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Posted to commits@kafka.apache.org by gu...@apache.org on 2018/09/01 16:48:58 UTC
[kafka] branch trunk updated: KAFKA-7326: KStream.print() should
flush on each line for PrintStream (#5579)
This is an automated email from the ASF dual-hosted git repository.
guozhang pushed a commit to branch trunk
in repository https://gitbox.apache.org/repos/asf/kafka.git
The following commit(s) were added to refs/heads/trunk by this push:
new aa7358e KAFKA-7326: KStream.print() should flush on each line for PrintStream (#5579)
aa7358e is described below
commit aa7358e8cc0305dd9051fe0d281913247a39264d
Author: huxi <hu...@hotmail.com>
AuthorDate: Sun Sep 2 00:48:50 2018 +0800
KAFKA-7326: KStream.print() should flush on each line for PrintStream (#5579)
Reviewers: Matthias J. Sax <ma...@confluent.io>, Guozhang Wang <gu...@confluent.io>, Bill Bejeck <bi...@confluent.io>, Kamal Chandraprakash <ka...@gmail.com>
---
docs/streams/developer-guide/dsl-api.html | 1 +
streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java | 3 +++
.../org/apache/kafka/streams/kstream/internals/PrintForeachAction.java | 3 +++
3 files changed, 7 insertions(+)
diff --git a/docs/streams/developer-guide/dsl-api.html b/docs/streams/developer-guide/dsl-api.html
index f61f052..01931c8 100644
--- a/docs/streams/developer-guide/dsl-api.html
+++ b/docs/streams/developer-guide/dsl-api.html
@@ -654,6 +654,7 @@
caveats.
(<a class="reference external" href="../../../javadoc/org/apache/kafka/streams/kstream/KStream.html#print--">details</a>)</p>
<p>Calling <code class="docutils literal"><span class="pre">print()</span></code> is the same as calling <code class="docutils literal"><span class="pre">foreach((key,</span> <span class="pre">value)</span> <span class="pre">-></span> <span class="pre">System.out.println(key</span> <span class="pre">+</span> <span class="pre">",</span> <span class="pre">"</span> <span class="pre">+</span> <span class="pre">value))</span></code></p>
+ <p><code class="docutils literal"><span class="pre">print</span></code> is mainly for debugging/testing purposes, and it will try to flush on each record print. Hence it <strong>should not</strong> be used for production usage if performance requirements are concerned.</p>
<div class="last highlight-java"><div class="highlight"><pre><span></span><span class="n">KStream</span><span class="o"><</span><span class="kt">byte</span><span class="o">[],</span> <span class="n">String</span><span class="o">></span> <span class="n">stream</span> <span class="o">=</span> <span class="o">...;</span>
<span class="c1">// print to sysout</span>
<span class="n">stream</span><span class="o">.</span><span class="na">print</span><span class="o">();</span>
diff --git a/streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java b/streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java
index ae3b28a..cf2ce75 100644
--- a/streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java
+++ b/streams/src/main/java/org/apache/kafka/streams/kstream/KStream.java
@@ -359,6 +359,9 @@ public interface KStream<K, V> {
/**
* Print the records of this KStream using the options provided by {@link Printed}
+ * Note that this is mainly for debugging/testing purposes, and it will try to flush on each record print.
+ * It <em>SHOULD NOT</em> be used for production usage if performance requirements are concerned.
+ *
* @param printed options for printing
*/
void print(final Printed<K, V> printed);
diff --git a/streams/src/main/java/org/apache/kafka/streams/kstream/internals/PrintForeachAction.java b/streams/src/main/java/org/apache/kafka/streams/kstream/internals/PrintForeachAction.java
index 174319f..861dfd3 100644
--- a/streams/src/main/java/org/apache/kafka/streams/kstream/internals/PrintForeachAction.java
+++ b/streams/src/main/java/org/apache/kafka/streams/kstream/internals/PrintForeachAction.java
@@ -51,6 +51,9 @@ public class PrintForeachAction<K, V> implements ForeachAction<K, V> {
public void apply(final K key, final V value) {
final String data = String.format("[%s]: %s", label, mapper.apply(key, value));
printWriter.println(data);
+ if (!closable) {
+ printWriter.flush();
+ }
}
public void close() {