[HDFS-10796] libhdfs++: rationalize ioservice interactions

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: hdfs-client
• Assignee: James Clampffer
• Reporter: Bob Hansen
• Created: 25/Aug/16 14:16
• Updated: 22/Mar/18 21:57
• Resolved: 09/Dec/16 23:07

Description

Firstly, we should be pulling the number of threads from options.io_threads (which should default to std::thread::hardware_concurrency()). The library should pass all tests always with io_threads set to 1 or to <a very high number>

Secondly, we should have a constructor where the consumer doesn't need to manage the IOService explicitly, and the FileSystemImpl should create its own internally.

Since the FileSystem is defined as being for a particular user/identity, there is a valid use case for the consumer to be constructing many FileSystem instances to represent many authenticated users in the same process, but want to share resources (notably have a single io_service shared amongst them all). In this case, the consumer would want to own the IOService and pass the same instance to multiple FileSystem instances.