Step 6: Create a Hyperledger Fabric Channel

In Hyperledger Fabric, a ledger exists in the scope of a channel. The ledger can be shared across the entire network if every member is operating on a common channel. A channel also can be privatized to include only a specific set of participants. Members can be in your AWS account, or they can be members that you invite from other AWS accounts.

In this step, you set up a basic channel. Later on in the tutorial, in Step 8: Invite Another AWS Account to be a Member and Create a Multi-Member Channel, you go through a similar process to set up a channel that includes another member.

Note

All Hyperledger Fabric networks on Managed Blockchain support a maximum of 8 channels per network, regardless of network edition.

Step 6.1: Create configtx for Hyperledger Fabric Channel Creation

The configtx.yaml file contains details of the channel configuration. For more information, see Channel Configuration (configtx) in the Hyperledger Fabric documentation.

This configtx.yaml enables application features associated with Hyperledger Fabric 1.4. It is not compatible with Hyperledger Fabric 1.2. For a configtx.yaml compatible with Hyperledger Fabric 1.2, see Work with Channels.

Use a text editor to create a file with the following contents and save it as configtx.yaml on your Hyperledger Fabric client. Note the following placeholders and values.

• Replace MemberID with the MemberID you returned previously. For example m-K46ICRRXJRCGRNNS4ES4XUUS5A.

• The MSPDir is set to the same directory location, /opt/home/admin-msp, that you established using the CORE_PEER_MSPCONFIGPATH environment variable in the Docker container for the Hyperledger Fabric CLI in step 3.4.

Important

This file is sensitive. Artifacts from pasting can cause the file to fail with marshalling errors. We recommend using emacs to edit it. You can also use VI, but before using VI, enter :set paste, press i to enter insert mode, paste the contents, press escape, and then enter :set nopaste before saving.

################################################################################
#
# Section: Organizations
#
# - This section defines the different organizational identities which will
# be referenced later in the configuration.
#
################################################################################
Organizations:
    - &Org1
        # member id defines the organization
        Name: MemberID
        # ID to load the MSP definition as
        ID: MemberID
        #msp dir of org1 in the docker container
        MSPDir: /opt/home/admin-msp
        # AnchorPeers defines the location of peers which can be used
        # for cross org gossip communication. Note, this value is only
        # encoded in the genesis block in the Application section context
        AnchorPeers:
            - Host:
              Port:
################################################################################
#
#   CAPABILITIES
#
#   This section defines the capabilities of fabric network. This is a new
#   concept as of v1.1.0 and should not be utilized in mixed networks with
#   v1.0.x peers and orderers.  Capabilities define features which must be
#   present in a fabric binary for that binary to safely participate in the
#   fabric network.  For instance, if a new MSP type is added, newer binaries
#   might recognize and validate the signatures from this type, while older
#   binaries without this support would be unable to validate those
#   transactions.  This could lead to different versions of the fabric binaries
#   having different world states.  Instead, defining a capability for a channel
#   informs those binaries without this capability that they must cease
#   processing transactions until they have been upgraded.  For v1.0.x if any
#   capabilities are defined (including a map with all capabilities turned off)
#   then the v1.0.x peer will deliberately crash.
#
################################################################################
Capabilities:
    # Channel capabilities apply to both the orderers and the peers and must be
    # supported by both.
    # Set the value of the capability to true to require it.
    # Note that setting a later Channel version capability to true will also
    # implicitly set prior Channel version capabilities to true. There is no need
    # to set each version capability to true (prior version capabilities remain
    # in this sample only to provide the list of valid values).
    Channel: &ChannelCapabilities
        # V1.4.3 for Channel is a catchall flag for behavior which has been
        # determined to be desired for all orderers and peers running at the v1.4.3
        # level, but which would be incompatible with orderers and peers from
        # prior releases.
        # Prior to enabling V1.4.3 channel capabilities, ensure that all
        # orderers and peers on a channel are at v1.4.3 or later.
        V1_4_3: true
        # V1.3 for Channel enables the new non-backwards compatible
        # features and fixes of fabric v1.3
        V1_3: false
        # V1.1 for Channel enables the new non-backwards compatible
        # features and fixes of fabric v1.1
        V1_1: false
    # Application capabilities apply only to the peer network, and may be safely
    # used with prior release orderers.
    # Set the value of the capability to true to require it.
    # Note that setting a later Application version capability to true will also
    # implicitly set prior Application version capabilities to true. There is no need
    # to set each version capability to true (prior version capabilities remain
    # in this sample only to provide the list of valid values).
    Application: &ApplicationCapabilities
        # V1.4.2 for Application enables the new non-backwards compatible
        # features and fixes of fabric v1.4.2
        V1_4_2: true
        # V1.3 for Application enables the new non-backwards compatible
        # features and fixes of fabric v1.3.
        V1_3: false
        # V1.2 for Application enables the new non-backwards compatible
        # features and fixes of fabric v1.2 (note, this need not be set if
        # later version capabilities are set)
        V1_2: false
        # V1.1 for Application enables the new non-backwards compatible
        # features and fixes of fabric v1.1 (note, this need not be set if
        # later version capabilities are set).
        V1_1: false
################################################################################
#
# SECTION: Application
#
# - This section defines the values to encode into a config transaction or
# genesis block for application related parameters
#
################################################################################
Application: &ApplicationDefaults
    # Organizations is the list of orgs which are defined as participants on
    # the application side of the network
    Organizations:
    Capabilities:
        <<: *ApplicationCapabilities
################################################################################
#
# Profile
#
# - Different configuration profiles may be encoded here to be specified
# as parameters to the configtxgen tool
#
################################################################################
Profiles:
    OneOrgChannel:
        Consortium: AWSSystemConsortium
        Application:
            <<: *ApplicationDefaults
            Organizations:
                - *Org1

Run the following command to generate the configtx peer block:

docker exec cli configtxgen \
-outputCreateChannelTx /opt/home/mychannel.pb \
-profile OneOrgChannel -channelID mychannel \
--configPath /opt/home/

Important

Hyperledger Fabric requires that a channel ID contain only lowercase ASCII alphanumeric characters, dots (.), and dashes (-). It must start with a letter, and must be fewer than 250 characters.

Step 6.2: Set Environment Variables for the Orderer

Set the $ORDERER environment variable for convenience. Replace orderer.n-MWY63ZJZU5HGNCMBQER7IN6OIU.managedblockchain.amazonaws.com:30001 with the OrderingServiceEndpoint returned by the aws managedblockchain get-network command and listed on the network details page of the Managed Blockchain console.

export ORDERER=orderer.n-MWY63ZJZU5HGNCMBQER7IN6OIU.managedblockchain.amazonaws.com:30001

This variable must be exported each time you log out of the client. To persist the variable across sessions, add the export statement to your ~/.bash_profile as shown in the following example.

# .bash_profile
...other configurations
export ORDERER=orderer.n-MWY63ZJZU5HGNCMBQER7IN6OIU.managedblockchain.amazonaws.com:30001

After updating .bash_profile, apply the changes:

source ~/.bash_profile

Step 6.3: Create the Channel

Run the following command to create a channel using the variables that you established and the configtx peer block that you created:

docker exec cli peer channel create -c mychannel \
-f /opt/home/mychannel.pb -o $ORDERER \
--cafile /opt/home/managedblockchain-tls-chain.pem --tls

Step 6.4: Join Your Peer Node to the Channel

Run the following command to join the peer node that you created earlier to the channel:

docker exec cli peer channel join -b mychannel.block \
-o $ORDERER --cafile /opt/home/managedblockchain-tls-chain.pem --tls