#
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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
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# http://www.apache.org/licenses/LICENSE-2.0
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import sys
import json
from py4j.java_gateway import java_import
from pyspark import since, keyword_only
from pyspark.sql.column import _to_seq
from pyspark.sql.readwriter import OptionUtils, to_str
from pyspark.sql.types import StructType, StructField, StringType
from pyspark.sql.utils import ForeachBatchFunction, StreamingQueryException
__all__ = ["StreamingQuery", "StreamingQueryManager", "DataStreamReader", "DataStreamWriter"]
[docs]class StreamingQuery(object):
"""
A handle to a query that is executing continuously in the background as new data arrives.
All these methods are thread-safe.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
def __init__(self, jsq):
self._jsq = jsq
@property
@since(2.0)
def id(self):
"""Returns the unique id of this query that persists across restarts from checkpoint data.
That is, this id is generated when a query is started for the first time, and
will be the same every time it is restarted from checkpoint data.
There can only be one query with the same id active in a Spark cluster.
Also see, `runId`.
"""
return self._jsq.id().toString()
@property
@since(2.1)
def runId(self):
"""Returns the unique id of this query that does not persist across restarts. That is, every
query that is started (or restarted from checkpoint) will have a different runId.
"""
return self._jsq.runId().toString()
@property
@since(2.0)
def name(self):
"""Returns the user-specified name of the query, or null if not specified.
This name can be specified in the `org.apache.spark.sql.streaming.DataStreamWriter`
as `dataframe.writeStream.queryName("query").start()`.
This name, if set, must be unique across all active queries.
"""
return self._jsq.name()
@property
@since(2.0)
def isActive(self):
"""Whether this streaming query is currently active or not.
"""
return self._jsq.isActive()
[docs] @since(2.0)
def awaitTermination(self, timeout=None):
"""Waits for the termination of `this` query, either by :func:`query.stop()` or by an
exception. If the query has terminated with an exception, then the exception will be thrown.
If `timeout` is set, it returns whether the query has terminated or not within the
`timeout` seconds.
If the query has terminated, then all subsequent calls to this method will either return
immediately (if the query was terminated by :func:`stop()`), or throw the exception
immediately (if the query has terminated with exception).
throws :class:`StreamingQueryException`, if `this` query has terminated with an exception
"""
if timeout is not None:
if not isinstance(timeout, (int, float)) or timeout < 0:
raise ValueError("timeout must be a positive integer or float. Got %s" % timeout)
return self._jsq.awaitTermination(int(timeout * 1000))
else:
return self._jsq.awaitTermination()
@property
@since(2.1)
def status(self):
"""
Returns the current status of the query.
"""
return json.loads(self._jsq.status().json())
@property
@since(2.1)
def recentProgress(self):
"""Returns an array of the most recent [[StreamingQueryProgress]] updates for this query.
The number of progress updates retained for each stream is configured by Spark session
configuration `spark.sql.streaming.numRecentProgressUpdates`.
"""
return [json.loads(p.json()) for p in self._jsq.recentProgress()]
@property
def lastProgress(self):
"""
Returns the most recent :class:`StreamingQueryProgress` update of this streaming query or
None if there were no progress updates
.. versionadded:: 2.1.0
Returns
-------
dict
"""
lastProgress = self._jsq.lastProgress()
if lastProgress:
return json.loads(lastProgress.json())
else:
return None
[docs] def processAllAvailable(self):
"""Blocks until all available data in the source has been processed and committed to the
sink. This method is intended for testing.
.. versionadded:: 2.0.0
Notes
-----
In the case of continually arriving data, this method may block forever.
Additionally, this method is only guaranteed to block until data that has been
synchronously appended data to a stream source prior to invocation.
(i.e. `getOffset` must immediately reflect the addition).
"""
return self._jsq.processAllAvailable()
[docs] @since(2.0)
def stop(self):
"""Stop this streaming query.
"""
self._jsq.stop()
[docs] def explain(self, extended=False):
"""Prints the (logical and physical) plans to the console for debugging purpose.
.. versionadded:: 2.1.0
Parameters
----------
extended : bool, optional
default ``False``. If ``False``, prints only the physical plan.
Examples
--------
>>> sq = sdf.writeStream.format('memory').queryName('query_explain').start()
>>> sq.processAllAvailable() # Wait a bit to generate the runtime plans.
>>> sq.explain()
== Physical Plan ==
...
>>> sq.explain(True)
== Parsed Logical Plan ==
...
== Analyzed Logical Plan ==
...
== Optimized Logical Plan ==
...
== Physical Plan ==
...
>>> sq.stop()
"""
# Cannot call `_jsq.explain(...)` because it will print in the JVM process.
# We should print it in the Python process.
print(self._jsq.explainInternal(extended))
[docs] def exception(self):
"""
.. versionadded:: 2.1.0
Returns
-------
:class:`StreamingQueryException`
the StreamingQueryException if the query was terminated by an exception, or None.
"""
if self._jsq.exception().isDefined():
je = self._jsq.exception().get()
msg = je.toString().split(': ', 1)[1] # Drop the Java StreamingQueryException type info
stackTrace = '\n\t at '.join(map(lambda x: x.toString(), je.getStackTrace()))
return StreamingQueryException(msg, stackTrace, je.getCause())
else:
return None
[docs]class StreamingQueryManager(object):
"""A class to manage all the :class:`StreamingQuery` StreamingQueries active.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
def __init__(self, jsqm):
self._jsqm = jsqm
@property
def active(self):
"""Returns a list of active queries associated with this SQLContext
.. versionadded:: 2.0.0
Examples
--------
>>> sq = sdf.writeStream.format('memory').queryName('this_query').start()
>>> sqm = spark.streams
>>> # get the list of active streaming queries
>>> [q.name for q in sqm.active]
['this_query']
>>> sq.stop()
"""
return [StreamingQuery(jsq) for jsq in self._jsqm.active()]
[docs] def get(self, id):
"""Returns an active query from this SQLContext or throws exception if an active query
with this name doesn't exist.
.. versionadded:: 2.0.0
Examples
--------
>>> sq = sdf.writeStream.format('memory').queryName('this_query').start()
>>> sq.name
'this_query'
>>> sq = spark.streams.get(sq.id)
>>> sq.isActive
True
>>> sq = sqlContext.streams.get(sq.id)
>>> sq.isActive
True
>>> sq.stop()
"""
return StreamingQuery(self._jsqm.get(id))
[docs] @since(2.0)
def awaitAnyTermination(self, timeout=None):
"""Wait until any of the queries on the associated SQLContext has terminated since the
creation of the context, or since :func:`resetTerminated()` was called. If any query was
terminated with an exception, then the exception will be thrown.
If `timeout` is set, it returns whether the query has terminated or not within the
`timeout` seconds.
If a query has terminated, then subsequent calls to :func:`awaitAnyTermination()` will
either return immediately (if the query was terminated by :func:`query.stop()`),
or throw the exception immediately (if the query was terminated with exception). Use
:func:`resetTerminated()` to clear past terminations and wait for new terminations.
In the case where multiple queries have terminated since :func:`resetTermination()`
was called, if any query has terminated with exception, then :func:`awaitAnyTermination()`
will throw any of the exception. For correctly documenting exceptions across multiple
queries, users need to stop all of them after any of them terminates with exception, and
then check the `query.exception()` for each query.
throws :class:`StreamingQueryException`, if `this` query has terminated with an exception
"""
if timeout is not None:
if not isinstance(timeout, (int, float)) or timeout < 0:
raise ValueError("timeout must be a positive integer or float. Got %s" % timeout)
return self._jsqm.awaitAnyTermination(int(timeout * 1000))
else:
return self._jsqm.awaitAnyTermination()
[docs] def resetTerminated(self):
"""Forget about past terminated queries so that :func:`awaitAnyTermination()` can be used
again to wait for new terminations.
.. versionadded:: 2.0.0
Examples
--------
>>> spark.streams.resetTerminated()
"""
self._jsqm.resetTerminated()
[docs]class DataStreamReader(OptionUtils):
"""
Interface used to load a streaming :class:`DataFrame <pyspark.sql.DataFrame>` from external
storage systems (e.g. file systems, key-value stores, etc).
Use :attr:`SparkSession.readStream <pyspark.sql.SparkSession.readStream>` to access this.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
def __init__(self, spark):
self._jreader = spark._ssql_ctx.readStream()
self._spark = spark
def _df(self, jdf):
from pyspark.sql.dataframe import DataFrame
return DataFrame(jdf, self._spark)
[docs] def schema(self, schema):
"""Specifies the input schema.
Some data sources (e.g. JSON) can infer the input schema automatically from data.
By specifying the schema here, the underlying data source can skip the schema
inference step, and thus speed up data loading.
.. versionadded:: 2.0.0
Parameters
----------
schema : :class:`pyspark.sql.types.StructType` or str
a :class:`pyspark.sql.types.StructType` object or a DDL-formatted string
(For example ``col0 INT, col1 DOUBLE``).
Notes
-----
This API is evolving.
Examples
--------
>>> s = spark.readStream.schema(sdf_schema)
>>> s = spark.readStream.schema("col0 INT, col1 DOUBLE")
"""
from pyspark.sql import SparkSession
spark = SparkSession.builder.getOrCreate()
if isinstance(schema, StructType):
jschema = spark._jsparkSession.parseDataType(schema.json())
self._jreader = self._jreader.schema(jschema)
elif isinstance(schema, str):
self._jreader = self._jreader.schema(schema)
else:
raise TypeError("schema should be StructType or string")
return self
[docs] def option(self, key, value):
"""Adds an input option for the underlying data source.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
Examples
--------
>>> s = spark.readStream.option("x", 1)
"""
self._jreader = self._jreader.option(key, to_str(value))
return self
[docs] def options(self, **options):
"""Adds input options for the underlying data source.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
Examples
--------
>>> s = spark.readStream.options(x="1", y=2)
"""
for k in options:
self._jreader = self._jreader.option(k, to_str(options[k]))
return self
[docs] def load(self, path=None, format=None, schema=None, **options):
"""Loads a data stream from a data source and returns it as a
:class:`DataFrame <pyspark.sql.DataFrame>`.
.. versionadded:: 2.0.0
Parameters
----------
path : str, optional
optional string for file-system backed data sources.
format : str, optional
optional string for format of the data source. Default to 'parquet'.
schema : :class:`pyspark.sql.types.StructType` or str, optional
optional :class:`pyspark.sql.types.StructType` for the input schema
or a DDL-formatted string (For example ``col0 INT, col1 DOUBLE``).
**options : dict
all other string options
Notes
-----
This API is evolving.
Examples
--------
>>> json_sdf = spark.readStream.format("json") \\
... .schema(sdf_schema) \\
... .load(tempfile.mkdtemp())
>>> json_sdf.isStreaming
True
>>> json_sdf.schema == sdf_schema
True
"""
if format is not None:
self.format(format)
if schema is not None:
self.schema(schema)
self.options(**options)
if path is not None:
if type(path) != str or len(path.strip()) == 0:
raise ValueError("If the path is provided for stream, it needs to be a " +
"non-empty string. List of paths are not supported.")
return self._df(self._jreader.load(path))
else:
return self._df(self._jreader.load())
[docs] def json(self, path, schema=None, primitivesAsString=None, prefersDecimal=None,
allowComments=None, allowUnquotedFieldNames=None, allowSingleQuotes=None,
allowNumericLeadingZero=None, allowBackslashEscapingAnyCharacter=None,
mode=None, columnNameOfCorruptRecord=None, dateFormat=None, timestampFormat=None,
multiLine=None, allowUnquotedControlChars=None, lineSep=None, locale=None,
dropFieldIfAllNull=None, encoding=None, pathGlobFilter=None,
recursiveFileLookup=None, allowNonNumericNumbers=None):
"""
Loads a JSON file stream and returns the results as a :class:`DataFrame`.
`JSON Lines <http://jsonlines.org/>`_ (newline-delimited JSON) is supported by default.
For JSON (one record per file), set the ``multiLine`` parameter to ``true``.
If the ``schema`` parameter is not specified, this function goes
through the input once to determine the input schema.
.. versionadded:: 2.0.0
Parameters
----------
path : str
string represents path to the JSON dataset,
or RDD of Strings storing JSON objects.
schema : :class:`pyspark.sql.types.StructType` or str, optional
an optional :class:`pyspark.sql.types.StructType` for the input schema
or a DDL-formatted string (For example ``col0 INT, col1 DOUBLE``).
Other Parameters
----------------
Extra options
For the extra options, refer to
`Data Source Option <https://spark.apache.org/docs/latest/sql-data-sources-json.html#data-source-option>`_
in the version you use.
.. # noqa
Notes
-----
This API is evolving.
Examples
--------
>>> json_sdf = spark.readStream.json(tempfile.mkdtemp(), schema = sdf_schema)
>>> json_sdf.isStreaming
True
>>> json_sdf.schema == sdf_schema
True
"""
self._set_opts(
schema=schema, primitivesAsString=primitivesAsString, prefersDecimal=prefersDecimal,
allowComments=allowComments, allowUnquotedFieldNames=allowUnquotedFieldNames,
allowSingleQuotes=allowSingleQuotes, allowNumericLeadingZero=allowNumericLeadingZero,
allowBackslashEscapingAnyCharacter=allowBackslashEscapingAnyCharacter,
mode=mode, columnNameOfCorruptRecord=columnNameOfCorruptRecord, dateFormat=dateFormat,
timestampFormat=timestampFormat, multiLine=multiLine,
allowUnquotedControlChars=allowUnquotedControlChars, lineSep=lineSep, locale=locale,
dropFieldIfAllNull=dropFieldIfAllNull, encoding=encoding,
pathGlobFilter=pathGlobFilter, recursiveFileLookup=recursiveFileLookup,
allowNonNumericNumbers=allowNonNumericNumbers)
if isinstance(path, str):
return self._df(self._jreader.json(path))
else:
raise TypeError("path can be only a single string")
[docs] def orc(self, path, mergeSchema=None, pathGlobFilter=None, recursiveFileLookup=None):
"""Loads a ORC file stream, returning the result as a :class:`DataFrame`.
.. versionadded:: 2.3.0
Other Parameters
----------------
Extra options
For the extra options, refer to
`Data Source Option <https://spark.apache.org/docs/latest/sql-data-sources-orc.html#data-source-option>`_
in the version you use.
.. # noqa
Examples
--------
>>> orc_sdf = spark.readStream.schema(sdf_schema).orc(tempfile.mkdtemp())
>>> orc_sdf.isStreaming
True
>>> orc_sdf.schema == sdf_schema
True
"""
self._set_opts(mergeSchema=mergeSchema, pathGlobFilter=pathGlobFilter,
recursiveFileLookup=recursiveFileLookup)
if isinstance(path, str):
return self._df(self._jreader.orc(path))
else:
raise TypeError("path can be only a single string")
[docs] def parquet(self, path, mergeSchema=None, pathGlobFilter=None, recursiveFileLookup=None,
datetimeRebaseMode=None, int96RebaseMode=None):
"""
Loads a Parquet file stream, returning the result as a :class:`DataFrame`.
.. versionadded:: 2.0.0
Parameters
----------
path : str
the path in any Hadoop supported file system
Other Parameters
----------------
Extra options
For the extra options, refer to
`Data Source Option <https://spark.apache.org/docs/latest/sql-data-sources-parquet.html#data-source-option>`_.
in the version you use.
.. # noqa
Examples
--------
>>> parquet_sdf = spark.readStream.schema(sdf_schema).parquet(tempfile.mkdtemp())
>>> parquet_sdf.isStreaming
True
>>> parquet_sdf.schema == sdf_schema
True
"""
self._set_opts(mergeSchema=mergeSchema, pathGlobFilter=pathGlobFilter,
recursiveFileLookup=recursiveFileLookup,
datetimeRebaseMode=datetimeRebaseMode, int96RebaseMode=int96RebaseMode)
if isinstance(path, str):
return self._df(self._jreader.parquet(path))
else:
raise TypeError("path can be only a single string")
[docs] def text(self, path, wholetext=False, lineSep=None, pathGlobFilter=None,
recursiveFileLookup=None):
"""
Loads a text file stream and returns a :class:`DataFrame` whose schema starts with a
string column named "value", and followed by partitioned columns if there
are any.
The text files must be encoded as UTF-8.
By default, each line in the text file is a new row in the resulting DataFrame.
.. versionadded:: 2.0.0
Parameters
----------
paths : str or list
string, or list of strings, for input path(s).
Other Parameters
----------------
Extra options
For the extra options, refer to
`Data Source Option <https://spark.apache.org/docs/latest/sql-data-sources-text.html#data-source-option>`_
in the version you use.
.. # noqa
Notes
-----
This API is evolving.
Examples
--------
>>> text_sdf = spark.readStream.text(tempfile.mkdtemp())
>>> text_sdf.isStreaming
True
>>> "value" in str(text_sdf.schema)
True
"""
self._set_opts(
wholetext=wholetext, lineSep=lineSep, pathGlobFilter=pathGlobFilter,
recursiveFileLookup=recursiveFileLookup)
if isinstance(path, str):
return self._df(self._jreader.text(path))
else:
raise TypeError("path can be only a single string")
[docs] def csv(self, path, schema=None, sep=None, encoding=None, quote=None, escape=None,
comment=None, header=None, inferSchema=None, ignoreLeadingWhiteSpace=None,
ignoreTrailingWhiteSpace=None, nullValue=None, nanValue=None, positiveInf=None,
negativeInf=None, dateFormat=None, timestampFormat=None, maxColumns=None,
maxCharsPerColumn=None, maxMalformedLogPerPartition=None, mode=None,
columnNameOfCorruptRecord=None, multiLine=None, charToEscapeQuoteEscaping=None,
enforceSchema=None, emptyValue=None, locale=None, lineSep=None,
pathGlobFilter=None, recursiveFileLookup=None, unescapedQuoteHandling=None):
r"""Loads a CSV file stream and returns the result as a :class:`DataFrame`.
This function will go through the input once to determine the input schema if
``inferSchema`` is enabled. To avoid going through the entire data once, disable
``inferSchema`` option or specify the schema explicitly using ``schema``.
Parameters
----------
path : str or list
string, or list of strings, for input path(s).
schema : :class:`pyspark.sql.types.StructType` or str, optional
an optional :class:`pyspark.sql.types.StructType` for the input schema
or a DDL-formatted string (For example ``col0 INT, col1 DOUBLE``).
.. versionadded:: 2.0.0
Other Parameters
----------------
Extra options
For the extra options, refer to
`Data Source Option <https://spark.apache.org/docs/latest/sql-data-sources-csv.html#data-source-option>`_
in the version you use.
.. # noqa
Notes
-----
This API is evolving.
Examples
--------
>>> csv_sdf = spark.readStream.csv(tempfile.mkdtemp(), schema = sdf_schema)
>>> csv_sdf.isStreaming
True
>>> csv_sdf.schema == sdf_schema
True
"""
self._set_opts(
schema=schema, sep=sep, encoding=encoding, quote=quote, escape=escape, comment=comment,
header=header, inferSchema=inferSchema, ignoreLeadingWhiteSpace=ignoreLeadingWhiteSpace,
ignoreTrailingWhiteSpace=ignoreTrailingWhiteSpace, nullValue=nullValue,
nanValue=nanValue, positiveInf=positiveInf, negativeInf=negativeInf,
dateFormat=dateFormat, timestampFormat=timestampFormat, maxColumns=maxColumns,
maxCharsPerColumn=maxCharsPerColumn,
maxMalformedLogPerPartition=maxMalformedLogPerPartition, mode=mode,
columnNameOfCorruptRecord=columnNameOfCorruptRecord, multiLine=multiLine,
charToEscapeQuoteEscaping=charToEscapeQuoteEscaping, enforceSchema=enforceSchema,
emptyValue=emptyValue, locale=locale, lineSep=lineSep,
pathGlobFilter=pathGlobFilter, recursiveFileLookup=recursiveFileLookup,
unescapedQuoteHandling=unescapedQuoteHandling)
if isinstance(path, str):
return self._df(self._jreader.csv(path))
else:
raise TypeError("path can be only a single string")
def table(self, tableName):
"""Define a Streaming DataFrame on a Table. The DataSource corresponding to the table should
support streaming mode.
.. versionadded:: 3.1.0
Parameters
----------
tableName : str
string, for the name of the table.
Returns
--------
:class:`DataFrame`
Notes
-----
This API is evolving.
Examples
--------
>>> spark.readStream.table('input_table') # doctest: +SKIP
"""
if isinstance(tableName, str):
return self._df(self._jreader.table(tableName))
else:
raise TypeError("tableName can be only a single string")
[docs]class DataStreamWriter(object):
"""
Interface used to write a streaming :class:`DataFrame <pyspark.sql.DataFrame>` to external
storage systems (e.g. file systems, key-value stores, etc).
Use :attr:`DataFrame.writeStream <pyspark.sql.DataFrame.writeStream>`
to access this.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
def __init__(self, df):
self._df = df
self._spark = df.sql_ctx
self._jwrite = df._jdf.writeStream()
def _sq(self, jsq):
from pyspark.sql.streaming import StreamingQuery
return StreamingQuery(jsq)
[docs] def outputMode(self, outputMode):
"""Specifies how data of a streaming DataFrame/Dataset is written to a streaming sink.
.. versionadded:: 2.0.0
Options include:
* `append`: Only the new rows in the streaming DataFrame/Dataset will be written to
the sink
* `complete`: All the rows in the streaming DataFrame/Dataset will be written to the sink
every time these are some updates
* `update`: only the rows that were updated in the streaming DataFrame/Dataset will be
written to the sink every time there are some updates. If the query doesn't contain
aggregations, it will be equivalent to `append` mode.
Notes
-----
This API is evolving.
Examples
--------
>>> writer = sdf.writeStream.outputMode('append')
"""
if not outputMode or type(outputMode) != str or len(outputMode.strip()) == 0:
raise ValueError('The output mode must be a non-empty string. Got: %s' % outputMode)
self._jwrite = self._jwrite.outputMode(outputMode)
return self
[docs] def option(self, key, value):
"""Adds an output option for the underlying data source.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
self._jwrite = self._jwrite.option(key, to_str(value))
return self
[docs] def options(self, **options):
"""Adds output options for the underlying data source.
.. versionadded:: 2.0.0
Notes
-----
This API is evolving.
"""
for k in options:
self._jwrite = self._jwrite.option(k, to_str(options[k]))
return self
[docs] def partitionBy(self, *cols):
"""Partitions the output by the given columns on the file system.
If specified, the output is laid out on the file system similar
to Hive's partitioning scheme.
.. versionadded:: 2.0.0
Parameters
----------
cols : str or list
name of columns
Notes
-----
This API is evolving.
"""
if len(cols) == 1 and isinstance(cols[0], (list, tuple)):
cols = cols[0]
self._jwrite = self._jwrite.partitionBy(_to_seq(self._spark._sc, cols))
return self
[docs] def queryName(self, queryName):
"""Specifies the name of the :class:`StreamingQuery` that can be started with
:func:`start`. This name must be unique among all the currently active queries
in the associated SparkSession.
.. versionadded:: 2.0.0
Parameters
----------
queryName : str
unique name for the query
Notes
-----
This API is evolving.
Examples
--------
>>> writer = sdf.writeStream.queryName('streaming_query')
"""
if not queryName or type(queryName) != str or len(queryName.strip()) == 0:
raise ValueError('The queryName must be a non-empty string. Got: %s' % queryName)
self._jwrite = self._jwrite.queryName(queryName)
return self
[docs] @keyword_only
def trigger(self, *, processingTime=None, once=None, continuous=None):
"""Set the trigger for the stream query. If this is not set it will run the query as fast
as possible, which is equivalent to setting the trigger to ``processingTime='0 seconds'``.
.. versionadded:: 2.0.0
Parameters
----------
processingTime : str, optional
a processing time interval as a string, e.g. '5 seconds', '1 minute'.
Set a trigger that runs a microbatch query periodically based on the
processing time. Only one trigger can be set.
once : bool, optional
if set to True, set a trigger that processes only one batch of data in a
streaming query then terminates the query. Only one trigger can be set.
continuous : str, optional
a time interval as a string, e.g. '5 seconds', '1 minute'.
Set a trigger that runs a continuous query with a given checkpoint
interval. Only one trigger can be set.
Notes
-----
This API is evolving.
Examples
--------
>>> # trigger the query for execution every 5 seconds
>>> writer = sdf.writeStream.trigger(processingTime='5 seconds')
>>> # trigger the query for just once batch of data
>>> writer = sdf.writeStream.trigger(once=True)
>>> # trigger the query for execution every 5 seconds
>>> writer = sdf.writeStream.trigger(continuous='5 seconds')
"""
params = [processingTime, once, continuous]
if params.count(None) == 3:
raise ValueError('No trigger provided')
elif params.count(None) < 2:
raise ValueError('Multiple triggers not allowed.')
jTrigger = None
if processingTime is not None:
if type(processingTime) != str or len(processingTime.strip()) == 0:
raise ValueError('Value for processingTime must be a non empty string. Got: %s' %
processingTime)
interval = processingTime.strip()
jTrigger = self._spark._sc._jvm.org.apache.spark.sql.streaming.Trigger.ProcessingTime(
interval)
elif once is not None:
if once is not True:
raise ValueError('Value for once must be True. Got: %s' % once)
jTrigger = self._spark._sc._jvm.org.apache.spark.sql.streaming.Trigger.Once()
else:
if type(continuous) != str or len(continuous.strip()) == 0:
raise ValueError('Value for continuous must be a non empty string. Got: %s' %
continuous)
interval = continuous.strip()
jTrigger = self._spark._sc._jvm.org.apache.spark.sql.streaming.Trigger.Continuous(
interval)
self._jwrite = self._jwrite.trigger(jTrigger)
return self
[docs] def foreach(self, f):
"""
Sets the output of the streaming query to be processed using the provided writer ``f``.
This is often used to write the output of a streaming query to arbitrary storage systems.
The processing logic can be specified in two ways.
#. A **function** that takes a row as input.
This is a simple way to express your processing logic. Note that this does
not allow you to deduplicate generated data when failures cause reprocessing of
some input data. That would require you to specify the processing logic in the next
way.
#. An **object** with a ``process`` method and optional ``open`` and ``close`` methods.
The object can have the following methods.
* ``open(partition_id, epoch_id)``: *Optional* method that initializes the processing
(for example, open a connection, start a transaction, etc). Additionally, you can
use the `partition_id` and `epoch_id` to deduplicate regenerated data
(discussed later).
* ``process(row)``: *Non-optional* method that processes each :class:`Row`.
* ``close(error)``: *Optional* method that finalizes and cleans up (for example,
close connection, commit transaction, etc.) after all rows have been processed.
The object will be used by Spark in the following way.
* A single copy of this object is responsible of all the data generated by a
single task in a query. In other words, one instance is responsible for
processing one partition of the data generated in a distributed manner.
* This object must be serializable because each task will get a fresh
serialized-deserialized copy of the provided object. Hence, it is strongly
recommended that any initialization for writing data (e.g. opening a
connection or starting a transaction) is done after the `open(...)`
method has been called, which signifies that the task is ready to generate data.
* The lifecycle of the methods are as follows.
For each partition with ``partition_id``:
... For each batch/epoch of streaming data with ``epoch_id``:
....... Method ``open(partitionId, epochId)`` is called.
....... If ``open(...)`` returns true, for each row in the partition and
batch/epoch, method ``process(row)`` is called.
....... Method ``close(errorOrNull)`` is called with error (if any) seen while
processing rows.
Important points to note:
* The `partitionId` and `epochId` can be used to deduplicate generated data when
failures cause reprocessing of some input data. This depends on the execution
mode of the query. If the streaming query is being executed in the micro-batch
mode, then every partition represented by a unique tuple (partition_id, epoch_id)
is guaranteed to have the same data. Hence, (partition_id, epoch_id) can be used
to deduplicate and/or transactionally commit data and achieve exactly-once
guarantees. However, if the streaming query is being executed in the continuous
mode, then this guarantee does not hold and therefore should not be used for
deduplication.
* The ``close()`` method (if exists) will be called if `open()` method exists and
returns successfully (irrespective of the return value), except if the Python
crashes in the middle.
.. versionadded:: 2.4.0
Notes
-----
This API is evolving.
Examples
--------
>>> # Print every row using a function
>>> def print_row(row):
... print(row)
...
>>> writer = sdf.writeStream.foreach(print_row)
>>> # Print every row using a object with process() method
>>> class RowPrinter:
... def open(self, partition_id, epoch_id):
... print("Opened %d, %d" % (partition_id, epoch_id))
... return True
... def process(self, row):
... print(row)
... def close(self, error):
... print("Closed with error: %s" % str(error))
...
>>> writer = sdf.writeStream.foreach(RowPrinter())
"""
from pyspark.rdd import _wrap_function
from pyspark.serializers import PickleSerializer, AutoBatchedSerializer
from pyspark.taskcontext import TaskContext
if callable(f):
# The provided object is a callable function that is supposed to be called on each row.
# Construct a function that takes an iterator and calls the provided function on each
# row.
def func_without_process(_, iterator):
for x in iterator:
f(x)
return iter([])
func = func_without_process
else:
# The provided object is not a callable function. Then it is expected to have a
# 'process(row)' method, and optional 'open(partition_id, epoch_id)' and
# 'close(error)' methods.
if not hasattr(f, 'process'):
raise AttributeError("Provided object does not have a 'process' method")
if not callable(getattr(f, 'process')):
raise TypeError("Attribute 'process' in provided object is not callable")
def doesMethodExist(method_name):
exists = hasattr(f, method_name)
if exists and not callable(getattr(f, method_name)):
raise TypeError(
"Attribute '%s' in provided object is not callable" % method_name)
return exists
open_exists = doesMethodExist('open')
close_exists = doesMethodExist('close')
def func_with_open_process_close(partition_id, iterator):
epoch_id = TaskContext.get().getLocalProperty('streaming.sql.batchId')
if epoch_id:
epoch_id = int(epoch_id)
else:
raise RuntimeError("Could not get batch id from TaskContext")
# Check if the data should be processed
should_process = True
if open_exists:
should_process = f.open(partition_id, epoch_id)
error = None
try:
if should_process:
for x in iterator:
f.process(x)
except Exception as ex:
error = ex
finally:
if close_exists:
f.close(error)
if error:
raise error
return iter([])
func = func_with_open_process_close
serializer = AutoBatchedSerializer(PickleSerializer())
wrapped_func = _wrap_function(self._spark._sc, func, serializer, serializer)
jForeachWriter = \
self._spark._sc._jvm.org.apache.spark.sql.execution.python.PythonForeachWriter(
wrapped_func, self._df._jdf.schema())
self._jwrite.foreach(jForeachWriter)
return self
[docs] def foreachBatch(self, func):
"""
Sets the output of the streaming query to be processed using the provided
function. This is supported only the in the micro-batch execution modes (that is, when the
trigger is not continuous). In every micro-batch, the provided function will be called in
every micro-batch with (i) the output rows as a DataFrame and (ii) the batch identifier.
The batchId can be used deduplicate and transactionally write the output
(that is, the provided Dataset) to external systems. The output DataFrame is guaranteed
to exactly same for the same batchId (assuming all operations are deterministic in the
query).
.. versionadded:: 2.4.0
Notes
-----
This API is evolving.
Examples
--------
>>> def func(batch_df, batch_id):
... batch_df.collect()
...
>>> writer = sdf.writeStream.foreachBatch(func)
"""
from pyspark.java_gateway import ensure_callback_server_started
gw = self._spark._sc._gateway
java_import(gw.jvm, "org.apache.spark.sql.execution.streaming.sources.*")
wrapped_func = ForeachBatchFunction(self._spark, func)
gw.jvm.PythonForeachBatchHelper.callForeachBatch(self._jwrite, wrapped_func)
ensure_callback_server_started(gw)
return self
[docs] def start(self, path=None, format=None, outputMode=None, partitionBy=None, queryName=None,
**options):
"""Streams the contents of the :class:`DataFrame` to a data source.
The data source is specified by the ``format`` and a set of ``options``.
If ``format`` is not specified, the default data source configured by
``spark.sql.sources.default`` will be used.
.. versionadded:: 2.0.0
Parameters
----------
path : str, optional
the path in a Hadoop supported file system
format : str, optional
the format used to save
outputMode : str, optional
specifies how data of a streaming DataFrame/Dataset is written to a
streaming sink.
* `append`: Only the new rows in the streaming DataFrame/Dataset will be written to the
sink
* `complete`: All the rows in the streaming DataFrame/Dataset will be written to the
sink every time these are some updates
* `update`: only the rows that were updated in the streaming DataFrame/Dataset will be
written to the sink every time there are some updates. If the query doesn't contain
aggregations, it will be equivalent to `append` mode.
partitionBy : str or list, optional
names of partitioning columns
queryName : str, optional
unique name for the query
**options : dict
All other string options. You may want to provide a `checkpointLocation`
for most streams, however it is not required for a `memory` stream.
Notes
-----
This API is evolving.
Examples
--------
>>> sq = sdf.writeStream.format('memory').queryName('this_query').start()
>>> sq.isActive
True
>>> sq.name
'this_query'
>>> sq.stop()
>>> sq.isActive
False
>>> sq = sdf.writeStream.trigger(processingTime='5 seconds').start(
... queryName='that_query', outputMode="append", format='memory')
>>> sq.name
'that_query'
>>> sq.isActive
True
>>> sq.stop()
"""
self.options(**options)
if outputMode is not None:
self.outputMode(outputMode)
if partitionBy is not None:
self.partitionBy(partitionBy)
if format is not None:
self.format(format)
if queryName is not None:
self.queryName(queryName)
if path is None:
return self._sq(self._jwrite.start())
else:
return self._sq(self._jwrite.start(path))
def toTable(self, tableName, format=None, outputMode=None, partitionBy=None, queryName=None,
**options):
"""
Starts the execution of the streaming query, which will continually output results to the
given table as new data arrives.
The returned :class:`StreamingQuery` object can be used to interact with the stream.
.. versionadded:: 3.1.0
Parameters
----------
tableName : str
string, for the name of the table.
format : str, optional
the format used to save.
outputMode : str, optional
specifies how data of a streaming DataFrame/Dataset is written to a
streaming sink.
* `append`: Only the new rows in the streaming DataFrame/Dataset will be written to the
sink
* `complete`: All the rows in the streaming DataFrame/Dataset will be written to the
sink every time these are some updates
* `update`: only the rows that were updated in the streaming DataFrame/Dataset will be
written to the sink every time there are some updates. If the query doesn't contain
aggregations, it will be equivalent to `append` mode.
partitionBy : str or list, optional
names of partitioning columns
queryName : str, optional
unique name for the query
**options : dict
All other string options. You may want to provide a `checkpointLocation`.
Notes
-----
This API is evolving.
For v1 table, partitioning columns provided by `partitionBy` will be respected no matter
the table exists or not. A new table will be created if the table not exists.
For v2 table, `partitionBy` will be ignored if the table already exists. `partitionBy` will
be respected only if the v2 table does not exist. Besides, the v2 table created by this API
lacks some functionalities (e.g., customized properties, options, and serde info). If you
need them, please create the v2 table manually before the execution to avoid creating a
table with incomplete information.
Examples
--------
>>> sdf.writeStream.format('parquet').queryName('query').toTable('output_table')
... # doctest: +SKIP
>>> sdf.writeStream.trigger(processingTime='5 seconds').toTable(
... 'output_table',
... queryName='that_query',
... outputMode="append",
... format='parquet',
... checkpointLocation='/tmp/checkpoint') # doctest: +SKIP
"""
self.options(**options)
if outputMode is not None:
self.outputMode(outputMode)
if partitionBy is not None:
self.partitionBy(partitionBy)
if format is not None:
self.format(format)
if queryName is not None:
self.queryName(queryName)
return self._sq(self._jwrite.toTable(tableName))
def _test():
import doctest
import os
import tempfile
from pyspark.sql import SparkSession, SQLContext
import pyspark.sql.streaming
os.chdir(os.environ["SPARK_HOME"])
globs = pyspark.sql.streaming.__dict__.copy()
try:
spark = SparkSession.builder.getOrCreate()
except py4j.protocol.Py4JError: # noqa: F821
spark = SparkSession(sc) # noqa: F821
globs['tempfile'] = tempfile
globs['os'] = os
globs['spark'] = spark
globs['sqlContext'] = SQLContext.getOrCreate(spark.sparkContext)
globs['sdf'] = \
spark.readStream.format('text').load('python/test_support/sql/streaming')
globs['sdf_schema'] = StructType([StructField("data", StringType(), True)])
globs['df'] = \
globs['spark'].readStream.format('text').load('python/test_support/sql/streaming')
(failure_count, test_count) = doctest.testmod(
pyspark.sql.streaming, globs=globs,
optionflags=doctest.ELLIPSIS | doctest.NORMALIZE_WHITESPACE | doctest.REPORT_NDIFF)
globs['spark'].stop()
if failure_count:
sys.exit(-1)
if __name__ == "__main__":
_test()