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4.4 Running a local dev node

Prerequisites

Overview

In this tutorial, you will learn how to run up a local development node with gnodev. By spinning up a local gno.land node, users can simulate the blockchain environment locally on their machines, allowing them to easily see how their code behaves before deploying it to a remote gno.land network.

This tutorial will show you how to use gnodev, a local development solution stack offering a built-in gno.land node with a hot-reload feature for packages and realms, as well as a built-in instance of gnoweb.

Primary features

Apart from providing a built-in gno.land node and a gnoweb instance, gnodev also provides an array of other useful features. Let's explore the three most prominent ones:

  1. Automatic package deployment
  2. Premining balances
  3. Hot reload

If you're familiar with the features above, jump to the practical example section.

gnodev also provides many useful features such as loading genesis transactions, resolving packages from remote networks, modifying the built-in node parameters, etc. Check out the full gnodev developer guide for more information.

1. Automatic deployment

gnodev automatically deploys your contracts to the built-in node, making them readily accessible via gnoweb. This means that developers do not need to manually deploy their contracts during local development.

Packages and realms are deployed with a default Gno address1, which can be changed via the -deploy-key flag.

Detecting package paths

If the current working directory contains a gno.mod file, gnodev deploys the package to the pkgpath specified inside.

If no gno.mod file is found, gnodev searches for a .gno file containing a package name and deploys it under gno.land/r/dev/<pkgname>.

Deploying example packages

In addition to your working directory, gnodev automatically deploys all packages and realms located in the examples/ folder from the monorepo it was installed from. This makes all packages in the examples/ folder available for use during development. gnodev also provides the option to resolve packages from a remote testnet, which can be set via the -resolver flag. // XX should we include this here?

2. Premining balances

gnodev automatically detects your Gno keys from the local gnokey keybase, and pre-mines a large amount of testnet GNOT to all of your addresses, which can then be used for testing applications.

You can verify the balance of your addresses by pressing A when gnodev is running:

Accounts    ┃ I (2) known keys
            ┃   table=
            ┃   │ KeyName  Address                                   Balance
            ┃   │ test1    g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5  10000000000000ugnot
            ┃   │ MyKey    g1q4q3uegdnq9rsvf3xgxydr3yqd2v6w2tww5920  10000000000000ugnot

This simplifies development by removing the need to manually acquire testnet GNOT. This is not the case for remote testnets, where users must obtain testnet GNOT from faucets, such as the ones found on faucet.gno.land.

3. Hot reload

gnodev watches the current working directory for any changes that happen within your code, and automatically reloads the built-in node, while trying to replay previous transactions to maintain the state of your smart contracts between code changes.

Directory watching, as well as transaction replaying, can be disabled with the -no-watch and -no-replay flags, respectively.

With the main features of gnodev out of the way, let's dive into a practical example.

Practical example

Let's use the local file structure we set up in the previous tutorial:

counter/
    ├─ gno.mod
    ├─ counter.gno

Let's go into the counter folder and run gnodev:

cd counter
gnodev

You should receive an output similar to the following:

❯ gnodev
Loader      ┃ I guessing directory path path=gno.land/r/example/counter dir={your_pwd}
Accounts    ┃ I default address imported name=test1 addr=g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5
Node        ┃ I packages paths=[gno.land/r/example/counter]
Event       ┃ I sending event to clients clients=0 type=NODE_RESET event=&{}
GnoWeb      ┃ I gnoweb started lisn=http://127.0.0.1:8888
--- READY   ┃ I for commands and help, press `h` took=1.391020125s

By opening the gnoweb listener address, http://localhost:8888, we should see the render of our counter realm:

Current counter value: 0

Modifying Render()

Let's modify the Render() function inside counter.gno as follows, importing the strconv package:

func Render(_ string) string {
	return "My amazing counter value: " + strconv.Itoa(count)
}

gnodev will automatically detect the change in the file and reload both the node and gnoweb. The render of our realm will then change:

My amazing counter value: 0

Interacting with the realm

To interact with our counter realm, let's create a simple transaction calling the Increment() function with gnokey, using the key we created in the previous tutorial. Running the following command in your terminal will execute the transaction:

gnokey maketx call \
-pkgpath "gno.land/r/example/counter" \
-func "Increment" \
-args "42" \
-gas-fee 1000000ugnot \
-gas-wanted 20000000 \
-broadcast \
{MYKEY}

After entering the keypair password, you should get a response similar to this:

Enter password.
(42 int)

OK!
GAS WANTED: 20000000
GAS USED:   126933
HEIGHT:     203
EVENTS:     []
TX HASH:    k+WuKgPpoAg+EcR2EnzqxeWqUXB4KhOhg3l6zthSy0I=

Looking at the render of our realm, we'll see that the value of the counter has increased, as expected:

My amazing counter value: 42

:::info

The above section showcases a simple gnokey command that will execute a transaction executing Increment(42) in the counter realm, which lives on the gno.land/r/example/counter package path on the local node.

A detailed explanation how to use gnokey will be provided in an upcoming tutorial.

:::

After running gnodev, you can access several components:

  1. A local version of gnoweb
  2. A local blockchain instance for testing
  3. The web-based gnodev UI to monitor your node

Conclusion

That's it! 🎉

We covered the main features of gnodev. Next, we will go onto a full development example, where we build a minimal social media app.

Footnotes

  1. The default deployer address is g1jg8mtutu9khhfwc4nxmuhcpftf0pajdhfvsqf5, a.k.a. test1 - the mnemonic phrase for this address is publicly known. ↩