To add a little more information about ambiguous/inconsistent matchers, the current version of Alertmanager allows the following:
{foo=}} equivalent to {foo="}"}, but I think this should be an error {{foo=} is an error because of two {{, unlike the above {foo=~} could be either {foo=~""} or {foo="~"}, it's interpreted in current versions as {foo=~""} {foo=,} is equivalent to {foo=""}, but I think should be an error as a comma with no value has a high likelihood of being human error {foo=,,} is an error, unlike {foo=,} or {foo=}} {foo= } is equivalent to {foo=""} {foo= b} and {foo=b } are equivalent to {foo="b"}, but {foo=b b} is equivalent to {foo="b b"} The changes proposed here would also restrict all of the examples above as 1. trailing commas are rejected and 2. unquoted text must match the regular expression [a-zA-Z_:][a-zA-Z0-9_:]*. On Tuesday, May 9, 2023 at 10:05:49 AM UTC+1 George Robinson wrote: > Hi, all! 👋 > > I've opened a pull request for the Alertmanager here > <https://github.com/prometheus/alertmanager/pull/3353> that adds support > for parsing UTF-8 matchers while also adding restrictions on > ambiguous matchers that are permitted in the current version of > Alertmanager. > > https://github.com/prometheus/alertmanager/pull/3353 > > *Background* > > As explained in #3319 > <https://github.com/prometheus/alertmanager/issues/3319>, Alertmanager > constrains label names to the characters ^[a-zA-Z_][a-zA-Z0-9_]*$ - the > same as Prometheus. > > However, because Alertmanager is such a well known and popular open source > project it makes sense to use it for other kinds of alert generators too, > and not just Prometheus. An example of this is Grafana, where Alertmanager > is used to manage alerts created from both Prometheus and non-Prometheus > like datasources, including Graphite, InfluxDB, SQL, Loki and more. The > issue with this though is that these other datasources do not share the > same constraints as Prometheus when it comes to label names, and so using > them with Alertmanager requires some kind of normalization to ensure label > matchers match the set of allowed characters before the alert can be sent > to the Alertmanager. > > *What this pull request does* > > @yuri-tceretian <https://github.com/yuri-tceretian> has proposed adding > support for UTF-8 characters in #3321 > <https://github.com/prometheus/alertmanager/pull/3321> that updates the > existing regular expression to support double quoted UTF-8 sequences as > label names, while keeping unquoted label names the same. > > In this pull request I wanted to propose a different option to where we > would add a "simple" LL(1) parser to Alertmanager to parse matchers instead. > > *Motivation* > > The original motivation for writing this parser was to add support for > matching label names containing . and spaces to grafana/grafana > <https://github.com/grafana/grafana>. However, about the same time I > learned that Prometheus maintainers agreed to add support for UTF-8 > labels in Alertmanager > <https://docs.google.com/document/d/11LC3wJcVk00l8w5P3oLQ-m3Y37iom6INAMEu2ZAGIIE/edit#bookmark=id.wm24eue9w2eg>, > > and so I decided to further the work to see if it could be upstreamed to > Alertmanager instead. > > The original source code can be found at grobinson-grafana/matchers > <https://github.com/grobinson-grafana/matchers>. > > *Breaking changes* > > *Expressions must start and end with open and closing braces* > > All expressions must start and end with { and }, although this can be > relaxed if required. For example foo=bar is not valid, it must be > {foo=bar}. > > *Trailing commas are not permitted* > > Trailing commas are not permitted. For example {foo=bar,} is not valid, > it must be {foo=bar}. > > *All non [a-zA-Z_:][a-zA-Z0-9_:]* values must be double quoted* > > The set of unquoted characters is now the same on both sides of the > expression. In other words, both label names and label values without > double quotes must match the regular expression [a-zA-Z_:][a-zA-Z0-9_:]*. > For example {foo=!bar} is not valid, it must be {foo="!bar"}. In current > versions of Alertmanager, unquoted label values can contain all UTF-8 code > points with the exception of comma, such as {foo=!bar}. > > There are two reasons for this: > > 1. > > It's no longer possible to write ambiguous matchers which I feel is > something Alertmanager should fix. For example is {foo=~} equivalent > to {foo="~"} or {foo=~""}? > 2. > > If we restrict the =, !, ~ characters to double quotes we can keep the > grammar LL(1). Without this restriction lookahead/backtrack is required to > parse matchers such as {foo==~!=!~bar} which are valid in current > versions of Alertmanager. > > *Errors* > > One of the goals with this LL(1) parser is to provide better error > messages than what is possible using just a regular expression. This work > is still in progress as error messages are not as useful as I would like > for EOF, but here is an example of what it looks like for non-EOF cases: > {foo=bar 🙂} 9:13: 🙂: invalid input: expected comma or closing '}' {foo > with spaces=bar with spaces} 5:9: unexpected with: expected an operator > such as '=', '!=', '=~' or '!~' > *Benchmarks* > > I've also provided a number of benchmarks of both the LL(1) parser and > regex parser that supports UTF-8. These can be found at > grobinson-grafana/matchers-benchmarks > <https://github.com/grobinson-grafana/matchers-benchmarks>. However, to > run them go.mod must be updated to use the branch > https://github.com/grafana/prometheus-alertmanager/tree/yuri-tceretian/utf-8-label-names > here. > BenchmarkMatchersSimple, BenchmarkPrometheusSimple {foo="bar"} > BenchmarkMatchersComplex, BenchmarkPrometheusComplex {foo="bar",bar="foo > 🙂","baz"!=qux,qux!="baz 🙂"} BenchmarkMatchersRegexSimple, > BenchmarkPrometheusRegexSimple {foo=~"[a-zA-Z_:][a-zA-Z0-9_:]*"} > BenchmarkMatchersRegexComplex, BenchmarkPrometheusRegexComplex > {foo=~"[a-zA-Z_:][a-zA-Z0-9_:]*",bar=~"[a-zA-Z_:]","baz"!~"[a-zA-Z_:][a-zA-Z0-9_:]*",qux!~"[a-zA-Z_:]"} > > > go test -bench=. -benchmem goos: darwin goarch: arm64 pkg: > github.com/grobinson-grafana/matchers-benchmarks > BenchmarkMatchersRegexSimple-8 > <http://github.com/grobinson-grafana/matchers-benchmarksBenchmarkMatchersRegexSimple-8> > > 488295 2425 ns/op 3248 B/op 49 allocs/op BenchmarkMatchersRegexComplex-8 > 138081 9074 ns/op 11448 B/op 169 allocs/op BenchmarkPrometheusRegexSimple-8 > 329244 3496 ns/op 3531 B/op 58 allocs/op BenchmarkPrometheusRegexComplex-8 > 95188 12554 ns/op 12619 B/op 204 allocs/op BenchmarkMatchersSimple-8 > 2888340 414.9 ns/op 56 B/op 2 allocs/op BenchmarkMatchersComplex-8 741590 > 1628 ns/op 248 B/op 7 allocs/op BenchmarkPrometheusSimple-8 1919209 613.9 > ns/op 233 B/op 8 allocs/op BenchmarkPrometheusComplex-8 425430 2803 ns/op > 1015 B/op 31 allocs/op PASS ok > github.com/grobinson-grafana/matchers-benchmarks 11.766s > -- You received this message because you are subscribed to the Google Groups "Prometheus Developers" group. 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