Comp150CPA: Clouds and Power-Aware Computing
Classroom Exercise 11
Service-Oriented Datastores
Spring 2011
group member 1: ____________________________ login: ______________
group member 2: ____________________________ login: ______________
group member 3: ____________________________ login: ______________
group member 4: ____________________________ login: ______________
group member 5: ____________________________ login: ______________
In class we have studied how to think of a cloud application as a service,
including choices for front-facing cloud datastores.
Let's explore that in more detail.
- What is the CAP class of a database server running on
a single machine? Why?
- Is there a reasonable use for cloud datastores in CAP class CA?
What might it be?
- I claimed in lecture that LinkedIn stores the results of a Pig
job in a NoSQL datastore. For assignment 4,
what is the key in this datastore, and what is the value?
- In Amazon Dynamo,
the datastore key for shopping cart contents
is the content of a cookie stored locally in your browser.
Suppose that one user opens two instances of a
shopping cart in two panes of the same browser, and proceeds to update
each one by deleting a different item. Draw a picture showing why
this is a conflict in the vector clock algorithm. Then describe what
the vector clock algorithm might do to resolve this situation,
to business advantage.
- (Advanced) A key feature of Amazon's Dynamo is what is called
"business-logic based recovery". If a server is lost during a post,
so that the database is in an inconsistent state, consistency is
restored according to business rules rather than computer science
concepts. What are the appropriate business rules for merging
versions of a purchase transaction, or a return authorization?
Why?