Slava0135 / blockchan

Worthless service implementing PoW blockchain with at most 3 nodes using UDP sockets

Blockchan

About

Worthless service implementing PoW blockchain with at most 3 nodes using UDP sockets.

Building

To build docker image:

docker build -t blockchan .

To run docker compose (3 nodes) in interactive mode:

docker compose -f "docker-compose.yml" up

To run single node in interactive mode:

docker run -it blockchan:latest -genesis

Available flags:

Usage of ./blockchan:
  -addr string
        address node will be running (default "localhost:8888")
  -debug
        enable debug level logging
  -genesis
        generate genesis block on start?
  -name string
        node name for logging (default "NONAME")
  -timeout duration
        timeout for missing blocks request (default 100ms)

Node connections are configured through arguments:

docker run -it blockchan:latest localhost:8001 localhost:8002 ...

Tests

To run tests:

go test -timeout 10s -count 1 ./...

Add -v flag for verbose output

To get test coverage data:

go test -coverprofile=c.out ./... && go tool cover -html c.out -o cover.html

Benchmarks

To run benchmarks only:

go test ./... -bench . -benchmem -run ignoretests

Fuzzing

To run single fuzz test:

go test >>package<< -fuzz >>name<< -run ignoretests

Example:

go test ./messages -fuzz . -run ignoretests

Algorithm

• One node should be configured to generate first (genesis) block.
• Nodes compete with each other trying to generate a hash ending with 0x0000 for the next block.
• When succeded node sends mined block to others and they verify it
• If two nodes mined blocks at the same time then third node verifies first block it got and tells "loser" to drop their block.
• If node missed any blocks it asks other nodes to resend them. Longest chain is accepted.

Structure

package blockgen - block generation and validation

package encode - block json encoding

package mesh - virtual "mesh" connecting "forks" which may represent local node or remote nodes connected through "links"

package messages - messages that nodes send to communicate with each other

package node - node initialisation and blockchain generation

package protocol - nodes communication protocol

package validate - blockchain validation

./tests - integration tests

network.go - networking code

Output Files

Every node writes verified blocks (to docker volume blockchan) to file /blockchan/${name}.txt

You can then access them directly on host mountpoint or using docker:

docker run -it --rm -v /path/on/host:/vol busybox ls -l /vol

And read and take diff (host path may be different):

docker run -it --rm -v /var/lib/docker/volumes/blockchan_blockchan/_data:/blockchan busybox cat /blockchan/ZERO.txt

docker run -it --rm -v /var/lib/docker/volumes/blockchan_blockchan/_data:/blockchan busybox diff /blockchan/ZERO.txt /blockchan/FIRST.txt