Follow by Email

Saturday, 24 August 2019

frontend vs backend development

I am sure you might have got into discussion of frontend vs backend development or some engineers want to do only one type of development.


Image result for frontend vs backend

I am passionate engineer for more than decade and have got opportunity to see full spectrum.  I have done development on extreme end of both the side.

In this post i will share something on front-end engineering that is hidden and things that is not discussed openly.

Lets start ..

Back-end 
In this part of the work every one understands that it is a world of data structure , algorithm and writing bare metal code, handling scale etc.


Front-end
In this part of world most of us think is only about building engaging and secure User Interface, but i will say it is just one part of it.
As a frontend developer you are exposed to so many engineering challenges. Lets discuss about it.

Getting started
For any backend related task you can write the quick code or that code can come from Stackoverflow and go and run from IDE.

Frontend getting code is just small part but after that you need some webserver/container to host the code and then know the browser/client that you want to use and then finally code runs.

This is just small example and you can get idea of extra number of steps required to see your code running.

Synchronous vs Asynchronous 
On backend system you have option to choose if code is Sync vs Async but on frontend most of the operations has to be asynchronous otherwise end user experience is very bad.

On frontend you are exposed to this on day one but on backend it will take months or year before you get to state where start thinking about sync vs async .

I am sure if you have done any concurrent programming then you know how hard it is to coordinate async tasks.

Distributed Computing
 Now distributed computing has become so common that now it is hard to think of system that is not making distributed calls.

As a backend developer you are guarded or gets late exposure to distributed computing but on frontend every call to get data is remote call, so you have to aware about failures that can happen when remote call is made and slowness it adds.

Proper error handling becomes optional in backend system but on frotnend it is not the option because user will noticed it and complain about it.

Frontend is the last gate so it has to handle all the errors that are thrown or  suppressed by backend systems, so end user experience is smooth.

You experienced distributed computing very early once you are on frontend side.

Network 
We read many text book that "network is not reliable" and as a backend engineer you don't get directly exposed to this because library and framework handles it for you but on frontend you get first hand experience to deal with and come up with strategy

All the backend application gets benefit of fast network ("100 GBs network") because it runs in data center but for frontend application is data center is end user device which will be browser/handheld device.
Many time network is dial up( i.e KBs) and application has to work on slow network.

Compute and In-memory 
This one is interesting because when backend program is slow first option is increase compute or memory because elastic infra allows to do that that but on end user side no elasticity, so first option is no option for front-end friends.

Approach taken to optimize frontend is very creative and innovative as compared to backend. This also put design pressure on front application.

Algorithm 
Backend systems has more options on algorithm that can be used to solve program for example Disk based algorithm are very common for many data intensive backend application but on frontend side this option is not available or in very limited way and you have to very creative in how do you use it.

I think many chapters of algo book is Not Applicable for frontend.

Patterns
On frontend side industry is inventing new patterns every day but backend side does not move at that pace for eg functional composition , incremental rendering , state management using immutable DS , event driven systems, chunking of requests , late arrival of information due to slow network etc


Artifact/Packaging
Backend system are never seen from lens on how big jar/exe/dll is but this is first challenge to be solved on front-end side because package must be small so that it can be downloaded quickly by clients.
Network play role in this remember 100GBs vs Kbs ?

Requirements
This can be little controversial but in many case frontend are built with fuzzy or no requirement and later requirement is added. Requirement is must for backend! 

Testing
This is the hardest part for frontend. I will leave this for now because it needs multi series blog just for this topic.

Conclusion

I know it might look like i am just trying to sell frontend development is more complex but my point is you become better engineer when you move to frontend.
If you are not doing any frontend then find way to do that or learn about these hard problem from frontend engineers and incase they say "i don't think about these challenges" then educate & help them.

If you like the post then you can follow me on twitter .





Saturday, 17 August 2019

JVM with no garbage collection

JVM community keeps on adding new GC and recently new one was added and it is called Epsilon and is very special one. Epsilon only allocates memory but will not reclaim any memory.

Image result for garbage collection

It might look like what is use of GC that does not perform any garbage collection. This type of Garbage Collector has special use and we will look into some.

Where this shinny GC can be used ?
Performance Testing

If you are developing solution that has tight latency requirement and limited memory budget then this GC can be used to test limit of program.

Memory Pressure Testing
Want to know extract transient memory requirement by your application. I find this useful if you are building some pure In-Memory solution.

Bench marking Algorithm.
Many time we want to test the real performance of new cool algorithm based on our understanding of BIG (O) notion but garbage collector adds noise during testing.

Low Garbage
Many times we do some optimization in algorithm to reduce garbage produced and GC like epsilon helps in scientific verification of optimization.

How to enable epsilon GC

JVM engineers have taken special care that this GC should not enabled by default in production , so to use this GC we have to use below JVM options

-XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xlog:gc


One question that might be coming in your mind what happens when memory is exhausted ? JVM will stop with OutofMemory Error.

Lets look at some code to test GC

How to know if epsilon is used in JVM process?

Java has good management API that allows to query current GC being used, this can also be used to verify what is the default GC in different version of java.

Run above code with below options
-XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC VerifyCurrentGC

How does code behave when memory is exhausted. 

I will use below code to show how new GC works.

Running above code with default GC and requesting 5GB allocation causes no issue (java -Xlog:gc -Dmb=5024 MemoryAllocator) and it produces below output

[0.016s][info][gc] Using G1
[0.041s][info][gc] Periodic GC disabled
Start allocation of 5024 MBs
[0.197s][info][gc] GC(0) Pause Young (Concurrent Start) (G1 Humongous Allocation) 116M->0M(254M) 3.286ms
[0.197s][info][gc] GC(1) Concurrent Cycle
[0.203s][info][gc] GC(1) Pause Remark 20M->20M(70M) 4.387ms
[0.203s][info][gc] GC(1) Pause Cleanup 22M->22M(70M) 0.043ms
[1.600s][info][gc] GC(397) Concurrent Cycle 6.612ms
[1.601s][info][gc] GC(398) Pause Young (Concurrent Start) (G1 Humongous Allocation) 52M->0M(117M) 1.073ms
[1.601s][info][gc] GC(399) Concurrent Cycle
I was Alive after allocation
[1.606s][info][gc] GC(399) Pause Remark 35M->35M(117M) 0.382ms

[1.607s][info][gc] GC(399) Pause Cleanup 35M->35M(117M) 0.093ms
[1.607s][info][gc] GC(399) Concurrent Cycle 6.062ms

Lets add some memory limit ( java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xlog:gc -Xmx1g -Dmb=5024 MemoryAllocator)

[0.011s][info][gc] Resizeable heap; starting at 253M, max: 1024M, step: 128M
[0.011s][info][gc] Using TLAB allocation; max: 4096K
[0.011s][info][gc] Elastic TLABs enabled; elasticity: 1.10x
[0.011s][info][gc] Elastic TLABs decay enabled; decay time: 1000ms
[0.011s][info][gc] Using Epsilon
Start allocation of 5024 MBs
[0.147s][info][gc] Heap: 1024M reserved, 253M (24.77%) committed, 52640K (5.02%) used
[0.171s][info][gc] Heap: 1024M reserved, 253M (24.77%) committed, 103M (10.10%) used
[0.579s][info][gc] Heap: 1024M reserved, 1021M (99.77%) committed, 935M (91.35%) used
[0.605s][info][gc] Heap: 1024M reserved, 1021M (99.77%) committed, 987M (96.43%) used

Terminating due to java.lang.OutOfMemoryError: Java heap space

This particular run caused OOM error and is good confirmation that after 1GB this program will crashed.

Same behavior is true multi thread program also, refer to MultiThreadMemoryAllocator.java for sample.

Unit Tests are available to test features of this special GC.

I think Epsilon will find more use case and adoption in future and this is definitely a good step to increase reach of JVM.

All the code samples are available Github repo

If you like the post then you can follow me on twitter .


Wednesday, 14 August 2019

Need driven software development using Mocks

Excellent paper on mocking framework by jmock author. This paper was written in 2004 that is 18 years ago but has many tips of building maintainable software system.

Related image

In this post i will highlight key ideas from this paper but suggest you to read the paper to get big ideas behind mocking and programming practice.

 Mock objects are extension of test driven development.

Mock objects can be useful when we start thinking about writing test first as this allows to mock parts that is still not developed. Think like better way of building prototype system.

Mock object are less interesting as a technique for isolating tests from third-party libraries.

This is common misconception about mock and i have seen/written many codes using mock like this. This was really eye opening fact that comes from author of mocking framework.

Writing test is design activity

This is so much true but as engineer we take shortcut many time to throw away best part of writing test. Design that is driven from test also gives insights about real problem and it lead to invention because developer has to think hard about problem  and avoid over engineering

Coupling and cohesion 

As we start wiring test it gives good idea on coupling & cohesion decision we make. Good software will have low coupling and high cohesion. This also lead to functional decomposition of task.
Another benefit of well design system is that it does not have Law_of_Demeter, this is one of the common problem that gets introduced in system unknowingly. Lots of micro services suffer from this anti pattern.

Need driven development
As mocking requires explicit code/setup, so it comes from need/demand of test case. You don't code based on forecast that some feature will required after 6 months, so this allows to focus on need of customer. All the interfaces that is produce as result of test is narrow and fit for purpose. This type of development is also called top down development.

Quote from paper
"""
We find that Need-Driven Development helps us stay focused on the requirements in hand and to develop coherent objects.
"""


Programming by composition

Test first approach allows you to think about Composability of components, every thing is passed as constructor arguments or as method parameter.
Once system is build using such design principal it is very easy to test/replace part of system.
Mock objects allows to think about Composability so that some parts of system are mocked.

Mock test becomes too complicated
One observation in paper talks about complexity of Mock Test.
If system design is weak then mocking will be hard and complicated. It does amplification of problems like coupling, separation of concern.  I think this is best use of mock objects to get feedback on design and use it like motivator to make system better.

Don't add behavior to mock
As per paper we should never add behavior to stub and in case if you get the temptation to do that then it is sign of misplaced responsibility.

If you like the post then you can follow me on twitter to be notified about random stuff that i write.