From 6cfe341ee89baa952929e91d33b9ecbca73a3ea0 Mon Sep 17 00:00:00 2001
From: Shixiong Zhu <shixiong@databricks.com>
Date: Tue, 5 Jan 2016 13:48:47 -0800
Subject: [SPARK-12511] [PYSPARK] [STREAMING] Make sure
 PythonDStream.registerSerializer is called only once

There is an issue that Py4J's PythonProxyHandler.finalize blocks forever. (https://github.com/bartdag/py4j/pull/184)

Py4j will create a PythonProxyHandler in Java for "transformer_serializer" when calling "registerSerializer". If we call "registerSerializer" twice, the second PythonProxyHandler will override the first one, then the first one will be GCed and trigger "PythonProxyHandler.finalize". To avoid that, we should not call"registerSerializer" more than once, so that "PythonProxyHandler" in Java side won't be GCed.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #10514 from zsxwing/SPARK-12511.
---
 python/pyspark/streaming/context.py                | 33 ++++++++++++++++------
 python/pyspark/streaming/util.py                   |  3 +-
 .../apache/spark/streaming/StreamingContext.scala  | 12 ++++++++
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/python/pyspark/streaming/context.py b/python/pyspark/streaming/context.py
index 3deed52be0..5cc4bbde39 100644
--- a/python/pyspark/streaming/context.py
+++ b/python/pyspark/streaming/context.py
@@ -98,8 +98,28 @@ class StreamingContext(object):
 
         # register serializer for TransformFunction
         # it happens before creating SparkContext when loading from checkpointing
-        cls._transformerSerializer = TransformFunctionSerializer(
-            SparkContext._active_spark_context, CloudPickleSerializer(), gw)
+        if cls._transformerSerializer is None:
+            transformer_serializer = TransformFunctionSerializer()
+            transformer_serializer.init(
+                SparkContext._active_spark_context, CloudPickleSerializer(), gw)
+            # SPARK-12511 streaming driver with checkpointing unable to finalize leading to OOM
+            # There is an issue that Py4J's PythonProxyHandler.finalize blocks forever.
+            # (https://github.com/bartdag/py4j/pull/184)
+            #
+            # Py4j will create a PythonProxyHandler in Java for "transformer_serializer" when
+            # calling "registerSerializer". If we call "registerSerializer" twice, the second
+            # PythonProxyHandler will override the first one, then the first one will be GCed and
+            # trigger "PythonProxyHandler.finalize". To avoid that, we should not call
+            # "registerSerializer" more than once, so that "PythonProxyHandler" in Java side won't
+            # be GCed.
+            #
+            # TODO Once Py4J fixes this issue, we should upgrade Py4j to the latest version.
+            transformer_serializer.gateway.jvm.PythonDStream.registerSerializer(
+                transformer_serializer)
+            cls._transformerSerializer = transformer_serializer
+        else:
+            cls._transformerSerializer.init(
+                SparkContext._active_spark_context, CloudPickleSerializer(), gw)
 
     @classmethod
     def getOrCreate(cls, checkpointPath, setupFunc):
@@ -116,16 +136,13 @@ class StreamingContext(object):
         gw = SparkContext._gateway
 
         # Check whether valid checkpoint information exists in the given path
-        if gw.jvm.CheckpointReader.read(checkpointPath).isEmpty():
+        ssc_option = gw.jvm.StreamingContextPythonHelper().tryRecoverFromCheckpoint(checkpointPath)
+        if ssc_option.isEmpty():
             ssc = setupFunc()
             ssc.checkpoint(checkpointPath)
             return ssc
 
-        try:
-            jssc = gw.jvm.JavaStreamingContext(checkpointPath)
-        except Exception:
-            print("failed to load StreamingContext from checkpoint", file=sys.stderr)
-            raise
+        jssc = gw.jvm.JavaStreamingContext(ssc_option.get())
 
         # If there is already an active instance of Python SparkContext use it, or create a new one
         if not SparkContext._active_spark_context:
diff --git a/python/pyspark/streaming/util.py b/python/pyspark/streaming/util.py
index abbbf6eb93..e617fc9ce9 100644
--- a/python/pyspark/streaming/util.py
+++ b/python/pyspark/streaming/util.py
@@ -89,11 +89,10 @@ class TransformFunctionSerializer(object):
     it uses this class to invoke Python, which returns the serialized function
     as a byte array.
     """
-    def __init__(self, ctx, serializer, gateway=None):
+    def init(self, ctx, serializer, gateway=None):
         self.ctx = ctx
         self.serializer = serializer
         self.gateway = gateway or self.ctx._gateway
-        self.gateway.jvm.PythonDStream.registerSerializer(self)
         self.failure = None
 
     def dumps(self, id):
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala b/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
index c4a10aa2dd..a5ab666975 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala
@@ -902,3 +902,15 @@ object StreamingContext extends Logging {
     result
   }
 }
+
+private class StreamingContextPythonHelper {
+
+  /**
+   * This is a private method only for Python to implement `getOrCreate`.
+   */
+  def tryRecoverFromCheckpoint(checkpointPath: String): Option[StreamingContext] = {
+    val checkpointOption = CheckpointReader.read(
+      checkpointPath, new SparkConf(), SparkHadoopUtil.get.conf, false)
+    checkpointOption.map(new StreamingContext(null, _, null))
+  }
+}
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