Channel

What is a Channel?

A Hyperledger Fabric channel functions as a network inside a network. When two or more users want to create a separate environment for interaction without involving other parties, they create a channel. Each channel has a separate ledger that only channel members can read or write to. This makes Hyperledger Fabric one of the best private blockchains.

How to Create a Channel?

Go to the Channels tab and click Create channel.

Provide the following:

Name

Every channel has a unique name on the platform.

Sometimes you cannot create a channel with a new name because other organizations in your network already used that name for a channel your organization doesn't participate in.

Policy

The channel policy is the governing model for the channel — it controls validation of transactions, addition of new organizations, and chaincode-related actions.

Organizations

At least one organization is required at creation. Add more later. Parameters for each organization:

• Organization — Only consortium members can be added during channel creation

• Anchor peers — Required for peer discovery; each organization must have at least one

• Joined peers — Peers from your organization that will join the channel

• Consenters — Subset of ordering nodes from the system channel responsible for ordering transactions; at least one required

Starting from Catalyst Blockchain Manager v2.3.0, you can join an organization to a channel even if it doesn't host any ordering node.

• Rights: Admin (channel configurations), Writer (update ledger), Reader (query ledger), Endorser (approve chaincode)

Each role should be covered by at least one organization while creating a channel.

Click Create. The channel appears under the Channel tab only after at least one peer has been added.

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Channel Details

After creating or joining a channel, configure it under the Channels tab.

The Download last block button allows downloading the channel configuration in JSON or protobuf format.

Organizations Tab

Shows organizations with their rights and peers that are part of the channel.

Add an organization:

Click Add organization. The organization must be in your partners list first.

Only one consenter can be added per organization. This consenter must also be present in the consenters list on the system channel. You can skip adding a consenter if the organization will use an external orderer.

This action may create a proposal first. See the Proposals section below.

Remove an organization:

Removes the organization along with its consenter.

If the organization has more than one consenter in the channel, remove the extra consenters first before removing the organization.

If you are removing your own organization: do not commit the proposal yourself — let another organization in the channel commit it.

Edit rights, add peers, update anchor peers:

Available under the Organizations tab. You can only update peers belonging to your own organization.

We recommend having at least one anchor peer per organization for service discovery.

Ordering Tab

Shows orderer organizations and their consenters.

Keep your orderer endpoints synced with the list of your consenters in the channel. If you see "No consenters" in the Consenters block, check if each consenter is reflected in the orderer endpoints list.

We do not recommend removing your last consenter from the channel. Remove your organization instead, which will remove the organization and consenter together.

Channel Configuration Tab

Shows the channel genesis block configuration with an Edit option.

Blocklist Tab

Shows blocks representing transactions that have happened sequentially over the channel. You can see the number of transactions per block and their details.

Proposals Tab

Proposals are channel configuration changes that require approval according to the channel's policy.

A proposal is created automatically when:

• A channel has a MAJORITY or ALL policy and there is more than one admin organization

• An organization without admin rights initiates an action

Status	Description
Created	The proposal is ready to be voted on
Voting	Voted by at least one organization, but policy not satisfied yet
Voted	Policy is satisfied; proposal can be completed
Completed	All approvals done; proposal successfully completed
Canceled	Proposal was canceled

A new proposal cannot be initiated until the existing proposal is complete or deleted. A channel snapshot is always taken when a proposal is created.

Proposals (voting functionality) are implemented as a system chaincode integrated into the peer images. We recommend using the IntellectEU Hyperledger Fabric peer image (intellecteu/fabric-peer). If another peer image is used, proposals will not be available.

Chaincodes Tab

Approve and commit chaincodes to the channel. You can also test your chaincode using query or invoke methods, or subscribe to chaincode events after it is committed.

Only the organization that previously approved the chaincode can commit it to the channel.

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How to Join a Channel?

1

Organization 1 adds Organization 2

Organization 1 clicks Add organization, selects at least one of Organization 2's consenters, defines the rights, and clicks Submit.

You can skip adding a consenter if the organization will use an external orderer.

2

Organization 2 joins the channel

Organization 2 goes to the peer section and clicks Join to channel. Enter the channel's exact name and click Join.

The channel name is case-sensitive. There is no dropdown menu to select channels for security reasons.

Sometimes you need to wait a few minutes after being added to a channel before a peer can join.

After joining, the channel appears under the Channels tab where you can update anchor peers, add more peers, add or delete consenters, and more.