How to replay a Workflow Execution in Go

Use the worker.WorkflowReplayer to replay an existing Workflow Execution from its Event History to replicate errors.

For example, the following code retrieves the Event History of a Workflow:

import (
    "context"

    "go.temporal.io/api/enums/v1"
    "go.temporal.io/api/history/v1"
    "go.temporal.io/sdk/client"
)

func GetWorkflowHistory(ctx context.Context, client client.Client, id, runID string) (*history.History, error) {
    var hist history.History
    iter := client.GetWorkflowHistory(ctx, id, runID, false, enums.HISTORY_EVENT_FILTER_TYPE_ALL_EVENT)
    for iter.HasNext() {
        event, err := iter.Next()
        if err != nil {
            return nil, err
        }
        hist.Events = append(hist.Events, event)
    }
    return &hist, nil
}

This history can then be used to replay. For example, the following code creates a WorkflowReplayer and register the YourWorkflow Workflow function. Then it calls the ReplayWorkflowHistory to replay the Event History and return an error code.

import (
    "context"

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

func ReplayWorkflow(ctx context.Context, client client.Client, id, runID string) error {
    hist, err := GetWorkflowHistory(ctx, client, id, runID)
    if err != nil {
        return err
    }
    replayer := worker.NewWorkflowReplayer()
    replayer.RegisterWorkflow(YourWorkflow)
    return replayer.ReplayWorkflowHistory(nil, hist)
}

The code above will cause the Worker to re-execute the Workflow's Workflow Function using the original Event History. If a noticeably different code path was followed or some code caused a deadlock, it will be returned in the error code. Replaying a Workflow Execution locally is a good way to see exactly what code path was taken for given input and events.