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https://issues.apache.org/jira/browse/KAFKA-6938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16500970#comment-16500970
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ASF GitHub Bot commented on KAFKA-6938:
---------------------------------------
guozhangwang closed pull request #5128: KAFKA-6938: Add documentation for
accessing Headers on Kafka Streams Processor API
URL: https://github.com/apache/kafka/pull/5128
This is a PR merged from a forked repository.
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diff --git a/docs/streams/developer-guide/processor-api.html
b/docs/streams/developer-guide/processor-api.html
index 8236ded5c82..e07efb16580 100644
--- a/docs/streams/developer-guide/processor-api.html
+++ b/docs/streams/developer-guide/processor-api.html
@@ -53,6 +53,7 @@
</ul>
</li>
<li><a class="reference internal"
href="#connecting-processors-and-state-stores" id="id8">Connecting Processors
and State Stores</a></li>
+ <li><a class="reference internal"
href="#accessing-processor-context" id="id10">Accessing Processor
Context</a></li>
</ul>
</div>
<div class="section" id="overview">
@@ -351,6 +352,22 @@ <h2>
your store.</p>
</div>
</div>
+ <div class="section" id="accessing-processor-context">
+ <h2><a class="toc-backref" href="#id10">Accessing Processor
Context</a><a class="headerlink" href="#accessing-processor-context"
title="Permalink to this headline"></a></h2>
+ <p>As we have mentioned in
<href=#defining-a-stream-processor>Defining a Stream Processor<\href>, a
<code>ProcessorContext</code> control the processing workflow, such as
scheduling a punctuation function, and committing the current processed
state.</p>
+ <p>This object can also be used to access the metadata related
with the application like
+ <code class="docutils literal"><span
class="pre">applicationId</span></code>, <code class="docutils literal"><span
class="pre">taskId</span></code>,
+ and <code class="docutils literal"><span
class="pre">stateDir</span></code>, and also record related metadata as <code
class="docutils literal"><span class="pre">topic</span></code>,
+ <code class="docutils literal"><span
class="pre">partition</span></code>, <code class="docutils literal"><span
class="pre">offset</span></code>, <code class="docutils literal"><span
class="pre">timestamp</span></code> and
+ <code class="docutils literal"><span
class="pre">headers</span></code>.</p>
+ <p>Here is an example implementation of how to add a new header to
the record:</p>
+ <div class="highlight-java"><div
class="highlight"><pre><span></span><span class="n">public void process(String
key, String value) {</span>
+
+ <span class="c1">// add a heaeder to the elements</span>
+ <span class="n">context()</span><span class="o">.</span><span
class="na">headers</span><span class="o">()</span><span class="o">.</span><span
class="na">add</span><span class="o">.</span><span class="o">(</span><span
class="s">"key"</span><span class="o">,</span> <span
class="s">"key"</span>
+ <span class="o">}</span>
+ </pre></div>
+ </div>
<div class="section" id="connecting-processors-and-state-stores">
<h2><a class="toc-backref" href="#id8">Connecting Processors and
State Stores</a><a class="headerlink"
href="#connecting-processors-and-state-stores" title="Permalink to this
headline"></a></h2>
<p>Now that a <a class="reference internal"
href="#streams-developer-guide-stream-processor"><span class="std
std-ref">processor</span></a> (WordCountProcessor) and the
@@ -399,8 +416,8 @@ <h2><a class="toc-backref" href="#id8">Connecting
Processors and State Stores</a
runtime, indicating the state store is not accessible from
this processor.</p>
<p>Now that you have fully defined your processor topology in your
application, you can proceed to
<a class="reference internal"
href="running-app.html#streams-developer-guide-execution"><span class="std
std-ref">running the Kafka Streams application</span></a>.</p>
-</div>
-</div>
+ </div>
+ </div>
</div>
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> Add documentation for accessing Headers on Kafka Streams Processor API
> ----------------------------------------------------------------------
>
> Key: KAFKA-6938
> URL: https://issues.apache.org/jira/browse/KAFKA-6938
> Project: Kafka
> Issue Type: Improvement
> Components: documentation, streams
> Affects Versions: 2.0.0
> Reporter: Jorge Quilcate
> Assignee: Jorge Quilcate
> Priority: Major
> Fix For: 2.0.0
>
>
> Document changes implemented on KIP-244.
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