New StreamingFileSink ( introduced in 1.6 Flink version ) use HadoopRecoverableFsDataOutputStream wrapper to write data in HDFS.
HadoopRecoverableFsDataOutputStream is a wrapper for FSDataOutputStream to have an ability to restore from a certain point of the file after failure and continue to write data. To achieve this recovery functionality the HadoopRecoverableFsDataOutputStream uses "truncate" method which was introduced only in Hadoop 2.7.
FLINK-14170 has enabled the usage of StreamingFileSink for OnCheckpointRollingPolicy, but it is still not possible to use StreamingFileSink with DefaultRollingPolicy, which makes writing of the data to HDFS unpractical in scale for HDFS < 2.7.
Unfortunately, there are a few official Hadoop distributives which latest version still use Hadoop 2.6 (This distributives: Cloudera, Pivotal HD ). As the result Flinks Hadoop connector can't work with this distributives.
Flink declares that supported Hadoop from version 2.4.0 upwards (https://ci.apache.org/projects/flink/flink-docs-release-1.6/start/building.html#hadoop-versions)
I guess we should emulate the functionality of "truncate" method for older Hadoop versions.