background_tasks

Last updated: 2024-09-17 21:08:37.957511 File source: link on GitLab

background_tasks

Specification

1. Description

The background_tasks package is an internal package responsible for managing background jobs within DMS. It contains a scheduler that registers tasks and run them according to the schedule defined by the task definition.

proposed Other packages that have their own background tasks register through this package:

Registration
1. The task itself, the arguments it needs
2. priority
3. event (time period or other event to trigger task)
Start , Stop, Resume
Algorithm that accounts for the event and priority of the task (not yet clear)
Monitor resource usage of tasks (not yet clear)

2. Structure and Organisation

Here is quick overview of the contents of this pacakge:

README: Current file which is aimed towards developers who wish to use and modify the package functionality.
init: This file initializes OpenTelemetry-based Zap logger.
scheduler: This file This file defines a background task scheduler that manages task execution based on triggers, priority, and retry policies.
task: This file contains background task structs and their properties.
trigger: This file defines various trigger types (PeriodicTrigger, EventTrigger, OneTimeTrigger) for background tasks, allowing execution based on time intervals, cron expressions, or external events

Files with *_test.go naming convention contain unit tests of the functionality in corresponding file.

3. Class Diagram

Source

background_tasks class diagram

Rendered from source file

!$rootUrlGitlab = "https://gitlab.com/nunet/device-management-service/-/raw/main"
!$packageRelativePath = "/internal/background_tasks"
!$packageUrlGitlab = $rootUrlGitlab + $packageRelativePath
 
!include $packageUrlGitlab/specs/class_diagram.puml

4. Functionality

NewScheduler

signature: NewScheduler(maxRunningTasks int) *Scheduler
input: maximum no of running tasks
output: internal.background_tasks.Scheduler

NewScheduler function creates a new scheduler which takes maxRunningTasks argument to limit the maximum number of tasks to run at a time.

Scheduler methods

Scheduler struct is the orchestrator that manages and runs the tasks. If the Scheduler task queue is full, remaining tasks that are triggered will wait until there is a slot available in the scheduler.

It has the following methods:

AddTask

signature: AddTask(task *Task) *Task
input: internal.background_tasks.Task
output: internal.background_tasks.Task

AddTask registers a task to be run when triggered.

RemoveTask

signature: RemoveTask(taskID int)
input: identifier of the Task
output: None

RemoveTask removes a task from the scheduler. Tasks with only OneTimeTrigger will be removed automatically once run.

Start

signature: Start()
input: None
output: None

Start starts the scheduler to monitor tasks.

Stop

signature: Stop()
input: None
output: None

Stop stops the scheduler.

runTask

signature: runTask(taskID int)
input: identifier of the Task
output: None

runTask executes a task and manages its lifecycle and retry policy.

runTasks

signature: runTasks()
input: None
output: None

runTasks checks and runs tasks based on their triggers and priority.

runningTasksCount

signature: runningTasksCount() int
input: None
output: number of running tasks

runningTasksCount returns the count of running tasks.

Trigger Interface

type Trigger interface {
	IsReady() bool // Returns true if the trigger condition is met.
	Reset()        // Resets the trigger state.
}

Its methods are explained below:

IsReady

signature: IsReady() bool
input: None
output: bool

IsReady should return true if the task should be run.

Reset

signature: Reset()
input: None
output: None

Reset resets the trigger until the next event happens.

There are different implementations for the Trigger interface.

PeriodicTrigger: Defines a trigger based on a duration interval or a cron expression.
EventTrigger: Defines a trigger that is set by a trigger channel.
OneTimeTrigger: A trigger that is only triggered once after a set delay.

5. Data Types

internal.background_tasks.Scheduler

// Scheduler orchestrates the execution of tasks based on their triggers and priority.
type Scheduler struct {
	tasks           map[int]internal.background_tasks.Task // Map of tasks by their ID.
	runningTasks    map[int]bool  // Map to keep track of running tasks.
	ticker          *time.Ticker  // Ticker for periodic checks of task triggers.
	stopChan        chan struct{} // Channel to signal stopping the scheduler.
	maxRunningTasks int           // Maximum number of tasks that can run concurrently.
	lastTaskID      int           // Counter for assigning unique IDs to tasks.
	mu              sync.Mutex    // Mutex to protect access to task maps.
}

internal.background_tasks.RetryPolicy

// RetryPolicy defines the policy for retrying tasks on failure.
type RetryPolicy struct {
	MaxRetries int           // Maximum number of retries.
	Delay      time.Duration // Delay between retries.
}

internal.background_tasks.Execution

// Execution records the execution details of a task.
type Execution struct {
	StartedAt time.Time   // Start time of the execution.
	EndedAt   time.Time   // End time of the execution.
	Status    string      // Status of the execution (e.g., "SUCCESS", "FAILED").
	Error     string      // Error message if the execution failed.
	Event     interface{} // Event associated with the execution.
	Results   interface{} // Results of the execution.
}

internal.background_tasks.Task

Task is a struct that defines a job. It includes the task's ID, Name, the function that is going to be run, the arguments for the function, the triggers that trigger the task to run, retry policy, etc.

// Task represents a schedulable task.
type Task struct {
	ID            int                          // Unique identifier for the task.
	Name          string                       // Name of the task.
	Description   string                       // Description of the task.
	Triggers      []internal.background_tasks.Trigger                    // List of triggers for the task.
	Function      func(args interface{}) error // Function to execute as the task.
	Args          []interface{}                // Arguments for the task function.
	RetryPolicy   internal.background_tasks.RetryPolicy                  // Retry policy for the task.
	Enabled       bool                         // Flag indicating if the task is enabled.
	Priority      int                          // Priority of the task for scheduling.
	ExecutionHist []internal.background_tasks.Execution                  // History of task executions.
}

internal.background_tasks.PeriodicTrigger

// PeriodicTrigger triggers at regular intervals or based on a cron expression.
type PeriodicTrigger struct {
	Interval      time.Duration // Interval for periodic triggering.
	CronExpr      string        // Cron expression for triggering.
	lastTriggered time.Time     // Last time the trigger was activated.
}

internal.background_tasks.EventTrigger

// EventTrigger triggers based on an external event signaled through a channel
type EventTrigger struct {
	Trigger chan bool // Channel to signal an event.
}

internal.background_tasks.OneTimeTrigger

// OneTimeTrigger triggers once after a specified delay.
type OneTimeTrigger struct {
	Delay        time.Duration // The delay after which to trigger.
	registeredAt time.Time     // Time when the trigger was set.
}

6. Testing

Unit tests for each functionality are defined in files with *_test.go naming convention.

7. Proposed Functionality / Requirements

List of issues

All issues that are related to the implementation of internal package can be found below. These include any proposals for modifications to the package or new functionality needed to cover the requirements of other packages.

internal package implementation TBD

8. References

Previousinternal Nextconfig

Last updated 1 day ago