rpc - Backend-frontend two way communication

We currently have a django app serving our frontend website to the users over Apache.The frontend queries our backend, which is a separate Python app (Flask) served a different server.So far, the frontend has been required to query the backend for data but not the other way around.We are now introducing data alerts that users can choose to receive regarding data changes in the system.The process for checking whether an alert has happened has to occur on the backend, as it is closely coupled with the data model.Hence, the frontend sends a reques...Read more

rpc - Go-Ethereum | How to connect to public Ropsten(testnet) running on local

Basically I want to connect to the public Ropsten testnet. I run geth on local with several options. (--testnet, --rpc, --rpcapi, console).I thought I can get my (ropsten) account and check how much 'ether' or 'erc20 tokens' that I have on ropsten testnet. However, it didn't recognize the ether that my account had. For example, I successfully sent some 'ether' and 'custom erc20 tokens' to my account using "ethereum wallet". I could see the correct amounts on metamask when I connected to 'Ropsten Test Network' to click the dropdown bar at top of...Read more

Is RabbitMQ practical for RPC-esque bidirectional use during request processing?

Super simple question, I couldn't find a concrete answer out there.Is RabbitMQ suitable for RPC-like operations when processing HTTP requests?I'm interested in firing off a message when a user HTTP request is received, waiting for the response from a backend server, and then sending the response to the client.Is that a common use scenario? Are people doing it with success? Any pitfalls? Any examples or common design patterns?...Read more

rpc - at-most-once and exactly-once

I am studying Distributed Systems and when it comes to the RPC part, I have heard about these two semantics (at-most-once and exactly-once). I understand that the at-most-once is used on databases for instances, when we don't want duplicate execution.First question:How is this achieved? How does the server know that it shouldnt execute the request again? It might be a duplicate but it might be a legitimate request as well.The second question is:What is the difference between the two semantics in the title? I can read :). I know that at-most-onc...Read more

RPC semantics of gRPC

I am trying the find out what RPC semantics the gRPC library provides? Is it at-most once? Does it guarantee that an RPC call made by a client is not executed more than once on a server? I couldn't find this explicitly mentioned anywhere in the docs.From what I understand, gRPC channels have an exponential back-off based retry mechanism of re-initiating TCP connections after transient failures. So, if a server fails after executing an RPC call but before responding, and later comes back up, a client RPC may end up getting executed twice.Can som...Read more

rpc - Communication Between Microservices

Say you have microservice A,B, and C which all currently communicate through HTTP. Say service A sends a request to service B which results in a response. The data returned in that response must then be sent to service C for some processing before finally being returned to service A. Service A can now display the results on the web page. I know that latency is an inherent issue with implementing a microservice architecture, and I was wondering what are some common ways of reducing this latency? Also, I have been doing some reading on how Apache...Read more

rpc - Data validation in AVRO

I am new to AVRO and please excuse me if it is a simple question.I have a use case where I am using AVRO schema for record calls.Let's say I have avro schema { "name": "abc", "namepsace": "xyz", "type": "record", "fields": [ {"name": "CustId", "type":"string"}, {"name": "SessionId", "type":"string"}, ]}Now if the input is like{ "CustId" : "abc1234" "sessionID" : "000-0000-00000"}I want to use some regex validations for these fields and I want take this input only if it comes in particular format shown as abov...Read more

Do we really need to import Corda's code for RPC ? How in the future?

I know that Corda is in the process of removing its web server module and in the documentation they suggest the use of other frameworks.In one example ("spring-observable-stream") they use Spring Boot for the server-side APIs and use an RPC call to the actual running Corda node. That's fine and comparable with what I have to do.In that example, the author import the specific Corda's RPC code, along with the code of the actual flow (and states) needed.What I want to ask here is if it's possible to avoid that tangle and keep the web server APIs i...Read more

Corda webserver produces exception "User not authorized to perform RPC call nodeInfo with target"

I am trying to restrict a node to perform certain flow, For Example, I have two flows FlowOne and FlowTwo. For PartyA, I want to give permission for FlowOne, For PartyB permission for FlowTwo. Permission to the rpc calls should be there also.Here is my rpcUsers configurationPartyA: rpcUsers = [[ user: "user1", "password": "test", "permissions": ["StartFlow.net.corda.mortgage.msr.flows.FlowOne","InvokeRpc.startFlow"]]]PartyB: rpcUsers = [[ user: "user2", "password": "test", "permissions": ["StartFlow.net.corda.mortgage.msr.flows.FlowTwo","Invok...Read more

Can we do RPC connection to corda using NodeJs?

I know CordaRPCClient is there to do the RPC connection to the network.Is there any possibility, can we do that happen in NodeJS so that I can write my middle ware in nodejs.Is there something corda team is planning to build for client library for NodeJS implementation of RPCops....Read more

rpc - Corda view consumed states in terminal

is there an easy way to view the consumed states in the terminal with the CordaRPCOps interface? It seems that vaultQuery returns unconsumed states by default and I can't figure out how to use vaultQueryBy or anything with the criteria. I know that there should be consumed states because I can see them with H2...Read more