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Core application - Go SDK

The Foundations section of the Temporal Developer's guide covers the minimum set of concepts and implementation details needed to build and run a Temporal Application—that is, all the relevant steps to start a Workflow Execution that executes an Activity.

In this section you can find the following:

How to install the Temporal CLI and run a development server​

This section describes how to install the Temporal CLI and run a development Temporal Service. The local development Temporal Service comes packaged with the Temporal Web UI.

For information on deploying and running a self-hosted production Temporal Service, see the Self-hosted guide, or sign up for Temporal Cloud and let us run your production Temporal Service for you.

The Temporal CLI is a tool for interacting with a Temporal Service from the command line and it includes a distribution of the Temporal Server and Web UI. This local development Temporal Service runs as a single process with zero runtime dependencies and it supports persistence to disk and in-memory mode through SQLite.

Install the Temporal CLI

The Temporal CLI is available on macOS, Windows, and Linux.

macOS​

How to install the Temporal CLI on macOS

Choose one of the following install methods to install the Temporal CLI on macOS:

Install the Temporal CLI with Homebrew

brew install temporal

Install the Temporal CLI from CDN

  1. Select the platform and architecture needed.

  1. Extract the downloaded archive.

  2. Add the temporal binary to your PATH.

Linux​

How to install the Temporal CLI on Linux

Choose one of the following install methods to install the Temporal CLI on Linux:

Install the Temporal CLI with Homebrew

brew install temporal

Install the Temporal CLI from CDN

  1. Select the platform and architecture needed.

  1. Extract the downloaded archive.

  2. Add the temporal binary to your PATH.

Windows​

How to install the Temporal CLI on Windows

Follow these instructions to install the Temporal CLI on Windows:

Install the Temporal CLI from CDN

  1. Select the platform and architecture needed and download the binary.

  1. Extract the downloaded archive.

  2. Add the temporal.exe binary to your PATH.

Start the Temporal Development Server​

Start the Temporal Development Server by using the server start-dev command.

temporal server start-dev

This command automatically starts the Web UI, creates the default Namespace, and uses an in-memory database.

The Temporal Server should be available on localhost:7233 and the Temporal Web UI should be accessible at http://localhost:8233.

The server's startup configuration can be customized using command line options. For a full list of options, run:

temporal server start-dev --help

How to install a Temporal SDK​

A Temporal SDK provides a framework for Temporal Application development.

An SDK provides you with the following:

Add the Temporal Go SDK to your project:

go get go.temporal.io/sdk

Or clone the Go SDK repo to your preferred location:

git clone git@github.com:temporalio/sdk-go.git

How to find the Go SDK API reference​

The Temporal Go SDK API reference is published on pkg.go.dev.

Where are SDK-specific code examples?​

You can find a complete list of executable code samples in Temporal's GitHub repository.

Additionally, several of the Tutorials are backed by a fully executable template application.

How to develop a basic Workflow​

Workflows are the fundamental unit of a Temporal Application, and it all starts with the development of a Workflow Definition.

In the Temporal Go SDK programming model, a Workflow Definition is an exportable function. Below is an example of a basic Workflow Definition.

View the source code

in the context of the rest of the application code.

package yourapp

import (
    "time"

    "go.temporal.io/sdk/workflow"
)
// ...

// YourSimpleWorkflowDefinition is the most basic Workflow Definition.
func YourSimpleWorkflowDefinition(ctx workflow.Context) error {
    // ...
    return nil
}

How to define Workflow parameters​

Temporal Workflows may have any number of custom parameters. However, we strongly recommend that objects are used as parameters, so that the object's individual fields may be altered without breaking the signature of the Workflow. All Workflow Definition parameters must be serializable.

The first parameter of a Go-based Workflow Definition must be of the workflow.Context type. It is used by the Temporal Go SDK to pass around Workflow Execution context, and virtually all the Go SDK APIs that are callable from the Workflow require it. It is acquired from the go.temporal.io/sdk/workflow package.

The workflow.Context entity operates similarly to the standard context.Context entity provided by Go. The only difference between workflow.Context and context.Context is that the Done() function, provided by workflow.Context, returns workflow.Channel instead of the standard Go chan.

Additional parameters can be passed to the Workflow when it is invoked. A Workflow Definition may support multiple custom parameters, or none. These parameters can be regular type variables or safe pointers. However, the best practice is to pass a single parameter that is of a struct type, so there can be some backward compatibility if new parameters are added.

All Workflow Definition parameters must be serializable and can't be channels, functions, variadic, or unsafe pointers.

View the source code

in the context of the rest of the application code.

package yourapp

import (
    "time"

    "go.temporal.io/sdk/workflow"
)

// YourWorkflowParam is the object passed to the Workflow.
type YourWorkflowParam struct {
    WorkflowParamX string
    WorkflowParamY int
}
// ...
// YourWorkflowDefinition is your custom Workflow Definition.
func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) (*YourWorkflowResultObject, error) {
// ...
}

How to define Workflow return parameters​

Workflow return values must also be serializable. Returning results, returning errors, or throwing exceptions is fairly idiomatic in each language that is supported. However, Temporal APIs that must be used to get the result of a Workflow Execution will only ever receive one of either the result or the error.

A Go-based Workflow Definition can return either just an error or a customValue, error combination. Again, the best practice here is to use a struct type to hold all custom values. A Workflow Definition written in Go can return both a custom value and an error. However, it's not possible to receive both a custom value and an error in the calling process, as is normal in Go. The caller will receive either one or the other. Returning a non-nil error from a Workflow indicates that an error was encountered during its execution and the Workflow Execution should be terminated, and any custom return values will be ignored by the system.

View the source code

in the context of the rest of the application code.

package yourapp

import (
    "time"

    "go.temporal.io/sdk/workflow"
)
// ...

// YourWorkflowResultObject is the object returned by the Workflow.
type YourWorkflowResultObject struct {
    WFResultFieldX string
    WFResultFieldY int
}
// ...
// YourWorkflowDefinition is your custom Workflow Definition.
func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) (*YourWorkflowResultObject, error) {
// ...
    if err != nil {
        return nil, err
    }
    // Make the results of the Workflow Execution available.
    workflowResult := &YourWorkflowResultObject{
        WFResultFieldX: activityResult.ResultFieldX,
        WFResultFieldY: activityResult.ResultFieldY,
    }
    return workflowResult, nil
}

How to customize Workflow Type in Go​

In Go, by default, the Workflow Type name is the same as the function name.

To customize the Workflow Type, set the Name parameter with RegisterOptions when registering your Workflow with a Worker.

View the source code

in the context of the rest of the application code.

package main

import (
    "log"

    "go.temporal.io/sdk/activity"
    "go.temporal.io/sdk/client"
    "go.temporal.io/sdk/worker"
    "go.temporal.io/sdk/workflow"

    "documentation-samples-go/yourapp"
)
// ...
func main() {
// ...
    yourWorker := worker.New(temporalClient, "your-custom-task-queue-name", worker.Options{})
// ...
    // Use RegisterOptions to set the name of the Workflow Type for example.
    registerWFOptions := workflow.RegisterOptions{
        Name: "JustAnotherWorkflow",
    }
    yourWorker.RegisterWorkflowWithOptions(yourapp.YourSimpleWorkflowDefinition, registerWFOptions)
// ...
}

How to develop Workflow logic​

Workflow logic is constrained by deterministic execution requirements. Therefore, each language is limited to the use of certain idiomatic techniques. However, each Temporal SDK provides a set of APIs that can be used inside your Workflow to interact with external (to the Workflow) application code.

In Go, Workflow Definition code cannot directly do the following:

  • Iterate over maps using range, because with range the order of the map's iteration is randomized. Instead you can collect the keys of the map, sort them, and then iterate over the sorted keys to access the map. This technique provides deterministic results. You can also use a Side Effect or an Activity to process the map instead.
  • Call an external API, conduct a file I/O operation, talk to another service, etc. (Use an Activity for these.)

The Temporal Go SDK has APIs to handle equivalent Go constructs:

  • workflow.Now() This is a replacement for time.Now().
  • workflow.Sleep() This is a replacement for time.Sleep().
  • workflow.GetLogger() This ensures that the provided logger does not duplicate logs during a replay.
  • workflow.Go() This is a replacement for the go statement.
  • workflow.Channel This is a replacement for the native chan type. Temporal provides support for both buffered and unbuffered channels.
  • workflow.Selector This is a replacement for the select statement. Learn more on the Go SDK Selectors page.
  • workflow.Context This is a replacement for context.Context. See Tracing for more information about context propagation.

How to develop an Activity Definition in Go​

In the Temporal Go SDK programming model, an Activity Definition is an exportable function or a struct method. Below is an example of both a basic Activity Definition and of an Activity defined as a Struct method. An Activity struct can have more than one method, with each method acting as a separate Activity Type. Activities written as struct methods can use shared struct variables, such as:

  • an application level DB pool
  • client connection to another service
  • reusable utilities
  • any other expensive resources that you only want to initialize once per process

Because this is such a common need, the rest of this guide shows Activities written as struct methods.

View the source code

in the context of the rest of the application code.

package yourapp

import (
    "context"

    "go.temporal.io/sdk/activity"
)
// ...

// YourSimpleActivityDefinition is a basic Activity Definition.
func YourSimpleActivityDefinition(ctx context.Context) error {
    return nil
}

// YourActivityObject is the struct that maintains shared state across Activities.
// If the Worker crashes this Activity object loses its state.
type YourActivityObject struct {
    Message *string
    Number  *int
}

// YourActivityDefinition is your custom Activity Definition.
// An Activity Definition is an exportable function.
func (a *YourActivityObject) YourActivityDefinition(ctx context.Context, param YourActivityParam) (*YourActivityResultObject, error) {
// ...
}

How to develop Activity Parameters​

There is no explicit limit to the total number of parameters that an Activity Definition may support. However, there is a limit to the total size of the data that ends up encoded into a gRPC message Payload.

A single argument is limited to a maximum size of 2 MB. And the total size of a gRPC message, which includes all the arguments, is limited to a maximum of 4 MB.

Also, keep in mind that all Payload data is recorded in the Workflow Execution Event History and large Event Histories can affect Worker performance. This is because the entire Event History could be transferred to a Worker Process with a Workflow Task.

Some SDKs require that you pass context objects, others do not. When it comes to your application data—that is, data that is serialized and encoded into a Payload—we recommend that you use a single object as an argument that wraps the application data passed to Activities. This is so that you can change what data is passed to the Activity without breaking a function or method signature.

The first parameter of an Activity Definition is context.Context. This parameter is optional for an Activity Definition, though it is recommended, especially if the Activity is expected to use other Go SDK APIs.

An Activity Definition can support as many other custom parameters as needed. However, all parameters must be serializable (parameters can't be channels, functions, variadic, or unsafe pointers), and it is recommended to pass a single struct that can be updated later.

View the source code

in the context of the rest of the application code.

// YourActivityParam is the struct passed to your Activity.
// Use a struct so that your function signature remains compatible if fields change.
type YourActivityParam struct {
    ActivityParamX string
    ActivityParamY int
}
// ...
func (a *YourActivityObject) YourActivityDefinition(ctx context.Context, param YourActivityParam) (*YourActivityResultObject, error) {
// ...
}

How to define Activity return values​

All data returned from an Activity must be serializable.

Activity return values are subject to payload size limits in Temporal. The default payload size limit is 2MB, and there is a hard limit of 4MB for any gRPC message size in the Event History transaction (see Cloud limits here). Keep in mind that all return values are recorded in a Workflow Execution Event History.

A Go-based Activity Definition can return either just an error or a customValue, error combination (same as a Workflow Definition). You may wish to use a struct type to hold all custom values, just keep in mind they must all be serializable.

View the source code

in the context of the rest of the application code.

// YourActivityResultObject is the struct returned from your Activity.
// Use a struct so that you can return multiple values of different types.
// Additionally, your function signature remains compatible if the fields change.
type YourActivityResultObject struct {
    ResultFieldX string
    ResultFieldY int
}
// ...
func (a *YourActivityObject) YourActivityDefinition(ctx context.Context, param YourActivityParam) (*YourActivityResultObject, error) {
// ...
    result := &YourActivityResultObject{
        ResultFieldX: "Success",
        ResultFieldY: 1,
    }
    // Return the results back to the Workflow Execution.
    // The results persist within the Event History of the Workflow Execution.
    return result, nil
}

How to customize Activity Type in Go​

To customize the Activity Type, set the Name parameter with RegisterOptions when registering your Activity with a Worker.

View the source code

in the context of the rest of the application code.

func main() {
// ...
    yourWorker := worker.New(temporalClient, "your-custom-task-queue-name", worker.Options{})
// ...
    // Use RegisterOptions to change the name of the Activity Type for example.
    registerAOptions := activity.RegisterOptions{
        Name: "JustAnotherActivity",
    }
    yourWorker.RegisterActivityWithOptions(yourapp.YourSimpleActivityDefinition, registerAOptions)
    // Run the Worker
    err = yourWorker.Run(worker.InterruptCh())
// ...
}
// ...

How to start an Activity Execution​

Calls to spawn Activity Executions are written within a Workflow Definition. The call to spawn an Activity Execution generates the ScheduleActivityTask Command. This results in the set of three Activity Task related Events (ActivityTaskScheduled, ActivityTaskStarted, and ActivityTask[Closed])in your Workflow Execution Event History.

A single instance of the Activities implementation is shared across multiple simultaneous Activity invocations. Activity implementation code should be idempotent.

The values passed to Activities through invocation parameters or returned through a result value are recorded in the Execution history. The entire Execution history is transferred from the Temporal Service to Workflow Workers when a Workflow state needs to recover. A large Execution history can thus adversely impact the performance of your Workflow.

Therefore, be mindful of the amount of data you transfer through Activity invocation parameters or Return Values. Otherwise, no additional limitations exist on Activity implementations.

To spawn an Activity Execution, call ExecuteActivity() inside your Workflow Definition. The API is available from the go.temporal.io/sdk/workflow package. The ExecuteActivity() API call requires an instance of workflow.Context, the Activity function name, and any variables to be passed to the Activity Execution. The Activity function name can be provided as a variable object (no quotations) or as a string. The benefit of passing the actual function object is that the framework can validate the parameters against the Activity Definition. The ExecuteActivity call returns a Future, which can be used to get the result of the Activity Execution.

View the source code

in the context of the rest of the application code.

func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) (*YourWorkflowResultObject, error) {
    // Set the options for the Activity Execution.
    // Either StartToClose Timeout OR ScheduleToClose is required.
    // Not specifying a Task Queue will default to the parent Workflow Task Queue.
    activityOptions := workflow.ActivityOptions{
        StartToCloseTimeout: 10 * time.Second,
    }
    ctx = workflow.WithActivityOptions(ctx, activityOptions)
    activityParam := YourActivityParam{
        ActivityParamX: param.WorkflowParamX,
        ActivityParamY: param.WorkflowParamY,
    }
    // Use a nil struct pointer to call Activities that are part of a struct.
    var a *YourActivityObject
    // Execute the Activity and wait for the result.
    var activityResult YourActivityResultObject
    err := workflow.ExecuteActivity(ctx, a.YourActivityDefinition, activityParam).Get(ctx, &activityResult)
    if err != nil {
        return nil, err
    }
// ...
}

How to set the required Activity Timeouts​

Activity Execution semantics rely on several parameters. The only required value that needs to be set is either a Schedule-To-Close Timeout or a Start-To-Close Timeout. These values are set in the Activity Options.

To set an Activity Timeout in Go, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the Activity Timeout field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

Available timeouts are:

  • StartToCloseTimeout
  • ScheduleToClose
  • ScheduleToStartTimeout
activityOptions := workflow.ActivityOptions{
  // Set Activity Timeout duration
  ScheduleToCloseTimeout: 10 * time.Second,
  // StartToCloseTimeout: 10 * time.Second,
  // ScheduleToStartTimeout: 10 * time.Second,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

Go ActivityOptions reference​

Create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package and use WithActivityOptions() to apply it to the instance of workflow.Context.

The instance of workflow.Context is then passed to the ExecuteActivity() call.

FieldRequiredType
ActivityIDNostring
TaskQueueNameNostring
ScheduleToCloseTimeoutYes (or StartToCloseTimeout)time.Duration
ScheduleToStartTimeoutNotime.Duration
StartToCloseTimeoutYes (or ScheduleToCloseTimeout)time.Duration
HeartbeatTimeoutNotime.Duration
WaitForCancellationNobool
OriginalTaskQueueNameNostring
RetryPolicyNoRetryPolicy

ActivityID​

  • Type: string
  • Default: None
activityOptions := workflow.ActivityOptions{
  ActivityID: "your-activity-id",
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

TaskQueueName​

  • Type: string
  • Default: Inherits the TaskQueue name from the Workflow.
activityOptions := workflow.ActivityOptions{
  TaskQueueName: "your-task-queue-name",
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

ScheduleToCloseTimeout​

To set a Schedule-To-Close Timeout, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the ScheduleToCloseTimeout field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

This or StartToCloseTimeout must be set.

  • Type: time.Duration
  • Default: ∞ (infinity - no limit)
activityOptions := workflow.ActivityOptions{
  ScheduleToCloseTimeout: 10 * time.Second,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

ScheduleToStartTimeout​

To set a Schedule-To-Start Timeout, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the ScheduleToStartTimeout field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

  • Type: time.Duration
  • Default: ∞ (infinity - no limit)
activityOptions := workflow.ActivityOptions{
  ScheduleToStartTimeout: 10 * time.Second,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

StartToCloseTimeout​

To set a Start-To-Close Timeout, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the StartToCloseTimeout field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

This or ScheduleToCloseTimeout must be set.

  • Type: time.Duration
  • Default: Same as the ScheduleToCloseTimeout
activityOptions := workflow.ActivityOptions{
  StartToCloseTimeout: 10 * time.Second,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

HeartbeatTimeout​

To set a Heartbeat Timeout, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the RetryPolicy field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

activityOptions := workflow.ActivityOptions{
  HeartbeatTimeout: 10 * time.Second,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

WaitForCancellation​

If true the Activity Execution will finish executing should there be a Cancellation request.

  • Type: bool
  • Default: false
activityOptions := workflow.ActivityOptions{
  WaitForCancellation: false,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

OriginalTaskQueueName​

activityOptions := workflow.ActivityOptions{
  OriginalTaskQueueName: "your-original-task-queue-name",
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

RetryPolicy​

To set a RetryPolicy, create an instance of ActivityOptions from the go.temporal.io/sdk/workflow package, set the RetryPolicy field, and then use the WithActivityOptions() API to apply the options to the instance of workflow.Context.

retryPolicy := &temporal.RetryPolicy{
  InitialInterval:    time.Second,
  BackoffCoefficient: 2.0,
  MaximumInterval:    time.Second * 100, // 100 * InitialInterval
  MaximumAttempts:    0, // Unlimited
  NonRetryableErrorTypes: []string, // empty
}

Providing a Retry Policy here is a customization that overwrites individual Field defaults.

retryPolicy := &temporal.RetryPolicy{
  InitialInterval:    time.Second,
  BackoffCoefficient: 2.0,
  MaximumInterval:    time.Second * 100,
}

activityOptions := workflow.ActivityOptions{
  RetryPolicy: retryPolicy,
}
ctx = workflow.WithActivityOptions(ctx, activityOptions)
var yourActivityResult YourActivityResult
err = workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam).Get(ctx, &yourActivityResult)
if err != nil {
  // ...
}

How to get the results of an Activity Execution​

The call to spawn an Activity Execution generates the ScheduleActivityTask Command and provides the Workflow with an Awaitable. Workflow Executions can either block progress until the result is available through the Awaitable or continue progressing, making use of the result when it becomes available.

The ExecuteActivity API call returns an instance of workflow.Future which has the following two methods:

  • Get(): Takes an instance of the workflow.Context, that was passed to the Activity Execution, and a pointer as parameters. The variable associated with the pointer is populated with the Activity Execution result. This call blocks until the results are available.
  • IsReady(): Returns true when the result of the Activity Execution is ready.

Call the Get() method on the instance of workflow.Future to get the result of the Activity Execution. The type of the result parameter must match the type of the return value declared by the Activity function.

func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) (YourWorkflowResponse, error) {
 // ...
 future := workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam)
 var yourActivityResult YourActivityResult
 if err := future.Get(ctx, &yourActivityResult); err != nil {
   // ...
 }
 // ...
}

Use the IsReady() method first to make sure the Get() call doesn't cause the Workflow Execution to wait on the result.

func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) (YourWorkflowResponse, error) {
 // ...
 future := workflow.ExecuteActivity(ctx, YourActivityDefinition, yourActivityParam)
 // ...
 if(future.IsReady()) {
   var yourActivityResult YourActivityResult
   if err := future.Get(ctx, &yourActivityResult); err != nil {
     // ...
   }
 }
 // ...
}

It is idiomatic to invoke multiple Activity Executions from within a Workflow. Therefore, it is also idiomatic to either block on the results of the Activity Executions or continue on to execute additional logic, checking for the Activity Execution results at a later time.

How to develop a Worker in Go​

Create an instance of Worker by calling worker.New(), available through the go.temporal.io/sdk/worker package, and pass it the following parameters:

  1. An instance of the Temporal Go SDK Client.
  2. The name of the Task Queue that it will poll.
  3. An instance of worker.Options, which can be empty.

Then, register the Workflow Types and the Activity Types that the Worker will be capable of executing.

Lastly, call either the Start() or the Run() method on the instance of the Worker. Run accepts an interrupt channel as a parameter, so that the Worker can be stopped in the terminal. Otherwise, the Stop() method must be called to stop the Worker.

tip

If you have gow installed, the Worker Process automatically "reloads" when you update the Worker file:

go install github.com/mitranim/gow@latest
gow run worker/main.go # automatically reloads when file changes

View the source code

in the context of the rest of the application code.

package main

import (
    "log"

    "go.temporal.io/sdk/activity"
    "go.temporal.io/sdk/client"
    "go.temporal.io/sdk/worker"
    "go.temporal.io/sdk/workflow"

    "documentation-samples-go/yourapp"
)

func main() {
    // Create a Temporal Client
    // A Temporal Client is a heavyweight object that should be created just once per process.
    temporalClient, err := client.Dial(client.Options{})
    if err != nil {
        log.Fatalln("Unable to create client", err)
    }
    defer temporalClient.Close()
    // Create a new Worker.
    yourWorker := worker.New(temporalClient, "your-custom-task-queue-name", worker.Options{})
    // Register your Workflow Definitions with the Worker.
    // Use the RegisterWorkflow or RegisterWorkflowWithOptions method for each Workflow registration.
    yourWorker.RegisterWorkflow(yourapp.YourWorkflowDefinition)
// ...
    // Register your Activity Definitons with the Worker.
    // Use this technique for registering all Activities that are part of a struct and set the shared variable values.
    message := "This could be a connection string or endpoint details"
    number := 100
    activities := &yourapp.YourActivityObject{
        Message: &message,
        Number:  &number,
    }
    // Use the RegisterActivity or RegisterActivityWithOptions method for each Activity.
    yourWorker.RegisterActivity(activities)
// ...
    // Run the Worker
    err = yourWorker.Run(worker.InterruptCh())
    if err != nil {
        log.Fatalln("Unable to start Worker", err)
    }
}
// ...

How to set WorkerOptions in Go​

Create an instance of Options from the go.temporal.io/sdk/worker package, set any of the optional fields, and pass the instance to the New call.

FieldRequiredType
MaxConcurrentActivityExecutionSizeNoint
WorkerActivitiesPerSecondNofloat64
MaxConcurrentLocalActivityExecutionSizeNoint
WorkerLocalActivitiesPerSecondNofloat64
TaskQueueActivitiesPerSecondNofloat64
MaxConcurrentActivityTaskPollersNoint
MaxConcurrentWorkflowTaskExecutionSizeNoint
MaxConcurrentWorkflowTaskPollersNoint
EnableLoggingInReplayNobool
DisableStickyExecutionNobool
StickyScheduleToStartTimeoutNotime.Duration
BackgroundActivityContextNocontext.Context
WorkflowPanicPolicyNoWorkflowPanicPolicy
WorkerStopTimeoutNotime.Duration
EnableSessionWorkerNobool
MaxConcurrentSessionExecutionSizeNoint
WorkflowInterceptorChainFactoriesNo[]WorkflowInterceptor
LocalActivityWorkerOnlyNobool
IdentityNostring
DeadlockDetectionTimeoutNotime.Duration

MaxConcurrentActivityExecutionSize​

Sets the maximum concurrent Activity Executions for the Worker.

  • Type: int
  • Default: 1000

A value of 0 sets to the default.

// ...
workerOptions := worker.Options{
  MaxConcurrentActivityExecutionSize: 1000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

WorkerActivitiesPerSecond​

Rate limits the number of Activity Task Executions started per second for the Worker.

  • Type: float64
  • Default: 100000

A value of 0 sets to the default.

Intended use case is to limit resources used by the Worker.

Notice that the value type is a float so that the value can be less than 1 if needed. For example, if set to 0.1, Activity Task Executions will happen once every ten seconds. This can be used to protect down stream services from flooding with requests.

// ...
workerOptions := worker.Options{
    WorkerActivitiesPerSecond: 100000,
  // ..
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

MaxConcurrentLocalActivityExecutionSize​

Set the maximum concurrent Local Activity Executions for the Worker.

  • Type: int
  • Default: 1000

A value of 0 sets to the default value.

// ...
workerOptions := worker.Options{
    MaxConcurrentLocalActivityExecutionSize: 1000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

WorkerLocalActivitiesPerSecond​

Rate limits the number of Local Activity Executions per second executed for the Worker.

  • Type: float64
  • Default: 100000

A value of 0 sets to the default value.

Intended use case is to limit resources used by the Worker.

Notice that the value type is a float so that the value can be less than 1 if needed. For example, if set to 0.1, Local Activity Task Executions will happen once every ten seconds. This can be used to protect down stream services from flooding with requests.

// ...
workerOptions := worker.Options{
    WorkerLocalActivitiesPerSecond: 100000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

TaskQueueActivitiesPerSecond​

Rate limits the number of Activity Executions that can be started per second.

  • Type: float64
  • Default: 100000

A value of 0 sets to the default value.

This rate is managed by the Temporal Service and limits the Activity Tasks per second for the entire Task Queue. This is in contrast to WorkerActivityTasksPerSecond controls Activities only per Worker.

Notice that the number is represented in float, so that you can set it to less than 1 if needed. For example, set the number to 0.1 means you want your Activity to be executed once for every 10 seconds. This can be used to protect down stream services from flooding.

// ...
workerOptions := worker.Options{
    TaskQueueActivitiesPerSecond: 100000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

MaxConcurrentActivityTaskPollers​

Sets the maximum number of goroutines to concurrently poll the Task Queue for Activity Tasks.

  • Type: int
  • Default: 2

Changing this value will affect the rate at which the Worker is able to consume Activity Tasks from the Task Queue.

// ...
workerOptions := worker.Options{
    MaxConcurrentActivityTaskPollers: 2,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

MaxConcurrentWorkflowTaskExecutionSize​

Sets the maximum number of concurrent Workflow Task Executions the Worker can have.

  • Type: int
  • Default: 1000

A value of 0 sets to the default value.

// ...
workerOptions := worker.Options{
    MaxConcurrentWorkflowTaskExecutionSize: 1000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

MaxConcurrentWorkflowTaskPollers​

Sets the maximum number of goroutines that will concurrently poll the Task Queue for Workflow Tasks.

  • Type: int
  • Default: 2

Changing this value will affect the rate at which the Worker is able to consume Workflow Tasks from the Task Queue.

// ...
workerOptions := worker.Options{
    MaxConcurrentWorkflowTaskPollers: 2,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

EnableLoggingInReplay​

Set to enable logging in Workflow Execution replays.

  • type: bool
  • Default: false

In Workflow Definitions you can use workflow.GetLogger(ctx) to write logs. By default, the logger will skip logging during replays, so you do not see duplicate logs.

This is only really useful for debugging purpose.

// ...
workerOptions := worker.Options{
    EnableLoggingInReplay: false,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

DisableStickyExecution​

Deprecated

When DisableStickyExecution is true it can harm performance. It will be removed soon. See SetStickyWorkflowCacheSize instead.

Set to disable Sticky Executions

  • Type: bool
  • Default: false

Sticky Execution runs Workflow Tasks of a Workflow Execution on same host (could be a different Worker, as long as it is on the same host). This is an optimization for Workflow Executions. When sticky execution is enabled, Worker keeps the Workflow state in memory. New Workflow Task contains the new history events will be dispatched to the same Worker. If this Worker crashes, the sticky Workflow Task will timeout after StickyScheduleToStartTimeout, and Temporal Service will clear the stickiness for that Workflow Execution and automatically reschedule a new Workflow Task that is available for any Worker to pick up and resume the progress.

// ...
workerOptions := worker.Options{
    StickyScheduleToStartTimeout: time.Second(5),
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

StickyScheduleToStartTimeout​

Sets the Sticky Execution Schedule-To-Start Timeout for Workflow Tasks.

The resolution is in seconds.

// ...
workerOptions := worker.Options{
    StickyScheduleToStartTimeout: time.Second(5),
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

BackgroundActivityContext​

Not recommended

This method of passing dependencies between Activity Task Executions is not recommended anymore.

Instead, we recommend using a struct with fields that contain dependencies and develop Activity Definitions as struct methods and then pass all the dependencies on the structure initialization.

Sets the background context.Context for all Activity Types registered with the Worker.

The context can be used to pass external dependencies such as database connections to Activity Task Executions.

// ...
ctx := context.WithValue(context.Background(), "your-key", "your-value")
workerOptions := worker.Options{
    BackgroundActivityContext: ctx,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

WorkflowPanicPolicy​

Sets how the Workflow Worker handles a non-deterministic Workflow Execution History Event and other panics from Workflow Definition code.

// ...
workerOptions := worker.Options{
    DisableStickyExecution: internal.BlockWorkflow,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

WorkerStopTimeout​

Sets the Worker's graceful stop timeout

Value resolution is in seconds.

// ...
workerOptions := worker.Options{
    WorkerStopTimeout: time.Second(0),
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

EnableSessionWorker​

Enables Sessions for Activity Workers.

  • Type: bool
  • Default: false

When true the Activity Worker creates a Session to sequentially process Activity Tasks for the given Task Queue.

// ...
workerOptions := worker.Options{
    EnableSessionWorker: true,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

MaxConcurrentSessionExecutionSize​

Sets the maximum number of concurrent Sessions that the Worker can support.

  • Type: int
  • Default: 1000
// ...
workerOptions := worker.Options{
    MaxConcurrentSessionExecutionSize: 1000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

WorkflowInterceptorChainFactories​

Specifies the factories used to instantiate the Workflow interceptor chain.

The chain is instantiated for each replay of a Workflow Execution.

LocalActivityWorkerOnly​

Sets the Worker to only handle Workflow Tasks and local Activity Tasks.

  • Type: bool
  • Default: false
// ...
workerOptions := worker.Options{
    LocalActivityWorkerOnly: 1000,
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

Identity​

Sets the Temporal Client-level Identity value, overwriting the existing one.

  • Type: string
  • Default: client identity
// ...
workerOptions := worker.Options{
    Identity: "your_custom_identity",
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

DeadlockDetectionTimeout​

Sets the maximum time that a Workflow Task can execute for.

Resolution is in seconds.

// ...
workerOptions := worker.Options{
    DeadlockDetectionTimeout: time.Second(1),
  // ...
}
w := worker.New(c, "your_task_queue_name", workerOptions)
// ...

How to run a Temporal Cloud Worker​

To run a Worker that uses Temporal Cloud, you need to provide additional connection and client options that include the following:

  • An address that includes your Cloud Namespace Name and a port number: <Namespace>.<ID>.tmprl.cloud:<port>.
  • mTLS CA certificate.
  • mTLS private key.

For more information about managing and generating client certificates for Temporal Cloud, see How to manage certificates in Temporal Cloud.

For more information about configuring TLS to secure inter- and intra-network communication for a Temporal Service, see Temporal Customization Samples.

To run a Worker that talks to Temporal Cloud, you need the following:

For more information about managing and generating client certificates for Temporal Cloud, see How to manage certificates in Temporal Cloud.

For more information about configuring TLS to secure inter- and intra-network communication for a Temporal Service, see Temporal Customization Samples.

View the source code

in the context of the rest of the application code.

package main

import (
    "crypto/tls"
    "log"

    "go.temporal.io/sdk/client"
    "go.temporal.io/sdk/worker"

    "documentation-samples-go/cloud"
)

func main() {
    // Get the key and cert from your env or local machine
    clientKeyPath := "./secrets/yourkey.key"
    clientCertPath := "./secrets/yourcert.pem"
    // Specify the host and port of your Temporal Cloud Namespace
    // Host and port format: namespace.unique_id.tmprl.cloud:port
    hostPort := "<yournamespace>.<id>.tmprl.cloud:7233"
    namespace := "<yournamespace>.<id>"
    // Use the crypto/tls package to create a cert object
    cert, err := tls.LoadX509KeyPair(clientCertPath, clientKeyPath)
    if err != nil {
        log.Fatalln("Unable to load cert and key pair.", err)
    }
    // Add the cert to the tls certificates in the ConnectionOptions of the Client
    temporalClient, err := client.Dial(client.Options{
        HostPort:  hostPort,
        Namespace: namespace,
        ConnectionOptions: client.ConnectionOptions{
            TLS: &tls.Config{Certificates: []tls.Certificate{cert}},
        },
    })
    if err != nil {
        log.Fatalln("Unable to connect to Temporal Cloud.", err)
    }
    defer temporalClient.Close()
    // Create a new Worker.
    yourWorker := worker.New(temporalClient, "cloud-connection-example-go-task-queue", worker.Options{})
// ...
}

How to register types​

All Workers listening to the same Task Queue name must be registered to handle the exact same Workflows Types and Activity Types.

If a Worker polls a Task for a Workflow Type or Activity Type it does not know about, it fails that Task. However, the failure of the Task does not cause the associated Workflow Execution to fail.

The RegisterWorkflow() and RegisterActivity() calls essentially create an in-memory mapping between the Workflow Types and their implementations, inside the Worker process.

Registering Activity structs

Per Activity Definition best practices, you might have an Activity struct that has multiple methods and fields. When you use RegisterActivity() for an Activity struct, that Worker has access to all exported methods.

Registering multiple Types

To register multiple Activity Types and/or Workflow Types with the Worker Entity, just make multiple Activity registration calls, but make sure each Type name is unique:

w.RegisterActivity(ActivityA)
w.RegisterActivity(ActivityB)
w.RegisterActivity(ActivityC)
w.RegisterWorkflow(WorkflowA)
w.RegisterWorkflow(WorkflowB)
w.RegisterWorkflow(WorkflowC)

How to set RegisterWorkflowOptions in Go​

Create an instance of RegisterOptions from the go.temporal.io/sdk/workflow package and pass it to the RegisterWorkflowWithOptions call when registering the Workflow Type with the Worker.

  • Used to set options for registering a Workflow
FieldRequiredType
NameNostring
DisableAlreadyRegisteredCheckNobool

Name​

See How to customize a Workflow Type in Go

DisableAlreadyRegisteredCheck​

Disables the check to see if the Workflow Type has already been registered.

  • Type: bool
  • Default: false
// ...
w := worker.New(temporalClient, "your_task_queue_name", worker.Options{})
registerOptions := workflow.RegisterOptions{
  DisableAlreadyRegisteredCheck: `false`,
  // ...
}
w.RegisterWorkflowWithOptions(YourWorkflowDefinition, registerOptions)
// ...

How to set RegisterActivityOptions in Go​

Create an instance of RegisterOptions from the go.temporal.io/sdk/activity package and pass it to the RegisterActivityWithOptions call when registering the Activity Type with the Worker.

Options for registering an Activity

FieldRequiredType
NameNostring
DisableAlreadyRegisteredCheckNobool
SkipInvalidStructFunctionsNobool

Name​

See How to customize Activity Type in Go.

DisableAlreadyRegisteredCheck​

Disables the check to see if the Activity has already been registered.

  • Type: bool
  • Default: false
// ...
w := worker.New(temporalClient, "your_task_queue_name", worker.Options{})
registerOptions := activity.RegisterOptions{
  DisableAlreadyRegisteredCheck: false,
  // ...
}
w.RegisterActivityWithOptions(a.YourActivityDefinition, registerOptions)
// ...

SkipInvalidStructFunctions​

When registering a struct that has Activities, skip functions that are not valid. If false, registration panics.

  • Type: bool
  • Default: false
// ...
w := worker.New(temporalClient, "your_task_queue_name", worker.Options{})
registerOptions := activity.RegisterOptions{
  SkipInvalidStructFunctions: false,
  // ...
}
w.RegisterActivityWithOptions(a.YourActivityDefinition, registerOptions)
// ...