James Clampffer created HDFS-12427:
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Summary: libhdfs++: Prevent Requests from holding dangling pointer
to RpcEngine
Key: HDFS-12427
URL: https://issues.apache.org/jira/browse/HDFS-12427
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: James Clampffer
Assignee: James Clampffer
Priority: Critical
The lifetime of Request objects is tied to the worker thread(s) in the async
event loop. In the current code there's nothing that prevents a request from
outliving the RpcEngine (bound to FileSystem) while it's waiting for IO. If
the Request, or a task that makes a new request, outlives the RpcEngine it
attempts to dereference a dangling pointer and either crashes or continues to
run with bad data.
Proposed fix is to reference count the RpcEngine via shared_ptr so that
Requests can hold a weak_ptr to it. When a request or RpcConnection attempting
to make a request needs something from the RpcEngine like a call id number it
can promote the weak_ptr to a shared_ptr. If it's unable to promote because
the RpcEngine has been destroyed the Request's handler can be invoked with an
appropriate error message. A weak_ptr must be used rather than a shared_ptr to
avoid reference cycles.
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