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https://reviews.apache.org/r/16485/
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Review request for accumulo.
Bugs: ACCUMULO-2103
https://issues.apache.org/jira/browse/ACCUMULO-2103
Repository: accumulo
Description
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This is the work on ZooSession to better support closure of ZK connections
under ACCUMULO-2026 and/or future work. Here's a tour.
First, the logic in ZooSession to connect to ZooKeeper was moved to a new
ZooKeeperFactory class. This also makes it possible to mock the logic for unit
tests, or swap in newer / better implementations later. The factory will throw
a new ZooKeeperFactoryException (unchecked) for most problems, but does throw
InterruptedException when appropriate (instead of eating it). Otherwise, the
logic is the same.
Before this, ZooSession was a set of static methods oriented around connecting
to ZooKeeper. With this set of commits, ZooSession objects are used, each of
which contains a ZooKeeper connection object as well as its key (formed and
used as before).
The ZooSession class still uses a static map of known sessions, so that the
same connection may be reused by several clients. The map now also remembers
the watcher object associated with the connection (possibly a prior oversight),
and a reference count. Whenever a new connection is established or it is
reused, the reference count is increased. When a session is closed, the
reference count is decreased, and the connection itself is only closed when the
reference count is depleted. Cleanup of closed session objects occurs as it did
before, lazily upon request of a new one (see the removeIfClosed method).
The getSession methods are deprecated since they return the actual ZK
connection objects instead of sessions. In their place are open methods. The
deprecated methods do not participate in reference counting.
ZooSession now includes a clear method for simply wiping out its session
tracking and a forceCloseAll method for forcibly closing all known connections.
These methods are useful for ensuring that connections are wiped clean, so that
it isn't necessary to hunt down and close all sessions before, say, a process
exits.
ZooReader was modified to remember the session that it is using (with its
reference to the ZK connection) instead of continuously asking ZooSession for
it. When a ZooReader is closed, it closes its session instead of closing the ZK
connection itself; this allows the reference counting to work.
This set of commits adds a unit test for ZooSession. ZooSession is defined to
implement Closeable, but ZooReader is not.
Diffs
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src/core/pom.xml 77a4a72b3d32283e82d7a9d3b1b6b4690520c88e
src/core/src/main/java/org/apache/accumulo/core/zookeeper/ZooCache.java
cbb39182e93c568363a58d7e3344b9b85337cfc0
src/core/src/main/java/org/apache/accumulo/core/zookeeper/ZooKeeperFactory.java
PRE-CREATION
src/core/src/main/java/org/apache/accumulo/core/zookeeper/ZooKeeperFactoryException.java
PRE-CREATION
src/core/src/main/java/org/apache/accumulo/core/zookeeper/ZooReader.java
aabc0f223bf2c6187e915b9a1e9569d714bce852
src/core/src/main/java/org/apache/accumulo/core/zookeeper/ZooSession.java
b3db26f107139c1e2854a545e3f1f11de1b28b02
src/core/src/test/java/org/apache/accumulo/core/zookeeper/ZooSessionTest.java
PRE-CREATION
Diff: https://reviews.apache.org/r/16485/diff/
Testing
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Unit tests; functional tests; continuous ingest.
Thanks,
Bill Havanki
