Advanced Fabric (2) -- Adding Peers to an Existing Organization

The initial number of peers in a Fabric network is fixed when the network is created, but in real application scenarios you may need to add peers to an organization dynamically. Using balance-transfer v1.0 as an example (2 orgs, 4 peers), this post shows how to add a third peer to org1.

1. Add the New Peer's Identity Material

First, add the new peer's certificate and private key to the MSP directory of org1. This mainly uses the cryptogen tool (v1.1.0 or later).

1. Edit cryptogen.yaml (or create a new file): set the count parameter in the Template field to the total number of peers the organization should have. Several peers can be added at once.

Only one peer is added to org1 here, so the modified part of cryptogen.yaml looks like this:

PeerOrgs:
  - Name: Org1
    Domain: org1.example.com
    CA:
       Hostname: ca 
    Template:
      Count: 3
      SANS:
        - "localhost"
    Users:
      Count: 1

2. Run the extend command to add the material
In the artifacts/channel directory, run:

./cryptogen extend --config=./cryptogen.yaml

Note: the --config flag should point to the actual name and path of your config file.

2. Write the Docker Config File for the New Peer

Next, write a Docker config file to start the new peer. It is fairly simple: take the config of an existing peer and make a few small changes, making sure the container ports don't conflict.

I named the new peer's config file new-peer.yaml and put it in the artifacts directory. Its contents are as follows:

version: '2'

services:

  peer2.org1.example.com:
    container_name: peer2.org1.example.com
    extends:
      file:   base.yaml
      service: peer-base
    environment:
      - CORE_PEER_ID=peer2.org1.example.com
      - CORE_PEER_LOCALMSPID=Org1MSP
      - CORE_PEER_ADDRESS=peer2.org1.example.com:7051
    ports:
      - 7151:7051
      - 7153:7053
    volumes:
        - ./channel/crypto-config/peerOrganizations/org1.example.com/peers/peer2.org1.example.com/:/etc/hyperledger/crypto/peer

Start the new peer container by running this in the directory that contains the config file:

docker-compose -f new-peer.yaml up -d

3. Update the Network Config File

The network config file network-config.json tells the application the addresses and other details of the network nodes. It is what lets the app communicate with the nodes, so the new peer's information needs to be added to it.
Note: since balance-transfer 1.1, this file has been replaced by network-config.js.

In the org1 section of the JSON file, add a "peer3" entry after the existing entries in the peers field. The ip, port, and related settings must match the Docker config file above. The entry looks like this:

"peer3": {
    "requests": "grpcs://localhost:7151",
    "events": "grpcs://localhost:7153",
    "server-hostname": "peer2.org1.example.com",
    "tls_cacerts": "../artifacts/channel/crypto-config/peerOrganizations/org1.example.com/peers/peer2.org1.example.com/tls/ca.crt"
}

4. Join the New Peer to the Channel

At this point the new peer has joined the blockchain network, but it hasn't joined any channel yet, so it has no ledger data. Send a request to join it to the channel:

curl -s -X POST \
    http://localhost:4000/channels/mychannel/peers \
    -H "authorization: Bearer $ORG1_TOKEN" \
    -H "content-type: application/json" \
    -d '{
    "peers": ["peer3"]
  }'

In the request, $ORG1_TOKEN is the org1 token obtained through registration, and "peer3" is the alias of the new peer set in the network config file.

After the peer joins the channel successfully, its logs show it starting to sync blocks from the other peers:

docker logs peer2.org1.example.com

5. Install the Chaincode

Once it has joined the channel, peer3 can already take part in maintaining the ledger, but it can't yet be targeted for queries or transactions. For that, send a request to install the chaincode:

curl -s -X POST \
    http://localhost:$PORT/chaincodes \
    -H "authorization: Bearer $ORG1_TOKEN" \
    -H "content-type: application/json" \
    -d '{
    "peers": ["peer3"],
    "chaincodeName":"mycc",
    "chaincodePath":"github.com/example_cc",
    "chaincodeVersion":"v0"
  }'

After the installation succeeds, targeting the new peer for a query or transaction automatically builds the chaincode image for that peer and starts a container to run the chaincode. That completes the process of adding a new peer to an existing organization!