How to be an Engineer, IMHO (Basic Part I)

My favorite quote in my engineering career is "Asking good questions is the first step to solve great problems". One of the interesting characteristics of an engineer is to ask a lot of questions. A good engineer selects a subset of those questions that are most relevant to the problem to be solved. So, what are good questions? IMHO, there is no definition for it because it depends on what approach you choose to solve the problem. Different approach has different questions to ask to meet different objective.

When a person is facing a problem, one of the sensible approaches for problem solving is by "searching" for solutions. This approach works fine when the problem has to be solved in a timely manner (i.e. within minutes or days) because the quality of the solution is a ratio of K * (Quality of the Solution)/(Time taken to solve). The approach makes use of past experiences as the initialization points of a solution set. Solutions that are closed to the initialization points might also be included into the final solution set. To solve the problem, pick one of solutions from the solution set that can maximize the objective.

There is an assumption in the above approach that usually goes unnoticed and that is the knowledge about the problem at hand. For instance, your boss says "We have a problem of not meeting the deadlines aggressively in the team". One might attempt to solve the problem by using the approach above. If it works fine every time, then I wouldn't blog about it :). But what if this approach fails even you and your team are trying very hard? Have you ever wondered what is the cause of the failure and explore other approaches to solve this problem?

Another approach for problem solving that I always keep in my solution bag is to redefine the problem. It goes a little bit deeper than what it sounds like. It uses common senses as the starting point of the solution set and reshape the problem by asking relevant questions. Common sense is an interesting thing; it means "what people in common would agree on". The actual definition of common sense is not very important for this approach to work well. Common sense serves primarily as an initialization tool; it allows us to look at the problem from many different perspective. Asking good questions to reshape the problem can lead to what many people called "thinking outside of the box". This is trivial using this approach because there is no box to begin with. The questions are aimed to elicit the real problem without introducing a priori assumptions about the problem at hand. Using this approach might simplify the problem tremendously especially for problems that are ill-defined.

The first two approaches might sound common to many problem solvers. The third approach that I will also consider is to use the first and second approach altogether. The problem with the second approach is that it might take very long to obtain a relatively good solution and it requires a lot of skills in order to ask those "good" questions. The third approach starts by using the first approach to acquire experience about the problem and then it uses the second approach to fine-tune the problem. Once the problem is understood better, then the first approach can be used to solve the fine-tuned problem. This process continues until a solution is found. The third approach requires an unlearning process when switching between the first approach and the second approach. Also, it requires a lot of adaptations during the process of problem solving.

Which approach you choose to solve a problem depends on what problem you are facing. However, there are some general rules to follow which I might blog about it in the future post :)

References

- How to be an Engineer, IMHO (Introduction)

My Thought on Extreme Transaction Processing (XTP) in Financial Services

Today, I have a discussion with a customer through emails regarding Extreme Transaction Processing (XTP) system for Order Management System (OMS) using GigaSpaces XAP. I found the discussion interesting and would like to also share it with you all. The discussion was about measuring system performance in XTP which usually involves Latency and Throughput. Here is the detail in the email:

Although latency is an important performance metric for an OMS, we also need to consider other aspects such as the system throughput. Measuring independently the latency and the throughput using different test cases will not reflect the performance of the system in the real world as the test case might aim to optimize the performance of a specific system parameter (in this case the latency) by trading off other important aspects of performance (such as the throughput and the ACID properties). In optimization theory, the optimization complexity increases with the number of variable in the system. In the real-world application, this complexity arises frequently and GigaSpaces does a good job, if not the best, to solve this problem.

We believe that the single-threaded approach to optimize out the object locking in order to shave off any possible latency will actually impact the throughput of the system as this approach can only update ONE order information at a time; limiting the system concurrency and utilization. Also, the single-threaded approach DOES NOT satisfy all the ACID properties even in this simple test case which affects the system reliability.

In fact, GigaSpaces can achieve the same latency using the single-threaded approach (i.e. polling container with single consumer in GigaSpaces). It can achieve even lower latency using embedded space. Also, in addition to the single-threaded approach, GigaSpaces provides standard transaction support. It has several implementation of Spring's PlatformTransactionManager which allow user to utilize Spring's rich support for declarative transaction management (which is reliable and standard), instead of coding an in-house transaction manager which might be error-prone and complex.

In reality, there will be more than 1 application using the XTP. The denominator for all these applications is the same which boils down to data consistency. It is very easy to achieve weak consistency in which many XTP solutions can/only provide. However, for some applications, strong consistency is a must. Therefore, we need to evaluate an enterprise XTP solution from a broader perspective and how much flexibility that it can provide in order to achieve the desired performance, manageability and security. When the usage of a XTP solution is beyond the basic and many different applications rely on it, these functionalities are not just "nice-to-have" but essential foundations for any enterprise application.

At the end of the day, what we would like to achieve in Extreme Transaction Processing is to keep latency low and throughput high while the processing (the business logic) is done transactionally (i.e. to provide ACID guarantee). Therefore, the performance of a XTP should be measured against all 3 properties as a whole in order to get a better idea of the capability of the solution.