Using the Hadoop S3A connector with Content Gateway S3

The Apache Hadoop S3 connector "S3A" works with Content Gateway S3. Here is a small but complete example, using a single-node hadoop system that can be easily run on any docker server. It shows bucket listing, distcp, and a simple mapreduce job against a bucket in a Swarm domain.

• Create a container using the docker image from https://github.com/sequenceiq/hadoop-docker

  $ docker run -it sequenceiq/hadoop-docker:2.7.0 /etc/bootstrap.sh -bash

• At the container's shell prompt, add the path containing the "hadoop" binary:

  PATH=/usr/local/hadoop/bin:$PATH

• Copy the jar's needed for the S3A libraries:

  cd /usr/local/hadoop-2.7.0/share/hadoop/tools/lib/ && cp -p hadoop-aws-2.7.0.jar aws-java-sdk-1.7.4.jar jackson-core-2.2.3.jar jackson-databind-2.2.3.jar jackson-annotations-2.2.3.jar /usr/local/hadoop-2.7.0/share/hadoop/hdfs/lib/

• Make sure your domain (mydomain.example.com) and bucket (hadoop-test) have been Created and that your /etc/hosts or DNS are configured to resolve http://mydomain.example.com/hadoop-test [https://jam.cloud.caringo.com/hadoop-test] to your cloudgateway server's S3 port.
• Create an S3 token

  curl -i -u USERNAME -X POST --data-binary '' -H 'X-User-Secret-Key-Meta: secret' -H 'X-User-Token-Expires-Meta: +90' http://mydomain.example.com/.TOKEN/

  HTTP/1.1 201 Created

  ...

  Token e181dcb1d01d5cf24f76dd276b95a638 issued for USERNAME in [root] with secret secret

• List your bucket (should be empty)

  hadoop fs -Dfs.s3a.access.key=e181dcb1d01d5cf24f76dd276b95a638 -Dfs.s3a.secret.key=secret -Dfs.s3a.endpoint=mydomain.example.com -ls s3a://hadoop-test/

  Note: error ls: `s3a://hadoop-test': No such file or directory is expected if bucket is empty OR if you forget the trailing slash.

• Copy the sample "input" files into your bucket:

  hadoop distcp -Dfs.s3a.access.key=e181dcb1d01d5cf24f76dd276b95a638 -Dfs.s3a.secret.key=secret -Dfs.s3a.endpoint=jam.cloud.caringo.com input s3a://hadoop-test/input

• Verify with "-ls" or in Content Gateway ui that the bucket now has ~31 streams.

  hadoop fs -Dfs.s3a.access.key=e181dcb1d01d5cf24f76dd276b95a638 -Dfs.s3a.secret.key=secret -Dfs.s3a.endpoint=jam.cloud.caringo.com -ls s3a://hadoop-test/input/

Found 31 items ...

• Run the sample mapreduce job that grep's the input files

  hadoop jar /usr/local/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.0.jar grep -Dfs.s3a.access.key=e181dcb1d01d5cf24f76dd276b95a638 -Dfs.s3a.secret.key=secret -Dfs.s3a.endpoint=mydomain.example.com s3a://hadoop-test/input s3a://hadoop-test/output 'dfs[a-z.]+'

• Display the results in the "output" file

  hadoop fs -Dfs.s3a.access.key=e181dcb1d01d5cf24f76dd276b95a638 -Dfs.s3a.secret.key=secret -Dfs.s3a.endpoint=mydomain.example.com -cat s3a://hadoop-test/output/part-r-00000 6 dfs.audit.logger 4 dfs.class 3 dfs.server.namenode. 2 dfs.period 2 dfs.audit.log.maxfilesize ...

  PS: https://wiki.apache.org/hadoop/AmazonS3 [https://wiki.apache.org/hadoop/AmazonS3] makes a good point:

  "S3 is not a filesystem. The Hadoop S3 filesystem bindings make it pretend to be a filesystem, but it is not. It can act as a source of data, and as a destination -though in the latter case, you must remember that the output may not be immediately visible."