I'm using Cygnus 0.5 with default configuration for HDFS sink. In order make it to run, I have deactivated the "ds" interceptor (otherwise I get an error at start time that precludes Cygnus to start, related with not finding the matching table file).
Cygnus seems to work, but the file in which entity information is stored in HDFS gets a weird name: "null.txt". How can I fix this?
First of all do no deactivate the DestinationExtractor interceptor. This is the piece of code infering the destination the context data notified by Orion is going to be persisted. Please observe the destination may refer to a HDFS file name, a MySQL table name or a CKAN resource name, it depends on the sinks you have configured. Once infered, the destination is added to the internal Flume event as a header called destination in order the sinks know where to persist. Thus, if deactivated, such a header is not found by the sinks and a null name is used as the destination name.
Regarding the "matching table file not found" problem you experienced (and which leaded you yo deactivate the Interceptor), it was due to the Cygnus configuration template had a bad default value for the cygnusagent.sources.http-source.interceptors.de.matching_table parameter. This has been solved in Cygnus 0.5.1.
A workaround while Cygnus 0.5.1 gets released is:
DestinatonExtractor (as @frb says in his answer)touch /tmp/dummy_table.conf then set in the cygnus configuration file: cygnusagent.sources.http-source.interceptors.de.matching_table = /tmp/dummy_table.conf