This paper examines a Library use-case and the lender/borrower relationship. We provide an in-depth analysis of a development of a smart contract and client application running on the HyperLedger platform.
The following are required:
Git client
Go version 1.14.x
Docker version 18.03 or later
SoftHSM
jq
Using VS Code...
// TODO: the Cicero language and cli
Peer2Peer Library Contract.
----
"Paul Power" (the Lender) agrees to lend "Alan O'Neill" (the Borrower)
the itemName "The Da Vinci Code" (IBSN "9780552149518") which is currently
graded as "VG".
In the case of the late return of the item, the Borrower shall pay to Lender
a fine amounting to 0.25 (EUR) for every 1 days the item was returned overdue.
Any fractional part of a days is to be considered a full days. The total amount
of fine shall not however, exceed 50.0% of the total value of the borrowed item.
The contract provides a provision to waive late penalties in the event of
extenuating circumstances. This is wholely at the discretion of the Lender
and all decisions are final in this matter.
// TODO:
Any formatting of the contract text requires careful attention to corresponding requests and tests.
The following error prevented test cases passing successfully.
From a development perspective, being able to develop locally with minimal dependencies is desireable. Since we cannot attach a debugger directly to chaincode running on-chain, we need to be able to test without a HyperLedger Fabric network involved.
Thankfully, we can use our Mocha tests and attach the debugger as normal.
Using the HyperLedger Fabric sample "test-network", we create a two org network with a single peer in each org.
➜ msc-smartcontract-hyperledger git:(peer2peerlibrary) ✗ docker ps --format='table {{.ID}}\t{{.Image}}\t{{.Command}}\t{{.RunningFor}}\t{{.Names}}'
CONTAINER ID IMAGE COMMAND CREATED NAMES
8e7c5c4fbaa0 hyperledger/fabric-peer:latest "peer node start" About an hour ago peer0.org2.lend.me
285a4056e6ca hyperledger/fabric-peer:latest "peer node start" About an hour ago peer0.org1.lend.me
b5fa8eddfc25 hyperledger/fabric-orderer:latest "orderer" About an hour ago orderer.lend.me
a78446f8b90b couchdb:3.1.1 "tini -- /docker-ent…" About an hour ago couchdb0
99005fdf8795 couchdb:3.1.1 "tini -- /docker-ent…" About an hour ago couchdb1
6c0e78fac51d hyperledger/fabric-ca:latest "sh -c 'fabric-ca-se…" About an hour ago ca_org2
5f9a6585a79e hyperledger/fabric-ca:latest "sh -c 'fabric-ca-se…" About an hour ago ca_orderer
fae62de87479 hyperledger/fabric-ca:latest "sh -c 'fabric-ca-se…" About an hour ago ca_org1
By stopping one of the chain-code containers, what happens when submitting another transaction?
docker stop dev-peer0.org1.lend.me-peer2peerlibrary_1.0.0-ae83f25e52b526eda8126766069f34bd1a3f7a2d79e3c7f5b5aa8ad6eba4ea53
We try to trigger a transaction and we receive a consensus error:
2020-10-25T09:42:58.932Z - warn: [TransactionEventHandler]: strategyFail: commit failure for transaction "70944848533e78d554f0f7ec1358913ba70c74a77874a7a25e3145d89346c719": TransactionError: Commit of transaction 70944848533e78d554f0f7ec1358913ba70c74a77874a7a25e3145d89346c719 failed on peer peer0.org1.lend.me:7051 with status ENDORSEMENT_POLICY_FAILURE
******** FAILED to run the application: TransactionError: Commit of transaction 70944848533e78d554f0f7ec1358913ba70c74a77874a7a25e3145d89346c719 failed on peer peer0.org1.lend.me:7051 with status ENDORSEMENT_POLICY_FAILURE
Container orchestration layer such as Kubernetes would attempt to guarantee desired state so this would be beneficial to ensure consistency at the container level and thus ensure consensus.
// TODO: how to debug smart contracts locally since they cannot be debugged after installed on chain?
Real-world smart contracts will likely contain functions using complex types or verbose data that is passed via arguments. This makes testing with the Fabric cli difficult e.g. passing contract verbiage or json payloads. A more realistic and manageable approach would be to develop a client application using a supported language and leverage common libraries and utilities that are available.
Using the tutorial sample applications, we develop a client application that interacts with the ledger and smart contract chain-code for the described use-case. We will use Javascript initially and compare the development of other chain-code languages if time permits.
https://hyperledger-fabric.readthedocs.io/en/latest/write_first_app.html
The samples provide utilities to create and register users and wallets.
User identities from previous tests cannot be reused and must be deleted. The client app will then recreate and register the users.
Failed to register user : Error: fabric-ca request register failed with errors [[ { code: 0,
message:
'Registration of \'appUser\' failed: Identity \'appUser\' is already registered' } ]]
******** FAILED to run the application: Error: Identity not found in wallet: appUser
Upgrade issues
WARNING Local fabric-ca binaries and docker images are out of sync. This may cause problems.
- Use CLI container
- Use docker client to run HLF commands on specific containers. For example:
docker exec peer0.org1.lend.me peer chaincode query -C mychannel -n peer2peerlibrary -c '{"function":"queryState","Args":["CTR_100002"]}'
// TODO:
https://dl.acm.org/doi/pdf/10.1109/WETSEB.2019.00013?download=true https://iopscience.iop.org/article/10.1088/1742-6596/1187/5/052005/pdf