dlmarion opened a new pull request, #3180:
URL: https://github.com/apache/accumulo/pull/3180

   When creating Hadoop FileSystem objects the FileSystem class caches 
FileSystem objects using the filesystem URI scheme and authority fields. Prior 
to this change, the Accumulo VolumeManager would create FileSystem objects (one 
per volume) using the standard Hadoop Configuration files and resources. 
However, user-supplied Hadoop configuration files (core-site.xml and 
hdfs-site.xml) don't allow the user to specify different properties for 
different filesystems. For example, a user can create a core-site.xml and 
hdfs-site.xml file locally and create FileSystem objects that connect to 
different HDFS clusters. A property specified in the Hadoop configuration will 
apply to all FileSystem objects.
   
   With this change users can specify Hadoop configuration overrides in the 
Accumulo configuration using the property format: 
general.custom.<volume-uri>.<property-name>=<property-value>
   
   This enables a user with multiple filesystems specified in the 
instance.volumes property to provide different Hadoop configuration overrides 
for each volume. For example, the following would allow different hedged read 
thread sizes for two different volumes:
   
   
instance.volumes=hdfs://namespace-a:8020/accumulo,hdfs://namespace-b:8020/accumulo
 
general.custom.hdfs://namespace-a:8020/accumulo.dfs.client.hedged.read.threadpool.size=10
 
general.custom.hdfs://namespace-b:8020/accumulo.dfs.client.hedged.read.threadpool.size=20
   
   Note: When specifying property names that contain colons in the 
accumulo.properties files, they need to be escaped with a backslash


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