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From "Tsuyoshi OZAWA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11498) Bump the version of HTrace to 3.1.0-incubating
Date Mon, 26 Jan 2015 07:58:35 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14291551#comment-14291551
] 

Tsuyoshi OZAWA commented on HADOOP-11498:
-----------------------------------------

[~iwasakims] This patch changes the semantics at error time in TraceSamplerFactory.createSampler():

{code}
+    conf.set(HTRACE_CONF_PREFIX + SamplerBuilder.SAMPLER_CONF_KEY, samplerStr);
+    if (samplerStr.equals("ProbabilitySampler")) {
       double percentage =
           conf.getDouble("htrace.probability.sampler.percentage", 0.01d);
+      conf.setDouble(
+          HTRACE_CONF_PREFIX + ProbabilitySampler.SAMPLER_FRACTION_CONF_KEY,
+          percentage / 100.0d);
       LOG.info("HTrace is ON for " + percentage + "% of top-level spans.");
-      return new ProbabilitySampler(percentage / 100.0d);
-    } else {
-      throw new RuntimeException("Can't create sampler " + samplerStr +
-          ".  Available samplers are NeverSampler, AlwaysSampler, " +
-          "and ProbabilitySampler.");
     }
+    return new SamplerBuilder(wrapHadoopConf(conf)).build();
{code}

TraceSamplerFactory#createSampler don't throw RuntimeException with this patch. As a result,
traceSampler in DFSClient can be null:
{code}
    traceSampler = TraceSamplerFactory.createSampler(conf);
{code

Then, I think startSpan() can raise NPE since s is null:

{code}
  public static <T> TraceScope startSpan(String description, Sampler<T> s, T info)
{
    Span span = null;
    if (isTracing() || s.next(info)) {
      span = Tracer.getInstance().createNew(description);
    }
    return continueSpan(span);
  }
{code}

What do you think? 

> Bump the version of HTrace to 3.1.0-incubating
> ----------------------------------------------
>
>                 Key: HADOOP-11498
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11498
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Masatake Iwasaki
>            Assignee: Masatake Iwasaki
>         Attachments: HADOOP-11498.001.patch
>
>
> The package is renamed from org.htrace to org.apache.htrace.



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