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From "Olivier Tardieu" <>
Subject Re: Shared Context in OpenWhisk
Date Wed, 05 Dec 2018 17:39:26 GMT

I did not see an attachment or a link in your email.


Some thoughts about the relationship between contexts and conductor 

1. Contexts are very useful. Love it!

2. Conductor actions depend on managing contexts. So contexts and 
conductors are not orthogonal concerns.

3. Conductor actions make it possible to hide unnecessary context from an 
invoked action but preserve the context so it is still available 
downstream. So one can leverage conductor action for _some_ context 
management including managing a context stack in an invocation tree.

4. Conductor actions piggy back on the parameter object to manage contexts 
and rely on conventions about reserved parameter names. Having a separate 
context table (key/value pair) would have clear advantages. No 
disagreement here. :)

5. For conductor actions, we considered implementing a context separate 
from the parameter object but chickened out basically because it touches a 
lot of OpenWhisk components. This potentially affects all the runtimes, 
the messaging, the activation records, the payload and record sizes, the 
controller memory footprint, the quotas...

6. Conductor actions give the flexibility to customize the context 
management because we can write arbitrary action code to manage context 
propagation. Should we manage the context as a stack? Should it be flat? 
Should an asynchronous invocation preserve or drop the current context? It 
all depends on use cases. If the context becomes a pure runtime facility 
however, implicitly managed and propagated, we loose some of that 
flexibility. So we need to make sure that we identify and support all the 
important patterns beforehand (including obviously conductor action 



From:   "Erez Hadad" <>
Date:   12/05/2018 11:58 AM
Subject:        Shared Context in OpenWhisk

Hi folks,

Following today's call, here is the presentation. Note the additional 
implementation details in the "Backup" section.

Please comment!

-- Erez

Erez Hadad, PhD
Cloud System Technologies
IBM Research - Haifa
phone: +972-4-829-6509

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