I am thinking of one thing for the transaction history data. Whether there is an API call, maybe RPC call or REST call, that we can query target wallet address transaction history? I am trying for making a wallet, I think if we can show users their transaction history, it is a good feature for the user experience.
For this question, there are maybe some ways:
Call Bcsscan or Ethereumscan API, directly.
Start your own server, subscribe to all events, and store them to DB and query events in DB.
Any other good ideas for this feature.
For method 2) Currently to extract the full address interaction history you need to walk through all blockchain blocks and then all transactions in those using EVM tracing.
For method 1) You can also get some details over Etherscan API, but please note that this is not an open-source product and you need to contact their paid product support to understand what data is available over their API and what are the API limitations.
Related
I am planning out a new project in which I need to connect one particular Fiat payment gateway to my smart contract. I don't want to have a system with a centralized backend, so I am exploring the possibility to use Chainlink to communicate with API and then pass response to my smart contract. I know that Chainlink allows any contract to access any external data source through their decentralized oracle network. The problem is I can't approximate how much LINK it will cost me to get a response from 1 oracle. Is there some average cost of a 1 response from an oracle and what determines such cost
I tried to look up this information, but it does not seem that this topic is discussed much. Also probably I didn't look in the right place
The problem is I can't approximate how much LINK it will cost me to
get response from 1 oracle.
Nobody can. When you make a request to oracle, you are calling a smart contract function and this will cost you gas which varies depending on the congestion in the system. if system is busy, it will cost more gas. Also when you interact with the chainlink, you are actually passing data to chainlink smart contract which makes some calculations, so you pay for those gas too.
Calling one oracle is sending a request to one oracle. oracle is a chainlink node operator, and it set its own price. But sending a request to only one node is not a decentralized approach even though each node have multiple data resources. you should make a request to several nodes meaning that you need to pay each node operator. when you make a request to several nodes, you receive the average of those responses.
The service you want to use is Chainlink Any Api, and in the service the cost of LINK depends on the node operator you are using.
There is a fee required by node operator. When you send a request, you actually require Chainlink node to provide a service. Usually the service is not free and the fee of a request is set by the node operator. The fee varies across different node operators. If you are only a consumer to use service provided by node operators, you just need to check the fee of different node operators.
you, of course, also has to pay gas fee for your transaction, but that it it costed in ETH rather than LINK (as you asking how much LINK it will cost, I assume you know it).
If you are a node operator and want to run the service for yourself, you may want to consider the following 2 factors:
Congestion of the system mentioned by #Yilmaz. When the blockchain you are using is very busy, the gas price is high so that the more gas fee, which is the result of (gas price) x(gas limit), will be cost more.
The logic of fulfill function in your contract. Fulfillment function is the "callback" function of Chainlink Any Api. Oracle node will fetch the data demand in the request and then call the fulfill function in consumer contract. In fulfill function, logics varies from simply saving the data in a variable or doing some calculations. The more complex logics, the more gas limit required.
Hope it helps!
Using OpenEthereum, which is the json rpc call allowing to do it?
I found the parity_pubsub module but I ve no idea of the parameter for getting not yet confirmed transactions.
I also found https://web3js.readthedocs.io/en/v1.2.11/web3-eth-subscribe.html#subscribe-pendingtransactions in the web3 module but it doesn t allows to filter transactions and the documentation doesn t explains how to use the full web3 api along OpenEthereum.
The purpose
The aim is to frontrun transactions for arbitrage by always maintinning the highest gas price until the next block is mined.
This involve detecting competiting transactions (those targetting the same Ethereum address as mine and with a higher gas price than me) with the lowest latency as possible in order to replace them as soon as possible (either for abortting the trade or changing the gas price again). So this exclude constantly polling for the answer as the requirement is to have the lowest number of context switches.
I need some assistance. I am working on a smart contract that will allow a user to save a string (mapping(address=>string)). The only problem, I would like the contract to pay for the gas for the user to save the string. Any idea on how to
This is a proposed feature but not yet implemented: https://github.com/ethereum/EIPs/issues/1776
This feature is known as meta-transaction: the sender of the transaction doesn't pay for gas.
While there is no native way to conduct meta-transactions yet, there are third-party efforts to implement it, searching the web with meta-transaction keyword should yield useful stuff.
Have a look at the Gas Station Network Alliance:
https://blog.zeppelinos.org/gas-station-network-alliance/
Depending on your use case, if you don't need to save strings directly on chain, an alternative would be something like Peepeth - microblogging with a soul. Peepeth batches signed messages stored in IPFS and anchors the batched data on chain: https://peepeth.com/a/free
I am studying blockchain with Ethereum, and I want to use past transaction data in the Smart contract using Solidity.
If I use Web3.js module in the program written in javascript, I can get these data easily.
But I can't get these data in the Smart contract using Solidity.
Reference of Solidity says that we can get current block number, blockhash, etc., by using "block.number" and "block.blockhash(uint blockNumber)" functions, but doesn't mention getting transaction data.
(http://solidity.readthedocs.io/en/latest/units-and-global-variables.html#special-variables-and-functions)
please help me.
The answer is simple. Unfortunately, you simply can’t access old transaction or block data onchain from Solidity. At most, you can access hashes of last 256 blocks (see blockhash in documentation )
Alternatively, as a workaround you could consider using Oraclize. Oraclize represents way to read offchain data onchain, so you could try to read transaction data from Etherscan web API. The way Oraclize works is that :
You request to Oraclize smart contract what data you want to fetch from internet (some URL)
Oraclize offchain servers then detect your on-chain request
The look up the data you wanted (they'll make some http request to the URL you provided)
Once they get response, they will send transaction to your contract (calling specific callback method) containing data you requested
With such approach however, you are relying that:
EtherScan is up and running
Oraclize is up un running.
If you only care about transaction data related to your smart contracts, another way would be to store that transaction data onchain. Maybe we could gave you some more suggestions if you tell us more about what specific problem are you solving.
We are thinking of building a dapp for finding salon near me and allowing booking. In such application end users has to be shown the salons which are at a certain distance from their current location. Where would be query that data from. Cause I don't think so that kind of querying is possible in solidity. Do we need to bring in any RDBMS in such a scenario to store salon data so that we can query it easily and booking information can be sent to blockchain.
Is hybrid application the only way out? People are talking about IPFS should be used for storing the images, videos and other data. Is that the solution, if yes then how would we query it from there? Moreover, would it be fast enough?
TL;DR: Short answer: you might, but you shouldn't.
The real question here is what do you need ethereum for in this project?
In Ethereum, each write operation is costly whereas reading data isn't. Write operations are transactions, read are calls.
It means that "uploading" your salon list will cost you money (i.e. gas), but also each data update (opening hours, booking ..).
For the mysql specific part of your question, well Ethereum is not designed for that kind of operation.
Something with an oracle might do the trick but it's truly not designed for. See Ethereum like a way to intermediate transactions between peers that stores every transaction publicly and permanently.
According to the Wikipedia page blockchains are basically a "continuously growing list of records". Ethereum has the possibility to make workers run some code in exchange of gas.
This code (or Smart Contract) only purpose "to facilitate, verify, or enforce the negotiation or performance of a contract" (here contract is a legally binding contract).
From what you described, IMO a simple web application with "standard" SQL is more than enough.
You just have to store the salons' GPS coordinates and do the closest match(es) from the user's GPS coordinates.
You likely want to separate your application into two parts:
- The part which shows the available booking times
- The part which makes a new booking