spark技术分享ConsoleProgressBar
ConsoleProgressBar shows the progress of active stages to standard error, i.e. stderr. It uses SparkStatusTracker to poll the status of stages periodically and print out active stages with more than one task. It keeps overwriting itself to hold in one line for at most 3 first concurrent stages at a time.
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[Stage 0:====> (316 + 4) / 1000][Stage 1:> (0 + 0) / 1000][Stage 2:> (0 + 0) / 1000]]] |
The progress includes the stage id, the number of completed, active, and total tasks.
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Tip
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ConsoleProgressBar may be useful when you ssh to workers and want to see the progress of active stages.
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ConsoleProgressBar is created when SparkContext starts with spark.ui.showConsoleProgress enabled and the logging level of org.apache.spark.SparkContext logger as WARN or higher (i.e. less messages are printed out and so there is a “space” for ConsoleProgressBar).
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import org.apache.log4j._ Logger.getLogger("org.apache.spark.SparkContext").setLevel(Level.WARN) |
To print the progress nicely ConsoleProgressBar uses COLUMNS environment variable to know the width of the terminal. It assumes 80 columns.
The progress bar prints out the status after a stage has ran at least 500 milliseconds every spark.ui.consoleProgress.update.interval milliseconds.
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Note
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The initial delay of 500 milliseconds before ConsoleProgressBar show the progress is not configurable.
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See the progress bar in Spark shell with the following:
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$ ./bin/spark-shell --conf spark.ui.showConsoleProgress=true (1) scala> sc.setLogLevel("OFF") (2) import org.apache.log4j._ scala> Logger.getLogger("org.apache.spark.SparkContext").setLevel(Level.WARN) (3) scala> sc.parallelize(1 to 4, 4).map { n => Thread.sleep(500 + 200 * n); n }.count (4) [Stage 2:> (0 + 4) / 4] [Stage 2:==============> (1 + 3) / 4] [Stage 2:=============================> (2 + 2) / 4] [Stage 2:============================================> (3 + 1) / 4] |
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Make sure
spark.ui.showConsoleProgressistrue. It is by default. -
Disable (
OFF) the root logger (that includes Spark’s logger) -
Make sure
org.apache.spark.SparkContextlogger is at leastWARN. -
Run a job with 4 tasks with 500ms initial sleep and 200ms sleep chunks to see the progress bar.
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Tip
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Watch the short video that show ConsoleProgressBar in action. |
You may want to use the following example to see the progress bar in full glory – all 3 concurrent stages in console (borrowed from a comment to [SPARK-4017] show progress bar in console #3029):
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> ./bin/spark-shell scala> val a = sc.makeRDD(1 to 1000, 10000).map(x => (x, x)).reduceByKey(_ + _) scala> val b = sc.makeRDD(1 to 1000, 10000).map(x => (x, x)).reduceByKey(_ + _) scala> a.union(b).count() |
Creating ConsoleProgressBar Instance
ConsoleProgressBar requires a SparkContext.
When being created, ConsoleProgressBar reads spark.ui.consoleProgress.update.interval configuration property to set up the update interval and COLUMNS environment variable for the terminal width (or assumes 80 columns).
ConsoleProgressBar starts the internal timer refresh progress that does refresh and shows progress.
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Note
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ConsoleProgressBar is created when SparkContext starts, spark.ui.showConsoleProgress configuration property is enabled, and the logging level of org.apache.spark.SparkContext logger is WARN or higher (i.e. less messages are printed out and so there is a “space” for ConsoleProgressBar).
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Note
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Once created, ConsoleProgressBar is available internally as _progressBar.
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finishAll Method
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Caution
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FIXME |
stop Method
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stop(): Unit |
stop cancels (stops) the internal timer.
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Note
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stop is executed when SparkContext stops.
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