Hi Aaron,
Just out of curiosity, have you considered using asynchbase?
https://github.com/OpenTSDB/asynchbase
On Fri, Dec 19, 2014 at 9:00 AM, Nick Dimiduk <ndimi...@apache.org> wrote:
> Hi Aaron,
>
> Your analysis is spot on and I do not believe this is by design. I see the
> write buffer is owned by the table, while I would have expected there to be
> a buffer per table all managed by the connection. I suggest you raise a
> blocker ticket vs the 1.0.0 release that's just around the corner to give
> this the attention it needs. Let me know if you're not into JIRA, I can
> raise one on your behalf.
>
> cc Lars, Enis.
>
> Nice work Aaron.
> -n
>
> On Wed, Dec 17, 2014 at 6:44 PM, Aaron Beppu <abe...@siftscience.com>
> wrote:
> >
> > Hi All,
> >
> > TLDR; in the absence of HTablePool, if HTable instances are short-lived,
> > how should clients use buffered writes?
> >
> > I’m working on migrating a codebase from using 0.94.6 (CDH4.4) to 0.98.6
> > (CDH5.2). One issue I’m confused by is how to effectively use buffered
> > writes now that HTablePool has been deprecated[1].
> >
> > In our 0.94 code, a pathway could get a table from the pool, configure it
> > with table.setAutoFlush(false); and write Puts to it. Those writes would
> > then go to the table instance’s writeBuffer, and those writes would only
> be
> > flushed when the buffer was full, or when we were ready to close out the
> > pool. We were intentionally choosing to have fewer, larger writes from
> the
> > client to the cluster, and we knew we were giving up a degree of safety
> in
> > exchange (i.e. if the client dies after it’s accepted a write but before
> > the flush for that write occurs, the data is lost). This seems to be a
> > generally considered a reasonable choice (cf the HBase Book [2] SS
> 14.8.4)
> >
> > However in the 0.98 world, without HTablePool, the endorsed pattern [3]
> > seems to be to create a new HTable via table =
> > stashedHConnection.getTable(tableName, myExecutorService). However, even
> if
> > we do table.setAutoFlush(false), because that table instance is
> > short-lived, its buffer never gets full. We’ll create a table instance,
> > write a put to it, try to close the table, and the close call will
> trigger
> > a (synchronous) flush. Thus, not having HTablePool seems like it would
> > cause us to have many more small writes from the client to the cluster,
> and
> > basically wipe out the advantage of turning off autoflush.
> >
> > 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
> > }
> >
> > It seems like the only way to avoid this is to have long-lived HTable
> > instances, which get reused for multiple writes. However, since the
> actual
> > writes are driven from highly concurrent code, and since HTable is not
> > threadsafe, this would involve having a number of HTable instances, and a
> > control mechanism for leasing them out to individual threads safely.
> Except
> > at this point it seems like we will have recreated HTablePool, which
> > suggests that we’re doing something deeply wrong.
> >
> > What am I missing here? Since the HTableInterface.setAutoFlush method
> still
> > exists, it must be anticipated that users will still want to buffer
> writes.
> > What’s the recommended way to actually buffer a meaningful number of
> > writes, from a multithreaded context, that doesn’t just amount to
> creating
> > a table pool?
> >
> > Thanks in advance,
> > Aaron
> >
> > [1] https://issues.apache.org/jira/browse/HBASE-6580
> > [2] http://hbase.apache.org/book/perf.writing.html
> > [3]
> >
> >
> https://issues.apache.org/jira/browse/HBASE-6580?focusedCommentId=13501302&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13501302
> >
> >
>
