Fix bug where data_async_generation.py would freeze. (#4989)

The data_async_generation.py process would print to stderr, but the main process would redirect it's stderr to a pipe. The main process never read from the pipe, so when the pipe was full, data_async_generation.py would stall on a write to stderr. This change makes data_async_generation.py not write to stdout/stderr.

official/recommendation/data_async_generation.py

@@ -23,7 +23,6 @@ import contextlib
 import datetime
 import gc
 import functools
-import logging
 import multiprocessing
 import json
 import os
@@ -40,7 +39,6 @@ import numpy as np
 import tensorflow as tf
 
 from absl import app as absl_app
-from absl import logging as absl_logging
 from absl import flags
 
 from official.datasets import movielens
@@ -48,15 +46,18 @@ from official.recommendation import constants as rconst
 from official.recommendation import stat_utils
 
 
+_log_file = None
+
+
 def log_msg(msg):
   """Include timestamp info when logging messages to a file."""
   if flags.FLAGS.redirect_logs:
     timestamp = datetime.datetime.now().strftime("%Y-%m-%dT%H:%M:%S")
-    absl_logging.info("[{}] {}".format(timestamp, msg))
+    print("[{}] {}".format(timestamp, msg), file=_log_file)
   else:
-    absl_logging.info(msg)
-  sys.stdout.flush()
-  sys.stderr.flush()
+    print(msg, file=_log_file)
+  if _log_file:
+    _log_file.flush()
 
 
 def get_cycle_folder_name(i):
@@ -395,61 +396,54 @@ def _generation_loop(
 
 
 def main(_):
+  global _log_file
   redirect_logs = flags.FLAGS.redirect_logs
   cache_paths = rconst.Paths(
       data_dir=flags.FLAGS.data_dir, cache_id=flags.FLAGS.cache_id)
 
 
   log_file_name = "data_gen_proc_{}.log".format(cache_paths.cache_id)
-  log_file = os.path.join(cache_paths.data_dir, log_file_name)
-  if log_file.startswith("gs://") and redirect_logs:
+  log_path = os.path.join(cache_paths.data_dir, log_file_name)
+  if log_path.startswith("gs://") and redirect_logs:
     fallback_log_file = os.path.join(tempfile.gettempdir(), log_file_name)
     print("Unable to log to {}. Falling back to {}"
-          .format(log_file, fallback_log_file))
-    log_file = fallback_log_file
+          .format(log_path, fallback_log_file))
+    log_path = fallback_log_file
 
   # This server is generally run in a subprocess.
   if redirect_logs:
-    print("Redirecting stdout and stderr to {}".format(log_file))
-    log_stream = open(log_file, "wt")  # Note: not tf.gfile.Open().
-    stdout = log_stream
-    stderr = log_stream
+    print("Redirecting output of data_async_generation.py process to {}"
+          .format(log_path))
+    _log_file = open(log_path, "wt")  # Note: not tf.gfile.Open().
   try:
-    if redirect_logs:
-      absl_logging.get_absl_logger().addHandler(
-          hdlr=logging.StreamHandler(stream=stdout))
-      sys.stdout = stdout
-      sys.stderr = stderr
-      print("Logs redirected.")
-    try:
-      log_msg("sys.argv: {}".format(" ".join(sys.argv)))
-
-      if flags.FLAGS.seed is not None:
-        np.random.seed(flags.FLAGS.seed)
-
-      _generation_loop(
-          num_workers=flags.FLAGS.num_workers,
-          cache_paths=cache_paths,
-          num_readers=flags.FLAGS.num_readers,
-          num_neg=flags.FLAGS.num_neg,
-          num_train_positives=flags.FLAGS.num_train_positives,
-          num_items=flags.FLAGS.num_items,
-          spillover=flags.FLAGS.spillover,
-          epochs_per_cycle=flags.FLAGS.epochs_per_cycle,
-          train_batch_size=flags.FLAGS.train_batch_size,
-          eval_batch_size=flags.FLAGS.eval_batch_size,
-      )
-    except KeyboardInterrupt:
-      log_msg("KeyboardInterrupt registered.")
-    except:
-      traceback.print_exc()
-      raise
+    log_msg("sys.argv: {}".format(" ".join(sys.argv)))
+
+    if flags.FLAGS.seed is not None:
+      np.random.seed(flags.FLAGS.seed)
+
+    _generation_loop(
+        num_workers=flags.FLAGS.num_workers,
+        cache_paths=cache_paths,
+        num_readers=flags.FLAGS.num_readers,
+        num_neg=flags.FLAGS.num_neg,
+        num_train_positives=flags.FLAGS.num_train_positives,
+        num_items=flags.FLAGS.num_items,
+        spillover=flags.FLAGS.spillover,
+        epochs_per_cycle=flags.FLAGS.epochs_per_cycle,
+        train_batch_size=flags.FLAGS.train_batch_size,
+        eval_batch_size=flags.FLAGS.eval_batch_size,
+    )
+  except KeyboardInterrupt:
+    log_msg("KeyboardInterrupt registered.")
+  except:
+    traceback.print_exc(file=_log_file)
+    raise
   finally:
     log_msg("Shutting down generation subprocess.")
     sys.stdout.flush()
     sys.stderr.flush()
     if redirect_logs:
-      log_stream.close()
+      _log_file.close()
 
 
 def define_flags():

official/recommendation/data_preprocessing.py

@@ -419,9 +419,7 @@ def instantiate_pipeline(dataset, data_dir, batch_size, eval_batch_size,
   tf.logging.info(
       "Generation subprocess command: {}".format(" ".join(subproc_args)))
 
-  proc = subprocess.Popen(args=subproc_args, stdin=subprocess.PIPE,
-                          stdout=subprocess.PIPE, stderr=subprocess.PIPE,
-                          shell=False, env=subproc_env)
+  proc = subprocess.Popen(args=subproc_args, shell=False, env=subproc_env)
 
   atexit.register(_shutdown, proc=proc)
   atexit.register(tf.gfile.DeleteRecursively,