Paul Rogers created DRILL-5169:
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Summary: Reconsider use of AutoCloseable within Drill
Key: DRILL-5169
URL: https://issues.apache.org/jira/browse/DRILL-5169
Project: Apache Drill
Issue Type: Improvement
Affects Versions: 1.8.0
Reporter: Paul Rogers
Priority: Minor
Drill has many resources that must be closed: value vectors, threads, operators
and on and on. The {{close()}} method may sometimes throw an exception or take
a long time. Drill has developed, or borrowed from Guava, many utilities to
help manage the close operation.
Java has two forms of "predefined" closeable interfaces: {{Closeable}} and
{{AutoCloseable}}. {{Closeable}} is for I/O resources and thus can throw an
{{IOException}}. {{AutoCloseable}} throws no exception, and is integrated into
the language for use in try-with-resources blocks. Because {{AutoCloseable}} is
intended only for this use, any creation or return of an {{AutoCloseable}}
outside of a try-with-resources block produces compiler warnings.
Neither of the two Java interfaces fit Drill's needs. {{Closeable}} throws a
particular exception ({{IOException}}) which Drill seldom throws, but does not
throw exceptions that Drill does throw.
Drill has settled on {{AutoCloseable}}, but few of Drill's resources are
limited in life to a single try-with-resources block. The result is either
hundreds of resource warnings (which developers learn to ignore), or hundreds
of insertions of {{@SuppressWarnings("resource")}} tags, which just clutter the
code.
Note that there is nothing special about either of the Java-provided
interfaces. {{Closeable}} is simply a convention to allow easy closing of IO
resources such as streams and so on. {{AutoCloseable}} exists for the sole
purpose of implementing try-with-resource blocks.
What we need is a Drill-specific interface that provides a common {{close()}}
method which throws only unchecked exceptions, but is not required to be used
in try-with-resources. Perhaps call this {{DrillCloseable}}.
Next, reimplement the various close utilities. For example:
{{DrillCloseables.closeAll()}} would close a set of resources, suppressing
exceptions, and throwing a single combined exception if any operations fail.
Then, convert all uses of {{AutoCloseable}} to {{DrillCloseable}}, or at least
all that are not used in try-with-resources block. Doing so will eliminate many
compiler warnings and or suppress warnings tags. Because Java allows classes to
implement multiple interfaces, it is even possible for a class to implement
both {{DrillCloseable}} and {{AutoCloseable}} in the rare instance where both
are needed.
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