Class SparkContext

Create a new SparkContext. At least the master and app name should be set,
either through the named parameters here or through C{conf}.

@param master: Cluster URL to connect to
       (e.g. mesos://host:port, spark://host:port, local[4]).
@param appName: A name for your job, to display on the cluster web UI.
@param sparkHome: Location where Spark is installed on cluster nodes.
@param pyFiles: Collection of .zip or .py files to send to the cluster
       and add to PYTHONPATH.  These can be paths on the local file
       system or HDFS, HTTP, HTTPS, or FTP URLs.
@param environment: A dictionary of environment variables to set on
       worker nodes.
@param batchSize: The number of Python objects represented as a single
       Java object.  Set 1 to disable batching or -1 to use an
       unlimited batch size.
@param serializer: The serializer for RDDs.
@param conf: A L{SparkConf} object setting Spark properties.
@param gateway: Use an existing gateway and JVM, otherwise a new JVM
       will be instatiated.


>>> from pyspark.context import SparkContext
>>> sc = SparkContext('local', 'test')

>>> sc2 = SparkContext('local', 'test2') # doctest: +IGNORE_EXCEPTION_DETAIL
Traceback (most recent call last):
    ...
ValueError:...

Overrides: object.__init__

Set a Java system property, such as spark.executor.memory. This must must be invoked before instantiating SparkContext.

Default level of parallelism to use when not given by user (e.g. for reduce tasks)

Decorators:

• @property

Default min number of partitions for Hadoop RDDs when not given by user

Decorators:

• @property

Distribute a local Python collection to form an RDD.

>>> sc.parallelize(range(5), 5).glom().collect()
[[0], [1], [2], [3], [4]]

Read a text file from HDFS, a local file system (available on all nodes), or any Hadoop-supported file system URI, and return it as an RDD of Strings.

>>> path = os.path.join(tempdir, "sample-text.txt")
>>> with open(path, "w") as testFile:
...    testFile.write("Hello world!")
>>> textFile = sc.textFile(path)
>>> textFile.collect()
[u'Hello world!']

Read a directory of text files from HDFS, a local file system (available on all nodes), or any Hadoop-supported file system URI. Each file is read as a single record and returned in a key-value pair, where the key is the path of each file, the value is the content of each file.

For example, if you have the following files:

 hdfs://a-hdfs-path/part-00000
 hdfs://a-hdfs-path/part-00001
 ...
 hdfs://a-hdfs-path/part-nnnnn

Do rdd = sparkContext.wholeTextFiles("hdfs://a-hdfs-path"), then rdd contains:

 (a-hdfs-path/part-00000, its content)
 (a-hdfs-path/part-00001, its content)
 ...
 (a-hdfs-path/part-nnnnn, its content)

NOTE: Small files are preferred, as each file will be loaded fully in memory.

>>> dirPath = os.path.join(tempdir, "files")
>>> os.mkdir(dirPath)
>>> with open(os.path.join(dirPath, "1.txt"), "w") as file1:
...    file1.write("1")
>>> with open(os.path.join(dirPath, "2.txt"), "w") as file2:
...    file2.write("2")
>>> textFiles = sc.wholeTextFiles(dirPath)
>>> sorted(textFiles.collect())
[(u'.../1.txt', u'1'), (u'.../2.txt', u'2')]

Build the union of a list of RDDs.

This supports unions() of RDDs with different serialized formats, although this forces them to be reserialized using the default serializer:

>>> path = os.path.join(tempdir, "union-text.txt")
>>> with open(path, "w") as testFile:
...    testFile.write("Hello")
>>> textFile = sc.textFile(path)
>>> textFile.collect()
[u'Hello']
>>> parallelized = sc.parallelize(["World!"])
>>> sorted(sc.union([textFile, parallelized]).collect())
[u'Hello', 'World!']

Broadcast a read-only variable to the cluster, returning a Broadcast object for reading it in distributed functions. The variable will be sent to each cluster only once.

Create an Accumulator with the given initial value, using a given AccumulatorParam helper object to define how to add values of the data type if provided. Default AccumulatorParams are used for integers and floating-point numbers if you do not provide one. For other types, a custom AccumulatorParam can be used.

Add a file to be downloaded with this Spark job on every node. The path passed can be either a local file, a file in HDFS (or other Hadoop-supported filesystems), or an HTTP, HTTPS or FTP URI.

To access the file in Spark jobs, use SparkFiles.get(path) to find its download location.

>>> from pyspark import SparkFiles
>>> path = os.path.join(tempdir, "test.txt")
>>> with open(path, "w") as testFile:
...    testFile.write("100")
>>> sc.addFile(path)
>>> def func(iterator):
...    with open(SparkFiles.get("test.txt")) as testFile:
...        fileVal = int(testFile.readline())
...        return [x * 100 for x in iterator]
>>> sc.parallelize([1, 2, 3, 4]).mapPartitions(func).collect()
[100, 200, 300, 400]

Add a .py or .zip dependency for all tasks to be executed on this SparkContext in the future. The path passed can be either a local file, a file in HDFS (or other Hadoop-supported filesystems), or an HTTP, HTTPS or FTP URI.

Set the directory under which RDDs are going to be checkpointed. The directory must be a HDFS path if running on a cluster.

Assigns a group ID to all the jobs started by this thread until the group ID is set to a different value or cleared.

Often, a unit of execution in an application consists of multiple Spark actions or jobs. Application programmers can use this method to group all those jobs together and give a group description. Once set, the Spark web UI will associate such jobs with this group.

The application can use SparkContext.cancelJobGroup to cancel all running jobs in this group.

>>> import thread, threading
>>> from time import sleep
>>> result = "Not Set"
>>> lock = threading.Lock()
>>> def map_func(x):
...     sleep(100)
...     raise Exception("Task should have been cancelled")
>>> def start_job(x):
...     global result
...     try:
...         sc.setJobGroup("job_to_cancel", "some description")
...         result = sc.parallelize(range(x)).map(map_func).collect()
...     except Exception as e:
...         result = "Cancelled"
...     lock.release()
>>> def stop_job():
...     sleep(5)
...     sc.cancelJobGroup("job_to_cancel")
>>> supress = lock.acquire()
>>> supress = thread.start_new_thread(start_job, (10,))
>>> supress = thread.start_new_thread(stop_job, tuple())
>>> supress = lock.acquire()
>>> print result
Cancelled

If interruptOnCancel is set to true for the job group, then job cancellation will result in Thread.interrupt() being called on the job's executor threads. This is useful to help ensure that the tasks are actually stopped in a timely manner, but is off by default due to HDFS-1208, where HDFS may respond to Thread.interrupt() by marking nodes as dead.

Get a local property set in this thread, or null if it is missing. See setLocalProperty

Cancel active jobs for the specified group. See SparkContext.setJobGroup for more information.