Steps to reproduce

Setup Prometheus and Swift Metrics:

        let client = PrometheusClient()
        
        // Setup Factory
        let factory = PrometheusMetricsFactory(client: client, configuration: .init(defaultRecorderBuckets: [
            0.05, 0.1, 0.5, 1, 5, 10, 25, 50, 75, 100
        ]))
        
        MetricsSystem.bootstrap(factory)
        
        // Collect Metrics
        app.get("metrics") { _ async throws -> String in
            return await client.collect()
        }

Create a Recorder and record a value:

Recorder(label: "x").record(100)

View output and see that bucket sizes are the default bucket sizes rather than the ones I've provided in the setup.

Expected behavior

Bucket sizes should be those which I provided to the factory

Actual behavior

Bucket sizes are instead the defaulted bucket sizes hard coded into the library

Environment

• OS version: 12.4
• Swift version: 5.6
• Serverside Swift Framework: Vapor
• Framework version: 4

Solution

The root cause appears to be that the makeHistogram function calls createHistogram which has a variable called buckets: Buckets = .defaultBuckets. This defaults to defaultBuckets which is incorrect, it should instead be set to configuration.defaultRecorderBuckets (which itself defaults to defaultBuckets but can be overridden by the user, me, as above).