Do you know Distributed transactions? 

"Monolithic architecture is old and gone". Be careful when you say that, because that's wrong. Well modularized and encapsulated monoliths can be better than having a miscroservices architecture. It all depends on the use case.

These videos of yours are so good, and easy to understand, it's insane! You are a great teacher!

Apricate your efforts to put all this information together! I like your style of explaining the things using comparison. Most (old) people know how things work in monolith and it's easier for then to understand how it works differently in microservices. Thanks! for all these videos on microservices, keep doing your good work.

Thank you for explaining the distributed transaction management in various ways.

12:46 when I am in an interview. BTW, nice explanation.

A great example of the tradeoffs one makes w/ microservices. Wish tech executives would understand this before they just decide that every system in a company is now going to be microservices.

Narendra, Thanks for producing unique and original content

You have explained so clearly. Thanks.

12:20 - "I'm not going to recommend anything as I haven't applied these on my projects yet, but this is what I've learned so far" That ladies and gentlemen, is a clear sign of an honest and generous person. Thank you.

Nice video, thanks a ton. For next video, can you please pickup this subject "How to protect your distributed system, or how to protect your endpoints from DDOS, i.e. security aspects of system design."

Hey, Thank you so much all your knowledge sharing. I am able to perform very nice in all my interviews. Keep up the good work. More power to you. Keep rocking!!!

Thanks so much for the videos, really good explanation on a very complex topic

Awesome content. Thanks for sharing knowledge. Appreciating your hard work.

This is a great video, thanks for sharing!

Oh, that's interesting. I had no idea about this extra microservice to deal with roll-backs for a saga. Makes sense.

Thanks, I was unaware of how distributed transactions are handled in microservices because quite honestly, I've never seen any of these in the systems I've worked on. Either transactions were handled in a relational database or there was no need for transactions. In the last scenario (sagas), I think we can imagine what might happen after a successful wallet check: Create a message that can be used to fulfill the order (eg. sufficient funds). Presumably, there are workers that pull these messages from the queue, and there is another set of services for order fulfillment, inventory, etc.

Thank you Sir. For making these videos and helping us.

Excellent job!Learned a lot from your video!

that knife attack on order microservice was a killer move!. Exxcellent video sir

@Tech Dummies : Wonderful video. You have a very easy explaining style. Keep it up.

superb video thammudu.. @RU-vidrs: THIS IS A MUST WATCH VIDEO for distributed transactions basics related to microservices.

Thanks for the nice video. I have a few questions: 1) Does each micro-service commit to their DB or it is done by the Co-ordinator? 2) For the "commit" part, assume CustomerWallet MS give "ok commit" whereas Order MS didn't report commit/fails; how does it work then?/ 3) Is Co-ordinator a generic component or custom made? who is providing it? I am aware of, in the context of the J2EE, it is provided by the Application server. Since we may not be using Application-Server all the time, who' providing the co-ordinator?

Very practical understandable enjoyable thanks

Congratulations about this video!!! Thanks so much, man!!!

Great explanation. Thank you

Nice explanation... Thank you !!

Thanks, keep going 👍

@Narendra Nice video. One correction though: In 2PC, If Prepare Phase is successful and then during Commit phase one of the parties cannot commit it, the co-ordinator retries that. The service that is not able to perform commit has lost it's right to say NO to this transaction. The Coordinator will keep on pushing the transaction to this service. Even if the service went down, when it comes up, it will be forced to apply this commit. This is one of the drawbacks as well.

Thank you!

Excellent!!!

Kudos on a great overview and explanation.

superb .. nice explanation

excellent video

very good topic. Well covered

Great explanation, thanks!

Thanks bro. Good video

Nice video, I looked a lot of your videos, You are doing good things to us, what I recommend is could you share some famous papers such as GFS, HDFS, Zookper, Paxos etc. in thefuture

thanks for making video,,,

Great bro..so fast

Good Explanation!!!

Great explanation thanks 🤗

First, I very much appreciate the video, but with 2 suggestions: I don't think the advantages of 3PC over 2PC are well-elaborated, and it would be better if the comparisons (pros and cons) of the 3 patterns are compared.

ek number bro, maza aagya, so simple and detailed explanation

Awesome

I was recently asked in an interview how do you rollback transaction in a microservice architecture and my answer was to wait for the response for an interval and if you don't get it it means your transaction has failed and use another microservice to roll back. Turns out thats what Saga actually does! I feel pretty cool now bcos i knew nothing about saga before this video!

Thank you so much !

Content is good. Would like to see this simple code example of order using saga or 2/3PC.

Good Content!

Narendra, great video. Keep it up.

amazing video

What a great video!

Thanks its really helped me to understand the concept

Narendra, in an Microservice ecosystem, will you have multiple coordinator services for say a 3 phased commits that are needed for more than say 4 services?

@Narendra, Nice explanation. In saga pattern explained, In case of failure of Wallet MS, rollback event is pushed to rollback event bus to get order rolled back. But the chances are that meanwhile a customer could read the above transaction from order MS but later on it was rolled back and then it won't appear in further reads. How do we solve this? Is there any way in SAGA pattern to solve that?

Nice video , I want to know how the amazon flash sale works? .can you make video on it in details? .Thanks in advance.

Can you please make a video on Coupon Management System? Thanks!

for the saga pattern if there are more than one instance of microservice M1 listening to the event... it is very critical to maintain the order in this case (maybe those events were required to be in sequence, like we have partition keys for kafka) . What are your thoughts on this?

Thanks for the nice explanation. Question : why cant order service call customer wallet serivce through api call and do the processing instead of having distributed transactions ?

Not super clear how Saga solves the distributed transaction problem since the example only considered a single microservice, but solid information. I can learn more myself now, thanks.

Hi Narendra, videos are awesome, can you please make the video with Oauth level with two level Authentication .

can u please make a video over grpc , why and when to use it, its pro ad cons and how is it compare to rest api

One note on your SAGA example. I opine that a decline message from Wallet goes to the original Order service ( not some other new service). The order service likely needs to understand creating, deleting, modifying, etc orders. You don't build a separate microservice for each function about orders, you have a service that understands all of the 'order' function. In the same way, I question the Wallet service responding to a successful order by replying to the caller. How does the wallet service know enough information to talk to the caller? All it should understand is how much money is in the wallet, and be able to add / subtract amounts. An 'OK' message should go to the Order service and let it tell the user that the order was successful.

in the last example shouldn't the customer wallet publish a rollback message that is consumed by the Order MS? Otherwise how does the record in the Order MS get rolled back (or updated to be in some sort of failure state)? If it is eventually rolled back by a message that is published by the Rollback MS what is the purpose of the Rollback MS? Would love to understand the benefits of an additional service if there is one:) one more nit: from what I understand only certain message/queue technologies such as Kafka have the capability of processing messages in order out of the box. do you know of many others or is there typically a way to add-on in-order processing to any queueing system? thanks for you videos!

Good video,could you please make a video about banking system design

Great tutorial...! Very useful for all..! #tamilcloudzone

Nice explanation. Thanks. A question- The co-ordinator we are talking about for 2 phase and 3 phase commit is nothing but doing orchestation work. Correct ? Or do we see any difference between co-ordinator and orchestrator?

Please elaborate more on SAGA, which is most popular and useful.

Thanks Narendra for this wonderful explanation. I have a question, What happens in 2phasecommit if let say in your example the commit order fails? Is the customer wallet rolled back?

What will happen if the ok wallet commit returns "ok" but the ok order commit doesn't return "ok" ? How do you undo the ok wallet commit as it is already committed ?

Microservices and Queue Servers need to be highly available in order to make the isolation work. For example, if the rollback message is stuck in the queue or not processed by the consumer microservice, there will be an inconsistent state for the system.

Awesome bro.. ❤️❤️

One of the best videos on this topic I have seen on youtube, very good explainations!

great explanation, but I did not understand how response will send back to UI/client when we use second(queue) based approach. I mean suppose I am one micro service receives https request from browser and this micro service pass on the request other micro service than which micro service will respond to browser ?

explanation is very nice .can you share 2 PC /SAGA implementation in microservice?

You explain really well. It is very rare for somebody to explain so clearly going through the ideas step by step.

Thaannksss

Great explanation. there are some library implementations of saga pattern if anyone is interested in the implementation Camunda: java based Apache Camel

perfect

Hi Narendra, You have explained it very well. I have few doubts here. I browsed these doubts all over the internet and I did not get proper answer in GPT as well. 1. What if the paricipants have multiple replicas ? How co-ordinator will make sure the prepare and commit request will always hit the same replica ? 2. I am thinking out this doubt in Java/Spring Implementation. I know transactions can be created using Transaction Annotation and a same thread will work until the transaction is committed. Once participant creates local transaction, it must be in a new transaction thread. So how this transaction thread is stopped from committing and how it commits after receiving the external request(http thread) from co-ordinator since both threads are different. In simple terms, how the two different threads are communicated ? one is new http thread(prepare or commit) and already created transaction thread ? I hope the understanding of doubt is clear. Please let me know if there is a problem. I will elaborate maybe. I am badly searching for the doubts.

I have a project with choreographed event driven microservuce architecture (Kafka for communicating these events). We have a need to have transaction across database and kafka (eventually other services). We plan to use transactional outboxing pattern. Do you have better alternative?

Please explain how transaction happens in Cassandra. I mean read write in Cassandra.

Narendra, isn't microservices and SOA defined by different authors differently? As I tried to investigate the differences between SOA and microservices, I came to the conclusion that there is no common agreement on what SOA is. Moreover, some people don't see the difference between SOA and microservices. Moreover, from my perspective, ideas are actually the same. Decoupled services that are part of a system and provide small pieces of functionality. To be honest, software development in 2019 is full of not-strictly-defined terms which really bugs me.

In saga patter, what if customer wallet ms also talks to a database and put the money into the database before sending message to next queue? I think the sequence should be like: 1. customer wallet ms writes to DB successfully. 2. customer wallet ms send message to output queue. 3. customer wallet ms commits offset in previous queue. Could you elaborate the failure model when a database is involved here?

In the SAGA example, what happens if - There are multple `Customer Wallet MS` hosts, scaled horizontally. - And two different Orders from message queue (q) for same customer is received by two different `Customer Wallet MS` hosts at the same time. - I guess we are again back to the same lock situation where same customer wallet will be tried to be read-write and may result in data coruption.

Saga, does solve the complexity in 2 or phase commit. But if a front-end is waiting to update the customer on an order, will it be polling a Queue/Datastore for update directly or indirectly through another microservice? Either ways, that also seems to be problematic????

what are typical choices for the sagas queues?

whats your point of adding three phase commits? seems the whole point is message queue which hands the problem very gracefully.

Hey Narendra, thanks for sharing this! But I still haven't 100% consumed the part of difference between 2-phase commit protocol and 3-phase commit protocol. Would you mind educating a little bit more on it?

Thanks for sharing the great information.I have a small question that why a third microservice would be required to rollback in case of SAGA pattern as you mentioned in your tutorial that no 2 microservices should share the same database and if we need a different service to rollback wouldn't it be calling the same database that was used by the 1st service in order to rollback?

In 2PC, why are you first checking customer wallet and then you are going for order creation? You should first create order and then check wallet like u did in SAGA Pattern.

Thank u 🙏🙏

Hello, is there any book or paper recommendation on database storage/engine/transaction design? thanks?

Hello brother , thanks for such type of videos but i have a question can you resolve it please. Suppose i have three table A,B,C and i am inserting data in all the three tables sequently. first in A then in B then in C . Now suppose while inserting data in C there comes an issue so the transacation will rollback. But I want that in table A and B data should be committed . So how can we do that ??? it will be thank full if you reply on the same :-)

Does SAGA really brings any advantage in speed considering that if some service fails all other participants must rollback previously committed transactions?

Very interesting, one question, In saga what if Order MS also looks up queue message to rollback order rather that new MS?

great video, but for those who have just started to learn

I recently implemented SAGA pattern, can you kindly implement the 2-phase commit with example

How rollback works in participant's failure in two phase commit??

If resources are not locked means dependent actions can happen before rollback is issued. So if you buy 100 ,before it is completed, sell of 50 is issued. How do we make sure that sell of 50 is not processed without waiting for distributed completion of previous action.that means something has to be synchronous. Some things can not be asynchronius.. commit or rollback must be synchronous or in the same queue in the same sequence before next sale of the same. Or before any dependent action. You can't have a rollback k in some async fashion without preventing dependent actiobs

My friend, your videos of 10 or 15 minutes are much better. Because we can learn more fast the concepts and start with a new one