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From "Matteo Bertozzi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11660) Make WAL reader follow contract for java.io.InputStream.available()
Date Mon, 04 Aug 2014 17:30:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14084934#comment-14084934

Matteo Bertozzi commented on HBASE-11660:

if I read it correctly advance() now will always return true (and the hasNext boolean can
be removed).
but this seems to work just because we know the number of items in the WAL ahead, or am I
missing something?
for (int i = 0; i < count; i++) {
      // Throw index out of bounds if our cell count is off
      if (!cells.advance()) {

WALEdit.java:    while (kvs.size() < expectedCount && cellDecoder.advance()) {

> Make WAL reader follow contract for java.io.InputStream.available()
> -------------------------------------------------------------------
>                 Key: HBASE-11660
>                 URL: https://issues.apache.org/jira/browse/HBASE-11660
>             Project: HBase
>          Issue Type: Bug
>          Components: wal
>            Reporter: Eric Hanson
>            Priority: Minor
>         Attachments: hbase-11660.01.patch
> In the process of building support to running HBase on Microsoft Azure HDInsight, I hit
an issue in the HBase WAL reading process that took a lot of time to debug. The WAL reading
code depends on available() for the log InputStream never returing 0 until end of file. This
is not the same as the contract in java.io.InputStream for available. 
> To prevent future grief for others that may want to port HBase onto storage systems other
than HDFS, I propose to change the HBase WAL reader so it does not assume that EOF has been
reached when available() == 0. It instead would treat available only as described in InputStream,
i.e. available() is merely the number of bytes that could be read from the stream without
blocking. That could be 0 even before EOF.

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