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https://issues.apache.org/jira/browse/HBASE-12728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14271185#comment-14271185
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Solomon Duskis commented on HBASE-12728:
----------------------------------------
bq. We're working to get away from the H-prefix in class names. How about
BufferedMutatorImpl? Can the ExceptionListener be a nested interface under it's
parent?
OK and will do
bq. nit: BufferedMutator#flushCommits can be just flush(); since HTable is
delegating, BufferedMutator is not bound to the old API.
OK
bq. Is there any place where a Lock implementation other than your
DoNothingLock would be used? All paths I read are using this no-op
implementation... which means they can only be used by a single thread? If I
want to share a BufferedMutator across threads, I just pass in a real Lock
implementation? I guess that would come it for a "BufferedTable".
It sounds like you have the gist of it. I'll show it in code in the example
you asked for.
bq. Agreed on locking down the BulkMutator constructor. I'm also not a fan of
exposing this class to the user API. I prefer the BufferedTable interface
discussed previously. Wrap it up nice and tidy like with new ConnectionFactory
methods.
Agreed and will do
bq. Can you add some example code so we can see how a use case like Aaron
Beppu's would be addressed?
Here's what I was thinking
{code}
public MyServlet implements Servlet {
private Connection connection;
private BulkMutator mutator;
public void init(ServletConfig config) {
connection = ...;
mutator = connection.getBulkMutator(tableName, new ReentrantLock(),
myExecutorService, myListener);
}
public void service(ServletRequest req, ServletResponse res) {
...
if (doDelete) {
try (Table table = connection.getTable(...)) {
table.delete(..);
}
} else {
mutator.put(..);
}
}
}
{code}
> buffered writes substantially less useful after removal of HTablePool
> ---------------------------------------------------------------------
>
> Key: HBASE-12728
> URL: https://issues.apache.org/jira/browse/HBASE-12728
> Project: HBase
> Issue Type: Bug
> Components: hbase
> Affects Versions: 0.98.0
> Reporter: Aaron Beppu
> Assignee: Solomon Duskis
> Priority: Blocker
> Fix For: 1.0.0, 2.0.0, 1.1.0
>
> Attachments: 12728.connection-owns-buffers.example.branch-1.0.patch,
> bulk-mutator.patch
>
>
> In previous versions of HBase, when use of HTablePool was encouraged, HTable
> instances were long-lived in that pool, and for that reason, if autoFlush was
> set to false, the table instance could accumulate a full buffer of writes
> before a flush was triggered. Writes from the client to the cluster could
> then be substantially larger and less frequent than without buffering.
> However, when HTablePool was deprecated, the primary justification seems to
> have been that creating HTable instances is cheap, so long as the connection
> and executor service being passed to it are pre-provided. A use pattern was
> encouraged where users should create a new HTable instance for every
> operation, using an existing connection and executor service, and then close
> the table. In this pattern, buffered writes are substantially less useful;
> writes are as small and as frequent as they would have been with
> autoflush=true, except the synchronous write is moved from the operation
> itself to the table close call which immediately follows.
> More concretely :
> ```
> // Given these two helpers ...
> private HTableInterface getAutoFlushTable(String tableName) throws
> IOException {
> // (autoflush is true by default)
> return storedConnection.getTable(tableName, executorService);
> }
> private HTableInterface getBufferedTable(String tableName) throws IOException
> {
> HTableInterface table = getAutoFlushTable(tableName);
> table.setAutoFlush(false);
> return table;
> }
> // it's my contention that these two methods would behave almost identically,
> // except the first will hit a synchronous flush during the put call,
> and the second will
> // flush during the (hidden) close call on table.
> private void writeAutoFlushed(Put somePut) throws IOException {
> try (HTableInterface table = getAutoFlushTable(tableName)) {
> table.put(somePut); // will do synchronous flush
> }
> }
> private void writeBuffered(Put somePut) throws IOException {
> try (HTableInterface table = getBufferedTable(tableName)) {
> table.put(somePut);
> } // auto-close will trigger synchronous flush
> }
> ```
> For buffered writes to actually provide a performance benefit to users, one
> of two things must happen:
> - The writeBuffer itself shouldn't live, flush and die with the lifecycle of
> it's HTableInstance. If the writeBuffer were managed elsewhere and had a long
> lifespan, this could cease to be an issue. However, if the same writeBuffer
> is appended to by multiple tables, then some additional concurrency control
> will be needed around it.
> - Alternatively, there should be some pattern for having long-lived HTable
> instances. However, since HTable is not thread-safe, we'd need multiple
> instances, and a mechanism for leasing them out safely -- which sure sounds a
> lot like the old HTablePool to me.
> See discussion on mailing list here :
> http://mail-archives.apache.org/mod_mbox/hbase-user/201412.mbox/%3CCAPdJLkEzmUQZ_kvD%3D8mrxi4V%3DhCmUp3g9MUZsddD%2Bmon%2BAvNtg%40mail.gmail.com%3E
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