PromQL Lexer and Parser

The goal of this project is to build a PromQL lexer and parser capable of parsing PromQL that conforms with Prometheus Query.

Example

To parse a simple instant vector selector expression:

use promql_parser::parser;

let promql = r#"
    http_requests_total{
        environment=~"staging|testing|development",
        method!="GET"
    } offset 5m
"#;

match parser::parse(promql) {
    Ok(expr) => {
        println!("Prettify:\n{}\n", expr.prettify());
        println!("AST:\n{expr:?}");
    }
    Err(info) => println!("Err: {info:?}"),
}

or you can directly run examples under this repo:

cargo run --example parser

This outputs:

Prettify:
http_requests_total{environment=~"staging|testing|development",method!="GET"} offset 5m

AST:
VectorSelector(VectorSelector { name: Some("http_requests_total"), matchers: Matchers { matchers: [Matcher { op: Re(staging|testing|development), name: "environment", value: "staging|testing|development" }, Matcher { op: NotEqual, name: "method", value: "GET" }] }, offset: Some(Pos(300s)), at: None })

PromQL compliance

This crate declares compatible with prometheus v3.8, which is released at 2025-11-28. Any revision on PromQL after this commit is not guaranteed.

Community Extensions

There are a number of community projects that extend promql-parser or provide integrations with other systems.

Language Bindings

• py-promql-parser Python.
• lua-promql-parser Lua.

Known Uses

Here are some of the projects known to use promql-parser:

• GreptimeDB Open Source & Cloud Native Distributed Time Series Database
• OpenObserve High performance, petabyte scale Elasticsearch/Splunk/Datadog alternative for (logs, metrics, traces, RUM, Error tracking, Session replay)

If your project is using promql-parser, feel free to make a PR to add it to this list.

Contributing

Contributions are highly encouraged!

Pull requests that add support for or fix a bug in a feature in the PromQL will likely be accepted after review.

Licensing

All code in this repository is licensed under the Apache License 2.0.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.