I'm working on a Go app that launches a blockchain p2p nodes. For now the user has to manually start the p2p nodes and submit data via terminal. I'm trying to add a HTTP server to add/read data from the blockchain via REST. The problem is that I'm handling the starting of the p2p nodes with Cobra CLI, so when I added another command to start a go-gin HTTP server. Starting the first p2p node returns a reference to the blockchain, and I'm struggling to pass that reference to the function that starts the http server.
structs:
type P2pConfig struct {
ListenF int
Target string
Secio bool
Seed int64
}
type HttpConfig struct {
HttpPort string
}
type Block struct {
Index int
Timestamp string
BPM string
Hash string
PrevHash string
}
type Chain struct {
BlockChain []Block
P2pConfig *P2pConfig
HttpConfig *HttpConfig
}
func NewBlockChain(c *P2pConfig, h *HttpConfig) *Chain {
return &Chain {
P2pConfig:c,
HttpConfig:h,
}
}
Cobra command to start a p2p node
func init() {
CommandServe = &cobra.Command{
Use: "bc",
Short: "Start the BlockChain",
Long: ``,
Run: func(CommandServe *cobra.Command, args []string) {
if _, err := serve(); err != nil {
fmt.Fprintln(os.Stderr, err)
}
},
}
CommandServe.Flags().IntVar(&p2pPort, "l", 8199, "port: wait for incoming connections")
CommandServe.Flags().StringVar(&target, "d", "", "target peer to dial")
CommandServe.Flags().BoolVar(&secio, "secio", true, "enable secio")
CommandServe.Flags().Int64Var(&seed, "seed", 0, "set random seed for id generation")
CommandServe.Flags().StringVar(&httpPort, "p", ":8090", "port of the http ledger")
}
func serve() (*core.Chain, error) {
c := core.NewBlockChain(&core.P2pConfig{
ListenF: p2pPort,
Target: target,
Secio: secio,
Seed: seed,
}, &core.HttpConfig{
HttpPort: httpPort})
log.Println("running p2p server")
nc, err := core.Launch(c)
if err != nil {
return nil, err
}
return nc, nil
}
Starting the HTTP server
func init() {
CommandServe = &cobra.Command{
Use: "hs",
Short: "Start the http server",
Long: ``,
Run: func(CommandServe *cobra.Command, args []string) {
if err := serve(); err != nil {
fmt.Fprintln(os.Stderr, err)
}
},
}
}
func serve() error {
log.Println("running http server")
go func() error {
err := nc.Run(":8090") //causing error here because nc is not recognizable yet
if err != nil {
return err
}
return nil
}()
return nil
}
The problem is passing the variable nc from the first command to the second command. It cannot be returned because it's inside Init() method, so I tried creating a global variable in the fist command's package, and then access it from the second's command package, but it's always nil and I don't understand why (probably a scope issue).
I tried mixing the two commands into a single one (start the p2p nodes and http server), use go routines and channels to pass nc, but that caused a problem because go routines run in the background, and starting the p2p nodes requires user interactivity.
Is there a better/smoother way to achieve this ?
