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Use framework-specific route info and handle consecutive path segments containing IDs in Collector #245

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merged 3 commits into from Feb 5, 2022

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@Sinjo Sinjo commented Feb 1, 2022

Fixes #233

While `PATH_INFO` is framework agnostic, and works for any Rack app,
some Ruby web frameworks pass a more useful piece of information into
the request env - the route that the request matched.

This means that rather than using our generic `:id` and `:uuid`
replacements in the `path` label for any path segments that look like
dynamic IDs, we can put the actual route that matched in there, with
correctly named parameters. For example, if a Sinatra app defined a
route like:

get "/foo/:bar" do
  ...
end

instead of containing `/foo/:id`, the `path` label would contain
`/foo/:bar`.

Sadly, Rails is a notable exception, and (as far as I can tell at the
time of writing) doesn't provide this info in the request env.

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>
Previously, we would fail to strip IDs from paths if they appeared in
consecutive path segments. This is because our regex that looked for IDs
and UUIDs would consume the `/` character that followed them, causing
the next one not to match.

This commit uses a lookahead to match against the `/` without consuming
it.

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>
@Sinjo Sinjo requested a review from dmagliola February 1, 2022 02:28
@Sinjo Sinjo added this to the v3.0.0 milestone Feb 1, 2022
Add note about improvements to path label generation in
`Prometheus::Middleware::Collector`.

Signed-off-by: Chris Sinjakli <chris@sinjakli.co.uk>
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Sinjo commented Feb 1, 2022

@dmagliola I've added the changes to UPGRADING.md to this PR as well, to save going through another one.

I'm going to add the CHANGELOG.md entry to #244 too.

@Sinjo Sinjo changed the title Use framework-specific route info and handle consecutive path segments containing IDs in collector Use framework-specific route info and handle consecutive path segments containing IDs in Collector Feb 1, 2022
@Sinjo Sinjo mentioned this pull request Feb 1, 2022
@Sinjo Sinjo merged commit 57feffb into master Feb 5, 2022
@Sinjo Sinjo deleted the sinjo-better-path-labels branch February 5, 2022 17:02
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better path handling
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