This tutorial illustrates the use of adding metadata to your chaincode installation. As of v1.1 the only metadata are the indexes that may be added to a CouchDB state database of your channel ledger.

For more information:

• getting started with Hyperledger Fabric
• setting up a CouchDB as the state database

The following assumes an understanding of the Hyperledger Fabric network (orderers and peers), and of Node application development, including the use of the Javascript Promise.

Overview

Fabric 1.1 has introduced the capability of defining indexes in a CouchDB state database to help improve performance of your queries made in your chaincode. The index definitions need to be in JSON format and in files with a .json extension. These definitions will be included in the chaincode installation package that is sent to the Fabric peer.

Modified API's that allow for metadata

• client.installChaincode() - There is a new attribute ('metadataPath') that may be included in the installation request. The value of the metadataPath is a string representing the absolute path to the directory structure containing the JSON index files.

Installing chaincode

The following example will install the chaincode 'my_chaincode' and include index files.

let targets = buildTargets(); //build the list of peers that will require this chaincode
let chaincode_path = path.resolve(__dirname, '../chaincode/src/node_cc/my_chaincode');
let metadata_path = path.resolve(__dirname, '../chaincode/my_indexes');

// send proposal to install
var request = {
	targets: targets,
	chaincodePath: chaincode_path,
	metadataPath: metadata_path, // notice this is the new attribute of the request
	chaincodeId: 'my_chaincode',
	chaincodeType: 'node',
	chaincodeVersion: 'v1'
};

client.installChaincode(request).then((results) => {
	var proposalResponses = results[0];
	// check the results
}, (err) => {
	console.log('Failed to send install proposal due to error: ' + err.stack ? err.stack : err);
	throw new Error('Failed to send install proposal due to error: ' + err.stack ? err.stack : err);
});

The following shows the path used as the metadataPath above. This is the required directory structure required under the path. The indexes directory will hold the files with the index definitions. The required directory structure and files with a 'json' extension will be included in the chaincode installation package under the 'META_INF' package directory. 'META-INF' should not be included in your local directory structure.

 ..
  <> chaincode
  │
  └─── <> my_indexes // here is where the 'metadataPath' will point to
       │
       └─── <> statedb //starting here are the required directories
            │
            └─── <> couchdb
                 │
                 └─── <> indexes // this directory will contain the index files
                         index-owner.json   // these will be the index files and must
                         index-address.json // have the file extension of 'json'

Each index must be defined in its own text file with an extension of *.json and contain the index definition formatted in JSON following the CouchDB index JSON syntax.

{"index":{"fields":["docType","owner"]},"ddoc":"indexOwnerDoc", "name":"indexOwner","type":"json"}

This work is licensed under a Creative Commons Attribution 4.0 International License.