gsrpc

README

Go Substrate RPC Client (GSRPC)

Substrate RPC client in Go. It provides APIs and types around Polkadot and any Substrate-based chain RPC calls. This client is modelled after polkadot-js/api.

State

This package is feature complete, but it is relatively new and might still contain bugs. We advice to use it with caution in production. It comes without any warranties, please refer to LICENCE for details.

Documentation & Usage Examples

Please refer to https://godoc.org/github.com/centrifuge/go-substrate-rpc-client

Contributing

1. Install dependencies by running make followed by make install
2. Run tests make test
3. Lint make lint (you can use make lint-fix to automatically fix issues)

Run tests in a Docker container against the Substrate Default Docker image

1. Run the docker container make test-dockerized

Run tests locally against the Substrate Default Docker image

1. Start the Substrate Default Docker image: make run-substrate-docker-v2
2. In another terminal, run the tests against that image: make test
3. Visit https://polkadot.js.org/apps for inspection

Run tests locally against any substrate endpoint

1. Set the endpoint: export RPC_URL="http://example.com:9933"
2. Run the tests make test

Documentation

Overview

Package gsrpc (Go Substrate RPC Client) provides APIs and types around Polkadot and any Substrate-based chain RPC calls. This client is modelled after polkadot-js/api(https://github.com/polkadot-js/api).

Calling RPC methods

Simply instantiate the gsrpc with a URL of your choice, e. g.

api, err := gsrpc.NewSubstrateAPI("wss://poc3-rpc.polkadot.io")

and run any of the provided RPC methods from the api:

hash, err := api.RPC.Chain.GetBlockHashLatest()

Further examples can be found below.

Signing extrinsics

In order to sign extrinsics, you need to have [subkey](https://github.com/paritytech/substrate/tree/master/subkey) installed. Please make sure that you use subkey in the version of your relay chain.

Types

The package [types](https://godoc.org/github.com/centrifuge/go-substrate-rpc-client/types/) exports a number of useful basic types including functions for encoding and decoding them.

To use your own custom types, you can simply create structs and arrays composing those basic types. Here are some examples using composition of a mix of these basic and builtin Go types:

1. Vectors, lists, series, sets, arrays, slices: https://godoc.org/github.com/centrifuge/go-substrate-rpc-client/types/#example_Vec_simple

2. Structs: https://godoc.org/github.com/centrifuge/go-substrate-rpc-client/types/#example_Struct_simple

There are some caveats though that you should be aware of:

1. The order of the values in your structs is of relevance to the encoding. The scale codec Substrate/Polkadot uses does not encode labels/keys.

2. Some types do not have corresponding types in Go. Working with them requires a custom struct with Encoding/Decoding methods that implement the Encodeable/Decodeable interfaces. Examples for that are enums, tuples and vectors with any types, you can find reference implementations of those here: types/enum_test.go , types/tuple_test.go and types/vec_any_test.go

For more information about the types sub-package, see https://godoc.org/github.com/centrifuge/go-substrate-rpc-client/types

Example (DisplaySystemEvents)

package main

import (
	"fmt"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
	"github.com/centrifuge/go-substrate-rpc-client/types"
)

func main() {
	// Query the system events and extract information from them. This example runs until exited via Ctrl-C

	// Create our API with a default connection to the local node
	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	meta, err := api.RPC.State.GetMetadataLatest()
	if err != nil {
		panic(err)
	}

	// Subscribe to system events via storage
	key, err := types.CreateStorageKey(meta, "System", "Events", nil, nil)
	if err != nil {
		panic(err)
	}

	sub, err := api.RPC.State.SubscribeStorageRaw([]types.StorageKey{key})
	if err != nil {
		panic(err)
	}
	defer sub.Unsubscribe()

	// outer for loop for subscription notifications
	for {
		set := <-sub.Chan()
		// inner loop for the changes within one of those notifications
		for _, chng := range set.Changes {
			if !types.Eq(chng.StorageKey, key) || !chng.HasStorageData {
				// skip, we are only interested in events with content
				continue
			}

			// Decode the event records
			events := types.EventRecords{}
			err = types.EventRecordsRaw(chng.StorageData).DecodeEventRecords(meta, &events)
			if err != nil {
				panic(err)
			}

			// Show what we are busy with
			for _, e := range events.Balances_Endowed {
				fmt.Printf("\tBalances:Endowed:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x, %v\n", e.Who, e.Balance)
			}
			for _, e := range events.Balances_DustLost {
				fmt.Printf("\tBalances:DustLost:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x, %v\n", e.Who, e.Balance)
			}
			for _, e := range events.Balances_Transfer {
				fmt.Printf("\tBalances:Transfer:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v, %v, %v\n", e.From, e.To, e.Value)
			}
			for _, e := range events.Balances_BalanceSet {
				fmt.Printf("\tBalances:BalanceSet:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v, %v, %v\n", e.Who, e.Free, e.Reserved)
			}
			for _, e := range events.Balances_Deposit {
				fmt.Printf("\tBalances:Deposit:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v, %v\n", e.Who, e.Balance)
			}
			for _, e := range events.Grandpa_NewAuthorities {
				fmt.Printf("\tGrandpa:NewAuthorities:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.NewAuthorities)
			}
			for _, e := range events.Grandpa_Paused {
				fmt.Printf("\tGrandpa:Paused:: (phase=%#v)\n", e.Phase)
			}
			for _, e := range events.Grandpa_Resumed {
				fmt.Printf("\tGrandpa:Resumed:: (phase=%#v)\n", e.Phase)
			}
			for _, e := range events.ImOnline_HeartbeatReceived {
				fmt.Printf("\tImOnline:HeartbeatReceived:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x\n", e.AuthorityID)
			}
			for _, e := range events.ImOnline_AllGood {
				fmt.Printf("\tImOnline:AllGood:: (phase=%#v)\n", e.Phase)
			}
			for _, e := range events.ImOnline_SomeOffline {
				fmt.Printf("\tImOnline:SomeOffline:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.IdentificationTuples)
			}
			for _, e := range events.Indices_IndexAssigned {
				fmt.Printf("\tIndices:IndexAssigned:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x%v\n", e.AccountID, e.AccountIndex)
			}
			for _, e := range events.Indices_IndexFreed {
				fmt.Printf("\tIndices:IndexFreed:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.AccountIndex)
			}
			for _, e := range events.Offences_Offence {
				fmt.Printf("\tOffences:Offence:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v%v\n", e.Kind, e.OpaqueTimeSlot)
			}
			for _, e := range events.Session_NewSession {
				fmt.Printf("\tSession:NewSession:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.SessionIndex)
			}
			for _, e := range events.Staking_Reward {
				fmt.Printf("\tStaking:Reward:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.Balance)
			}
			for _, e := range events.Staking_Slash {
				fmt.Printf("\tStaking:Slash:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x%v\n", e.AccountID, e.Balance)
			}
			for _, e := range events.Staking_OldSlashingReportDiscarded {
				fmt.Printf("\tStaking:OldSlashingReportDiscarded:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.SessionIndex)
			}
			for _, e := range events.System_ExtrinsicSuccess {
				fmt.Printf("\tSystem:ExtrinsicSuccess:: (phase=%#v)\n", e.Phase)
			}
			for _, e := range events.System_ExtrinsicFailed {
				fmt.Printf("\tSystem:ErtrinsicFailed:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%v\n", e.DispatchError)
			}
			for _, e := range events.System_CodeUpdated {
				fmt.Printf("\tSystem:CodeUpdated:: (phase=%#v)\n", e.Phase)
			}
			for _, e := range events.System_NewAccount {
				fmt.Printf("\tSystem:NewAccount:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#x\n", e.Who)
			}
			for _, e := range events.System_KilledAccount {
				fmt.Printf("\tSystem:KilledAccount:: (phase=%#v)\n", e.Phase)
				fmt.Printf("\t\t%#X\n", e.Who)
			}
		}
	}
}

Example (ListenToBalanceChange)

package main

import (
	"fmt"
	"math/big"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
	"github.com/centrifuge/go-substrate-rpc-client/types"
)

func main() {
	// This example shows how to instantiate a Substrate API and use it to connect to a node and retrieve balance
	// updates
	//
	// NOTE: The example runs until you stop it with CTRL+C

	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	meta, err := api.RPC.State.GetMetadataLatest()
	if err != nil {
		panic(err)
	}

	// Known account we want to use (available on dev chain, with funds)
	alice, err := types.HexDecodeString("0xd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d")
	if err != nil {
		panic(err)
	}

	key, err := types.CreateStorageKey(meta, "Balances", "FreeBalance", alice, nil)
	if err != nil {
		panic(err)
	}

	// Retrieve the initial balance
	var previous types.U128
	ok, err := api.RPC.State.GetStorageLatest(key, &previous)
	if err != nil || !ok {
		panic(err)
	}

	fmt.Printf("%#x has a balance of %v\n", alice, previous)
	fmt.Printf("You may leave this example running and transfer any value to %#x\n", alice)

	// Here we subscribe to any balance changes
	sub, err := api.RPC.State.SubscribeStorageRaw([]types.StorageKey{key})
	if err != nil {
		panic(err)
	}
	defer sub.Unsubscribe()

	// outer for loop for subscription notifications
	for {
		// inner loop for the changes within one of those notifications
		for _, chng := range (<-sub.Chan()).Changes {
			var current types.U128
			if err = types.DecodeFromBytes(chng.StorageData, &current); err != nil {
				panic(err)
			}

			// Calculate the delta
			var change = types.U128{Int: big.NewInt(0).Sub(current.Int, previous.Int)}

			// Only display positive value changes (Since we are pulling `previous` above already,
			// the initial balance change will also be zero)
			if change.Cmp(big.NewInt(0)) != 0 {
				previous = current
				fmt.Printf("New balance change of: %v\n", change)
				return
			}
		}
	}
}

Example (ListenToNewBlocks)

package main

import (
	"fmt"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
)

func main() {
	// This example shows how to subscribe to new blocks.
	//
	// It displays the block number every time a new block is seen by the node you are connected to.
	//
	// NOTE: The example runs until 10 blocks are received or until you stop it with CTRL+C

	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	sub, err := api.RPC.Chain.SubscribeNewHeads()
	if err != nil {
		panic(err)
	}
	defer sub.Unsubscribe()

	count := 0

	for {
		head := <-sub.Chan()
		fmt.Printf("Chain is at block: #%v\n", head.Number)
		count++

		if count == 10 {
			sub.Unsubscribe()
			break
		}
	}
}

Example (MakeASimpleTransfer)

package main

import (
	"fmt"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
	"github.com/centrifuge/go-substrate-rpc-client/signature"
	"github.com/centrifuge/go-substrate-rpc-client/types"
)

func main() {
	// This sample shows how to create a transaction to make a transfer from one an account to another.

	// Instantiate the API
	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	meta, err := api.RPC.State.GetMetadataLatest()
	if err != nil {
		panic(err)
	}

	// Create a call, transferring 12345 units to Bob
	bob, err := types.NewAddressFromHexAccountID("0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48")
	if err != nil {
		panic(err)
	}

	c, err := types.NewCall(meta, "Balances.transfer", bob, types.NewUCompactFromUInt(12345))
	if err != nil {
		panic(err)
	}

	// Create the extrinsic
	ext := types.NewExtrinsic(c)

	genesisHash, err := api.RPC.Chain.GetBlockHash(0)
	if err != nil {
		panic(err)
	}

	rv, err := api.RPC.State.GetRuntimeVersionLatest()
	if err != nil {
		panic(err)
	}

	key, err := types.CreateStorageKey(meta, "System", "Account", signature.TestKeyringPairAlice.PublicKey, nil)
	if err != nil {
		panic(err)
	}

	var accountInfo types.AccountInfo
	ok, err := api.RPC.State.GetStorageLatest(key, &accountInfo)
	if err != nil || !ok {
		panic(err)
	}

	nonce := uint32(accountInfo.Nonce)

	o := types.SignatureOptions{
		BlockHash:   genesisHash,
		Era:         types.ExtrinsicEra{IsMortalEra: false},
		GenesisHash: genesisHash,
		Nonce:       types.NewUCompactFromUInt(uint64(nonce)),
		SpecVersion: rv.SpecVersion,
		Tip:         types.NewUCompactFromUInt(0),
	}

	// Sign the transaction using Alice's default account
	err = ext.Sign(signature.TestKeyringPairAlice, o)
	if err != nil {
		panic(err)
	}

	// Send the extrinsic
	hash, err := api.RPC.Author.SubmitExtrinsic(ext)
	if err != nil {
		panic(err)
	}

	fmt.Printf("Transfer sent with hash %#x\n", hash)
}

Example (SimpleConnect)

package main

import (
	"fmt"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
)

func main() {
	// The following example shows how to instantiate a Substrate API and use it to connect to a node

	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	chain, err := api.RPC.System.Chain()
	if err != nil {
		panic(err)
	}
	nodeName, err := api.RPC.System.Name()
	if err != nil {
		panic(err)
	}
	nodeVersion, err := api.RPC.System.Version()
	if err != nil {
		panic(err)
	}

	fmt.Printf("You are connected to chain %v using %v v%v\n", chain, nodeName, nodeVersion)

}

Output:

You are connected to chain Development using Substrate Node v2.0.0-alpha.3

Example (TransactionWithEvents)

package main

import (
	"fmt"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
	"github.com/centrifuge/go-substrate-rpc-client/signature"
	"github.com/centrifuge/go-substrate-rpc-client/types"
)

func main() {
	// Display the events that occur during a transfer by sending a value to bob

	// Instantiate the API
	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	meta, err := api.RPC.State.GetMetadataLatest()
	if err != nil {
		panic(err)
	}

	// Create a call, transferring 12345 units to Bob
	bob, err := types.NewAddressFromHexAccountID("0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48")
	if err != nil {
		panic(err)
	}

	amount := types.NewUCompactFromUInt(12345)

	c, err := types.NewCall(meta, "Balances.transfer", bob, amount)
	if err != nil {
		panic(err)
	}

	// Create the extrinsic
	ext := types.NewExtrinsic(c)
	if err != nil {
		panic(err)
	}

	genesisHash, err := api.RPC.Chain.GetBlockHash(0)
	if err != nil {
		panic(err)
	}

	rv, err := api.RPC.State.GetRuntimeVersionLatest()
	if err != nil {
		panic(err)
	}

	// Get the nonce for Alice
	key, err := types.CreateStorageKey(meta, "System", "Account", signature.TestKeyringPairAlice.PublicKey, nil)
	if err != nil {
		panic(err)
	}

	var accountInfo types.AccountInfo
	ok, err := api.RPC.State.GetStorageLatest(key, &accountInfo)
	if err != nil || !ok {
		panic(err)
	}

	nonce := uint32(accountInfo.Nonce)

	o := types.SignatureOptions{
		BlockHash:   genesisHash,
		Era:         types.ExtrinsicEra{IsMortalEra: false},
		GenesisHash: genesisHash,
		Nonce:       types.NewUCompactFromUInt(uint64(nonce)),
		SpecVersion: rv.SpecVersion,
		Tip:         types.NewUCompactFromUInt(0),
	}

	fmt.Printf("Sending %v from %#x to %#x with nonce %v", amount, signature.TestKeyringPairAlice.PublicKey, bob.AsAccountID, nonce)

	// Sign the transaction using Alice's default account
	err = ext.Sign(signature.TestKeyringPairAlice, o)
	if err != nil {
		panic(err)
	}

	// Do the transfer and track the actual status
	sub, err := api.RPC.Author.SubmitAndWatchExtrinsic(ext)
	if err != nil {
		panic(err)
	}
	defer sub.Unsubscribe()

	for {
		status := <-sub.Chan()
		fmt.Printf("Transaction status: %#v\n", status)

		if status.IsInBlock {
			fmt.Printf("Completed at block hash: %#x\n", status.AsInBlock)
			return
		}
	}
}

Example (UnsubscribeFromListeningToUpdates)

package main

import (
	"fmt"
	"time"

	gsrpc "github.com/centrifuge/go-substrate-rpc-client"
	"github.com/centrifuge/go-substrate-rpc-client/config"
)

func main() {
	// This example shows how to subscribe to and later unsubscribe from listening to block updates.
	//
	// In this example we're calling the built-in unsubscribe() function after a timeOut of 20s to cleanup and
	// unsubscribe from listening to updates.

	api, err := gsrpc.NewSubstrateAPI(config.Default().RPCURL)
	if err != nil {
		panic(err)
	}

	sub, err := api.RPC.Chain.SubscribeNewHeads()
	if err != nil {
		panic(err)
	}
	defer sub.Unsubscribe()

	timeout := time.After(20 * time.Second)

	for {
		select {
		case head := <-sub.Chan():
			fmt.Printf("Chain is at block: #%v\n", head.Number)
		case <-timeout:
			sub.Unsubscribe()
			fmt.Println("Unsubscribed")
			return
		}
	}
}

Index

• type SubstrateAPI
  • func NewSubstrateAPI(url string) (*SubstrateAPI, error)

Examples

• Package (DisplaySystemEvents)
• Package (ListenToBalanceChange)
• Package (ListenToNewBlocks)
• Package (MakeASimpleTransfer)
• Package (SimpleConnect)
• Package (TransactionWithEvents)
• Package (UnsubscribeFromListeningToUpdates)

Types

type SubstrateAPI

type SubstrateAPI struct {
	RPC    *rpc.RPC
	Client client.Client
}

func NewSubstrateAPI

func NewSubstrateAPI(url string) (*SubstrateAPI, error)