从hadoop unix运行时增加jvm堆空间 [英] increase jvm heap space while runnig from hadoop unix

问题描述

我正在从hadoop命令运行java类test.java：

I am running a java class test.java from hadoop command :

$ hadoop test

我使用的是stringBuilder，其大小内存不足：

I am using a stringBuilder, and its size is going out of memory :

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Arrays.java:2882)
    at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.                                                                                        java:100)
    at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:572                                                                                        )
    at java.lang.StringBuffer.append(StringBuffer.java:320)
    at java.io.StringWriter.write(StringWriter.java:60)
    at org.json.JSONObject.quote(JSONObject.java:1287)
    at org.json.JSONObject.writeValue(JSONObject.java:1597)
    at org.json.JSONObject.write(JSONObject.java:1649)
    at org.json.JSONObject.writeValue(JSONObject.java:1574)
    at org.json.JSONArray.write(JSONArray.java:929)
    at org.json.JSONObject.writeValue(JSONObject.java:1576)
    at org.json.JSONObject.write(JSONObject.java:1649)
    at org.json.JSONObject.writeValue(JSONObject.java:1574)
    at org.json.JSONObject.write(JSONObject.java:1632)
    at org.json.JSONObject.toString(JSONObject.java:1443)

我知道在java中我们可以通过提供堆空间大小来运行java程序：

I know in java we can run a java program by providing a heap space size :

java -Xmx4G test

如何在运行时执行此操作hadoop，如果我像以下那样运行：

How can I do this while running with hadoop, if I run it like :

$ hadoop -Xmx4G test

它抛出异常：

Caused by: java.lang.ClassNotFoundException: java
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    Could not find the main class: java.  Program will exit.
    Error: No command named `-Xmx4g' was found. Perhaps you meant `hadoop Xmx4g'

我想永久地改变堆大小。

I would like to change the heap size permanently.

推荐答案

通常在执行类之前在终端中执行其中一个操作或将其放在bash脚本中。

Usually you do one of these in the terminal before executing the class or put it in a bash script.

export HADOOP_HEAPSIZE=4096
hadoop test

或者，

export HADOOP_OPTS="$HADOOP_OPTS -Xmx4G"
hadoop test

或者，如果上述方法不起作用，请尝试在 $ HADOOP_HOME / conf /中修改HADOOP_OPTS hadoop-env.sh

Or, if the above doesn't work, try modifying HADOOP_OPTS in $HADOOP_HOME/conf/hadoop-env.sh

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