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https://issues.apache.org/jira/browse/BEAM-8335?focusedWorklogId=397147&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-397147
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ASF GitHub Bot logged work on BEAM-8335:
----------------------------------------
Author: ASF GitHub Bot
Created on: 04/Mar/20 00:23
Start Date: 04/Mar/20 00:23
Worklog Time Spent: 10m
Work Description: robertwb commented on pull request #11005: [BEAM-8335]
Modify the StreamingCache to subclass the CacheManager
URL: https://github.com/apache/beam/pull/11005#discussion_r387373091
##########
File path:
sdks/python/apache_beam/runners/interactive/caching/streaming_cache.py
##########
@@ -19,15 +19,298 @@
from __future__ import absolute_import
+import itertools
+import os
+import shutil
+import tempfile
+import time
+
+import apache_beam as beam
+from apache_beam.portability.api.beam_interactive_api_pb2 import
TestStreamFileHeader
+from apache_beam.portability.api.beam_interactive_api_pb2 import
TestStreamFileRecord
from apache_beam.portability.api.beam_runner_api_pb2 import TestStreamPayload
+from apache_beam.runners.interactive.cache_manager import CacheManager
+from apache_beam.runners.interactive.cache_manager import
SafeFastPrimitivesCoder
+from apache_beam.testing.test_stream import ReverseTestStream
from apache_beam.utils import timestamp
-class StreamingCache(object):
+class StreamingCacheSink(beam.PTransform):
+ """A PTransform that writes TestStreamFile(Header|Records)s to file.
+
+ This transform takes in an arbitrary element stream and writes the
best-effort
+ list of TestStream events (as TestStreamFileRecords) to file.
+
+ Note that this PTransform is assumed to be only run on a single machine where
+ the following assumptions are correct: elements come in ordered, no two
+ transforms are writing to the same file. This PTransform is assumed to only
+ run correctly with the DirectRunner.
+ """
+ def __init__(
+ self,
+ cache_dir,
+ filename,
+ sample_resolution_sec,
+ coder=SafeFastPrimitivesCoder()):
+ self._cache_dir = cache_dir
+ self._filename = filename
+ self._sample_resolution_sec = sample_resolution_sec
+ self._coder = coder
+ self._path = os.path.join(self._cache_dir, self._filename)
+
+ @property
+ def path(self):
+ """Returns the path the sink leads to."""
+ return self._path
+
+ def expand(self, pcoll):
+ class StreamingWriteToText(beam.DoFn):
+ """DoFn that performs the writing.
+
+ Note that the other file writing methods cannot be used in streaming
+ contexts.
+ """
+ def __init__(self, full_path, coder=SafeFastPrimitivesCoder()):
+ self._full_path = full_path
+ self._coder = coder
+
+ # Try and make the given path.
+ os.makedirs(os.path.dirname(full_path), exist_ok=True)
+
+ def start_bundle(self):
+ # Open the file for 'append-mode' and writing 'bytes'.
+ self._fh = open(self._full_path, 'ab')
+
+ def finish_bundle(self):
+ self._fh.close()
+
+ def process(self, e):
+ """Appends the given element to the file.
+ """
+ self._fh.write(self._coder.encode(e))
+ self._fh.write(b'\n')
+
+ return (
+ pcoll
+ | ReverseTestStream(
+ output_tag=self._filename,
+ sample_resolution_sec=self._sample_resolution_sec,
+ output_format=ReverseTestStream.Format.
+ SERIALIZED_TEST_STREAM_FILE_RECORDS,
+ coder=self._coder)
+ | beam.ParDo(
+ StreamingWriteToText(full_path=self._path, coder=self._coder)))
+
+
+class StreamingCacheSource:
+ """A class that reads and parses TestStreamFile(Header|Reader)s.
+
+ This source operates in the following way:
+
+ 1. Wait for up to `timeout_secs` for the file to be available.
+ 2. Read, parse, and emit the entire contents of the file
+ 3. Wait for more events to come or until `is_cache_complete` returns True
+ 4. If there are more events, then go to 2
+ 5. Otherwise, stop emitting.
+
+ This class is used to read from file and send its to the TestStream via the
+ StreamingCacheManager.Reader.
+ """
+ def __init__(
+ self,
+ cache_dir,
+ labels,
+ is_cache_complete=None,
+ coder=SafeFastPrimitivesCoder()):
+ self._cache_dir = cache_dir
+ self._coder = coder
+ self._labels = labels
+ self._is_cache_complete = (
+ is_cache_complete if is_cache_complete else lambda: True)
+
+ def _wait_until_file_exists(self, timeout_secs=30):
+ """Blocks until the file exists for a maximum of timeout_secs.
+ """
+ f = None
+ now_secs = time.time()
+ timeout_timestamp_secs = now_secs + timeout_secs
+
+ # Wait for up to `timeout_secs` for the file to be available.
+ while f is None and now_secs < timeout_timestamp_secs:
+ now_secs = time.time()
+ try:
+ path = os.path.join(self._cache_dir, *self._labels)
+ f = open(path, mode='r')
+ except EnvironmentError as e:
+ # For Python2 and Python3 compatibility, this checks the
+ # EnvironmentError to see if the file exists.
+ # TODO: Change this to a FileNotFoundError when Python3 migration is
+ # complete.
+ import errno
+ if e.errno != errno.ENOENT:
+ # Raise the exception if it is not a FileNotFoundError.
+ raise
+ time.sleep(1)
+ if now_secs >= timeout_timestamp_secs:
+ raise RuntimeError(
+ "Timed out waiting for file '{}' to be available".format(path))
+ return f
+
+ def _emit_from_file(self, fh, tail):
+ """Emits the TestStreamFile(Header|Record)s from file.
+
+ This returns a generator to be able to read all lines from the given file.
+ If `tail` is True, then it will wait until the cache is complete to exit.
+ Otherwise, it will read the file only once.
+ """
+ # Always read at least once to read the whole file.
+ while True:
+ pos = fh.tell()
+ line = fh.readline()
+
+ # Check if we are at EOF.
+ if not line:
+ # Complete reading only when the cache is complete.
+ if self._is_cache_complete():
+ break
+
+ if not tail:
+ break
+
+ # Otherwise wait for new data in the file to be written.
+ time.sleep(0.5)
+ fh.seek(pos)
+ else:
+ # The first line at pos = 0 is always the header. Read the line without
+ # the new line.
+ if pos == 0:
+ header = TestStreamFileHeader()
+ header.ParseFromString(self._coder.decode(line[:-1]))
+ yield header
+ else:
+ record = TestStreamFileRecord()
+ record.ParseFromString(self._coder.decode(line[:-1]))
+ yield record
+
+ def read(self, tail):
+ """Reads all TestStreamFile(Header|TestStreamFileRecord)s from file.
+
+ This returns a generator to be able to read all lines from the given file.
+ If `tail` is True, then it will wait until the cache is complete to exit.
+ Otherwise, it will read the file only once.
+ """
+ with self._wait_until_file_exists() as f:
+ for e in self._emit_from_file(f, tail):
+ yield e
+
+
+class StreamingCache(CacheManager):
"""Abstraction that holds the logic for reading and writing to cache.
"""
- def __init__(self, readers):
- self._readers = readers
+ def __init__(
+ self, cache_dir, is_cache_complete=None, sample_resolution_sec=0.1):
+ self._sample_resolution_sec = sample_resolution_sec
+ self._is_cache_complete = is_cache_complete
+
+ if cache_dir:
+ self._cache_dir = cache_dir
+ else:
+ self._cache_dir = tempfile.mkdtemp(
+ prefix='interactive-temp-', dir=os.environ.get('TEST_TMPDIR', None))
+
+ # List of saved pcoders keyed by PCollection path. It is OK to keep this
+ # list in memory because once FileBasedCacheManager object is
+ # destroyed/re-created it loses the access to previously written cache
+ # objects anyways even if cache_dir already exists. In other words,
+ # it is not possible to resume execution of Beam pipeline from the
+ # saved cache if FileBasedCacheManager has been reset.
+ #
+ # However, if we are to implement better cache persistence, one needs
+ # to take care of keeping consistency between the cached PCollection
+ # and its PCoder type.
+ self._saved_pcoders = {}
+ self._default_pcoder = SafeFastPrimitivesCoder()
+
+ def exists(self, *labels):
+ path = os.path.join(self._cache_dir, *labels)
+ return os.path.exists(path)
+
+ # TODO(srohde): Modify this to return the correct version.
+ def read(self, *labels):
+ """Returns a generator to read all records from file.
+
+ Does not tail.
+ """
+ if not self.exists(*labels):
+ return [].__iter__(), -1
+
+ reader = StreamingCacheSource(
+ self._cache_dir, labels,
+ is_cache_complete=self._is_cache_complete).read(tail=False)
+ header = next(reader)
+ return StreamingCache.Reader([header], [reader]).read(), 1
+
+ def read_multiple(self, labels):
+ """Returns a generator to read all records from file.
+
+ Does tail until the cache is complete. This is because it is used in the
+ TestStreamServiceController to read from file which is only used during
+ pipeline runtime which needs to block.
+ """
+ readers = [
+ StreamingCacheSource(
+ self._cache_dir, l,
+ is_cache_complete=self._is_cache_complete).read(tail=True)
+ for l in labels
+ ]
+ headers = [next(r) for r in readers]
+ return StreamingCache.Reader(headers, readers).read()
+
+ def write(self, values, *labels):
+ """Writes the given values to cache.
+ """
+ to_write = [v.SerializeToString() for v in values]
Review comment:
Why is this not done in the loop below?
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Issue Time Tracking
-------------------
Worklog Id: (was: 397147)
Time Spent: 86h (was: 85h 50m)
> Add streaming support to Interactive Beam
> -----------------------------------------
>
> Key: BEAM-8335
> URL: https://issues.apache.org/jira/browse/BEAM-8335
> Project: Beam
> Issue Type: Improvement
> Components: runner-py-interactive
> Reporter: Sam Rohde
> Assignee: Sam Rohde
> Priority: Major
> Time Spent: 86h
> Remaining Estimate: 0h
>
> This issue tracks the work items to introduce streaming support to the
> Interactive Beam experience. This will allow users to:
> * Write and run a streaming job in IPython
> * Automatically cache records from unbounded sources
> * Add a replay experience that replays all cached records to simulate the
> original pipeline execution
> * Add controls to play/pause/stop/step individual elements from the cached
> records
> * Add ability to inspect/visualize unbounded PCollections
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