prometheus
stableFormats and parses Prometheus exposition text and provides a MetricRegistry class for building counter, gauge, histogram, and summary output.
use plugin prometheus::{format_counter, format_gauge, format_histogram_bucket, …} Plugin snippets can be edited in the Playground, but native capabilities are executed locally with the Zolo CLI.
Functions (16)
- format_counter Format a counter metric line
- format_gauge Format a gauge metric line
- format_histogram_bucket Format a histogram bucket line
- format_help Format a `# HELP` comment line
- format_type Format a `# TYPE` comment line
- format_metric Format a generic metric line with optional timestamp
- parse_metric_line Parse a metric exposition line
- format_summary Format a summary metric with quantiles
- MetricRegistry Creates a registry that tracks counter, gauge, and histogram definitions and their samples.
- register_counter Register a counter definition
- register_gauge Register a gauge definition
- register_histogram Register a histogram definition
- inc Increment a counter
- set_gauge Set a gauge value
- observe Record a histogram observation
- expose Render full Prometheus exposition text
From import to result
- 01Import only what you use
- 02Copy the smallest example
- 03Run it with the Zolo CLI
Format a counter metric line
Formats a single counter metric line. labels is an optional map of label key-value pairs.
use plugin prometheus::{format_counter}
let line = format_counter("http_requests_total", 142, #{"method": "GET", "status": "200"})
print(line)
// http_requests_total{method="GET",status="200"} 142Format a gauge metric line
Formats a gauge metric line. Identical format to a counter line — use context and # TYPE to distinguish.
use plugin prometheus::{format_gauge, format_help, format_type}
print(format_help("memory_bytes", "Current process memory usage in bytes"))
print(format_type("memory_bytes", "gauge"))
print(format_gauge("memory_bytes", 52428800))Format a histogram bucket line
Formats one histogram bucket line. le is the upper-bound string (use "+Inf" for the catch-all bucket).
use plugin prometheus::{format_histogram_bucket}
print(format_histogram_bucket("request_duration_seconds", "0.1", 45))
print(format_histogram_bucket("request_duration_seconds", "0.5", 89))
print(format_histogram_bucket("request_duration_seconds", "+Inf", 100))Format a `# HELP` comment line
Returns a # HELP line for a metric.
use plugin prometheus::{format_help}
print(format_help("rpc_errors_total", "Total number of RPC errors"))
// # HELP rpc_errors_total Total number of RPC errorsFormat a `# TYPE` comment line
Returns a # TYPE line. Valid type strings: counter, gauge, histogram, summary, untyped.
use plugin prometheus::{format_type}
print(format_type("rpc_errors_total", "counter"))
// # TYPE rpc_errors_total counterFormat a generic metric line with optional timestamp
Formats a metric line with optional labels and an optional Unix millisecond timestamp.
use plugin prometheus::{format_metric}
let line = format_metric("up", #{"job": "api"}, 1, 1609459200000)
print(line)
// up{job="api"} 1 1609459200000Parse a metric exposition line
Parses a single Prometheus text exposition line and returns #{name, labels, value}. Returns nil for blank or comment lines.
use plugin prometheus::{parse_metric_line}
let m = parse_metric_line('http_requests_total{method="GET"} 142')
print(m["name"]) // http_requests_total
print(m["value"]) // 142Format a summary metric with quantiles
Formats a complete summary block: quantile lines, _sum, and _count. quantiles is a table of #{quantile, value} entries.
use plugin prometheus::{format_summary}
let qs = [
#{"quantile": "0.5", "value": 0.23},
#{"quantile": "0.95", "value": 0.91},
#{"quantile": "0.99", "value": 1.42}
]
print(format_summary("request_latency_seconds", qs, 47.3, 200))Creates a registry that tracks counter, gauge, and histogram definitions and their samples.
Creates a registry that tracks counter, gauge, and histogram definitions and their samples. Use expose() to render the full text output.
use plugin prometheus::{MetricRegistry}
let reg = MetricRegistry()
reg.register_counter("api_calls_total", "Number of API calls")
reg.inc("api_calls_total", #{"endpoint": "/search"}, 1)
print(reg.expose())Register a counter definition
Registers a counter definition in the registry. Must be called before inc.
reg.register_counter("cache_hits_total", "Cache lookup hits")Register a gauge definition
Registers a gauge definition. Use set_gauge to update its value.
reg.register_gauge("active_connections", "Open TCP connections")
reg.set_gauge("active_connections", #{}, 42)Register a histogram definition
Registers a histogram. buckets is an optional array of upper bound floats. Defaults to standard HTTP latency buckets (0.005..10).
reg.register_histogram("response_time_seconds", "Request latency",
[0.01, 0.05, 0.1, 0.25, 0.5, 1.0, 5.0])Increment a counter
Increments a counter by amount (default 1). Labels is an optional map.
reg.inc("api_calls_total", #{"method": "POST"}, 1)
reg.inc("api_calls_total", #{"method": "GET"})Set a gauge value
Sets a gauge to an exact value. Replaces any existing value for the same name and label set.
reg.set_gauge("active_connections", #{}, 17)Record a histogram observation
Records an observation for a histogram. The value is sorted into the appropriate buckets on expose.
reg.observe("response_time_seconds", 0.043, #{"route": "/api/users"})Render full Prometheus exposition text
Renders the full Prometheus text exposition for all registered metrics.
use plugin prometheus::{MetricRegistry}
let reg = MetricRegistry()
reg.register_counter("requests_total", "Requests served")
reg.inc("requests_total", #{})
let output = reg.expose()
print(output)