Oracle Blockchain Quick Start Guide

Want to start learning Blockchain and be comfortable in building an enterprise blockchain solution using the Oracle Blockchain Platform? Hope this book "Oracle Blockchain Quick Start Guide - A practical approach to implementing blockchain in your enterprise" (Authored by Vivek Acharya, Nimesh Prakash, and Me, published by Packt) would help you.

This book is intended to become a quick reference to learn Blockchain, Hyperledger Fabric, Design strategies, and build chaincode on the Oracle Blockchain Platform.

This book covers,

• Exploring Blockchain and Blockchain-as-a-service (BaaS)
• Construing Distributed Ledger Tech and Blockchain
• Delving into Hyperledger Fabric
• Engage in Business Case on Blockchain platform
• Manage Solutions on Oracle Blockchain Platform
• Developing Solutions on Oracle Blockchain Platform

For the convenience of beginners and developers, this book also provides all the code samples to download and execute.

The book is Globally available on Packt, Amazon, Google, and Kobo.

Invoking/executing rich query in Oracle Blockchain Platform (OBP)

[OBP] This example is developed in NodeJS.

Hyperledger blockchain ledger is storing data in Key-Value pairs. So, if to fetch the data from the ledger, we will pass the key. But do you know, we can query the ledger without the key aswell.
Hyperledger blockchain is providing an option to query the ledger using a rich query. ChaincodeStub class has a method getQueryResult() which does this job. Please note that this method is supported only for state databases that support rich query. Below is the syntax of the method.

Syntax:
    <async> getQueryResult(query)

Input:
   A query string is in the native syntax of the underlying state database

Returns:
   Promise for StateQueryIterator Object

Below is the node JS code snippet to see the implementation of this method. In the below example, I am taking a product id from a user and fetching the set of keys and their JSON objects from the state database where the JSON object contains the given product id.

        let queryString = "SELECT key, valueJson FROM <STATE> WHERE json_extract(valueJson, '$.productid') = '" + args[0] + "'";
        let resultsIterator = await stub.getQueryResult(queryString);
        let results = [];

        while (true) {
            let oneRecord = {};
            let res = await resultsIterator.next();
            if (res.value && res.value.value.toString()) {
                let val = res.value.value.toString('utf8');
                try {
                    oneRecord.value = JSON.parse(val);
                } catch (err) {
                    console.log(err);
                    oneRecord.value = val;
                }
                results.push(oneRecord);
            }
            if (res.done) {
                await resultsIterator.close();
                return Buffer.from(JSON.stringify(results));
            }
        }

In the above example, the getQueryResult()  returns a promise object with an iterator. Hence, we need to call next() method of it to get the inside values.

Oracle blockchain error: chaincode fingerprint mismatch data mismatch

[#OBP]

There are two Organizations (one is the founder and the other is a participant) in a channel (channel name is team1)  in Oracle blockchain network. A chaincode (chain code name is "oow") is deployed and instantiated with version v1 in the founder. A line in the chaincode is changed and deployed the code in the participant with the same version v1. While executing the REST endpoints, below error occurred as Oracle blockchain tries to match the code and their versions in all the peers of the channel and the chaincode are not matching in the peers. Solution for this is to deploy the chaincode with the new version on all the organizations.

{

    "returnCode": "Failure",

    "info": {

        "proxyError": "Proposal not pass",

        "peerErrors": [

            {

                "peerId": "prodhonestpeer1",

                "errMsg": "Sending proposal to prodhonestpeer1 failed because of: gRPC failure=Status{code=UNKNOWN, description=error executing chaincode: could not get ChaincodeDeploymentSpec for oow:v1.2: get ChaincodeDeploymentSpec for oow/team1 from LSCC error: chaincode fingerprint mismatch data mismatch, cause=null}",

                "verified": false

            },

            {

                "peerId": "prodhonestpeer0",

                "errMsg": "Sending proposal to prodhonestpeer0 failed because of: gRPC failure=Status{code=UNKNOWN, description=error executing chaincode: could not get ChaincodeDeploymentSpec for oow:v1.2: get ChaincodeDeploymentSpec for oow/team1 from LSCC error: chaincode fingerprint mismatch data mismatch, cause=null}",

                "verified": false

            }

        ]

    },

    "txid": "973a7518438bf9c62db240ea41dce88ef78854caa20"

}

#OBP #OracleBlockchain #Blockchain