Step 4 - Configure a channel

Till now ..

• We have created the docker network with fabric-ca container

• Registered and enrolled the peers and users needed for the app

• Added peer nodes and couch dbs to the docker network

Next

• we will create a channel

Channel

• Channel is one of the most important concepts in a fabric network

• Inshort - channel is a logical group of organisations in a fabric network which share the same ledger smart contracts

• There can be x number of channels in a fabric network. Each has its own ledger (& world state) .Each channel can have y number of organisations as its participants

• Here we will create one channel with 2 orgs (investorOrg and managementOrg)

• Peers of each org will need to endorse a transaction before it can be added to the ledger

function configureChannel() {
 ......
  createChannelGenesisBlock

  createChannel
  infoln "Channel '$CHANNEL_NAME' created"

  ## Join all the peers to the channel
  infoln "Joining investorOrg peer to the channel..."
  joinChannel investorOrg
  infoln "Joining managementOrg peer to the channel..."
  joinChannel managementOrg

Lets review the script to configure the "votingChannel"

• Downloads the fabric helper binaries - most importantly configtxgen

• Create the genesis block for the channel ledger . The configtx.yaml contains the configuration for the channel .

  ./configtxgen -profile TwoOrgsApplicationGenesis -outputBlock ${BLOCKFILE} -channelID $CHANNEL_NAME

  • Amongst other important configs this has the endorsement policies for transaction. Majority Endorsement means majority of orgs in the channel have to endorse the transaction to be added to ledger

• configure channels on the ordering service

  ./osnadmin channel join --channelID $CHANNEL_NAME --config-block ${BLOCKFILE} -o localhost:7053 --ca-file "$ORDERER_CA" --client-cert "$ORDERER_ADMIN_TLS_SIGN_CERT" --client-key "$ORDERER_ADMIN_TLS_PRIVATE_KEY" >&log.txt

• join both the peers to the channel . take a note of the environment variables set before invoking peer binary. most importantly (CORE_PEER* variable) . this is how we control for which orgs peer invoke the peer command.

./peer channel join -b $BLOCKFILE >&log.txt