How do the different MSP roles (member, admin, peer, client) affect Hyperledger Fabric Endorsement policies?

Question

On the endorsement policy syntax documentation on https://hyperledger-fabric.readthedocs.io/en/release-1.2/endorsement-policies.html it is stated that principals are defined as MSP.ROLE where MSP is the MSP ID and the ROLE is either member, admin, client or peer

In the examples shown mostly member is used. It is states "MSP.member" would mean "any member", but what is a member? Currently, as most endorsement policy we use follow that syntax, we are assuming that it means any peer? But there is also the example of "MSP.peer".

And as this is an endorsement policy where it checks transactions have been endorsed, when are "admin" and "client" used?? (as it does not seem possible for an admin or client to endorse a transaction).

Is there a clear guide on when to use member, admin, client and peer for Endorsement Policies?

Answer 1

A Fabric network member is nothing but a user on the Blockchain network who indicates an organization.

The example given below indicates that in order for a transaction to be endorsed and sent to the orderer, a user from each organization needs to endorse.

AND('Org1.member', 'Org2.member', 'Org3.member') requests 1 signature from each of the three principals

Admins can add and remove members from the network and modify member settings.

Peers may be endorsing or regular (a peer that does not endorse but commits transactions).

Clients are usually organizations that invoke smart contracts on the Blockchain network.

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