FIFO Queue Hyperledger Fabric chaincode

HLFQueue chaincode stores and manages a FIFO queue. The code based on cckit framework which supports only Hyperledger 1.4.

Supported chaincode methods

Push - adds an item data to the tail of the queue and returns created queue item. ID of the item generated automatically as ULID (see https://github.com/oklog/ulid).

Pop - dequeues (extracts) an item from the head of the queue. If queue is empty it will raise an error "Empty queue".

Select - allows you to filter queue items using a query string in expr syntax (see https://github.com/antonmedv/expr/blob/master/docs/Language-Definition.md). Returns a list of matched queue items. Example query {.Amount > 1 and .Amount < 4} - select items where Amount between 1 and 4.

ListItems - returns a list of all item in queue.

Attach Data - attaches specified []byte data to an item ExtraData specified by ID (ULID string). Replaces existing item ExtraData.

MoveAfter - cuts the item and puts it after the specified item ID in the queue.

MoveBefore - cuts the item and puts it before the specified item ID in the queue.

Building

Dependencies

See sap-tutorials/Tutorials#4415

go get github.com/hyperledger/fabric-chaincode-go/shim
go get github.com/hyperledger/fabric/core/peer
go get github.com/hyperledger/fabric/common/util

Fix Docker package error at Windows

C:\Users\r3code\go\pkg\mod\github.com\docker\[email protected]\pkg\system\filesys_windows.go:112:24: cannot use uintptr(unsafe.Pointer(&sd[0])) (type uintptr) as type *"golang.org/x/sys/windows".SECURITY_DESCRIPTOR in assignment

Install a package:

go get github.com/docker/docker@2200d938a2d5e7cd7437489c22a32d37d9bb380d

Fix build errors

Replace in file paths a shim-path to

"github.com/hyperledger/fabric-chaincode-go/shim"

because hyperledger API path has changed.

Build and start the chaincode

First - start network.

Install the chaincode

docker exec -it chaincode bash
// output: root@d2629980e76b:/opt/gopath/src/chaincode

Сompile the chaincode

cd ./hlf-queue-example/cmd/hlfqueue
go build

Run the chaincode

CORE_PEER_ADDRESS=peer:7052 CORE_CHAINCODE_ID_NAME=mycc:0 ./hlfqueue

The chaincode is started with peer and chaincode logs indicating successful registration with the peer.

Prepare to use

docker exec -it cli bash
peer chaincode install -p chaincodedev/chaincode/hlf-queue-example/cmd/hlfqueue -n mycc -v 0
peer chaincode instantiate -n mycc -v 0 -c '{"Args":[]}' -C mychannel

Instantinate will init the ledger default states used by the chaincode.

Push an item to the queue

Push an item with data:

{
	"from": "A",
	"to": "B",
	"amount": 1
}

Execute a command:

peer chaincode invoke -n mycc -c '{"Args":["Push", "{\"From\":\"A\",\"To\":\"B\", \"Amount\": 1 }"]}' -C myc

Push an item with extra data:

{
	"From": "A",
	"To": "B",
	"Amount": 1,
	"ExtraData": "A to B"
}

Execute a command:

peer chaincode invoke -n mycc -c '{"Args":["Push", "{\"From\":\"A\",\"To\":\"B\", \"Amount\": 1, \"ExtraData\": \"A to B\" }"]}' -C myc

Pop an item from the queue

peer chaincode invoke -n mycc -c '{"Args":["Pop"]}' -C myc

Reordering queue items

Move after

Cut the item with ID 01D78XYFJ1PRM1WPBCBT3VITEM and put after 01D78XYFJ1PRM1WPBCBT3AFTER.

peer chaincode invoke -n mycc -c '{"Args":["MoveAfter", "01D78XYFJ1PRM1WPBCBT3VITEM", "01D78XYFJ1PRM1WPBCBT3AFTER"]}' -C myc

Move before

Cut the item with ID 01D78XYFJ1PRM1WPBCBT3VHOER and put before 01D78XYFJ1PRM1WPBCBT3VHMNV.

peer chaincode invoke -n mycc -c '{"Args":["MoveBefore", "01D78XYFJ1PRM1WPBCBT3VHOER", "01D78XYFJ1PRM1WPBCBT3VHMNV"]}' -C myc

Select queue items (filtering)

Select all items where From = "A" and Amount > 2

peer chaincode query -n mycc -c '{"Args":["Select", "{.From == \"A\" and .Amount > 2 }"]}' -C myc

Attach data to an item with specified ID

peer chaincode invoke -n mycc -c '{"Args":["AttachData", "01D78XYFJ1PRM1WPBCBT3VHMNV", "Data to attach"]}' -C myc

Extra

List queue items

peer chaincode invoke -n mycc -c '{"Args":["ListItems"]}' -C myc

Development

Testing

To run tests call:

go test

Debugging

Set CORE_CHAINCODE_LOGGING_LEVEL=debug to see a debug output. If you want to add your own Debug messages use c.Logger().Debug(msg)

In Windows PowerShell:

$env:CORE_CHAINCODE_LOGGING_LEVEL=debug
go test // will output "DEBU" prefixed messaged to STDOUT

In Linux:

$CORE_CHAINCODE_LOGGING_LEVEL=debug
go test // will output "DEBU" prefixed messaged to STDOUT