In our pre-1.0 API, HTable is considered a light-weight object that consumed by
a single thread at a time. The HTablePool class provided a means of sharing
multiple HTable instances across a number of threads. As an optimization,
HTable managed a "write buffer", accumulating edits and sending a "batch" all
at once. By default the batch was sent as the last step in invocations of
put(Put) and put(List<Put>). The user could disable the automatic flushing of
the write buffer, retaining edits locally and only sending the whole "batch"
once the write buffer has filled or when the flushCommits() method in invoked
explicitly. Explicit or implicit batch writing was controlled by the
setAutoFlushTo(boolean) method. A value of true (the default) had the write
buffer flushed at the completion of a call to put(Put) or put(List<Put>). A
value of false allowed for explicit buffer management. HTable also exposed the
buffer to consumers via getWriteBuffer().
The combination of HTable with setAutoFlushTo(false) and the HTablePool
provided a convenient mechanism by which multiple "Put-producing" threads could
share a common write buffer. Both HTablePool and HTable are deprecated, and
they are officially replaced in The new 1.0 API by Table and BufferedMutator.
Table, which replaces HTable, no longer exposes explicit write-buffer
management. Instead, explicit buffer management is exposed via BufferedMutator.
BufferedMutator is made safe for concurrent use. Where code would previously
retrieve and return HTables from an HTablePool, now that code creates and
shares a single BufferedMutator instance across all threads.
Summary: The reason of this change is to make us write implementation of ClusterManager not using ssh/unix signals.
Test Plan: The compilation is OK.
Reviewers: eclark, manukranthk
Differential Revision: https://reviews.facebook.net/D30201
Signed-off-by: Elliott Clark <eclark@apache.org>
Move from HConnection to ClusterConnection or Connection
Use unmanaged connections where we use managed previous
(used the jdk7 https://docs.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html idiom).
In ZKConfig, synchronize on Configuration rather than make a copy.
Making a copy we were dropping hbase configs in certain test context
(could not find the zk ensemble because default port).
In tests, some move to the new style connection setup but mostly
fixes for premature connection close or adding cleanup where it
was lacking.
