From 433e7c301a3f60574768e4c035546fb434efa252 Mon Sep 17 00:00:00 2001
From: Marcin Grzejszczak <mgrzejszczak@pivotal.io>
Date: Wed, 7 Mar 2018 08:43:22 -0500
Subject: [PATCH] Documented how to use spring cloud function; fixes gh-853

---
 .../main/asciidoc/spring-cloud-sleuth.adoc    | 32 +++++++++++++++++++
 .../zipkin2/ZipkinAutoConfiguration.java      | 10 ++++--
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/docs/src/main/asciidoc/spring-cloud-sleuth.adoc b/docs/src/main/asciidoc/spring-cloud-sleuth.adoc
index cd2b06b08..87a4c9c4f 100644
--- a/docs/src/main/asciidoc/spring-cloud-sleuth.adoc
+++ b/docs/src/main/asciidoc/spring-cloud-sleuth.adoc
@@ -869,6 +869,38 @@ Decorating Spring Integration Executor Channel with `TraceableExecutorService` w
 We're registering Zuul filters to propagate the tracing information (the request header is enriched with tracing data).
 To disable Zuul support set the `spring.sleuth.zuul.enabled` property to `false`.
 
+=== Spring Cloud Function
+
+Sleuth works out of the box with Spring Cloud Function. Since functions
+might be short living, it's best to make the Zipkin span reporting synchronous.
+Just define a `Reporter<Span>` bean as presented below:
+
+[source,java]
+----
+@Configuration
+class ReporterConfiguration {
+	@Bean
+	public Reporter<Span> reporter(
+			SpanMetricReporter spanMetricReporter,
+			ZipkinProperties zipkin,
+			Sender sender
+	) {
+		final AsyncReporter<Span> reporter = AsyncReporter.builder(sender)
+				.queuedMaxSpans(1000)
+				.messageTimeout(zipkin.getMessageTimeout(), TimeUnit.SECONDS)
+				.metrics(new ReporterMetricsAdapter(spanMetricReporter))
+				.build(zipkin.getEncoder());
+		return new Reporter<Span>() {
+			@Override public void report(Span span) {
+				reporter.report(span);
+				// make the reporter synchronous
+				reporter.flush();
+			}
+		};
+	}
+}
+----
+
 == Running examples
 
 You can find the running examples deployed in the https://run.pivotal.io/[Pivotal Web Services]. Check them out in the following links:
diff --git a/spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin2/ZipkinAutoConfiguration.java b/spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin2/ZipkinAutoConfiguration.java
index 2c64bb7f4..81075ecd5 100644
--- a/spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin2/ZipkinAutoConfiguration.java
+++ b/spring-cloud-sleuth-zipkin/src/main/java/org/springframework/cloud/sleuth/zipkin2/ZipkinAutoConfiguration.java
@@ -85,11 +85,17 @@ public class ZipkinAutoConfiguration {
 			ZipkinProperties zipkin,
 			Sender sender
 	) {
-		return AsyncReporter.builder(sender)
-				.queuedMaxSpans(1000) // historical constraint. Note: AsyncReporter supports memory bounds
+		final AsyncReporter<Span> reporter = AsyncReporter.builder(sender).queuedMaxSpans(
+				1000) // historical constraint. Note: AsyncReporter supports memory bounds
 				.messageTimeout(zipkin.getMessageTimeout(), TimeUnit.SECONDS)
 				.metrics(new ReporterMetricsAdapter(spanMetricReporter))
 				.build(zipkin.getEncoder());
+		return new Reporter<Span>() {
+			@Override public void report(Span span) {
+				reporter.report(span);
+				reporter.flush();
+			}
+		};
 	}
 
 	@Bean