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Table of Contents

Streams

My application failed to start, with the a rocksDB exception raised as "java.lang.ExceptionInInitializerError.. Unable to load the RocksDB shared libraryjava...". How to resolve this?

Streams API uses RocksDB as the default local persistent key-value store. And RocksDB JNI would try to statically load the sharedlibs into java.io.tmpdir. On Unix-like platforms, the default value of this system environment property is typically "/tmp", or "/var/tmp"; On Microsoft Windows systems the property is typically "C:\\WINNT\\TEMP".

If your application does not have permission to access these directories (or for Unix-like platforms if the pointed location is not mounted), the above error would be thrown. To fix this, you can either grant the permission to access this directory to your applications, or change this property when executing your application like "java -Djava.io.tmpdir=..".

My application's memory usage keeps increasing when running until it hits an OOM. Why?

The most common cause of this scenario is that you did not close an iterator from the state stores after completed using it. For persistent stores like RocksDB, an iterator is usually backed by some physical resources like open file handlers and in-memory caches. Not closing these iterators would effectively causing resource leaks.

For more details please read this javadoc.

I saw exceptions running my Streams app for the first time as "Extracted timestamp value is negative, which is not allowed." What does this mean?

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