Question

我希望执行“ execute”方法，以便避免对Spark进行延迟评估，而我想执行代码中的一个动作（saveAsTextFile）：

def execute(line1):
    line = line1.split(',')    
    print('Hi')
    session = driver.session()
    #vérifions si les noeuds n'existent pas encore et si oui créons les
    session.run("MERGE (n:Person {Tel: {v1} }) MERGE (m:Person {Tel: {v5}}) CREATE (n)-[:EMIT]->(c:Call {location:{v2}, start:{v3}, duration:{v4}})-[:RECEIVE]->(m) ", {'v1':line[0], 'v2':line[1], 'v3':line[3], 'v4':line[4], 'v5':line[5]})    
    session.close()
    return line

def toCSVLine(data):
    return ','.join(str(d) for d in data)

if __name__ == '__main__':
    sc = SparkContext()
    csvData = sc.textFile(sys.argv[1]).cache()    
    csvData.map(execute).map(toCSVLine).saveAsTextFile("doc")

但是我遇到以下错误：

 File "/home/josyanne/Documents/test/./appSpark.py", line 21, in <module>
csvData.map(execute).map(toCSVLine).saveAsTextFile("doc")
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 1585, in saveAsTextFile
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2489, in _jrdd
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2422, in _wrap_function
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/rdd.py", line 2408, in _prepare_for_python_RDD
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/serializers.py", line 568, in dumps
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/cloudpickle.py", line 918, in dumps
 File "/usr/local/spark/python/lib/pyspark.zip/pyspark/cloudpickle.py", line 249, in dump
_pickle.PicklingError: Could not serialize object: TypeError: Cannot serialize socket object

请有人帮我解决此错误

Answer 1

必须在每个节点上初始化驱动程序。为此，您应该使用mapPartitions或foreachPartition（如果您仅使用saveAsTextFile来评估事物，则应该使用

def execute(lines):
    driver = GraphDatabase.driver(...)

    for line in lines:
        line = line.split(',')    
        session = driver.session()
        session.run(...)
        session.close()
        yield line

csvData.mapPartitions(execute).map(toCSVLine).saveAsTextFile("doc")

由于PicklingError未能执行Pyspark动作

1 个答案: