getting-started.md

order	1

Getting started

This guide will help you get started with TrogonEventStore in your Go application. It covers the basic steps to connect to TrogonEventStore, create events, append them to streams, and read them back.

Required packages

Add the following dependencies to your go.mod file:

go get github.com/TrogonStack/TrogonEventStore-Client-Go/trogoneventstore

Connecting to TrogonEventStore

To connect your application to TrogonEventStore, you need to configure and create a client instance.

::: tip Insecure clusters The recommended way to connect to TrogonEventStore is using secure mode (which is the default). However, if your TrogonEventStore instance is running in insecure mode, you must explicitly set tls=false in your connection string or client configuration. :::

TrogonEventStore uses connection strings to configure the client connection. The connection string supports two protocols:

• esdb:// - for connecting directly to specific node endpoints (single node or multi-node cluster with explicit endpoints)
• trogoneventstore+discover:// - for connecting using cluster discovery via DNS or gossip endpoints

When using esdb://, you specify the exact endpoints to connect to. The client will connect directly to these endpoints. For multi-node clusters, you can specify multiple endpoints separated by commas, and the client will query each node's Gossip API to get cluster information, then picks a node based on the URI's node preference.

With trogoneventstore+discover://, the client uses cluster discovery to find available nodes. This is particularly useful when you have a DNS A record pointing to cluster nodes or when you want the client to automatically discover the cluster topology.

::: info Gossip support Since version 22.10, trogoneventstore supports gossip on single-node deployments, so trogoneventstore+discover:// can be used for any topology, including single-node setups. :::

For cluster connections using discovery, use the following format:

trogoneventstore+discover://admin:changeit@cluster.dns.name:2113

Where cluster.dns.name is a DNS A record that points to all cluster nodes.

For direct connections to specific endpoints, you can specify individual nodes:

esdb://admin:changeit@node1.dns.name:2113,node2.dns.name:2113,node3.dns.name:2113

Or for a single node:

esdb://admin:changeit@localhost:2113

There are a number of query parameters that can be used in the connection string to instruct the cluster how and where the connection should be established. All query parameters are optional.

Parameter	Accepted values	Default	Description
tls	true, false	true	Use secure connection, set to false when connecting to a non-secure server or cluster.
connectionName	Any string	None	Connection name
maxDiscoverAttempts	Number	10	Number of attempts to discover the cluster.
discoveryInterval	Number	100	Cluster discovery polling interval in milliseconds.
gossipTimeout	Number	5	Gossip timeout in seconds, when the gossip call times out, it will be retried.
nodePreference	leader, follower, random, readOnlyReplica	leader	Preferred node role. When creating a client for write operations, always use leader.
tlsVerifyCert	true, false	true	In secure mode, set to true when using an untrusted connection to the node if you don't have the CA file available. Don't use in production.
tlsCaFile	String, file path	None	Path to the CA file when connecting to a secure cluster with a certificate that's not signed by a trusted CA.
defaultDeadline	Number	None	Default timeout for client operations, in milliseconds. Most clients allow overriding the deadline per operation.
keepAliveInterval	Number	10	Interval between keep-alive ping calls, in seconds.
keepAliveTimeout	Number	10	Keep-alive ping call timeout, in seconds.
userCertFile	String, file path	None	User certificate file for X.509 authentication.
userKeyFile	String, file path	None	Key file for the user certificate used for X.509 authentication.

When connecting to an insecure instance, specify tls=false parameter. For example, for a node running locally use esdb://localhost:2113?tls=false. Note that usernames and passwords aren't provided there because insecure deployments don't support authentication and authorisation.

Creating a client

First, create a client and get it connected to the database.

settings, err := trogoneventstore.ParseConnectionString("esdb://localhost:2113?tls=false")

if err != nil {
  panic(err)
}

db, err := trogoneventstore.NewClient(settings)

The client instance can be used as a singleton across the whole application. It doesn't need to open or close the connection.

Creating an event

You can write anything to TrogonEventStore as events. The client needs a byte array as the event payload. Normally, you'd use a serialized object, and it's up to you to choose the serialization method.

The code snippet below creates an event object instance, serializes it, and adds it as a payload to the EventData structure, which the client can then write to the database.

type OrderItem struct {
  ProductId string  `json:"productId"`
  Quantity  int     `json:"quantity"`
  Price     float64 `json:"price"`
}

type OrderCreated struct {
  OrderId     string      `json:"orderId"`
  CustomerId  string      `json:"customerId"`
  Items       []OrderItem `json:"items"`
  TotalAmount float64     `json:"totalAmount"`
  Status      string      `json:"status"`
}

orderCreatedEvent := OrderCreated{
  OrderId:    uuid.NewString(),
  CustomerId: "customer-123",
  Items: []OrderItem{
    {ProductId: "product-456", Quantity: 2, Price: 29.99},
    {ProductId: "product-789", Quantity: 1, Price: 15.50},
  },
  TotalAmount: 75.48,
  Status:      "pending",
}

data, err := json.Marshal(orderCreatedEvent)

if err != nil {
  panic(err)
}

eventData := trogoneventstore.EventData{
  ContentType: trogoneventstore.ContentTypeJson,
  EventType:   "OrderCreated",
  Data:        data,
}

Appending events

Each event in the database has its own unique identifier (UUID). The database uses it to ensure idempotent writes, but it only works if you specify the stream revision when appending events to the stream.

In the snippet below, we append the event to the stream orders.

_, err = db.AppendToStream(context.Background(), "orders", trogoneventstore.AppendToStreamOptions{}, eventData)

Here we are appending events without checking if the stream exists or if the stream version matches the expected event version. See more advanced scenarios in appending events documentation.

Reading events

Finally, we can read events back from the orders stream.

stream, err := db.ReadStream(context.Background(), "orders", trogoneventstore.ReadStreamOptions{}, 10)

if err != nil {
  panic(err)
}

defer stream.Close()

for {
  event, err := stream.Recv()

  if errors.Is(err, io.EOF) {
    break
  }

  if err != nil {
    panic(err)
  }

  // Process the order event
  fmt.Printf("Order event: %s - %s\n", event.Event.EventType, string(event.Event.Data))
}