Thanks. I think about it, yes, the DAG engine should not have issue to build the right graph in different threads (at least in theory, it is not an issue).
So now I have another question: if I have a context initiated, but there is no operation on it for very long time, will there a timeout on it? How Spark to control/maintain/detect the live of the client spark context? Do I need to setup something special? Regards, Shuai From: Eugen Cepoi [mailto:cepoi.eu...@gmail.com] Sent: Thursday, February 05, 2015 5:39 PM To: Shuai Zheng Cc: Corey Nolet; Charles Feduke; user@spark.apache.org Subject: Re: How to design a long live spark application Yes you can submit multiple actions from different threads to the same SparkContext. It is safe. Indeed what you want to achieve is quite common. Expose some operations over a SparkContext through HTTP. I have used spray for this and it just worked fine. At bootstrap of your web app, start a sparkcontext, maybe preprocess some data and cache it, then start accepting requests against this sc. Depending where you place the initialization code, you can block the server from initializing until your context is ready. This is nice if you don't want to accept requests while the context is being prepared. Eugen 2015-02-05 23:22 GMT+01:00 Shuai Zheng <szheng.c...@gmail.com>: This example helps a lot J But I am thinking a below case: Assume I have a SparkContext as a global variable. Then if I use multiple threads to access/use it. Will it mess up? For example: My code: public static List<Tuple2<Integer, Double>> run(JavaSparkContext sparkContext, Map<Integer, List<ExposureInfo>> cache, Properties prop, List<EghInfo> el) throws IOException, InterruptedException { JavaRDD<EghInfo> lines = sparkContext.parallelize(el, 100); Lines.map(…) … Lines.count() } If I have two threads call this method at the same time and pass in the same SparkContext. Will SparkContext be thread-safe? I am a bit worry here, in traditional java, it should be, but in Spark context, I am not 100% sure. Basically the sparkContext need to smart enough to differentiate the different method context (RDD add to it from different methods), so create two different DAG for different method. Anyone can confirm this? This is not something I can easily test with code. Thanks! Regards, Shuai From: Corey Nolet [mailto:cjno...@gmail.com] Sent: Thursday, February 05, 2015 11:55 AM To: Charles Feduke Cc: Shuai Zheng; user@spark.apache.org Subject: Re: How to design a long live spark application Here's another lightweight example of running a SparkContext in a common java servlet container: https://github.com/calrissian/spark-jetty-server On Thu, Feb 5, 2015 at 11:46 AM, Charles Feduke <charles.fed...@gmail.com> wrote: If you want to design something like Spark shell have a look at: http://zeppelin-project.org/ Its open source and may already do what you need. If not, its source code will be helpful in answering the questions about how to integrate with long running jobs that you have. On Thu Feb 05 2015 at 11:42:56 AM Boromir Widas <vcsub...@gmail.com> wrote: You can check out https://github.com/spark-jobserver/spark-jobserver - this allows several users to upload their jars and run jobs with a REST interface. However, if all users are using the same functionality, you can write a simple spray server which will act as the driver and hosts the spark context+RDDs, launched in client mode. On Thu, Feb 5, 2015 at 10:25 AM, Shuai Zheng <szheng.c...@gmail.com> wrote: Hi All, I want to develop a server side application: User submit request à Server run spark application and return (this might take a few seconds). So I want to host the server to keep the long-live context, I don’t know whether this is reasonable or not. Basically I try to have a global JavaSparkContext instance and keep it there, and initialize some RDD. Then my java application will use it to submit the job. So now I have some questions: 1, if I don’t close it, will there any timeout I need to configure on the spark server? 2, In theory I want to design something similar to Spark shell (which also host a default sc there), just it is not shell based. Any suggestion? I think my request is very common for application development, here must someone has done it before? Regards, Shawn
