The "Almost Perfect" Paper -Christopher Francis Hyma Chilukiri

General observations from the paper : Scenario:1 " A framework can reject resources that do not satisfy its constraints in order to wait for ones that do. " section 3.2 Problem :- Starvation, Consider a scenario where a framework waits for a particular set of resources Also consider that mesos has a resource offer that has 1 less than those needed. According to the above statement the framework will reject the offer. Mesos does not offer a solution for a scenario where a cycle of offer and rejection occurs more than once "

Scenario : 2 " Mesos takes advantage of the fact that most tasks are short, and only reallocates resources when tasks finish for eg : if a framework’s share is 10% of the cluster, it needs to wait approximately 10% of the mean task length to receive its share. " section 3.3 Inference : - Tasks are short and we infer from the above statement that the amount of time a framework has to wait for its share is directly proportional to the number of resources utilized.Problem occurs if the task is of a longer duration.

Scenario 3 :- Killing a task if it exceeds guaranteed list "Killing a task has a low impact but it is harmful for frameworks with interdependent tasks" section 3.3 Inference :- We infer that if a framework with interdependent tasks exceeds the guaranteed allocation it would be killed and this would trigger a cascade reaction of several inconsistencies violating the ACID principle.

Scenario 4:- " Mesos performs well when frameworks can scale up and down elastically, tasks durations are homogeneous, and frameworks prefer all nodes equally but when different frameworks prefer different nodes Mesos emulates centralised scheduler." section 4 The paper does not account for the performance of mesos when 1.Frameworks such as MPI which are rigid and does not support elasticity 2. Task durations are heterogeneous which is a more practical scenario to consider.

Scenario 5: "We assume the amount of mandatory resources requested by a framework never exceeds its guaranteed share. This ensures that frameworks will not deadlock waiting for the mandatory resources to become free" section 4.1 This assumption is not practical

Evaluation benchmarks : * Every evaluation is compared with Hadoop static. for eg: All the tests Mesos + torque, Mesos + Spark are compared only with Hadoop static * Mesos emulates centralized scheduler when the tasks are heterogeneous but they do not compare the test results with centralized schedulers. * Organisation and maintenance of filters