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https://issues.apache.org/jira/browse/HBASE-12728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14287754#comment-14287754
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Solomon Duskis commented on HBASE-12728:
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I like the change to mutate() rather than put(). I'm also very grateful for
someone else having taken over this critical work. I do have a couple of
preferences:
1) I'm guessing that Delete objects won't be as big as Puts as far as heapSize
is concerned. It might not be appropriate to use the currentWriteBufferSize to
track Deletes like it is for Puts. Perhaps something more like a deleteCount
would be appropriate?
2) Since BufferedMutatorBuilder is passed into the Connection object, I'd
prefer that it doesn't have any references to internal classes such as
ClusterConnection, RpcRetryingCallerFactory and RpcControllerFactory. I'd also
prefer that it doesn't return a BufferedMutatorImpl, and that the Connection
would be responsible for the initialization.
> 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: Nick Dimiduk
> Priority: Blocker
> Fix For: 1.0.0, 2.0.0, 1.1.0
>
> Attachments: 12728.connection-owns-buffers.example.branch-1.0.patch,
> HBASE-12728-2.patch, HBASE-12728-3.patch, HBASE-12728-4.patch,
> HBASE-12728-5.patch, HBASE-12728.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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