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[SPARK-7504] [YARN] NullPointerException when initializing SparkContext in YARN-cluster mode #6083

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[SPARK-7504] [YARN] NullPointerException when initializing SparkContext in YARN-cluster mode #6083

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9f287c5
[SPARK-7504] [YARN] NullPointerException when initializing SparkConte…
zzvara May 12, 2015
39e4fa3
SPARK-7504 [YARN] NullPointerException when initializing SparkContext…
zzvara May 12, 2015
4924e01
[SPARK-7504] [YARN] NullPointerException when initializing SparkConte…
zzvara May 12, 2015
ea2a5fe
[SPARK-7504] [YARN] NullPointerException when initializing SparkConte…
zzvara May 12, 2015
7c89b6e
Remove false line.
zzvara May 12, 2015
926bd96
Moved check to SparkContext.
zzvara May 12, 2015
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1 change: 1 addition & 0 deletions core/src/main/scala/org/apache/spark/SparkConf.scala
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Expand Up @@ -448,6 +448,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging {
}
}
}

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I can probably remove this on merge, but there's a stray blank here.

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As I saw, usually there is a blank line before ending of long methods and classes. You might remove it if you will.

}

/**
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8 changes: 8 additions & 0 deletions core/src/main/scala/org/apache/spark/SparkContext.scala
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Expand Up @@ -371,6 +371,14 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
throw new SparkException("An application name must be set in your configuration")
}

// System property spark.yarn.app.id must be set if user code ran by AM on a YARN cluster
// yarn-standalone is deprecated, but still supported
if ((master == "yarn-cluster" || master == "yarn-standalone") &&
!_conf.contains("spark.yarn.app.id")) {
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Interesting related question came up just a moment ago; is this supposed to be spark.yarn.app.id? someone just suggested that it should always be spark.app.id. Thought I'd ask if you guys know.

Given the discussion, this seems like a reasonable change.

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AM writes spark.yarn.app.id, to system properties as well. spark.app.id is something different.

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yea, the suggestion was though that this should also be spark.app.id, since the two usages of spark.yarn.app.id are the only two in the code base: #6120 It might be worth resolving that first since it will matter to this change.

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isn't checking for master enough? It seems that checking for the app ID is not necessary here.

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This is an early and clean solution, rather than checking for the master. YARN cluster mode the SparkContext is launched as a separate user thread at container 0 and joined later.

@srowen If you resolve it, I will remove yarn from the configuration parameter, but you can do it afterwards. Just to keep pull-request timeline.

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It's necessary because that's what differentiates "user instantiating SparkContext in yarn-cluster mode" and "ApplicationMaster running user code that instantiates SparkContext in yarn-cluster mode". If you remove that check, yarn-cluster mode will always fail this check. See this code in ApplicationMaster:

    // Set the master property to match the requested mode.
    System.setProperty("spark.master", "yarn-cluster")

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I see... that's too bad. Maybe we should add a short comment to explain this cause it's not clear why we need it.

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What comment would you add?

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It's OK, I'll add it myself when I merge this.

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Oh never mind, I just noticed there's already a comment that explains this, though I was sure it wasn't there before... anyway, I merged this as is.

throw new SparkException("Detected yarn-cluster mode, but isn't running on a cluster. " +
"Deployment to YARN is not supported directly by SparkContext. Please use spark-submit.")
}

if (_conf.getBoolean("spark.logConf", false)) {
logInfo("Spark configuration:\n" + _conf.toDebugString)
}
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