From cb066cb5c91cf21be9bc53ae1c99f2eafebc3dce Mon Sep 17 00:00:00 2001
From: Kirill Ivanov <kipwoker@users.noreply.github.com>
Date: Tue, 23 Feb 2021 21:34:22 +0100
Subject: [PATCH] Add ForceFlush to TracerProvider (#1837)

* Add ForceFlush to TracerProvider

* Fixed inlinedoc

* Change the wording

* Remove creating activity

* Update src/OpenTelemetry/CHANGELOG.md

Co-authored-by: Cijo Thomas <cithomas@microsoft.com>

Co-authored-by: Cijo Thomas <cithomas@microsoft.com>
---
 .../.publicApi/net452/PublicAPI.Unshipped.txt |  1 +
 .../.publicApi/net46/PublicAPI.Unshipped.txt  |  1 +
 .../.publicApi/net461/PublicAPI.Unshipped.txt |  1 +
 .../netstandard2.0/PublicAPI.Unshipped.txt    |  1 +
 src/OpenTelemetry/CHANGELOG.md                |  2 +
 .../Trace/TracerProviderExtensions.cs         | 46 +++++++++++++++++++
 src/OpenTelemetry/Trace/TracerProviderSdk.cs  |  5 ++
 .../Trace/TracerProviderSdkTest.cs            | 15 ++++++
 8 files changed, 72 insertions(+)

diff --git a/src/OpenTelemetry/.publicApi/net452/PublicAPI.Unshipped.txt b/src/OpenTelemetry/.publicApi/net452/PublicAPI.Unshipped.txt
index e69de29bb2d..8b90281a056 100644
--- a/src/OpenTelemetry/.publicApi/net452/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry/.publicApi/net452/PublicAPI.Unshipped.txt
@@ -0,0 +1 @@
+static OpenTelemetry.Trace.TracerProviderExtensions.ForceFlush(this OpenTelemetry.Trace.TracerProvider provider, int timeoutMilliseconds = -1) -> bool
\ No newline at end of file
diff --git a/src/OpenTelemetry/.publicApi/net46/PublicAPI.Unshipped.txt b/src/OpenTelemetry/.publicApi/net46/PublicAPI.Unshipped.txt
index e69de29bb2d..6779d236a29 100644
--- a/src/OpenTelemetry/.publicApi/net46/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry/.publicApi/net46/PublicAPI.Unshipped.txt
@@ -0,0 +1 @@
+static OpenTelemetry.Trace.TracerProviderExtensions.ForceFlush(this OpenTelemetry.Trace.TracerProvider provider, int timeoutMilliseconds = -1) -> bool
diff --git a/src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt b/src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt
index e69de29bb2d..6779d236a29 100644
--- a/src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry/.publicApi/net461/PublicAPI.Unshipped.txt
@@ -0,0 +1 @@
+static OpenTelemetry.Trace.TracerProviderExtensions.ForceFlush(this OpenTelemetry.Trace.TracerProvider provider, int timeoutMilliseconds = -1) -> bool
diff --git a/src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt b/src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt
index e69de29bb2d..6779d236a29 100644
--- a/src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt
@@ -0,0 +1 @@
+static OpenTelemetry.Trace.TracerProviderExtensions.ForceFlush(this OpenTelemetry.Trace.TracerProvider provider, int timeoutMilliseconds = -1) -> bool
diff --git a/src/OpenTelemetry/CHANGELOG.md b/src/OpenTelemetry/CHANGELOG.md
index a0b04e6c57e..e3770cadff8 100644
--- a/src/OpenTelemetry/CHANGELOG.md
+++ b/src/OpenTelemetry/CHANGELOG.md
@@ -9,6 +9,8 @@ please check the latest changes
 
 ## Unreleased
 
+* Added `ForceFlush` to `TracerProvider`. ([#1837](https://github.com/open-telemetry/opentelemetry-dotnet/pull/1837))
+
 ## 1.0.1
 
 Released 2021-Feb-10
diff --git a/src/OpenTelemetry/Trace/TracerProviderExtensions.cs b/src/OpenTelemetry/Trace/TracerProviderExtensions.cs
index 302f85d5173..cfa331e179d 100644
--- a/src/OpenTelemetry/Trace/TracerProviderExtensions.cs
+++ b/src/OpenTelemetry/Trace/TracerProviderExtensions.cs
@@ -43,6 +43,52 @@ public static TracerProvider AddProcessor(this TracerProvider provider, BaseProc
             return provider;
         }
 
+        /// <summary>
+        /// Flushes the all the processors at TracerProviderSdk, blocks the current thread until flush
+        /// completed, shutdown signaled or timed out.
+        /// </summary>
+        /// <param name="provider">TracerProviderSdk instance on which ForceFlush will be called.</param>
+        /// <param name="timeoutMilliseconds">
+        /// The number of milliseconds to wait, or <c>Timeout.Infinite</c> to
+        /// wait indefinitely.
+        /// </param>
+        /// <returns>
+        /// Returns <c>true</c> when force flush succeeded; otherwise, <c>false</c>.
+        /// </returns>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown when the <c>timeoutMilliseconds</c> is smaller than -1.
+        /// </exception>
+        /// <remarks>
+        /// This function guarantees thread-safety.
+        /// </remarks>
+        public static bool ForceFlush(this TracerProvider provider, int timeoutMilliseconds = Timeout.Infinite)
+        {
+            if (provider == null)
+            {
+                throw new ArgumentNullException(nameof(provider));
+            }
+
+            if (provider is TracerProviderSdk tracerProviderSdk)
+            {
+                if (timeoutMilliseconds < 0 && timeoutMilliseconds != Timeout.Infinite)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(timeoutMilliseconds), timeoutMilliseconds, "timeoutMilliseconds should be non-negative.");
+                }
+
+                try
+                {
+                    return tracerProviderSdk.OnForceFlush(timeoutMilliseconds);
+                }
+                catch (Exception ex)
+                {
+                    OpenTelemetrySdkEventSource.Log.TracerProviderException(nameof(tracerProviderSdk.OnForceFlush), ex);
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
         /// <summary>
         /// Attempts to shutdown the TracerProviderSdk, blocks the current thread until
         /// shutdown completed or timed out.
diff --git a/src/OpenTelemetry/Trace/TracerProviderSdk.cs b/src/OpenTelemetry/Trace/TracerProviderSdk.cs
index d0759533a5e..a2e6dff3ba4 100644
--- a/src/OpenTelemetry/Trace/TracerProviderSdk.cs
+++ b/src/OpenTelemetry/Trace/TracerProviderSdk.cs
@@ -207,6 +207,11 @@ internal TracerProviderSdk AddProcessor(BaseProcessor<Activity> processor)
             return this;
         }
 
+        internal bool OnForceFlush(int timeoutMilliseconds)
+        {
+            return this.processor?.ForceFlush(timeoutMilliseconds) ?? true;
+        }
+
         /// <summary>
         /// Called by <c>Shutdown</c>. This function should block the current
         /// thread until shutdown completed or timed out.
diff --git a/test/OpenTelemetry.Tests/Trace/TracerProviderSdkTest.cs b/test/OpenTelemetry.Tests/Trace/TracerProviderSdkTest.cs
index e193cb9b5b6..64891ae7098 100644
--- a/test/OpenTelemetry.Tests/Trace/TracerProviderSdkTest.cs
+++ b/test/OpenTelemetry.Tests/Trace/TracerProviderSdkTest.cs
@@ -398,6 +398,21 @@ public void TracerProviderSdkBuildsWithSDKResource()
             Assert.Single(versionAttribute);
         }
 
+        [Fact]
+        public void TracerProviderSdkFlushesProcessorForcibly()
+        {
+            using TestActivityProcessor testActivityProcessor = new TestActivityProcessor();
+
+            using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+                        .AddProcessor(testActivityProcessor)
+                        .Build();
+
+            var isFlushed = tracerProvider.ForceFlush();
+
+            Assert.True(isFlushed);
+            Assert.True(testActivityProcessor.ForceFlushCalled);
+        }
+
         public void Dispose()
         {
             GC.SuppressFinalize(this);