hammerwork 2.0.0

A high-performance, database-driven job queue for Rust with PostgreSQL and MySQL support, featuring job prioritization, cron scheduling, event streaming (Kafka/Kinesis/PubSub), webhooks, rate limiting, Prometheus metrics, and comprehensive monitoring
Documentation
# Job Types and Configuration

Hammerwork supports various types of jobs with flexible configuration options.

## Basic Jobs

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
use hammerwork::job::Job;
use serde_json::json;

// Simple job
let job = Job::new("email_queue".to_string(), json!({
    "to": "user@example.com",
    "subject": "Welcome!",
    "body": "Thanks for signing up"
}));

queue.enqueue(job).await?;
# Ok(())
# }
```

## Job Priority

Jobs support five priority levels:

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
use hammerwork::{Job, JobPriority};

let high_priority_job = Job::new("urgent".to_string(), json!({"task": "urgent_task"}))
    .with_priority(JobPriority::High);

let background_job = Job::new("cleanup".to_string(), json!({"task": "cleanup"}))
    .with_priority(JobPriority::Background);
# Ok(())
# }
```

### Priority Levels
- `Critical` - Highest priority (4)
- `High` - High priority (3)  
- `Normal` - Default priority (2)
- `Low` - Low priority (1)
- `Background` - Lowest priority (0)

## Delayed Jobs

Schedule jobs to run at a specific time:

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
use chrono::{Utc, Duration};

let delayed_job = Job::with_delay("reminder".to_string(), json!({"user_id": 123}), Duration::hours(24)); // Run in 24 hours

let scheduled_job = Job::new("report".to_string(), json!({"type": "weekly"}))
    .with_scheduled_at(Utc::now() + Duration::days(7));
# Ok(())
# }
```

## Job Timeouts

Configure per-job or worker-level timeouts:

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
use std::time::Duration;

// Per-job timeout
let job = Job::new("long_task".to_string(), json!({"data": "..."}))
    .with_timeout(Duration::from_secs(300)); // 5 minute timeout

// Worker-level default timeout
let worker = Worker::new(queue, "default".to_string(), handler)
    .with_default_timeout(Duration::from_secs(120)); // 2 minute default
# Ok(())
# }
```

## Retry Configuration

Jobs automatically retry on failure with configurable limits:

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
let job = Job::new("api_call".to_string(), json!({"url": "https://api.example.com"}))
    .with_max_attempts(5); // At most 5 attempts in total (the first run plus 4 retries)

// Worker-level retry configuration. The job's max_attempts is the limit;
// with_max_retries only caps it for jobs processed by this worker.
let worker = Worker::new(queue, "default".to_string(), handler)
    .with_max_retries(3)
    .with_retry_delay(std::time::Duration::from_secs(30)); // Wait 30s between retries
# Ok(())
# }
```

## Cron Jobs

Schedule recurring jobs with cron expressions:

```rust,no_run
# #[allow(unused_imports)] use hammerwork::{*, queue::*, worker::*};
# #[allow(unused_imports)] use serde_json::json;
# #[allow(unused_imports)] use std::sync::Arc;
# #[allow(unused_variables)]
# async fn doc(queue: Arc<JobQueue<sqlx::Postgres>>, handler: JobHandler) -> std::result::Result<(), Box<dyn std::error::Error>> {
use hammerwork::cron::CronSchedule;

let schedule = CronSchedule::with_timezone("0 0 8 * * *", "America/New_York")?; // Every day at 8 AM
let cron_job = Job::new("daily_report".to_string(), json!({"type": "daily"}))
    .with_cron(schedule)?;

queue.enqueue_cron_job(cron_job).await?;
# Ok(())
# }
```

### Cron Examples
- `"0 */30 * * * *"` - Every 30 minutes
- `"0 0 9 * * MON-FRI"` - 9 AM on weekdays
- `"0 0 0 1 * *"` - First day of every month
- `"@daily"` - Once a day at midnight
- `"@hourly"` - Once an hour

## Job Status Lifecycle

Jobs progress through these states:

1. **Pending** - Waiting to be processed (also after a failed or timed-out run that will be retried)
2. **Running** - Currently being processed
3. **Completed** - Successfully finished
4. **Failed** - Failed without running out of attempts: set by `fail_job`, or when a
   job is cancelled because a dependency, its fail-fast workflow or its fail-fast batch
   failed. Terminal; `retry_job` re-runs it.
5. **Dead** - Failed permanently (its last attempt failed). `retry_dead_job` re-runs it.
6. **TimedOut** - Its last attempt exceeded the timeout (earlier timeouts are retried).
   `retry_dead_job` re-runs it.
7. **Retrying** - Scheduled for retry (used by `TestQueue`)

A job runs at most `max_attempts` times. Recurring (cron) jobs never end in a terminal
status from a worker: after a completed, dead or timed-out run they go back to
`Pending` for their next scheduled run.

Status changes are guarded. Manual transitions only apply from these statuses, and
return `HammerworkError::InvalidJobTransition` otherwise:

| Method | Allowed from |
|---|---|
| `complete_job`, `fail_job` | `Pending`, `Running`, `Retrying` |
| `retry_job` | `Running`, `Retrying`, `Failed`, `TimedOut` |
| `mark_job_dead` | `Pending`, `Running`, `Retrying`, `Failed`, `TimedOut` |
| `mark_job_timed_out` | `Running` |
| `reschedule_cron_job` | any status except `Completed` and `Archived` (recurring jobs only) |
| `retry_dead_job` | `Dead`, `TimedOut` |

Workers record their runs with `finish_job_run`, which only applies to the run the
worker dequeued (see [Worker Configuration](worker-configuration.md#recording-outcomes-and-zombie-workers)).

## Job Handlers

Define how jobs are processed:

```rust
use hammerwork::{HammerworkError, Job, worker::JobHandler};
use std::sync::Arc;
# async fn send_email(_to: &str) -> hammerwork::Result<()> { Ok(()) }
# async fn generate_report(_kind: &str) -> hammerwork::Result<()> { Ok(()) }

// Simple handler
let handler: JobHandler = Arc::new(|job: Job| {
    Box::pin(async move {
        match job.payload.get("task").and_then(|v| v.as_str()) {
            Some("send_email") => {
                let email = job.payload["email"].as_str().unwrap_or_default();
                send_email(email).await?;
            },
            Some("generate_report") => {
                let report_type = job.payload["type"].as_str().unwrap_or_default();
                generate_report(report_type).await?;
            },
            _ => {
                return Err(HammerworkError::Processing("Unknown task type".to_string()));
            }
        }
        Ok(())
    })
});
```

## Error Handling

Jobs can fail and be retried automatically:

```rust
# use hammerwork::{Job, worker::JobHandler};
# use std::sync::Arc;
# async fn process_job(_job: &Job) -> hammerwork::Result<String> { Ok(String::new()) }
let handler: JobHandler = Arc::new(|job: Job| {
    Box::pin(async move {
        // Your processing logic
        match process_job(&job).await {
            Ok(result) => {
                println!("Job completed: {:?}", result);
                Ok(())
            },
            Err(e) => {
                eprintln!("Job failed: {}", e);
                Err(e) // Will trigger retry if max_attempts not reached
            }
        }
    })
});
```