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Support matching JSON body with CEL expressions #1255

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@juho9000 juho9000 commented Jun 5, 2024

This PR implements parsing a JSON response from the body and checking the result using a CEL query. Looking for feedback on this.

Sample usage:

modules:
  http_2xx:
    prober: http
    http:
      fail_if_body_json_not_matches_cel: "body.foo.bar == 'baz'"

If response is {"foo": { "bar": "qux" } } the probe fails. fail_if_body_json_matches_cel is also implemented and should work as expected.

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juho9000 commented Jun 17, 2024

@roidelapluie @mem Ping :)

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A couple of minor comments.

CONFIGURATION.md Outdated Show resolved Hide resolved
CONFIGURATION.md Outdated Show resolved Hide resolved
@@ -297,6 +351,11 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
Help: "Indicates if probe failed due to regex",
})

probeFailedDueToCel = prometheus.NewGauge(prometheus.GaugeOpts{
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I'm thinking this should be added conditionally, if the configuration asks for validation using CEL expressions.

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I was following the same logic that is applied to regex checks, following your logic that should also be conditionally added, no?

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mem commented Jul 23, 2024

Thank you for this, this seems useful!

Question, I have no experience with CEL... is it possible to use it to match HTML, too? I see in the code that Eval takes a map[string]any, but I couldn't spot how that any is handled.

The reason I'm asking is because I'm trying to figure out if it's possible to extend this to more inputs, or if it needs to be restricted to JSON.

prober/http.go Outdated
}

if httpConfig.FailIfBodyJSONMatchesCel != nil {
result, details, err := httpConfig.FailIfBodyJSONMatchesCel.Eval(evalPayload)
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Question: shouldn't this be EvalContext instead? I'm not clear about the guarantees that the evaluation will terminate, and the fact that EvalContext exists suggests that there's a benefit from imposing a deadline.

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You're probably right, I've changed it to use ContextEval

@juho9000 juho9000 force-pushed the feature/cel-json-body branch 2 times, most recently from 0c9b9a0 to f9a0036 Compare August 1, 2024 12:56
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juho9000 commented Aug 1, 2024

Thank you for this, this seems useful!

Question, I have no experience with CEL... is it possible to use it to match HTML, too? I see in the code that Eval takes a map[string]any, but I couldn't spot how that any is handled.

The reason I'm asking is because I'm trying to figure out if it's possible to extend this to more inputs, or if it needs to be restricted to JSON.

I atleast do not know how CEL could be used to match HTML in any sane way. You might want to check this out https://github.com/google/cel-spec/blob/master/doc/langdef.md#json-data-conversion

Thanks for your comments and suggestions so far. Really hoping we can get this merged. I think that having the ability to validate JSON responses would be an awesome addition to blackbox exporter. :)

@juho9000 juho9000 requested a review from mem August 1, 2024 13:06
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zetaab commented Aug 7, 2024

@mem kindly ping :) we are interested about this feature and would like to see it as well

@juho9000 juho9000 force-pushed the feature/cel-json-body branch 3 times, most recently from fbb6791 to 9131539 Compare August 29, 2024 08:36
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zetaab commented Sep 3, 2024

@mem @roidelapluie any comments to this PR?

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juho9000 commented Oct 1, 2024

@electron0zero @mem I haven't heard from any of the maintainers in a while. I fixed or clarified everything that was mentioned in the review comments. The initial message I got was that this seems useful, but it seems that it's forgotten now. Any update? I'd love to get this merged in order to avoid maintaining my own fork. :)

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3 participants