prometheus-net

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using Microsoft.AspNetCore.Builder;
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using Microsoft.AspNetCore.Http;
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using Microsoft.AspNetCore.Routing;
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using System.ComponentModel;
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namespace Prometheus;
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public static class MetricServerMiddlewareExtensions
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{
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    private const string DefaultDisplayName = "Prometheus metrics";
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    /// <summary>
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    /// Starts a Prometheus metrics exporter using endpoint routing.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    public static IEndpointConventionBuilder MapMetrics(
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        this IEndpointRouteBuilder endpoints,
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        Action<MetricServerMiddleware.Settings> configure,
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        string pattern = "/metrics"
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    )
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    {
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        var pipeline = endpoints
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            .CreateApplicationBuilder()
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            .InternalUseMiddleware(configure)
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            .Build();
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        return endpoints
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            .Map(pattern, pipeline)
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            .WithDisplayName(DefaultDisplayName);
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    }
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    /// <summary>
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    /// Starts a Prometheus metrics exporter, filtering to only handle requests received on a specific port.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    public static IApplicationBuilder UseMetricServer(
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        this IApplicationBuilder builder,
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        int port,
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        Action<MetricServerMiddleware.Settings> configure,
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        string? url = "/metrics")
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    {
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        // If no URL, use root URL.
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        url ??= "/";
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        return builder
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            .Map(url, b => b.MapWhen(PortMatches(), b1 => b1.InternalUseMiddleware(configure)));
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        Func<HttpContext, bool> PortMatches()
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        {
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            return c => c.Connection.LocalPort == port;
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        }
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    }
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    /// <summary>
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    /// Starts a Prometheus metrics exporter.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    public static IApplicationBuilder UseMetricServer(
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        this IApplicationBuilder builder,
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        Action<MetricServerMiddleware.Settings> configure,
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        string? url = "/metrics")
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    {
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        if (url != null)
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            return builder.Map(url, b => b.InternalUseMiddleware(configure));
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        else
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            return builder.InternalUseMiddleware(configure);
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    }
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    #region Legacy methods without the configure action
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    /// <summary>
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    /// Starts a Prometheus metrics exporter using endpoint routing.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    [EditorBrowsable(EditorBrowsableState.Never)] // It is not exactly obsolete but let's de-emphasize it.
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    public static IEndpointConventionBuilder MapMetrics(
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        this IEndpointRouteBuilder endpoints,
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        string pattern = "/metrics",
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        CollectorRegistry? registry = null
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    )
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    {
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        return MapMetrics(endpoints, LegacyConfigure(registry), pattern);
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    }
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    /// <summary>
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    /// Starts a Prometheus metrics exporter, filtering to only handle requests received on a specific port.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    [EditorBrowsable(EditorBrowsableState.Never)] // It is not exactly obsolete but let's de-emphasize it.
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    public static IApplicationBuilder UseMetricServer(
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        this IApplicationBuilder builder,
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        int port,
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        string? url = "/metrics",
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        CollectorRegistry? registry = null)
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    {
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        return UseMetricServer(builder, port, LegacyConfigure(registry), url);
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    }
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    /// <summary>
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    /// Starts a Prometheus metrics exporter.
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    /// The default URL is /metrics, which is a Prometheus convention.
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    /// Use static methods on the <see cref="Metrics"/> class to create your metrics.
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    /// </summary>
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    [EditorBrowsable(EditorBrowsableState.Never)] // It is not exactly obsolete but let's de-emphasize it.
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    public static IApplicationBuilder UseMetricServer(
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        this IApplicationBuilder builder,
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        string? url = "/metrics",
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        CollectorRegistry? registry = null)
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    {
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        return UseMetricServer(builder, LegacyConfigure(registry), url);
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    }
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    private static Action<MetricServerMiddleware.Settings> LegacyConfigure(CollectorRegistry? registry) =>
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        (MetricServerMiddleware.Settings settings) =>
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        {
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            settings.Registry = registry;
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        };
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    #endregion
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    private static IApplicationBuilder InternalUseMiddleware(this IApplicationBuilder builder, Action<MetricServerMiddleware.Settings> configure)
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    {
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        var settings = new MetricServerMiddleware.Settings();
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        configure(settings);
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        return builder.UseMiddleware<MetricServerMiddleware>(settings);
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    }
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}
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