they were serial and in a way where order does not matter. So I would attempt to identify the concurrent tasks and verify that they each got the result that they would have obtained had they been applied in various serial fashions.
Imagine that DrTDD should be extended to support concurrent programming.
Then this is the question that we want to get answer.
I would look for a way to pass a set of repeatable tasks to DrTDD and let the testing framework run them in various orders then run them concurrently with interrupts and switching contexts.
James
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