如何在 Docker 容器中找到 openjdk？

Question

我尝试运行 pyspark 应用程序。为此，我首先从 pip 安装了 pyspark，然后拉下 openjdk:8 以设置 JAVA_HOME 变量

Docker 文件：

FROM python:3

ADD my_script.py /
COPY requirements.txt ./

ENV JAVA_HOME  /usr/lib/jvm/java-8-openjdk-amd64/

RUN pip install --no-cache-dir -r requirements.txt

CMD [ "python", "./my_script.py" ]

my_script.py：

from pyspark import SparkContext
from pyspark import SparkConf

#spark conf
conf1 = SparkConf()
conf1.setMaster("local[*]")
conf1.setAppName('hamza')
print(conf1)
sc = SparkContext(conf = conf1)


from pyspark.sql import SQLContext
sqlContext = SQLContext(sc)
print(sqlContext)

Requirements.txt：

pyspark

numpy

收到此错误：

C:\Users\hrafiq\Desktop\sample>docker run -it --rm --name data2 my-python-app
<pyspark.conf.SparkConf object at 0x7f4bd933ba58>
/usr/local/lib/python3.7/site-packages/pyspark/bin/spark-class: line 71: 
/usr/lib/jvm/java-8-openjdk-amd64//bin/java: No such file or directory
Traceback (most recent call last):
   File "./my_script.py", line 14, in <module>
    sc = SparkContext(conf = conf1)
  File "/usr/local/lib/python3.7/site-packages/pyspark/context.py", line 115, in __init__
    SparkContext._ensure_initialized(self, gateway=gateway, conf=conf)
  File "/usr/local/lib/python3.7/site-packages/pyspark/context.py", line 298, in _ensure_initialized
    SparkContext._gateway = gateway or launch_gateway(conf)
  File "/usr/local/lib/python3.7/site-packages/pyspark/java_gateway.py", line 94, in launch_gateway
    raise Exception("Java gateway process exited before sending its port number")
Exception: Java gateway process exited before sending its port number  

所以问题是如果没有找到 java 文件，那么我将如何找到该文件？我知道它存储在某个我们无权访问的虚拟硬盘中。

任何帮助将不胜感激

谢谢

Answer 1

设置 JAVA_HOME 环境变量是不够的。您需要在 docker 映像中实际安装 openjdk。

您的基础镜像 (python:3) 本身基于 Debian Stretch 镜像。所以你可以使用 apt-get install 来获取 JDK：

FROM python:3

RUN apt-get update && \
     apt-get install -y openjdk-8-jdk-headless && \
    rm -rf /var/lib/apt/lists/*
ENV JAVA_HOME  /usr/lib/jvm/java-8-openjdk-amd64/

COPY requirements.txt ./
RUN pip install --no-cache-dir -r requirements.txt

COPY my_script.py ./
CMD [ "python", "./my_script.py" ]

（在上面我已经优化了层顺序，这样当你的脚本改变时你就不需要重新构建 pip install 层）