MeterProviderBuilderSdk.cs

// <copyright file="MeterProviderBuilderSdk.cs" company="OpenTelemetry Authors">
// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// </copyright>

#nullable enable

using System.Diagnostics;
using System.Diagnostics.Metrics;
using System.Text.RegularExpressions;
using Microsoft.Extensions.DependencyInjection;
using OpenTelemetry.Internal;
using OpenTelemetry.Resources;

namespace OpenTelemetry.Metrics
{
    /// <summary>
    /// Stores state used to build a <see cref="MeterProvider"/>.
    /// </summary>
    internal sealed class MeterProviderBuilderSdk : MeterProviderBuilder, IMeterProviderBuilder
    {
        public const int MaxMetricsDefault = 1000;
        public const int MaxMetricPointsPerMetricDefault = 2000;
        private const string DefaultInstrumentationVersion = "1.0.0.0";

        private static readonly Regex InstrumentNameRegex = new(
            @"^[a-z][a-z0-9-._]{0,62}$", RegexOptions.IgnoreCase | RegexOptions.Compiled);

        private readonly IServiceProvider serviceProvider;
        private MeterProviderSdk? meterProvider;

        public MeterProviderBuilderSdk(IServiceProvider serviceProvider)
        {
            this.serviceProvider = serviceProvider;
        }

        public List<InstrumentationRegistration> Instrumentation { get; } = new();

        public ResourceBuilder? ResourceBuilder { get; private set; }

        public MeterProvider? Provider => this.meterProvider;

        public List<MetricReader> Readers { get; } = new();

        public List<string> MeterSources { get; } = new();

        public List<Func<Instrument, MetricStreamConfiguration?>> ViewConfigs { get; } = new();

        public int MaxMetricStreams { get; private set; } = MaxMetricsDefault;

        public int MaxMetricPointsPerMetricStream { get; private set; } = MaxMetricPointsPerMetricDefault;

        /// <summary>
        /// Returns whether the given instrument name is valid according to the specification.
        /// </summary>
        /// <remarks>See specification: <see href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument"/>.</remarks>
        /// <param name="instrumentName">The instrument name.</param>
        /// <returns>Boolean indicating if the instrument is valid.</returns>
        public static bool IsValidInstrumentName(string instrumentName)
        {
            if (string.IsNullOrWhiteSpace(instrumentName))
            {
                return false;
            }

            return InstrumentNameRegex.IsMatch(instrumentName);
        }

        /// <summary>
        /// Returns whether the given custom view name is valid according to the specification.
        /// </summary>
        /// <remarks>See specification: <see href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#instrument"/>.</remarks>
        /// <param name="customViewName">The view name.</param>
        /// <returns>Boolean indicating if the instrument is valid.</returns>
        public static bool IsValidViewName(string customViewName)
        {
            // Only validate the view name in case it's not null. In case it's null, the view name will be the instrument name as per the spec.
            if (customViewName == null)
            {
                return true;
            }

            return InstrumentNameRegex.IsMatch(customViewName);
        }

        public void RegisterProvider(MeterProviderSdk meterProvider)
        {
            Debug.Assert(meterProvider != null, "meterProvider was null");

            if (this.meterProvider != null)
            {
                throw new NotSupportedException("MeterProvider cannot be accessed while build is executing.");
            }

            this.meterProvider = meterProvider;
        }

        public override MeterProviderBuilder AddInstrumentation<TInstrumentation>(
            Func<TInstrumentation> instrumentationFactory)
        {
            Debug.Assert(instrumentationFactory != null, "instrumentationFactory was null");

            return this.AddInstrumentation(
                typeof(TInstrumentation).Name,
                typeof(TInstrumentation).Assembly.GetName().Version?.ToString() ?? DefaultInstrumentationVersion,
                instrumentationFactory!());
        }

        public MeterProviderBuilder AddInstrumentation(
            string instrumentationName,
            string instrumentationVersion,
            object instrumentation)
        {
            Debug.Assert(!string.IsNullOrWhiteSpace(instrumentationName), "instrumentationName was null or whitespace");
            Debug.Assert(!string.IsNullOrWhiteSpace(instrumentationVersion), "instrumentationVersion was null or whitespace");
            Debug.Assert(instrumentation != null, "instrumentation was null");

            this.Instrumentation.Add(
                new InstrumentationRegistration(
                    instrumentationName,
                    instrumentationVersion,
                    instrumentation!));

            return this;
        }

        public MeterProviderBuilder ConfigureResource(Action<ResourceBuilder> configure)
        {
            Debug.Assert(configure != null, "configure was null");

            var resourceBuilder = this.ResourceBuilder ??= ResourceBuilder.CreateDefault();

            configure!(resourceBuilder);

            return this;
        }

        public MeterProviderBuilder SetResourceBuilder(ResourceBuilder resourceBuilder)
        {
            Debug.Assert(resourceBuilder != null, "resourceBuilder was null");

            this.ResourceBuilder = resourceBuilder;

            return this;
        }

        public override MeterProviderBuilder AddMeter(params string[] names)
        {
            Debug.Assert(names != null, "names was null");

            foreach (var name in names!)
            {
                Guard.ThrowIfNullOrWhitespace(name);

                this.MeterSources.Add(name);
            }

            return this;
        }

        public MeterProviderBuilder AddReader(MetricReader reader)
        {
            Debug.Assert(reader != null, "reader was null");

            this.Readers.Add(reader!);

            return this;
        }

        public MeterProviderBuilder AddView(Func<Instrument, MetricStreamConfiguration?> viewConfig)
        {
            Debug.Assert(viewConfig != null, "viewConfig was null");

            this.ViewConfigs.Add(viewConfig!);

            return this;
        }

        public MeterProviderBuilder SetMaxMetricStreams(int maxMetricStreams)
        {
            this.MaxMetricStreams = maxMetricStreams;

            return this;
        }

        public MeterProviderBuilder SetMaxMetricPointsPerMetricStream(int maxMetricPointsPerMetricStream)
        {
            this.MaxMetricPointsPerMetricStream = maxMetricPointsPerMetricStream;

            return this;
        }

        public MeterProviderBuilder ConfigureBuilder(Action<IServiceProvider, MeterProviderBuilder> configure)
        {
            Debug.Assert(configure != null, "configure was null");

            configure!(this.serviceProvider, this);

            return this;
        }

        public MeterProviderBuilder ConfigureServices(Action<IServiceCollection> configure)
        {
            throw new NotSupportedException("Services cannot be configured after ServiceProvider has been created.");
        }

        MeterProviderBuilder IDeferredMeterProviderBuilder.Configure(Action<IServiceProvider, MeterProviderBuilder> configure)
            => this.ConfigureBuilder(configure);

        internal readonly struct InstrumentationRegistration
        {
            public readonly string Name;
            public readonly string Version;
            public readonly object Instance;

            internal InstrumentationRegistration(string name, string version, object instance)
            {
                this.Name = name;
                this.Version = version;
                this.Instance = instance;
            }
        }
    }
}