Scheduler Service (v1.0.0)

Service responsible for scheduling and triggering periodic tasks in the BookWorm e-commerce system.

Service Background Jobs Event Publisher Maintenance High Priority AsyncAPI V1

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Sends 2 messages

This service publishes messages to other services

Overview

The Scheduler Service is a critical infrastructure component within BookWorm’s microservices architecture, responsible for managing background jobs and automated maintenance tasks. Built using the TickerQ framework, this service orchestrates time-based operations that ensure system health, performance optimization, and reliable email delivery across the platform.

Key Responsibilities

  • Email Maintenance: Manages cleanup and retry operations for email notifications
  • System Health: Performs regular maintenance tasks to optimize system performance
  • Background Processing: Executes scheduled jobs without blocking user operations
  • Event Publishing: Triggers integration events for cross-service communication
  • Error Recovery: Implements retry mechanisms for failed operations
  • Resource Optimization: Manages system resources through automated cleanup processes

Component Diagram

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Architecture diagram

Scheduled Jobs

The Scheduler Service manages the following automated tasks:

JobSchedulePriorityPurposeTarget Service
CleanUpSentEmailJobDaily 00:00NormalCleanup processed email recordsNotification Service
ResendErrorEmailJobHourlyHighRetry failed email deliveriesNotification Service

Job Implementation Details

CleanUpSentEmailJob

  • Class: CleanUpSentEmailJob
  • Cron Expression: "0 0 * * *" (Daily at midnight)
  • Priority: Normal
  • Implementation: Publishes CleanUpSentEmailIntegrationEvent and saves changes to database

ResendErrorEmailJob

  • Class: ResendErrorEmailJob
  • Cron Expression: "0 * * * *" (Every hour)
  • Priority: TickerTaskPriority.High
  • Implementation: Publishes ResendErrorEmailIntegrationEvent and saves changes to database

Job Execution Flow

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Event Publishing

The service publishes integration events to trigger downstream processing:

Email Cleanup Event

  • Event: CleanUpSentEmailIntegrationEvent
  • Schedule: Daily at midnight (0 0 * * *)
  • Purpose: Triggers cleanup of successfully sent email records
  • Target: Notification Service outbox cleanup

Email Resend Event

  • Event: ResendErrorEmailIntegrationEvent
  • Schedule: Every hour (0 * * * *)
  • Priority: High priority processing
  • Purpose: Triggers retry mechanism for failed email deliveries
  • Target: Notification Service error recovery

Technical Architecture

Job Framework

  • Framework: TickerQ.Utilities for .NET
  • Execution Model: Background service with cron scheduling using [TickerFunction] attributes
  • Persistence: PostgreSQL for job state and operational store
  • Dashboard: Built-in TickerQ Dashboard at /tickerq endpoint with basic authentication
  • Concurrency: Max concurrency set to Environment.ProcessorCount
  • Instance Identification: Uses Environment.MachineName for instance identification

Database Configuration

  • Primary Database: Azure PostgreSQL via Aspire integration
  • Context: SchedulerDbContext implementing ISchedulerDbContext
  • Outbox Pattern: EntityFramework outbox for reliable event publishing
  • Migrations: EF Core migrations with operational store support

Event Integration

  • Message Bus: RabbitMQ via MassTransit
  • Pattern: Outbox pattern with EntityFramework for transactional messaging
  • Serialization: JSON with MassTransit envelope
  • Duplicate Detection: 5-minute duplicate detection window
  • Query Delay: 1-second query delay for outbox processing

Infrastructure

The Scheduler Service is deployed as a containerized application on Microsoft Azure, leveraging Azure PostgreSQL for persistence and RabbitMQ for event publishing. The service includes a built-in dashboard for monitoring job execution.

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Monitoring & Observability

Health Checks

  • Database Connectivity: Verifies PostgreSQL connection via Aspire health checks
  • Message Bus: Confirms RabbitMQ availability through MassTransit health checks
  • Job Status: Monitors active and failed job executions via TickerQ Dashboard

Logging

  • Structured Logging: Built-in .NET logging with structured data
  • Job Execution: TickerQ framework provides detailed execution logs
  • Error Tracking: Comprehensive error logging with stack traces
  • Dashboard Monitoring: Real-time job status and execution history via /tickerq endpoint

Management Dashboard

  • TickerQ Dashboard: Accessible at /tickerq endpoint
  • Authentication: Basic authentication enabled for security
  • Features: Job monitoring, execution history, error tracking, and manual job triggers
  • Real-time Updates: Live job status and execution statistics

Alerting

  • Failed Jobs: Immediate alerts for job execution failures
  • High Error Rate: Threshold-based alerts for email delivery issues
  • Resource Usage: Memory and CPU utilization monitoring

Security Considerations

  • Database Security: Encrypted connections with Azure SQL
  • Message Security: TLS encryption for RabbitMQ communication
  • Access Control: Service principal authentication
  • Audit Trail: Complete logging of all job executions
  • Resource Limits: CPU and memory constraints to prevent resource exhaustion

Performance Optimizations

  • Async Processing: All operations are fully asynchronous
  • Connection Pooling: Reuses database and message bus connections
  • Batch Operations: Groups related operations when possible
  • Resource Management: Proper disposal of resources and connections
  • Parallel Execution: Concurrent job processing with throttling limits
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