Add support for Prometheus metric categories #539
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I'll try to take a look at this in the next day or two... |
Thanks @mostynb! I'll let you have look before I address the current comments, since I assume reviewing is more convenient with fewer commits and without force-pushed commits. |
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I have cherry-picked the FindMissingCasBlobs metrics fix to the master branch- good catch. Re disabling Contains metrics, let's think this through a bit first, if it's not a big change I think it would be better to fix them than to disable them and then fix them. I have an idea for how to do this, that I need to run through in my head a bit. I think this should be dropped from this PR. Re the metrics categories change, I'll try to take a look tomorrow. |
See updated README.md file for description.
Thanks @mostynb!
OK, I removed that commit from this PR.
Thanks @mostynb! I now force-pushed the branch to address the comments so far. |
| Received headers that match a declared category name, but with a value outside | ||
| the declared allowed value set, is reported with the value "other" to | ||
| Prometheus. This is convenient for categories such as "branch", where it from a | ||
| cache hit ratio perspective often make sense to distinguish between "main" | ||
| branch and "other" branches. |
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I think we should mention here that only lowercase category names are allowed, otherwise it will likely be a common error that people will hit when first trying this feature. Also: are non lowercase values allowed?
| if grpcHeaders != nil { | ||
| grpcHeaderValues := grpcHeaders[categoryNameLowerCase] | ||
| if len(grpcHeaderValues) > 0 { | ||
| // Pick the first header with matching name if multiple headers with same name |
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I wonder if it would be less surprising to pick the last matching header instead of the first?
| // Pick the first header with matching name if multiple headers with same name | ||
| headerValue = grpcHeaderValues[0] | ||
| } | ||
| } else if httpHeaders != nil { |
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Just checking, when using grpc is it assumed that we should ignore http headers too?
| } | ||
| } else if httpHeaders != nil { | ||
| headerValue = httpHeaders.Get(categoryNameLowerCase) | ||
| } |
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nitpick: add an empty line after this
| @@ -351,6 +352,12 @@ func validateConfig(c *Config) error { | |||
| return errors.New("'access_log_level' must be set to either \"none\" or \"all\"") | |||
| } | |||
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| for categoryName := range c.MetricCategories { | |||
| if categoryName != strings.ToLower(categoryName) { | |||
| return fmt.Errorf("Names in 'metric_categories' must be in lower case: %s", categoryName) | |||
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nitpick: reword to "metric_categories names must be lowercase: %q", categoryName
| // Retrieves HTTP headers from context. Minimizes type safety issues. | ||
| func getHttpHeaders(ctx context.Context) *http.Header { | ||
| headers, ok := ctx.Value(httpHeadersContextKey{}).(*http.Header) | ||
| if !ok { | ||
| return nil | ||
| } | ||
| return headers | ||
| } | ||
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| func getGrpcHeaders(ctx context.Context) metadata.MD { | ||
| grpcHeaders, _ := metadata.FromIncomingContext(ctx) | ||
| return grpcHeaders | ||
| } |
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I wonder if it would be a little cleaner to find http/grpc headers in the server package (separately in http and grpc code), and then add them as a single custom value in the context? Then we could simplify addCategoryLabels a little.
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Sorry, I have not had time to address these comments. I’m going on vacation now and I’m back again in middle of August. Wish you a good summer! |
This pull request replaces my previous #350 and #358 PRs (@mostynb: feel free to close them if you want).
What do you think @mostynb? If you would like a subset of this PR, then I can restructure it. If you decide to not merge this PR that is also fine by me, since the context parameters and metrics decorator interface from the previous commits, allows me to maintain this as separate patch without too much effort.