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Add option to consume burst metrics from external service, inject as …
…header (retaildevcrews#61) * Add option to use burst service * address design review comments * Update option defaults * Make burstmetricsservice static * Address review comments * Add burst service vars as args/envvaroptions
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,177 @@ | ||
| // Copyright (c) Microsoft Corporation. All rights reserved. | ||
| // Licensed under the MIT License. See LICENSE in the project root for license information. | ||
|
|
||
| using System; | ||
| using System.Net.Http; | ||
| using System.Threading; | ||
| using System.Timers; | ||
| using Microsoft.AspNetCore.Http; | ||
| using Ngsa.Middleware; | ||
|
|
||
| /// <summary> | ||
| /// This service consumes burst metrics from an external service and will also | ||
| /// inject these metrics into a response header. | ||
| /// </summary> | ||
| namespace Ngsa.Application | ||
| { | ||
| public class BurstMetricsService : IDisposable | ||
| { | ||
| private const int ClientTimeout = 5; | ||
| private const int MetricsRefreshFrequency = 5; | ||
| private const string CapacityHeader = "X-Load-Feedback"; | ||
|
|
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| private static readonly NgsaLog Logger = new NgsaLog { Name = typeof(BurstMetricsService).FullName }; | ||
| private static HttpClient client; | ||
| private static System.Timers.Timer timer; | ||
| private static string burstMetricsPath; | ||
| private static string burstMetricsResult; | ||
| private static CancellationToken Token { get; set; } | ||
|
|
||
| /// <summary> | ||
| /// Initializes burst metrics service | ||
| /// </summary> | ||
| public static void Init(CancellationToken token) | ||
| { | ||
| burstMetricsResult = string.Empty; | ||
| Token = token; | ||
| burstMetricsPath = $"{App.Config.BurstServiceNs}/{App.Config.BurstServiceHPA}"; | ||
|
|
||
| // ensure version is set for client's user-agent | ||
| VersionExtension.Init(); | ||
|
|
||
| // setup http client | ||
| client = OpenHTTPClient(App.Config.BurstServiceEndpoint); | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Start consuming data from burst metrics service | ||
| /// </summary> | ||
| public static void Start() | ||
| { | ||
| // run timed burst metrics service | ||
| timer = new () | ||
| { | ||
| Enabled = true, | ||
| Interval = MetricsRefreshFrequency * 1000, | ||
| }; | ||
| timer.Elapsed += TimerWork; | ||
|
|
||
| // Run once before the timer | ||
| TimerWork(null, null); | ||
|
|
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| // Start the timer, it will be called after Interval | ||
| timer.Start(); | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Stop collecting burst metrics | ||
| /// </summary> | ||
| public static void Stop() | ||
| { | ||
| if (timer != null) | ||
| { | ||
| timer.Stop(); | ||
| timer.Dispose(); | ||
| timer = null; | ||
| } | ||
|
|
||
| if (client != null) | ||
| { | ||
| client.Dispose(); | ||
| client = null; | ||
| } | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Return burst metrics | ||
| /// </summary> | ||
| public static string GetBurstMetrics() | ||
| { | ||
| return burstMetricsResult; | ||
| } | ||
|
|
||
| /// <summary> | ||
| /// Inject burst metrics, if present, into the response header | ||
| /// </summary> | ||
| /// <param name="context">response context</param> | ||
| public static void InjectBurstMetricsHeader(HttpContext context) | ||
| { | ||
| if (App.Config.BurstHeader && !string.IsNullOrEmpty(burstMetricsResult)) | ||
| { | ||
| context.Response.Headers.Add(CapacityHeader, burstMetricsResult); | ||
| } | ||
| } | ||
|
|
||
| public void Dispose() | ||
| { | ||
| Dispose(true); | ||
| GC.SuppressFinalize(this); | ||
| } | ||
|
|
||
| protected virtual void Dispose(bool disposing) | ||
| { | ||
| if (disposing) | ||
| { | ||
| Stop(); | ||
| } | ||
| } | ||
|
|
||
| private static HttpClient OpenHTTPClient(string baseAddress) | ||
| { | ||
| try | ||
| { | ||
| // Create a http client | ||
| HttpClient client = new () | ||
| { | ||
| Timeout = new TimeSpan(0, 0, ClientTimeout), | ||
| BaseAddress = new Uri(baseAddress), | ||
| }; | ||
| client.DefaultRequestHeaders.Add("User-Agent", $"ngsa/{VersionExtension.ShortVersion}"); | ||
| return client; | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| throw new Exception("Unable to setup client to burst service endpoint.", ex); | ||
| } | ||
| } | ||
|
|
||
| private static async void TimerWork(object state, ElapsedEventArgs e) | ||
| { | ||
| // exit if cancelled | ||
| if (Token.IsCancellationRequested) | ||
| { | ||
| Stop(); | ||
| return; | ||
| } | ||
|
|
||
| // verify http client | ||
| if (client == null) | ||
| { | ||
| Logger.LogError("BurstMetricsServiceTimer", "Burst Metrics Service HTTP Client is null. Attempting to recreate."); | ||
|
|
||
| // recreate http client | ||
| client = OpenHTTPClient(App.Config.BurstServiceEndpoint); | ||
| return; | ||
| } | ||
|
|
||
| try | ||
| { | ||
| // process the response | ||
| using HttpResponseMessage resp = await client.GetAsync(burstMetricsPath).ConfigureAwait(false); | ||
| if (resp.IsSuccessStatusCode) | ||
| { | ||
| burstMetricsResult = await resp.Content.ReadAsStringAsync().ConfigureAwait(false); | ||
| } | ||
| else | ||
| { | ||
| burstMetricsResult = string.Empty; | ||
| Logger.LogWarning("BurstMetricsServiceTimer", "Received error status code from burst service.", new LogEventId((int)resp.StatusCode, resp.StatusCode.ToString())); | ||
| } | ||
| } | ||
| catch (Exception ex) | ||
| { | ||
| Logger.LogError("BurstMetricsServiceTimer", "Failed to get response from burst service.", ex: ex); | ||
| } | ||
| } | ||
| } | ||
| } |
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