This project is a wrapper around the S3 file system from the Presto project which shades all dependencies. Initial simple tests seem to indicate that it responds slightly faster and in a bit more lightweight manner to write/read/list requests, compared to the Hadoop s3a FS, but it has some semantic differences.

We also relocate the shaded Hadoop version to allow running in a different setup. For this to work, however, we needed to adapt Hadoop's Configuration class to load a (shaded) core-default-shaded.xml configuration with the relocated class names of classes loaded via reflection (in the future, we may need to extend this to mapred-default.xml and hdfs-defaults.xml and their respective configuration classes).

Changing the Hadoop Version

If you want to change the Hadoop version this project depends on, the following steps are required to keep the shading correct:

1. from the respective Hadoop jar (from the com.facebook.presto.hadoop/hadoop-apache2 resource, currently version 2.7.3-1 as of our pom.xml),

• copy org/apache/hadoop/conf/Configuration.java to src/main/java/org/apache/hadoop/conf/ and
  • replace core-default.xml with core-default-shaded.xml.
• copy org/apache/hadoop/util/NativeCodeLoader.java to src/main/java/org/apache/hadoop/util/ and
  • replace the static initializer with

static { LOG.info("Skipping native-hadoop library for flink-s3-fs-presto's relocated Hadoop... " + “using builtin-java classes where applicable”); }

  - copy `core-default.xml` to `src/main/resources/core-default-shaded.xml` and
    - change every occurrence of `org.apache.hadoop` into `org.apache.flink.fs.s3presto.shaded.org.apache.hadoop`
  - copy `core-site.xml` to `src/test/resources/core-site.xml` (as is)
2. verify the shaded jar:
  - does not contain any unshaded classes except for `org.apache.flink.fs.s3presto.S3FileSystemFactory`
  - all other classes should be under `org.apache.flink.fs.s3presto.shaded`
  - there should be a `META-INF/services/org.apache.flink.fs.s3presto.S3FileSystemFactory` file pointing to the `org.apache.flink.fs.s3presto.S3FileSystemFactory` class
  - other service files under `META-INF/services` should have their names and contents in the relocated `org.apache.flink.fs.s3presto.shaded` package
  - contains a `core-default-shaded.xml` file
  - does not contain a `core-default.xml` or `core-site.xml` file