# 📈 Gazan Prometheus Metrics Reference

This document outlines Prometheus metrics for the [Gazan](https://github.com/sadoyan/gazan) reverse proxy.
These metrics can be used for monitoring, alerting and performance analysis.

Exposed to `http://config_address/metrics`

By default `http://127.0.0.1:3000/metrics`

# 📊 Example Grafana dashboard during stress test :

![Gazan](https://netangels.net/utils/dash.png)

---

## 🛠️ Prometheus Metrics

### 1. `gazan_requests_total`

- **Type**: `Counter`
- **Purpose**: Total amount requests served by Gazan.

**PromQL example:**

```promql
rate(gazan_requests_total[5m])
```

---

### 2. `gazan_errors_total`

- **Type**: `Counter`
- **Purpose**: Count of requests that resulted in an error.

**PromQL example:**

```promql
rate(gazan_errors_total[5m])
```

---

### 3. `gazan_responses_total{status="200"}`

- **Type**: `CounterVec`
- **Purpose**: Count of responses by HTTP status code.

**PromQL example:**

```promql
rate(gazan_responses_total{status=~"5.."}[5m]) > 0
```

> Useful for alerting on 5xx errors.

---

### 4. `gazan_response_latency_seconds`

- **Type**: `Histogram`
- **Purpose**: Tracks the latency of responses in seconds.

**Example bucket output:**

```prometheus
gazan_response_latency_seconds_bucket{le="0.01"}  15
gazan_response_latency_seconds_bucket{le="0.1"}   120
gazan_response_latency_seconds_bucket{le="0.25"}  245
gazan_response_latency_seconds_bucket{le="0.5"}   500
...
gazan_response_latency_seconds_count  1023
gazan_response_latency_seconds_sum    42.6
```

| Metric                  | Meaning                                                       |
|-------------------------|---------------------------------------------------------------|
| `bucket{le="0.1"} 120`  | 120 requests were ≤ 100ms                                     |
| `bucket{le="0.25"} 245` | 245 requests were ≤ 250ms                                     |
| `count`                 | Total number of observations (i.e., total responses measured) |
| `sum`                   | Total time of all responses, in seconds                       |

### 🔍 How to interpret:

- `le` means “less than or equal to”.
- `count` is total amount of observations.
- `sum` is the total time (in seconds) of all responses.

**PromQL examples:**

🔹 **95th percentile latency**

```promql
histogram_quantile(0.95, rate(gazan_response_latency_seconds_bucket[5m]))

```

🔹 **Average latency**

```promql
rate(gazan_response_latency_seconds_sum[5m]) / rate(gazan_response_latency_seconds_count[5m])
```

---

## ✅ Notes

- Metrics are registered after the first served request.

---
✅ Summary of key metrics

| Metric Name                           | Type       | What it Tells You         |
|---------------------------------------|------------|---------------------------|
| `gazan_requests_total`                | Counter    | Total requests served     |
| `gazan_errors_total`                  | Counter    | Number of failed requests |
| `gazan_responses_total{status="200"}` | CounterVec | Response status breakdown |
| `gazan_response_latency_seconds`      | Histogram  | How fast responses are    |

📘 *Last updated: May 2025*