mirror of
https://github.com/rocky-linux/peridot.git
synced 2024-11-27 15:36:25 +00:00
200 lines
8.9 KiB
Go
200 lines
8.9 KiB
Go
// The MIT License
|
||
//
|
||
// Copyright (c) 2020 Temporal Technologies Inc. All rights reserved.
|
||
//
|
||
// Copyright (c) 2020 Uber Technologies, Inc.
|
||
//
|
||
// Permission is hereby granted, free of charge, to any person obtaining a copy
|
||
// of this software and associated documentation files (the "Software"), to deal
|
||
// in the Software without restriction, including without limitation the rights
|
||
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
||
// copies of the Software, and to permit persons to whom the Software is
|
||
// furnished to do so, subject to the following conditions:
|
||
//
|
||
// The above copyright notice and this permission notice shall be included in
|
||
// all copies or substantial portions of the Software.
|
||
//
|
||
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
||
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
||
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
||
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
||
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
||
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
||
// THE SOFTWARE.
|
||
|
||
/*
|
||
Package activity contains functions and types used to implement Temporal Activities.
|
||
|
||
An Activity is an implementation of a task to be performed as part of a larger Workflow. There is no limitation of
|
||
what an Activity can do. In the context of a Workflow, it is in the Activities where all operations that affect the
|
||
desired results must be implemented.
|
||
|
||
Overview
|
||
|
||
Temporal Go SDK does all the heavy lifting of handling the async communication between the Temporal
|
||
managed service and the Worker running the Activity. As such, the implementation of the Activity can, for the most
|
||
part, focus on the business logic. The sample code below shows the implementation of a simple Activity that accepts a
|
||
string parameter, appends a word to it and then returns the result.
|
||
|
||
import (
|
||
"context"
|
||
|
||
"go.temporal.io/sdk/activity"
|
||
)
|
||
|
||
func SimpleActivity(ctx context.Context, value string) (string, error) {
|
||
activity.GetLogger(ctx).Info("SimpleActivity called.", "Value", value)
|
||
return "Processed: ” + value, nil
|
||
}
|
||
|
||
The following sections explore the elements of the above code.
|
||
|
||
Declaration
|
||
|
||
In the Temporal programing model, an Activity is implemented with a function. The function declaration specifies the
|
||
parameters the Activity accepts as well as any values it might return. An Activity function can take zero or many
|
||
Activity specific parameters and can return one or two values. It must always at least return an error value. The
|
||
Activity function can accept as parameters and return as results any serializable type.
|
||
|
||
func SimpleActivity(ctx context.Context, value string) (string, error)
|
||
|
||
The first parameter to the function is context.Context. This is an optional parameter and can be omitted. This
|
||
parameter is the standard Go context.
|
||
|
||
The second string parameter is a custom Activity-specific parameter that can be used to pass in data into the Activity
|
||
on start. An Activity can have one or more such parameters. All parameters to an Activity function must be
|
||
serializable, which essentially means that params can’t be channels, functions, variadic, or unsafe pointer.
|
||
|
||
The Activity declares two return values: (string, error). The string return value is used to return the result of the
|
||
Activity. The error return value is used to indicate an error was encountered during execution.
|
||
|
||
Implementation
|
||
|
||
There is nothing special about Activity code. You can write Activity implementation code the same way you would any
|
||
other Go service code. You can use the usual loggers and metrics collectors. You can use the standard Go concurrency
|
||
constructs.
|
||
|
||
Failing the Activity
|
||
|
||
To mark an Activity as failed, all that needs to happen is for the Activity function to return an error via the error
|
||
return value.
|
||
|
||
Activity Heartbeating
|
||
|
||
For long running Activities, Temporal provides an API for the Activity code to report both liveness and progress back to
|
||
the Temporal managed service.
|
||
|
||
progress := 0
|
||
for hasWork {
|
||
// send heartbeat message to the server
|
||
activity.RecordHeartbeat(ctx, progress)
|
||
// do some work
|
||
...
|
||
progress++
|
||
}
|
||
|
||
When the Activity times out due to a missed heartbeat, the last value of the details (progress in the above sample) is
|
||
returned from the workflow.ExecuteActivity function as the details field of TimeoutError with TimeoutType_HEARTBEAT.
|
||
|
||
It is also possible to heartbeat an Activity from an external source:
|
||
|
||
// instantiate a Temporal service Client
|
||
client.Client client = client.NewClient(...)
|
||
|
||
// record heartbeat
|
||
err := client.RecordActivityHeartbeat(ctx, taskToken, details)
|
||
|
||
It expects an additional parameter, "taskToken", which is the value of the binary "TaskToken" field of the
|
||
"ActivityInfo" struct retrieved inside the Activity (GetActivityInfo(ctx).TaskToken). "details" is the serializable
|
||
payload containing progress information.
|
||
|
||
Activity Cancellation
|
||
|
||
When an Activity is canceled (or its Workflow execution is completed or failed) the context passed into its function
|
||
is canceled which sets its Done channel’s closed state. So an Activity can use that to perform any necessary cleanup
|
||
and abort its execution. Currently cancellation is delivered only to Activities that call RecordHeartbeat.
|
||
|
||
Async/Manual Activity Completion
|
||
|
||
In certain scenarios completing an Activity upon completion of its function is not possible or desirable.
|
||
|
||
One example would be the UberEATS order processing Workflow that gets kicked off once an eater pushes the “Place Order”
|
||
button. Here is how that Workflow could be implemented using Temporal and the “async Activity completion”:
|
||
|
||
- Activity 1: send order to restaurant
|
||
- Activity 2: wait for restaurant to accept order
|
||
- Activity 3: schedule pickup of order
|
||
- Activity 4: wait for courier to pick up order
|
||
- Activity 5: send driver location updates to eater
|
||
- Activity 6: complete order
|
||
|
||
Activities 2 & 4 in the above flow require someone in the restaurant to push a button in the Uber app to complete the
|
||
Activity. The Activities could be implemented with some sort of polling mechanism. However, they can be implemented
|
||
much simpler and much less resource intensive as a Temporal Activity that is completed asynchronously.
|
||
|
||
There are 2 parts to implementing an asynchronously completed Activity. The first part is for the Activity to provide
|
||
the information necessary to be able to be completed from an external system and notify the Temporal service that it is
|
||
waiting for that outside callback:
|
||
|
||
// retrieve Activity information needed to complete Activity asynchronously
|
||
activityInfo := activity.GetInfo(ctx)
|
||
taskToken := activityInfo.TaskToken
|
||
|
||
// send the taskToken to external service that will complete the Activity
|
||
...
|
||
|
||
// return from Activity function indicating the Temporal should wait for an async completion message
|
||
return "", activity.ErrResultPending
|
||
|
||
The second part is then for the external service to call the Temporal service to complete the Activity. To complete the
|
||
Activity successfully you would do the following:
|
||
|
||
// instantiate a Temporal service Client
|
||
// the same client can be used complete or fail any number of Activities
|
||
client.Client client = client.NewClient(...)
|
||
|
||
// complete the Activity
|
||
client.CompleteActivity(taskToken, result, nil)
|
||
|
||
And here is how you would fail the Activity:
|
||
|
||
// fail the Activity
|
||
client.CompleteActivity(taskToken, nil, err)
|
||
|
||
The parameters of the CompleteActivity function are:
|
||
|
||
- taskToken: This is the value of the binary “TaskToken” field of the
|
||
“ActivityInfo” struct retrieved inside the Activity.
|
||
- result: This is the return value that should be recorded for the Activity.
|
||
The type of this value needs to match the type of the return value
|
||
declared by the Activity function.
|
||
- err: The error code to return if the Activity should terminate with an
|
||
error.
|
||
|
||
If error is not null the value of the result field is ignored.
|
||
|
||
For a full example of implementing this pattern see the Expense sample.
|
||
|
||
Registration
|
||
|
||
In order to for some Workflow execution to be able to invoke an Activity type, the Worker process needs to be aware of
|
||
all the implementations it has access to. To do that, create a Worker and register the Activity like so:
|
||
|
||
```
|
||
c, err := client.NewClient(client.Options{})
|
||
if err != nil {
|
||
log.Fatalln("unable to create Temporal client", err)
|
||
}
|
||
defer c.Close()
|
||
w := worker.New(c, "SomeTaskQueue", worker.Options{})
|
||
w.RegisterActivity(SomeActivityFunction)
|
||
```
|
||
|
||
This call essentially creates an in-memory mapping inside the Worker process between the fully qualified function name
|
||
and the implementation. Unlike in Amazon SWF, Workflow and Activity types are not registered with the managed service.
|
||
If the Worker receives a request to start an Activity execution for an Activity type it does not know it will fail that
|
||
request.
|
||
|
||
*/
|
||
package activity
|