configtxlator.js

Hyperledger Fabric's configtxlator implemented as a js library

Motivation

If you are here you want to decode your block and convert it into a javascript object through fabric-sdk-node without using a local server of configtxlator in order to do it, then you came to the right place!

This first version will allow you to append a organization to a configblock given its json generated by configtxgen.

Install

You can install this lib by

npm i configtxlator.js

if you're using typescript

npm i @types/configtxlator.js

Adding an org to a channel

First get block.json from channel:

const block = await Channel.getChannelConfigFromOrderer()
//Replace snake_case to camelCase and sequence/version tags to int
//otherwise protobuf won't work
const channelBlock = JSON.parse(
    block.encodeJSON()
         .replace(/(_\w)\w+":/g, (match: String) => match[1].toUpperCase() + match.substring(2)),
    (key, value) =>
        key === "sequence" ? parseInt(value) : key === "version" ? parseInt(value) : value
);
// Create a replica that will be modified using same process
const newChannelBlock = JSON.parse(
    block.encodeJSON()
         .replace(/(_\w)\w+":/g, (match: String) => match[1].toUpperCase() + match.substring(2)),
    (key, value) =>
        key === "sequence" ? parseInt(value) : key === "version" ? parseInt(value) : value
);

Those parses are necessary once block.EncodeJSON() from fabric lib returns a json where all key entries are snake_case instead of camelCase (protobufjs doesn't recognizes snake_case entries).

Convert both channelBlock and newChannelBlock into common.Config protos:

const configBlock = fabProtos.common.Config.create({
    channelGroup: channelBlock.config.channelGroup,
    sequence: channelBlock.config.sequence
});
const newConfigBlock = fabProtos.common.Config.create({
    channelGroup: newChannelBlock.config.channelGroup,
    sequence: channelBlock.config.sequence
});

Convert new org's JSON got from configtxgen into a common.Config proto:

import configtxlator = require('configtxlator.js');
const translatedNewOrg = configtxlator.convertOrgJsonToConfigGroup(
    orgJson
);

Append new org config into application groups:

const orgs = newConfigBlock.channelGroup.groups.Application.groups;
newConfigBlock.channelGroup.groups.Application.groups = {
    ...orgs,
    [orgName]: translatedNewOrg
};

Create protos object back from protos interfaces:

const originalConfig = fabProtos.common.Config.create(configBlock);
const updatedConfig = fabProtos.common.Config.create(newConfigBlock);

Finally, compute delta set between both configs:

updatedBlock = await configtxlator.computeDeltaSet(originalConfig, updatedConfig);

updatedBlock.channelId = channelName; //Channel name is the channel you're trying to modify

//Convert updatedBlock into a Uint8Array
const updatedIntArray = fabProtos.common.ConfigUpdate.encode(updatedBlock).finish();

//Convert from Uint8Array to js Buffer
const updatedBuffer = Buffer.from(updatedIntArray, 0);

//Sign updatedChannelConfig buffer
const signatures = [Client.signChannelConfig(updatedBuffer)];

And then submit a updateChannel request proposal through fabric-sdk-node