Hyperledger Fabric Part 2

Intro to Hyperledger Fabric via the Docs

Updated: 03 September 2023

Add an Org to a Channel

This extends on the network from byfn by adding a new Organization to the channel. Chaincode updates are handled by an organization admin and not a chaincode or application developer

Environment Setup

First we set up the environment by using the byfn.sh script, we do this by first clearning up any previous artifacts, generating new artifacts, and launching the network as follows:

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./byfn.sh down
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./byfn.sh generate
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./byfn.sh up

If you run into a Permission denied error, run it again with sudo

Add Org3 to the Channel

Newt we should be able to add Org3 to the channel with the eyfn.sh script as follows

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./eyfn.sh up

We can also make use of the script to configure our network with a few different options with

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./byfn.sh up -c testchannel -s couchdb -l node

And then

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./eyfn.sh up -c testchannel -s couchdb -l node

Once we are done, we can look at the logs and then run the following script to bring down the network

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./eyfn.sh down

Add Org3 to the Channel Manually

Before starting, modify the docker-compose-cli.yaml in the first-network directory to set the FABRIC_LOGGING_SPEC to DEBUG

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cli:
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  container_name: cli
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  image: hyperledger/fabric-tools:$IMAGE_TAG
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  tty: true
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  stdin_open: true
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  environment:
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    - GOPATH=/opt/gopath
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    - CORE_VM_ENDPOINT=unix:///host/var/run/docker.sock
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    #- FABRIC_LOGGING_SPEC=INFO
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    - FABRIC_LOGGING_SPEC=DEBUG

And do the same for the docker-compose-org3.yaml file

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Org3cli:
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  container_name: Org3cli
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  image: hyperledger/fabric-tools:$IMAGE_TAG
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  tty: true
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  stdin_open: true
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  environment:
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    - GOPATH=/opt/gopath
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    - CORE_VM_ENDPOINT=unix:///host/var/run/docker.sock
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    #- FABRIC_LOGGING_SPEC=INFO
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    - FABRIC_LOGGING_SPEC=DEBUG

Now, bring up the initial network with the following commands:

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./byfn.sh generate
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./byfn.sh up

This will get us to the same network state as before we executed the ./eyfn.sh up command

Generate the Org3 Crypto Material

In a new terminal cd into the org3-artifacts directory and generate the crypto material for Org3 using the org3-crypto.yaml and the configtx.yaml files

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../../bin/cryptogen generate --config=./org3-crypto.yaml

This command reads the org3-crypto.yaml file and uses cryptogen to generate the keys and certificates for an Org3 CA and 2 Peers, the crypto material is then placed into the orypto-config subdirectory

Next we use the configtxgen tool to create the Org3 config material in JSON as follows

“bash export FABRIC_CFG_PATH=$PWD && ../../bin/configtxgen -printOrg Org3MSP > ../channel-artifacts/org3.json

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This command creates a JSON file that contains policy definitions for Org3 as well as the following certificates:
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- Admin user certificate
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- CA root cert
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- TLS root cert
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This JSON file will later be appended to the channel configuration
8

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Next, we'll make a copy of the Orderer's TLS root cert to allow for secure communication between Org3 entities and the Ordering node
10

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```bash
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cd ../ && cp -r crypto-config/ordererOrganizations org3-artifacts/crypto-config/

Now we have all the required material to update the channel

Prepare the CLI Environment

We will mak use of the configtxlator tool which provides a stateless REST API aside from the SDK as well as allows us to easily convert between different data representations/formats

First exec into the CLI container export the following variables

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docker exec -it cli bash

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export ORDERER_CA=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/ordererOrganizations/example.com/orderers/orderer.example.com/msp/tlscacerts/tlsca.example.com-cert.pem
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export CHANNEL_NAME=mychannel

If you need to restart the CLI container, you will need to redefine the above variables (obviously)

Fetch the Configuration

Now that we have defined the two environment variables we can fetch the most recent config block for the channel. We will then save a binary protobuf channel configuration block to a config_block.pb file with the following command

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peer channel fetch config config_block.pb -o orderer.example.com:7050 -c $CHANNEL_NAME --tls --cafile $ORDERER_CA

The last line of the output should say something like

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readBlock -> DEB 011 Received block: 2

From here we can see that the most recent block is from the byfn script and it was when the script defined Org2, The following are the configurations we have done so far

• Block 0 - Genesis Block
• Block1 - Org 1 Anchor Peer update
• Block 2 - Org 2 Anchor Peer update

Convert Config to JSON

We will now make use of the configxlator tool to decode the channel conifguration blok into JSON as well as strip away any metadata and creator signatures that are irrlevant to us as humans with the jq tool

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configtxlator proto_decode --input config_block.pb --type common.Block | jq .data.data[0].payload.data.config > config.json

Add the Org3 Crypto Material

Up until this point the steps for making any config update will be the same, from here the steps are specific to adding a channel

Now that we have the Channel config as JSON we can use jq to append the org3.json definition and save it as modified_config.json

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jq -s '.[0] * {"channel_group":{"groups":{"Application":{"groups": {"Org3MSP":.[1]}}}}}' config.json ./channel-artifacts/org3.json > modified_config.json

And thereafter we translate the config.json and modified_config.json to protobufs config.pb and modified_config.pb respectively so we can calculate the delta between the two configs

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configtxlator proto_encode --input config.json --type common.Config --output config.pb
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configtxlator proto_encode --input modified_config.json --type common.Config --output modified_config.pb

Then we can calculate the deltas

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configtxlator compute_update --channel_id $CHANNEL_NAME --original config.pb --updated modified_config.pb --output org3_update.pb

The file we just genreated org3_update.pb contains the Org3 definitions and is the definition of the deltas

Before submiting to the channel, we need to add some headers and additional content around the JSON file, we can do that by first getting a JSON version of our deltas

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configtxlator proto_decode --input org3_update.pb --type common.ConfigUpdate | jq . > org3_update.json

And wrapping it in some additional data and adding the meta back with jq

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echo '{"payload":{"header":{"channel_header":{"channel_id":"mychannel", "type":2}},"data":{"config_update":'$(cat org3_update.json)'}}}' | jq . > org3_update_in_envelope.json

Lastly, we will convert the final JSON deltas into a protobuf file as follows

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configtxlator proto_encode --input org3_update_in_envelope.json --type common.Envelope --output org3_update_in_envelope.pb

Sign and Submit the Update

We have the updated proto in the org3_update_in_envelope.json file in the conainerm however we need signatures from the required admin users before the conffig change can we written to the ledger

The modification policy is set to the default value of MAJORITY, since we have two peers, this means they oth need to sign the change otherwise the ordering service will reject the transaction

We can first sign the update as Org1 Admin as follows (since the CLI is bootstrapped with the Org1 MSP Material) by executing the following command

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peer channel signconfigtx -f org3_update_in_envelope.pb

Next we switch to Org2 by changing our environment credentials and running the peer channel update command

Note that realistically a single container would not have all the network’s crypto material

Export the Org2 environment variables

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export CORE_PEER_LOCALMSPID="Org2MSP"
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export CORE_PEER_TLS_ROOTCERT_FILE=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/peerOrganizations/org2.example.com/peers/peer0.org2.example.com/tls/ca.crt
3
export CORE_PEER_MSPCONFIGPATH=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/peerOrganizations/org2.example.com/users/Admin@org2.example.com/msp
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export CORE_PEER_ADDRESS=peer0.org2.example.com:7051

And then sign the update with this peer as well

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peer channel update -f org3_update_in_envelope.pb -c $CHANNEL_NAME -o orderer.example.com:7050 --tls --cafile $ORDERER_CA

Cofiguring Leader Election

The default leader mode is dynamic for new peers. New peers are bootstrapped with the genesis block that does not contain information about the Org they are in. New peers are unable to verify blocks until they get a channel configuration transaction, they therefore must have a leader mode in order to receive blocks from the Ordering service

Static:

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CORE_PEER_GOSSIP_USELEADERELECTION=false
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CORE_PEER_GOSSIP_ORGLEADER=true

Dynamic:

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CORE_PEER_GOSSIP_USELEADERELECTION=true
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CORE_PEER_GOSSIP_ORGLEADER=false

Join Org3 to the Channel

Until this point the channel config has been updated to include Org3, meaning that new peers on Org3 can jon the channel mychannel

We can set up Org3 by using the docker compose file for it

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docker-compose-org3-yaml up -d

And then we can exec into it with the following

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docker exec -it Org3cli bash

And export the key variables

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export ORDERER_CA=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/ordererOrganizations/example.com/orderers/orderer.example.com/msp/tlscacerts/tlsca.example.com-cert.pem
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export CHANNEL_NAME=mychannel

Next we can send a call to the ordering service to retrieve the block we just added

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peer channel fetch 0 mychannel.block -o orderer.example.com:7050 -c $CHANNEL_NAME --tls --cafile $ORDERER_CA

Note that the 0 we pass to the above command will retrieve the Genesis block and not the latest block in the chain

Next we can join the peer to the channel using the genesis block as follows

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peer channel join -b mychannel.block

We can then add a second peer to the block with:

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export CORE_PEER_TLS_ROOTCERT_FILE=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/peerOrganizations/org3.example.com/peers/peer1.org3.example.com/tls/ca.crt
2
export CORE_PEER_ADDRESS=peer1.org3.example.com:7051
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peer channel join -b mychannel.block

Upgrade and Invoke Chaincode

The new chaincode policy has been put in place to include Org3, we can install the updated chaincode on Org3 with the following:

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peer chaincode install -n mycc -v 2.0 -p github.com/chaincode/chaincode_example02/go/

And then from the original CLI container we can install the chaincode onto peer0.org1 and peer0.org2 with the following

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peer chaincode install -n mycc -v 2.0 -p github.com/chaincode/chaincode_example02/go/
2

3
export CORE_PEER_LOCALMSPID="Org1MSP"
4
export CORE_PEER_TLS_ROOTCERT_FILE=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt
5
export CORE_PEER_MSPCONFIGPATH=/opt/gopath/src/github.com/hyperledger/fabric/peer/crypto/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp
6
export CORE_PEER_ADDRESS=peer0.org1.example.com:7051
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peer chaincode install -n mycc -v 2.0 -p github.com/chaincode/chaincode_example02/go/

Now that the chaincode has been installed we can upgrade the chaincode and specify the new endorsement policy for transactions. Furthermore we can see that we are passing the initialize command with a few arguments

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peer chaincode upgrade -o orderer.example.com:7050 --tls $CORE_PEER_TLS_ENABLED --cafile $ORDERER_CA -C $CHANNEL_NAME -n mycc -v 2.0 -c '{"Args":["init","a","90","b","210"]}' -P "OR ('Org1MSP.peer','Org2MSP.peer','Org3MSP.peer')"

Next we can query the chaincode, invoke it, and query it again to see that it works as follows

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peer chaincode query -C $CHANNEL_NAME -n mycc -c '{"Args":["query","a"]}'
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peer chaincode invoke -o orderer.example.com:7050  --tls $CORE_PEER_TLS_ENABLED --cafile $ORDERER_CA -C $CHANNEL_NAME -n mycc -c '{"Args":["invoke","a","b","10"]}'
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peer chaincode query -C $CHANNEL_NAME -n mycc -c '{"Args":["query","a"]}'

Chaincode for Developers

Chaincode is a program in Go, Node or Java that implements the prescribed Chaincode Interface. It runs in a secured docker container isolated from the peer process and intiializes and manages ledger state by way of transactions

Chaincode handles business logic agreed by members of a network, similar to a smart contract. Chaincode can be invoked to update or query the ledger, and with the correct permissions even invoke other chaincode

The Chaincode API

Any chaincode program must implement the Chaincode interface, whose methods are called in response to received transactions. Particularly the Init method is called when a chaincode receives an instantiate or upgrade transaction

The other interface available is the ChaincodeStubInterface and allows chaincodes to access and modify the ledger and make invocations to other chaincode

Simple Asset Chaincode

We will make use of a simple chaincode built with Go (I will look at implementing this with Node as well, but the documentation uses Go for the time being)

Firstly, you will need to install Go and create the following directories (For more info on Go and how the Go file system needs to look - check out the notes on that here

The Go Installation Instructions for Fabric can be found here

Make the directory in your Go workspace go/src/sacc. You can easily cd to this by using the $GOPATH environment variable, in the Go workspace, make the directory src/sacc in which we can add the chaincode

Housekeeping

The chaincode file will need to import the necessary packages and have a struct which can define the asset

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package main
2

3
import (
4
  "fmt"
5

6
  "github.com/hyperledger/fabric/core/chaincode/shim"
7
  "github.com/hyperledger/fabric/protos/peer"
8
)
9

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// SimpleAsset implements a simple chaincode to manage an asset
11
type SimpleAsset struct {
12
}

Initialization

We need to provide the Init function, this is called when te chaincode is initialized or when chaincode is upgraded. When writing a chaincode upgrade be sure to modify the Init function to be empty if there is no migration that needs to be done

Our Init function will be defined as follows:

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// Init is called during chaincode instantiation to initialize any data.
2
func (t *SimpleAsset) Init(stub shim.ChaincodeStubInterface) peer.Response {
3

4
}

It will make use of the GetStringArgs function, since we are expecting a key-value pair, we will need to have two arguments so we will check for that

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// Init is called during chaincode instantiation to initialize any
2
// data. Note that chaincode upgrade also calls this function to reset
3
// or to migrate data, so be careful to avoid a scenario where you
4
// inadvertently clobber your ledger's data!
5
func (t *SimpleAsset) Init(stub shim.ChaincodeStubInterface) peer.Response {
6
  // Get the args from the transaction proposal
7
  _, args := stub.GetFunctionAndParameters()
8
  if len(args) != 2 {
9
    return shim.Error("Incorrect arguments. Expecting a key and a value")
10
  }
11
}

Then we will store the state in the ledger using the PutState function with the key and value, and if that went well we will return a peer.Response

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// Init is called during chaincode instantiation to initialize any
2
// data. Note that chaincode upgrade also calls this function to reset
3
// or to migrate data, so be careful to avoid a scenario where you
4
// inadvertently clobber your ledger's data!
5
func (t *SimpleAsset) Init(stub shim.ChaincodeStubInterface) peer.Response {
6
  // Get the args from the transaction proposal
7
  _, args := stub.GetFunctionAndParameters()
8
  if len(args) != 2 {
9
    return shim.Error("Incorrect arguments. Expecting a key and a value")
10
  }
11

12
  // Set up any variables or assets here by calling stub.PutState()
13

14
  // We store the key and the value on the ledger
15
  err := stub.PutState(args[0], []byte(args[1]))
16
  if err != nil {
17
    return shim.Error(fmt.Sprintf("Failed to create asset: %s", args[0]))
18
  }
19
  return shim.Success(nil)
20
}

Invoking the Chaincode

Invoke is called per transaction, and may either be a get or set method. set will create a new asset by specifying the key-value pair

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// Invoke is called per transaction on the chaincode. Each transaction is
2
// either a 'get' or a 'set' on the asset created by Init function. The 'set'
3
// method may create a new asset by specifying a new key-value pair.
4
func (t *SimpleAsset) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
5

6
}

Once again, we need to extract the argumets from the ChaincodeStubInterface, our application has a get and a set function that allow the value of an asset to be set, or its current value to be retrieved. We first call the GetFunctionAndParameters to get the function name and params

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// Invoke is called per transaction on the chaincode. Each transaction is
2
// either a 'get' or a 'set' on the asset created by Init function. The Set
3
// method may create a new asset by specifying a new key-value pair.
4
func (t *SimpleAsset) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
5
    // Extract the function and args from the transaction proposal
6
    fn, args := stub.GetFunctionAndParameters()
7

8
}

Next, we will identify if the function is get or set and will call the respective functions, we do this simply as follows

1
// Invoke is called per transaction on the chaincode. Each transaction is
2
// either a 'get' or a 'set' on the asset created by Init function. The Set
3
// method may create a new asset by specifying a new key-value pair.
4
func (t *SimpleAsset) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
5
    // Extract the function and args from the transaction proposal
6
    fn, args := stub.GetFunctionAndParameters()
7

8
    var result string
9
    var err error
10
    if fn == "set" {
11
            result, err = set(stub, args)
12
    } else {
13
            result, err = get(stub, args)
14
    }
15
    if err != nil {
16
            return shim.Error(err.Error())
17
    }
18

19
    // Return the result as success payload
20
    return shim.Success([]byte(result))
21
}

Implementing the Chaincode Functionality

Next we can define the chaincode implementation by defining the get and set functions. We will make use of the PutState and GetState functions to do this

1
// Set stores the asset (both key and value) on the ledger. If the key exists,
2
// it will override the value with the new one
3
func set(stub shim.ChaincodeStubInterface, args []string) (string, error) {
4
    if len(args) != 2 {
5
            return "", fmt.Errorf("Incorrect arguments. Expecting a key and a value")
6
    }
7

8
    err := stub.PutState(args[0], []byte(args[1]))
9
    if err != nil {
10
            return "", fmt.Errorf("Failed to set asset: %s", args[0])
11
    }
12
    return args[1], nil
13
}
14

15
// Get returns the value of the specified asset key
16
func get(stub shim.ChaincodeStubInterface, args []string) (string, error) {
17
    if len(args) != 1 {
18
            return "", fmt.Errorf("Incorrect arguments. Expecting a key")
19
    }
20

21
    value, err := stub.GetState(args[0])
22
    if err != nil {
23
            return "", fmt.Errorf("Failed to get asset: %s with error: %s", args[0], err)
24
    }
25
    if value == nil {
26
            return "", fmt.Errorf("Asset not found: %s", args[0])
27
    }
28
    return string(value), nil
29
}

Starting the Chaincode

Lastly, we need to implement the main method that will call the shim.Start function

1
// main function starts up the chaincode in the container during instantiate
2
func main() {
3
    if err := shim.Start(new(SimpleAsset)); err != nil {
4
            fmt.Printf("Error starting SimpleAsset chaincode: %s", err)
5
    }
6
}

Final Chaincode

The overall chaincode will be as follows

1
package main
2

3
import (
4
    "fmt"
5

6
    "github.com/hyperledger/fabric/core/chaincode/shim"
7
    "github.com/hyperledger/fabric/protos/peer"
8
)
9

10
// SimpleAsset implements a simple chaincode to manage an asset
11
type SimpleAsset struct {
12
}
13

14
// Init is called during chaincode instantiation to initialize any
15
// data. Note that chaincode upgrade also calls this function to reset
16
// or to migrate data.
17
func (t *SimpleAsset) Init(stub shim.ChaincodeStubInterface) peer.Response {
18
    // Get the args from the transaction proposal
19
    _, args := stub.GetFunctionAndParameters()
20
    if len(args) != 2 {
21
            return shim.Error("Incorrect arguments. Expecting a key and a value")
22
    }
23

24
    // Set up any variables or assets here by calling stub.PutState()
25

26
    // We store the key and the value on the ledger
27
    err := stub.PutState(args[0], []byte(args[1]))
28
    if err != nil {
29
            return shim.Error(fmt.Sprintf("Failed to create asset: %s", args[0]))
30
    }
31
    return shim.Success(nil)
32
}
33

34
// Invoke is called per transaction on the chaincode. Each transaction is
35
// either a 'get' or a 'set' on the asset created by Init function. The Set
36
// method may create a new asset by specifying a new key-value pair.
37
func (t *SimpleAsset) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
38
    // Extract the function and args from the transaction proposal
39
    fn, args := stub.GetFunctionAndParameters()
40

41
    var result string
42
    var err error
43
    if fn == "set" {
44
            result, err = set(stub, args)
45
    } else { // assume 'get' even if fn is nil
46
            result, err = get(stub, args)
47
    }
48
    if err != nil {
49
            return shim.Error(err.Error())
50
    }
51

52
    // Return the result as success payload
53
    return shim.Success([]byte(result))
54
}
55

56
// Set stores the asset (both key and value) on the ledger. If the key exists,
57
// it will override the value with the new one
58
func set(stub shim.ChaincodeStubInterface, args []string) (string, error) {
59
    if len(args) != 2 {
60
            return "", fmt.Errorf("Incorrect arguments. Expecting a key and a value")
61
    }
62

63
    err := stub.PutState(args[0], []byte(args[1]))
64
    if err != nil {
65
            return "", fmt.Errorf("Failed to set asset: %s", args[0])
66
    }
67
    return args[1], nil
68
}
69

70
// Get returns the value of the specified asset key
71
func get(stub shim.ChaincodeStubInterface, args []string) (string, error) {
72
    if len(args) != 1 {
73
            return "", fmt.Errorf("Incorrect arguments. Expecting a key")
74
    }
75

76
    value, err := stub.GetState(args[0])
77
    if err != nil {
78
            return "", fmt.Errorf("Failed to get asset: %s with error: %s", args[0], err)
79
    }
80
    if value == nil {
81
            return "", fmt.Errorf("Asset not found: %s", args[0])
82
    }
83
    return string(value), nil
84
}
85

86
// main function starts up the chaincode in the container during instantiate
87
func main() {
88
    if err := shim.Start(new(SimpleAsset)); err != nil {
89
            fmt.Printf("Error starting SimpleAsset chaincode: %s", err)
90
    }
91
}

Build the Chaincode

We can compile the code with the following

1
go get -u github.com/hyperledger/fabric/core/chaincode/shim
2
go build

Test the Code

We can test the chaincode with the fabric-samples/docker-devmode folder. For this we will need 3 terminals

Terminal 1 - Start the Network

1
docker-compose -f docker-compose-simple.yaml up

Terminal 2 - Build and Start the Chaincode

1
docker exec -it chaincode bash

1
cd sacc
2
go build

Then run the chaincode with

1
CORE_PEER_ADDRESS=peer:7052 CORE_CHAINCODE_ID_NAME=mycc:0 ./sacc

Terminal 3 - Use the Chaincode

1
docker exec -it cli bash

1
peer chaincode install -p chaincodedev/chaincode/sacc -n mycc -v 0
2
peer chaincode instantiate -n mycc -v 0 -c '{"Args":["init","a","10"]}' -C myc
3
peer chaincode invoke -n mycc -c '{"Args":["set", "a", "20"]}' -C myc
4
peer chaincode query -n mycc -c '{"Args":["query","a"]}' -C myc

Note on the Instantiation Method

Note that the instantiation method in the official documentation for this tutorial does not make us of the init argument that should be passed in (This may result in it failing when using something like IBM Cloud Blockchain which by default passes in the init argument), for a better example of an Instantiation take a look at this page