Quite honestly, I don’t like to write summaries for this kind of paper. Here, the authors propose a vision for the future of cloud applications, and I feel that summarizing a vision often results in the misinterpretation of that vision. So I recommend reading the paper to draw your own unbiased conclusions.
That being said, here is my extremely high-level take on the paper in a few points:
- Application developers should focus on application logic, and not worry about implementation aspects of consistency, durability, availability, etc.
- It does not mean that developers do not care about consistency, availability, redundancy at all. Instead, they simply should know what they need, and let the cloud provide these. As such, developers should declare their consistency, availability, budgetary needs, etc., and have the cloud runtime enforce such declarations. This will free up the programmers and let them focus on the application logic instead and make this logic “unsoiled” by the other aspects of the distributed app.
- To help developers focus on their applications/tasks, we need domain-specific languages (DSLs). DSLs can hide a lot of “mechanical” work from the programmers and delegate it to the cloud runtime. A good example of a popular DSL we have been using for a very long time is SQL. It is declarative — programmers retrieve and update the data without worrying about how it is done under the hood.
- Despite potentially having many DSLs, we still want one comprehensive framework to run it on, so the visionary system here can compile DSL to some common Intermediary Representation (IR). The authors want the IR to be human-readable and optimizable, although I feel like this requirement is part of the “evolutionary” theme in the paper, and eventually, the importance of human optimizations may diminish.
- Achieving this highly declarative vision is hard, but the paper lists several developing and emerging techniques and research directions that may help evolve the cloud.
1) DSL. We have spent quite some time discussing DSLs and what does it mean to have many of them. For one, we already have a few successful ones, like SQL. Arguably, ML/AI and data processing systems also often have some form of DSLs. TensorFlow was brought as an example. One minor concern that was expressed in the group is that having many of these DSLs requires someone to make and maintain them. A more interesting DSL question is how specialized they should become? To bring SQL example again, while it is great for what it does, it is rarely used all by itself. So there will be a clear need to allow to mix and match these highly specialized DSLs, potentially making the problem of translating them to IR more difficult.
2) IR. A big part of the Hydro system vision is the IR language. The language itself may get rather complicated when it needs to support many IRs. A bigger challenge may be having to translate DSL logic to a human-readable IR code. The translations that are done must make sense to engineers, the logic should be clear and not obscure to allow people to make sense of it. This pursuit of human readability may result in less performance efficient IR. The readability may also depend on the individual DSLs.
Another point we discussed is whether programmers will just start writing code directly in IR if it is a good, readable, feature-rich language. Maybe this is exactly what the programmers need after all? A language made specifically for distributed applications.
3) How much of this is already in the cloud? DSLs exist, the serverless cloud is developing too, providing more consistency and durability than before. For example, Azure Durable Functions save their intermediate state and can be resumed in the face of failures. And surprisingly, many of these cloud offerings, like serverless, durable functions, serverless storage are easy to use. Last semester I gave a project in my Cloud Computing Systems that used blob storage, serverless functions, and durable functions. To my surprise, the students loved the project and were able to figure out all of this tech (which they had to do on their own since the tech aspect was not really part of the problem they were solving) in just a few days. So as it stands right now, the cloud is evolving quickly, with serverless computing and storage becoming more ad more capable. It is not a coherent single cloud runtime just yet, and probably won’t be there any time soon, but some aspects of the vision are there. Users can scale serverless compute, not worry about its availability, may opt into more durable options when needed, may use cloud-native storage with configured/declared consistency, take advantage of DSLs for many tasks in the cloud, like data management, ML/AI systems, etc…
4) Drivers of innovation? An interesting discussion happened at the end of our meeting. Some expressed the opinion that cloud vendors should know better in what direction to develop the cloud since they are in constant interaction with the clients and must adjust to what clients are asking. I, personally, disagreed with this opinion — cloud clients are not thinking about the long-term visions like this paper describes. Instead, they may have more immediate concerns that must be dealt with given all the technology they already use in the cloud. An example I used is the true invention of GUI by Xerox PARC. The vision was out there, but nobody was really asking for this back then, even Xerox did not really know what to do with it, and willingly let others copy the ideas. Yet, this innovation made modern consumer electronics/computing what it is today. I suspect, that if Xerox were asking clients about what to improve, they may have worked on something as boring as developing a console with 120-character lines instead of an 80-characters one to make existing systems more “user friendly.”
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