Sunday, April 16, 2017

Ruminating on the single-threaded model of NodeJS and Node-RED

Many developers and architects have asked me questions on the single-threaded nature of NodeJS and whether we can use it effectively on multi-core machines. Since Node-RED is based on NodeJS, whatever is valid for NodeJS is also valid for Node-RED.

NodeJS has a single thread per process model. When you start NodeJS, it would start a single process with one thread in it. Due to it's non-blocking IO paradigm, it can easily handle multiple client requests concurrently, as there is no thread that is blocking for any IO operation.

Now the next question is around the optimal usage of multi-core machines. If you have 8 core or 16 core machines on your cloud and just run one NodeJS process on it, then you are obviously under-utilizing the resources you have paid for. In order to use all the cores effectively, we have the following options in NodeJS:

1) For compute-intensive tasks: NodeJS can fork out child processes for heavy-duty stuff - e.g. if you are processing images or video files, you can fork out child NodeJS processes from the parent process. Communication between parent and child processes can happen over IPC.

2) For scaling REST APIs: You can start multiple NodeJS processes on a single server - e.g. if you have 8 cores, start 8 NodeJS processes. Put a load balancer (e.g. nginx) in front of these processes. You would anyways have some kind of load-balancing setup in your production environment and the same can be leveraged.

3) Cluster support in newer versions on NodeJS: In the latest versions of NodeJS, you have support for Clusters. Cluster enables us to start multiple NodeJS processes that all share the same server port - e.g. 8 NodeJS processes all listening to port 80.  This is the best OOTB option available today in NodeJS.

Hence it is indeed possible to effectively utilize NodeJS on multi-core machines. A good discussion on the same is available on StackOverflow here.

Another interesting question that is often asked is whether Java developers should jump ship and start development in NodeJS because of its speed and simplicity. Also, NodeJS evangelists keep harping about the fact that the single-threaded nature of Node removes the complexity of multi-threading, etc.

Here are my thoughts on this:

1) Today Java has first class support for non-blocking IO, similar to NodeJ. Take a look at the superb open-source  Netty library that powers all the cloud services at Apple.

2) Most of the complexity of multithreading is abstracted away by popular frameworks such as Spring - e.g. Spring Cloud enables developers to write highly scalable and modular distributed applications that are cloud-native without dealing with the complexities of multi-threading.

3) The Servlet 3.0 specification introduced async requests and the Spring REST MVC framework also supports non-blocking REST services as described here.  

Thus today, all the goodies of NodeJS are available on the Java platform. Also plenty of  Java OSS to kick start your development with all the necessary plumbing code.

Ruminating on a nifty tool called 'ngrok'

Many a times developers want to test their APIs running on their development machine against a mobile app. To do so, developers typically do the following:

Option A) Create a hotspot Wifi on their development machine and connect the mobile phone to this Wifi. Since both the mobile phone and their development machine is on the same network, the mobile app can call the APIs running on the localhost of the developer machine.

Option B) We host the APIs on a public cloud (with a public IP), so that the mobile app can access it. For this, the developer needs to setup a automated CI/CD process that would deploy the REST APIs on the middleware.

There is a third option where-in, the developer can run the API server on his local machine and just create a proxy server on the internet that would securely tunnel the request to this local machine through the firewall. This can be done using ngrok - https://ngrok.com/

ngrok can be setup on your local machine within minutes and can serve as a great debugging tool. It has a network sniffer built in that can be assessed from http://localhost:4040
We would highly recommend this tool for any mobile/API developer. 

Monday, February 13, 2017

IoT energy standards in Europe for Smart Home / Smart Grid

European governments are pretty energy conscious with a number of initiatives in the EMEA region around smart energy grids. Jotting down some of the energy standards that are relevant in Europe.

In order to successfully build a smart grid system, it is important to have standards through which home appliances can publish information on how much energy they are using in real-time, which in turn can be provided to consumers and energy management systems to manage energy demands more effectively.

Smart appliances are also technically very heterogeneous, and hence there is a need for standardized interfaces. The standardization can happen at two levels - the communication protocol level or the message-structure level.
  • SAREF (Smart Appliances REFerence) is a standard for exchange of energy related information between home appliances and the third-party energy management systems. SAREF creates a new reference language for energy-related data. 
  • EEBus - A non-profit organization for interoperability  in sectors of smart energy, smart home & building. EEBus has defined a message-structure standard called as SPINE (Smart Premises Interoperable Neutral-message Exchange). SPINE only defines message structure at the application level (OSI Layer 7) and is completely independent from the used transport protocol. SPINE can be considered a technical realization of the SAREF onthology. 
  • Energy@Home - Another non-profit organization that creating an ecosystem for smart-grid. 
  • SAREF4EE - The extension of SAREF for EEBus and Energy@Home initiatives. By using SAREF4EE, smart appliances from different manufacturers that support the EEBus or Energy@Home standards can easily communicate with each other using any energy management system at home or in the cloud.

A good presentation illustrating the current challenges in Smart Home is available here - http://www.slideshare.net/semanticsconference/laura-daniele-saref-and-saref4ee-towards-interoperability-for-smart-appliances-in-the-iot-world