aralez/METRICS.md

📈 Gazan Prometheus Metrics Reference

This document outlines Prometheus metrics for the 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

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🛠️ Prometheus Metrics

1. gazan_requests_total

• Type: Counter
• Purpose: Total amount requests served by Gazan.

PromQL example:

rate(gazan_requests_total[5m])

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2. gazan_errors_total

• Type: Counter
• Purpose: Count of requests that resulted in an error.

PromQL example:

rate(gazan_errors_total[5m])

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3. gazan_responses_total{status="200"}

• Type: CounterVec
• Purpose: Count of responses by HTTP status code.

PromQL example:

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

Useful for alerting on 5xx errors.

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4. gazan_response_latency_seconds

• Type: Histogram
• Purpose: Tracks the latency of responses in seconds.

Example bucket output:

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

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

🔹 Average latency

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

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✅ Notes

• Metrics are registered after the first served request.

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✅ 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