Backward compatibility fixes for 0.92
-------------------------------------
Key: HBASE-5204
URL: https://issues.apache.org/jira/browse/HBASE-5204
Project: HBase
Issue Type: Bug
Components: ipc
Affects Versions: 0.92.0
Reporter: Benoit Sigoure
Assignee: Benoit Sigoure
Attachments:
0001-Add-some-backward-compatible-support-for-reading-old.patch,
0002-Make-sure-that-a-connection-always-uses-a-protocol.patch,
0003-Change-the-code-used-when-serializing-HTableDescript.patch
Attached are 3 patches that are necessary to allow compatibility between HBase
0.90.x (and previous releases) and HBase 0.92.0.
First of all, I'm well aware that 0.92.0 RC4 has been thumbed up by a lot of
people and would probably wind up being released as 0.92.0 tomorrow, so I
sincerely apologize for creating this issue so late in the process. I spent a
lot of time trying to work around the quirks of 0.92 but once I realized that
with a few very quasi-trivial changes compatibility would be made significantly
easier, I immediately sent these 3 patches to Stack, who suggested I create
this issue.
The first patch is required as without it clients sending a 0.90-style RPC to a
0.92-style server causes the server to die uncleanly. It seems that 0.92 ships
with {{\-XX:OnOutOfMemoryError="kill \-9 %p"}}, and when a 0.92 server fails to
deserialize a 0.90-style RPC, it attempts to allocate a large buffer because it
doesn't read fields of 0.90-style RPCs properly. This allocation attempt
immediately triggers an OOME, which causes the JVM to die abruptly of a
{{SIGKILL}}. So whenever a 0.90.x client attempts to connect to HBase, it
kills whichever RS is hosting the {{\-ROOT-}} region.
The second patch fixes a bug introduced by HBASE-2002, which added support for
letting clients specify what "protocol" they want to speak. If a client
doesn't properly specify what protocol to use, the connection's {{protocol}}
field will be left {{null}}, which causes any subsequent RPC on that connection
to trigger an NPE in the server, even though the connection was successfully
established from the client's point of view. The fix is to simply give the
connection a default protocol, by assuming the client meant to speak to a
RegionServer.
The third patch fixes an oversight that slipped in HBASE-451, where a change to
{{HbaseObjectWritable}} caused all the codes used to serialize {{Writables}} to
shift by one. This was carefully avoided in other changes such as HBASE-1502,
which cleanly removed entries for {{HMsg}} and {{HMsg[]}}, so I don't think
this breakage in HBASE-451 was intended.
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