Typically, a threshold is set for each Young Generation object, and when that age is met, the object gets moved to the Old Generation. The Old Generation is used to store long-surviving objects. All minor garbage collections are “Stop the World” events, meaning that the JVM stops all application threads until the operation completes. When the Young Generation fills up, using its entire allocated memory, a minor garbage collection occurs. The Young Generation is where all new objects are allocated and aged, meaning their time in existence is monitored. The JVM heap consists of smaller parts or generations: Young Generation, Old Generation, and Permanent Generation. The JVM garbage collection process looks at heap memory, identifies which objects are in use and which are not, and deletes the unused objects to reclaim memory that can be leveraged for other purposes. It translates the instructions from its running programs into instructions and commands that run on the local operating system. The JVM runs on a local machine and functions as an operating system to the Java programs written to execute in it. Along the road, it helped us develop best practices around tuning the JVM for our scale which we hope others in the community will find useful. Preserving the reliability and performance of our internal data services required tuning the GC parameters and memory sizes and reducing the rate at which the system generated Java objects. Refining this core area of our data platform ensures that decision-makers within Uber get actionable business intelligence in a timely manner, letting us deliver the best possible services for our users, whether it’s connecting riders with drivers, restaurants with delivery people, or freight shippers with carriers. ![]() Increased memory consumption exposed a variety of issues, including long garbage collection ( GC ) pauses, memory corruption, out-of-memory ( OOM ) exceptions, and memory leaks. Uber’s growth over the last few years exponentially increased both the volume of data and the associated access loads required to process it, resulting in much more memory consumption from services. All of these services were built in Java or Scala and run on open source Java Virtual Machine (JVM). Our data platform leverages several open source projects (Apache Hive, Apache Presto, and Apache Spark ) for both interactive and long running queries, serving the myriad needs of different teams at Uber. Our Apache Hadoop-based data platform ingests hundreds of petabytes of analytical data with minimum latency and stores it in a data lake built on top of the Hadoop Distributed File System (HDFS). This would give the merged question a good selection of both direct answers and alternatives.Running queries on Uber’s data platform lets us make data -driven decisions at every level, from forecasting rider demand during high traffic events to identifying and addressing bottlenecks in the driver sign-up process. All of these are pretty specific to file-based sources, which is a general shortcoming, but not much can be done about that I could add a new answer to whatever the master question ends up being along those lines, I suppose.Īnother option, if a mod wants to spend some time on it, could be to merge 1 into 3 then mark 2 and 4 as a duplicate of 3. I do like my answer ) but really it contains no new information not scattered throughout the other three. ![]() Con: Doesn't have a direct answer to the specific question (which could be seen as a good thing I suppose, unless somebody is actually trying to find out how to reset a BufferedReader for some good reason and is not interested in an alternative). ![]() Pro: Sage advice from Ryan P and Jon Skeet, presenting alternatives.Pro: Has the best direct answer to accomplish the specific goal in the question.I'd like to mark three of them as a duplicate of one but can't decide on the master question. How to return to the beginning of a Bufferedreader?.Java BufferedReader back to the top of a text file?.How do I read a file again using buffered reader in Java?.Reset buffer with BufferedReader in Java?.Here are four essentially identical questions:
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