# Prometheus Metrics Integration

Ollama4j now includes comprehensive Prometheus metrics collection to help you monitor and observe your Ollama API usage. This feature allows you to track request counts, response times, model usage, and other operational metrics.

## Features

The metrics integration provides the following metrics:

- **Request Metrics**: Total requests, duration histograms, and response time summaries by endpoint
- **Model Usage**: Model-specific usage statistics and response times
- **Token Generation**: Token count tracking per model
- **Error Tracking**: Error counts by type and endpoint
- **Active Connections**: Current number of active API connections

## Quick Start

### 1. Enable Metrics Collection

```java
import io.github.ollama4j.Ollama;

// Create API instance with metrics enabled
Ollama ollama = new Ollama();
ollamaAPI.

setMetricsEnabled(true);
```

### 2. Start Metrics Server

```java
import io.prometheus.client.exporter.HTTPServer;

// Start Prometheus metrics HTTP server on port 8080
HTTPServer metricsServer = new HTTPServer(8080);
System.out.println("Metrics available at: http://localhost:8080/metrics");
```

### 3. Use the API (Metrics are automatically collected)

```java
// All API calls are automatically instrumented
boolean isReachable = ollama.ping();

Map<String, Object> format = new HashMap<>();
format.put("type", "json");
OllamaResult result = ollama.generateWithFormat(
    "llama2",
    "Generate a JSON object",
    format
);
```

## Available Metrics

### Request Metrics

- `ollama_api_requests_total` - Total number of API requests by endpoint, method, and status
- `ollama_api_request_duration_seconds` - Request duration histogram by endpoint and method
- `ollama_api_response_time_seconds` - Response time summary with percentiles

### Model Metrics

- `ollama_model_usage_total` - Model usage count by model name and operation
- `ollama_model_response_time_seconds` - Model response time histogram
- `ollama_tokens_generated_total` - Total tokens generated by model

### System Metrics

- `ollama_api_active_connections` - Current number of active connections
- `ollama_api_errors_total` - Error count by endpoint and error type

## Example Metrics Output

```
# HELP ollama_api_requests_total Total number of Ollama API requests
# TYPE ollama_api_requests_total counter
ollama_api_requests_total{endpoint="/api/generate",method="POST",status="success"} 5.0
ollama_api_requests_total{endpoint="/api/embed",method="POST",status="success"} 3.0

# HELP ollama_api_request_duration_seconds Duration of Ollama API requests in seconds
# TYPE ollama_api_request_duration_seconds histogram
ollama_api_request_duration_seconds_bucket{endpoint="/api/generate",method="POST",le="0.1"} 0.0
ollama_api_request_duration_seconds_bucket{endpoint="/api/generate",method="POST",le="0.5"} 2.0
ollama_api_request_duration_seconds_bucket{endpoint="/api/generate",method="POST",le="1.0"} 4.0
ollama_api_request_duration_seconds_bucket{endpoint="/api/generate",method="POST",le="+Inf"} 5.0
ollama_api_request_duration_seconds_sum{endpoint="/api/generate",method="POST"} 2.5
ollama_api_request_duration_seconds_count{endpoint="/api/generate",method="POST"} 5.0

# HELP ollama_model_usage_total Total number of model usage requests
# TYPE ollama_model_usage_total counter
ollama_model_usage_total{model_name="llama2",operation="generate_with_format"} 5.0
ollama_model_usage_total{model_name="llama2",operation="embed"} 3.0

# HELP ollama_tokens_generated_total Total number of tokens generated
# TYPE ollama_tokens_generated_total counter
ollama_tokens_generated_total{model_name="llama2"} 150.0
```

## Configuration

### Enable/Disable Metrics

```java
OllamaAPI ollama = new OllamaAPI();

// Enable metrics collection
ollama.setMetricsEnabled(true);

// Disable metrics collection (default)
ollama.setMetricsEnabled(false);
```

### Custom Metrics Server

```java
import io.prometheus.client.exporter.HTTPServer;

// Start on custom port
HTTPServer metricsServer = new HTTPServer(9090);

// Start on custom host and port
HTTPServer metricsServer = new HTTPServer("0.0.0.0", 9090);
```

## Integration with Prometheus

### Prometheus Configuration

Add this to your `prometheus.yml`:

```yaml
scrape_configs:
  - job_name: 'ollama4j'
    static_configs:
      - targets: ['localhost:8080']
    scrape_interval: 15s
```

### Grafana Dashboards

You can create Grafana dashboards using the metrics. Some useful queries:

- **Request Rate**: `rate(ollama_api_requests_total[5m])`
- **Average Response Time**: `rate(ollama_api_request_duration_seconds_sum[5m]) / rate(ollama_api_request_duration_seconds_count[5m])`
- **Error Rate**: `rate(ollama_api_requests_total{status="error"}[5m]) / rate(ollama_api_requests_total[5m])`
- **Model Usage**: `rate(ollama_model_usage_total[5m])`
- **Token Generation Rate**: `rate(ollama_tokens_generated_total[5m])`

## Performance Considerations

- Metrics collection adds minimal overhead (~1-2% in most cases)
- Metrics are collected asynchronously and don't block API calls
- You can disable metrics in production if needed: `ollama.setMetricsEnabled(false)`
- The metrics server uses minimal resources

## Troubleshooting

### Metrics Not Appearing

1. Ensure metrics are enabled: `ollama.setMetricsEnabled(true)`
2. Check that the metrics server is running: `http://localhost:8080/metrics`
3. Verify API calls are being made (metrics only appear after API usage)

### High Memory Usage

- Metrics accumulate over time. Consider restarting your application periodically
- Use Prometheus to scrape metrics regularly to avoid accumulation

### Custom Metrics

You can extend the metrics by accessing the Prometheus registry directly:

```java
import io.prometheus.client.CollectorRegistry;
import io.prometheus.client.Counter;

// Create custom metrics
Counter customCounter = Counter.build()
    .name("my_custom_metric_total")
    .help("My custom metric")
    .register();

// Use the metric
customCounter.inc();
```
