Category: Uncategorized

React-Native iOS application compilation errors in XCode 12.5 update

Error: Cannot initialize a parameter of type 'NSArray> *' with an rvalue of type 'NSArray *'

Solution:

Replace
(NSArray> *)modules
with
(NSArray *)modules

Well I have posted same question in Stackoverflow as well. you can check and answer for this here

We have ReactJS + NodeJS backend app running in Google GCP App Engine, but what we are experiencing is server down time for few min randomly. We have info Logs and error logs in code almost every api and every major functions and all catch blocks. I have also put global exception catch block

process.on('uncaughtException', (error) => {
Logger.error('--- Exception -----', error);
});

I also have error handler middleware in expressjs.

but whenever server restarts by itself i don’t see any exception in logs, it doesn’t even appear in process.on(‘uncaughtException’ block also.

One observation is GCP App engine is auto scaling when there is more traffic, but app is going down whenever there more traffic despite auto scaling is happening.

I want to know how to handle this, how to debug this to identify where exactly the issue is, is the issue is at code level if so why none of the exceptions are caught? or the issue is with GCP?

our production server also goes down many times randomly.

I tried using longjohn and setting NODE_DEBUG environment variable to net to get some hint as suggested in other SO Post

Update: We Ran Jmeter Performance test to check whether load on server is the main reason, as Rafael Lemos rightly pointed in comment, in our case “The instance exceeds the maximum memory for its configured instance_class” may be the reason behind server going down, with lot of trail and error, when we made minimum no of instances = 2 we are not observing server going down.

However jmeter tests are all running fine but when we do jmeter test as well as manual testing at a time , we are observing Socket Hangup Exception, this crash happens immediately as soon as we start using front end app, where as jmeter tests access our backend app. Both backend and front end are running in same app engine.

Kindly find our observations below

Now question is Why Socket Hangup is coming, when I explored this, I found a solution in some other SO post, to handle socket hangup exception I have put below code in app.js but its not working

app.use((req, res, next) => {
  if(res.socket.destroyed) {
    console.log('----- socketIsDestroyed-- ', res.socket.destroyed);
    res.end();
  } else {
    console.log('----- socketNotDestroyed-- ', res.socket.destroyed);
    next();
  }
})

And in Google App Engine Sys logs I see following error log multiple times

GET 503  /readiness_check failReason:"app lameducked"

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We have seen how to design platform architecture with multiple apps, we understood pros and cons of that approach in my previous article, Read it from below link

Read – Platform Architecture with Multiple Apps

For applications like Amazon, Netflix, Linked in the backend systems deals with billions of requests per second. It is not possible to handle such a huge traffic by having one consumer app or one seller app. The solution to such a huge systems is micro service architecture.

Probably Amazon has mastered in Micro Service Architecture which runs over more than 500 micro services, similarly Netflix has over 500 micro services and their API Gateway handles over 2 billion requests daily – Source

So dividing Amazon kind of apps into multiple micro services may have following services

Amazon Kind Of Platforms Micro Services

1. User & Identity Management Micro Service
2. Product Management Micro Service
3. Order Management Micro Service
4. Payment Management Micro Service
5. Delivery Management Micro Service
6. Data Mining Micro Service
7. AI Micro Service

The Micro Service Architecture Looks as follows for Amazon Kind of Platforms

Advantage of Micro Service Architecture

Highly Scalable: Systems of this kind are highly scalable, capable to handle billions of requests every day

Heterogenous Technology: Another major advantage is we can develop each micro service using different technology whichever is suitable for it. Example Order Management you can develop using nodejs and MongoDB, however for data mining management, you can use python and MongoDB. For payment management you can use Java with Postgres SQL

Easy to Build and Maintain: Your development team might have spread across the world, it is easy to maintain and build any service any time

Ever Evolving: Every micro service can evolve at any great extent without affecting other systems

After knowing all of these the question arises, is Micro Service architecture is the best? Should Every App has to adopt to it ?

The answer is NO : Architecture of every platform greatly varies depends upon the needs of the platform. Micro Services approach is suitable for highly scalable systems, however for smaller platforms having multiple apps under same platform is suitable.

To understand even better Read Case Studies of Different Platform Architectures

In our previous article we have seen why and how to design the platform as multiple apps running in independent server with their own database.

Read in Previous Article

API Gateway and Need of API Gateway in Platform Architecture

But for any platform the most important Managing the API Calls, what I mean here is there should be something in between clients and various services which will receive incoming requests, invokes various apis and return the appropriate results.

Also any backend platform should keep track of Api calls, rate limiting – it is defining the rate at which consumer can access apis, limit the number of api calls per second per user or per app, throttling – is controlling usage of apis for consumers for a given period of time, securing apis through api keys and user authentication.

in platform architecture API Gateway is like front facing for incoming client requests. Apigee is one very popular api gateway, however it is suitable for enterprise and big applications, for small apps and startups where one can’t afford Apigee, they can go for other API Gateways like Google Cloud End Points but it has very limited features OR Kong API gateway.

Boosting your Client Apps Performance and Stability by Adopting GraphQL

GraphQL is a query language for APIs, it is like giving control to clients/apps to fetch what exactly they want rather than decided by server.

Ask for What you need and Get exactly that 🙂

Send a GraphQL query to your API and get exactly what you want

//GraphQL Query to API
{
  product: {
    name,
    images,
    price
  }
}

//This will be input to your API and you will get only that in //response quickly

//Response
{
  product: {
    name: 'Micro Max G6',
    images: [],
    price: '6599 Rs'
  }
}

Get Multiple Information in Single Request

GraphQL will make your apps lightning speed which even out perform greatly in slow network speed as well, because GraphQL is powerful and returns multiple information in single request, which apps typically get it from different api calls.

There are multiple bunch of benefits of GraphQL and its worth to consider using GraphQL while architecting your Platform. Well where GraphQL fits in your platform architecture ? See the updated architecture diagram

Continue Reading About Micro-Service Platform Architecture