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Co-authored-by: M. J. Fromberger <fromberger@interchain.io>
Co-authored-by: Sergio Mena <sergio@informal.systems>
This commit is contained in:
William Banfield
2022-01-05 19:05:27 -05:00
committed by GitHub
parent 7241c2cce4
commit 17a214bcc0
1 changed files with 28 additions and 34 deletions
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62
docs/tutorials/go-built-in.md
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@@ -37,9 +37,10 @@ Verify that you have the latest version of Go installed:
```bash
$ go version
go version go1.17.x darwin/amd64
go version go1.17.5 darwin/amd64
```
Note that the exact patch number may differ as Go releases come out.
## 1.2 Creating a new Go project
We'll start by creating a new Go project.
@@ -76,13 +77,13 @@ Hello, Tendermint Core
## 1.3 Writing a Tendermint Core application
Tendermint Core communicates with an application through the Application
BlockChain Interface (ABCI). All of the message types Tendermint uses for
BlockChain Interface (ABCI) protocol. All of the message types Tendermint uses for
communicating with the application can be found in the ABCI [protobuf
file](https://github.com/tendermint/spec/blob/b695d30aae69933bc0e630da14949207d18ae02c/proto/tendermint/abci/types.proto).
We will begin by creating the basic scaffolding for an ABCI application in
a new `app.go` file. The first step is to create a new type, `KVStoreApplication`
with the methods that implement the abci `Application` interface.
with methods that implement the abci `Application` interface.
Create a file called `app.go` and add the following contents:
@@ -155,10 +156,10 @@ func (app *KVStoreApplication) ApplySnapshotChunk(abcitypes.RequestApplySnapshot
Our application will need to write its state out to persistent storage so that it
can stop and start without losing all of its data.
For this tutorial, we will use [badger](https://github.com/dgraph-io/badger).
For this tutorial, we will use [BadgerDB](https://github.com/dgraph-io/badger).
Badger is a fast embedded key-value store.
First, add badger as a dependency of your go module using the `go get` command:
First, add Badger as a dependency of your go module using the `go get` command:
`go get github.com/dgraph-io/badger`
@@ -178,9 +179,7 @@ And change the constructor to set the appropriate field when creating the applic
```go
func NewKVStoreApplication(db *badger.DB) *KVStoreApplication {
return &KVStoreApplication{
db: db,
}
return &KVStoreApplication{db: db}
}
```
@@ -211,11 +210,10 @@ func (app *KVStoreApplication) validateTx(tx []byte) uint32 {
// already stored the same transaction in the database before.
dbErr := app.db.View(func(txn *badger.Txn) error {
item, err := txn.Get(key)
if err != nil {
if err != badger.ErrKeyNotFound {
return err
}
if errors.Is(err, badger.ErrKeyNotFound) {
return nil
} else if err != nil {
return err
}
return item.Value(func(val []byte) error {
if bytes.Equal(val, value) {
@@ -225,7 +223,7 @@ func (app *KVStoreApplication) validateTx(tx []byte) uint32 {
})
})
// There was an error processing the transaction.
// There was an unexpected error processing the transaction.
// The application therefore cannot safely make progress so we crash.
if dbErr != nil {
panic(dbErr)
@@ -268,7 +266,8 @@ receive a block.
will be delivered to the application.
To implement these calls in our application we're going to make use of Badger's
transaction mechanism.
transaction mechanism. Bagder uses the term _transaction_ in the context of databases,
be careful not to confuse it with _blockchain transactions_.
First, let's create a new Badger `Txn` during `BeginBlock`:
@@ -279,7 +278,7 @@ func (app *KVStoreApplication) BeginBlock(req abcitypes.RequestBeginBlock) abcit
}
```
Next, let's modify `DeliverTx` to add the `key` and `value` to this `Txn` every time our application
Next, let's modify `DeliverTx` to add the `key` and `value` to the database `Txn` every time our application
receives a new `RequestDeliverTx`.
```go
@@ -288,11 +287,10 @@ func (app *KVStoreApplication) DeliverTx(req abcitypes.RequestDeliverTx) abcityp
return abcitypes.ResponseDeliverTx{Code: code}
}
parts := bytes.Split(req.Tx, []byte("="))
parts := bytes.SplitN(req.Tx, []byte("="), 2)
key, value := parts[0], parts[1]
err := app.currentBatch.Set(key, value)
if err != nil {
if err := app.currentBatch.Set(key, value); err != nil {
panic(err)
}
@@ -300,7 +298,7 @@ func (app *KVStoreApplication) DeliverTx(req abcitypes.RequestDeliverTx) abcityp
}
```
Note that we check the validity of the transaction _again_ during `DeliverTx`.
Transactions are not guaranteed to be valid when they are delivered to to an
Transactions are not guaranteed to be valid when they are delivered to an
application.
Also note that we don't commit the Badger `Txn` we are building during `DeliverTx`.
@@ -327,8 +325,7 @@ To do this, let's implement the `Query` method in `app.go`:
```go
func (app *KVStoreApplication) Query(req abcitypes.RequestQuery) abcitypes.ResponseQuery {
var resp abcitypes.ResponseQuery
resp.Key = req.Data
resp := abcitypes.ResponseQuery{Key: req.Data}
dbErr := app.db.View(func(txn *badger.Txn) error {
item, err := txn.Get(req.Data)
@@ -393,17 +390,13 @@ import (
var homeDir string
func init() {
flag.StringVar(&homeDir, "tm-home", "", "Path to the tendermint 'home' directory")
flag.StringVar(&homeDir, "tm-home", "", "Path to the tendermint config directory (if empty, uses $HOME/.tendermint)")
}
func main() {
flag.Parse()
if homeDir == "" {
h, err := os.UserHomeDir()
if err != nil {
panic(err)
}
homeDir = fmt.Sprintf("%s/%s", h, ".tendermint")
homeDir = os.ExpandEnv("$HOME/.tendermint")
}
config := cfg.DefaultValidatorConfig()
@@ -411,22 +404,23 @@ func main() {
viper.SetConfigFile(fmt.Sprintf("%s/%s", homeDir, "config/config.toml"))
if err := viper.ReadInConfig(); err != nil {
panic(err)
log.Fatalf("Reading config: %v", err)
}
if err := viper.Unmarshal(config); err != nil {
panic(err)
log.Fatalf("Decoding config: %v", err)
}
if err := config.ValidateBasic(); err != nil {
panic(err)
log.Fatalf("Invalid configuration data: %v", err)
}
gf, err := types.GenesisDocFromFile(config.GenesisFile())
if err != nil {
panic(err)
log.Fatalf("Loading genesis document: %v", err)
}
db, err := badger.Open(badger.DefaultOptions("./badger").WithTruncate(true))
dbPath := filepath.Join(homeDir, "badger")
db, err := badger.Open(badger.DefaultOptions(dbPath).WithTruncate(true))
if err != nil {
panic(err)
log.Fatalf("Opening database: %v", err)
}
defer db.Close()
app := NewKVStoreApplication(db)
@@ -609,7 +603,7 @@ The request returns a `json` object with a `key` and `value` field set.
...
"key": "dGVuZGVybWludA==",
"value": "cm9ja3M=",
...
...
```
Those values don't look like the `key` and `value` we sent to Tendermint,