promerge

Promerge provides minimalistic and easy to use API to parse and manipulate Prometheus metrics. A simple usecase could be collecting metrics from several servers and combining and exposing them as single metrics endpoint, adding namespace and custom (Key,Value) pairs to each Prometheus exposition line.

Example:

```rust use promerge::promerge::Context;

fn main() { // example from: https://prometheus.io/docs/instrumenting/expositionformats/ let metrics = r#"# HELP httprequests_total The total number of HTTP requests.

TYPE httprequeststotal counter

httprequeststotal{method="post",code="200"} 1027 1395066363000 httprequeststotal{method="post",code="400"} 3 1395066363000

Escaping in label values:

msdosfileaccesstimeseconds{path="C:\DIR\FILE.TXT",error="Cannot find file:\n\"FILE.TXT\""} 1.458255915e9

Minimalistic line:

metricwithouttimestampandlabels 12.47

A weird metric from before the epoch:

something_weird{problem="division by zero"} +Inf -3982045

A histogram, which has a pretty complex representation in the text format:

HELP httprequestduration_seconds A histogram of the request duration.

TYPE httprequestduration_seconds histogram

httprequestdurationsecondsbucket{le="0.05"} 24054 httprequestdurationsecondsbucket{le="0.1"} 33444 httprequestdurationsecondsbucket{le="0.2"} 100392 httprequestdurationsecondsbucket{le="0.5"} 129389 httprequestdurationsecondsbucket{le="1"} 133988 httprequestdurationsecondsbucket{le="+Inf"} 144320 httprequestdurationsecondssum 53423 httprequestdurationsecondscount 144320

Finally a summary, which has a complex representation, too:

HELP rpcdurationseconds A summary of the RPC duration in seconds.

TYPE rpcdurationseconds summary

rpcdurationseconds{quantile="0.01"} 3102 rpcdurationseconds{quantile="0.05"} 3272 rpcdurationseconds{quantile="0.5"} 4773 rpcdurationseconds{quantile="0.9"} 9001 rpcdurationseconds{quantile="0.99"} 76656 rpcdurationsecondssum 1.7560473e+07 rpcdurationsecondscount 2693"#;

// add new (k,v) pairs into Prometheus metric exposition
let pairs = [("custom_key".into(), "custom_value".into())];
// add a prefix to metrics
let mut metrics = Context::with_prefix_and_pairs(&metrics, "some_prefix_", &pairs);

// parse and evaluate
{
let ctx = &mut metrics;
match ctx.run() {
    Ok(output) => {
    println!("first run: {}", output);
    },
    Err(err) => {
    eprintln!("{}", err);
    }
};
}

// append new metrics with difference prefix
{
    let block = r#"# New minimalistic line:

newmetricwithouttimestampandlabels 24.81"#;
let ctx = &mut metrics; match ctx.combinewithprefix(block, "secondprefix_") { Ok(output) => { println!("second run: {}", output); }, Err(err) => { eprintln!("{}", err); } }; }

/* Final Output ->

# HELP some_prefix_http_requests_total The total number of HTTP requests.
# TYPE some_prefix_http_requests_total counter
some_prefix_http_requests_total{method="post",code="200",custom_key="custom_value"} 1027 1395066363000
some_prefix_http_requests_total{method="post",code="400",custom_key="custom_value"} 3 1395066363000

# Escaping in label values:
some_prefix_msdos_file_access_time_seconds{path="C:\\DIR\\FILE.TXT",error="Cannot find file:\n\"FILE.TXT\"",custom_key="custom_value"} 1.458255915e9

# Minimalistic line:
some_prefix_metric_without_timestamp_and_labels{custom_key="custom_value"} 12.47

# A weird metric from before the epoch:
some_prefix_something_weird{problem="division by zero",custom_key="custom_value"} +Inf -3982045

# A histogram, which has a pretty complex representation in the text format:
# HELP some_prefix_http_request_duration_seconds A histogram of the request duration.
# TYPE some_prefix_http_request_duration_seconds histogram
some_prefix_http_request_duration_seconds_bucket{le="0.05",custom_key="custom_value"} 24054
some_prefix_http_request_duration_seconds_bucket{le="0.1",custom_key="custom_value"} 33444
some_prefix_http_request_duration_seconds_bucket{le="0.2",custom_key="custom_value"} 100392
some_prefix_http_request_duration_seconds_bucket{le="0.5",custom_key="custom_value"} 129389
some_prefix_http_request_duration_seconds_bucket{le="1",custom_key="custom_value"} 133988
some_prefix_http_request_duration_seconds_bucket{le="+Inf",custom_key="custom_value"} 144320
some_prefix_http_request_duration_seconds_sum 53423
some_prefix_http_request_duration_seconds_count 144320

# Finally a summary, which has a complex representation, too:
# HELP some_prefix_rpc_duration_seconds A summary of the RPC duration in seconds.
# TYPE some_prefix_rpc_duration_seconds summary
some_prefix_rpc_duration_seconds{quantile="0.01",custom_key="custom_value"} 3102
some_prefix_rpc_duration_seconds{quantile="0.05",custom_key="custom_value"} 3272
some_prefix_rpc_duration_seconds{quantile="0.5",custom_key="custom_value"} 4773
some_prefix_rpc_duration_seconds{quantile="0.9",custom_key="custom_value"} 9001
some_prefix_rpc_duration_seconds{quantile="0.99",custom_key="custom_value"} 76656
some_prefix_rpc_duration_seconds_sum 1.7560473e+07
some_prefix_rpc_duration_seconds_count 2693

# New minimalistic line:
second_prefix_new_metric_without_timestamp_and_labels 24.81

 */

} ```