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https://issues.apache.org/jira/browse/HIVE-2147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13040006#comment-13040006
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[email protected] commented on HIVE-2147:
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bq. On 2011-05-25 03:43:30, Carl Steinbach wrote:
bq. > trunk/metastore/if/hive_metastore.thrift, line 348
bq. > <https://reviews.apache.org/r/738/diff/1/?file=18685#file18685line348>
bq. >
bq. > Identifying the message type using an integer seems brittle. This
won't work if you have more than one application that is firing events at the
metastore.
bq.
bq. Ashutosh Chauhan wrote:
bq. There are two other alternatives that I thought of before settling on
this one.
bq. 1) Add specific apis for different message types. This would have made
doing this generic api redundant but then this will result in application
specific apis in the metastore. E.g., in HCatalog we want to send a message for
"set of partitions" telling Metastore to mark them as done. What does
finalizePartition() mean in metastore api when Metastore itself is not aware of
this concept as this is application specific. This would be confusing.
bq. 2) Use enums instead of integer. This will result in similar problem
as above though on a lower scale. Enums give compile time safety so we have to
define them in Metastore code. Defining application specific enums doesnt look
like a good idea because of similar reasons.
Another approach would be to serialize the events, and then wrap the serialized
event object in a Thrift struct that also contains a field with the fully
qualified class name of the event. When the server receives the event struct it
would pass the class name to each of the listeners, which then have the option
of deserializing the event if they are capable of handling it.
Using qualified event class names would help to eliminate the burden of
coordinating the event id namespace, and it would also make it much easier to
emit meaningful logging information on the server side.
bq. On 2011-05-25 03:43:30, Carl Steinbach wrote:
bq. >
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java,
line 3126
bq. > <https://reviews.apache.org/r/738/diff/1/?file=18694#file18694line3126>
bq. >
bq. > So the event model is that each event may be handled by at most one
event handler?
bq.
bq. Ashutosh Chauhan wrote:
bq. Yes.
Why not give each listener the opportunity to handle every event? It seems like
a pretty conventional use case that you would want to have more than one
listener operate on some events. This also seems like a more conventional
policy for a pluggable listener framework.
bq. On 2011-05-25 03:43:30, Carl Steinbach wrote:
bq. > trunk/metastore/if/hive_metastore.thrift, line 347
bq. > <https://reviews.apache.org/r/738/diff/1/?file=18685#file18685line347>
bq. >
bq. > Having separate calls for sending request and response messages
looks unnecessary. A sendMessage() function with separate request and response
message types should work just as well, and will help to avoid confusion --
otherwise I think people will assume that receiveMessage is a polling call.
bq. >
bq. > This is starting to look like a general purpose messaging/rpc
framework. Is that the intent?
bq. >
bq.
bq. Ashutosh Chauhan wrote:
bq. >> A sendMessage() function with separate request and response message
types should work just as well.
bq. That is correct. But semantically they are different. In sendMessage()
user is just notifying Metastore of an event and is not bothered of return
value. recvMessage() user is asking for a response for his message. This
distinction is further enforced by return types. We could just have one api
sendMessage() for both as you suggested, but having distinct apis for sending
and receiving makes it easier for client to understand the semantics.
bq.
bq. >> This is starting to look like a general purpose messaging/rpc
framework.
bq. Well general purpose rpc framework would be much more sophisticated. I
am not aiming for that.
bq. > Well general purpose rpc framework would be much more sophisticated. I am
not aiming for that.
Sorry, I shouldn't have said "general purpose", but it does sound like adding
an extensible RPC mechanism is one of the goals of this patch. This seems like
a significant departure from the goal of HIVE-2038, which I think was more
narrowly focused on adding an event framework, or at least that's what I
remember discussing at the contrib meeting. RPCs are quite different from
events, and if if we add this feature it shouldn't be conflated with events. I
think the RPC modifications should be proposed in a separate ticket, and we
should keep the focus in this ticket on adding an event framework.
bq. On 2011-05-25 03:43:30, Carl Steinbach wrote:
bq. >
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/MetaStoreEventListener.java,
line 86
bq. > <https://reviews.apache.org/r/738/diff/1/?file=18697#file18697line86>
bq. >
bq. > canProcessSendMessage() looks like a redundant call. Is there any
reason that this can't be be rolled into processSendMessage()?
bq. >
bq.
bq. Ashutosh Chauhan wrote:
bq. Event model is every event is handled by atmost one handler. If we
roll this in processSendMsg() then we have to make this method return boolean
which will tell whether this event got serviced by this handler or not. Then
how will it communicate back the actual return value. In case of sendMsg() this
is fine, but recvMsg() returns a valid value which is then need to be returned
to a client. So, we first ask handler if it can handle the message and then
expect a valid return value in processRecvMsg() call.
I wasn't sure before if these changes were supposed to enable RPCs. Now that
that's clear, I don't think this code belongs in MetaStoreEventListener. It
belongs in MetaStoreGenericRPCHandler, or something like that. Can you please
remove the RPC code, and change the names of the event code (e.g. one way
communication from client to server) to make it clear that these are events,
and not something more generic like RPCs?
- Carl
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/738/#review713
-----------------------------------------------------------
On 2011-05-12 21:03:29, Ashutosh Chauhan wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/738/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2011-05-12 21:03:29)
bq.
bq.
bq. Review request for hive and Carl Steinbach.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. Updated patch to include missing ASF license and generated thrift code.
bq.
bq.
bq. This addresses bug HIVE-2147.
bq. https://issues.apache.org/jira/browse/HIVE-2147
bq.
bq.
bq. Diffs
bq. -----
bq.
bq. trunk/metastore/if/hive_metastore.thrift 1102450
bq. trunk/metastore/src/gen/thrift/gen-cpp/ThriftHiveMetastore.h 1102450
bq. trunk/metastore/src/gen/thrift/gen-cpp/ThriftHiveMetastore.cpp 1102450
bq.
trunk/metastore/src/gen/thrift/gen-cpp/ThriftHiveMetastore_server.skeleton.cpp
1102450
bq.
trunk/metastore/src/gen/thrift/gen-javabean/org/apache/hadoop/hive/metastore/api/ThriftHiveMetastore.java
1102450
bq.
trunk/metastore/src/gen/thrift/gen-php/hive_metastore/ThriftHiveMetastore.php
1102450
bq.
trunk/metastore/src/gen/thrift/gen-py/hive_metastore/ThriftHiveMetastore-remote
1102450
bq.
trunk/metastore/src/gen/thrift/gen-py/hive_metastore/ThriftHiveMetastore.py
1102450
bq. trunk/metastore/src/gen/thrift/gen-rb/thrift_hive_metastore.rb 1102450
bq.
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java
1102450
bq.
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStoreClient.java
1102450
bq.
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/IMetaStoreClient.java
1102450
bq.
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/MetaStoreEventListener.java
1102450
bq.
trunk/metastore/src/java/org/apache/hadoop/hive/metastore/events/MessageEvent.java
PRE-CREATION
bq.
trunk/metastore/src/test/org/apache/hadoop/hive/metastore/DummyListener.java
1102450
bq.
trunk/metastore/src/test/org/apache/hadoop/hive/metastore/TestMetaStoreEventListener.java
1102450
bq.
bq. Diff: https://reviews.apache.org/r/738/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq. Updated TestMetaStoreEventListener to test new api.
bq.
bq.
bq. Thanks,
bq.
bq. Ashutosh
bq.
bq.
> Add api to send / receive message to metastore
> ----------------------------------------------
>
> Key: HIVE-2147
> URL: https://issues.apache.org/jira/browse/HIVE-2147
> Project: Hive
> Issue Type: Improvement
> Components: Metastore
> Reporter: Ashutosh Chauhan
> Assignee: Ashutosh Chauhan
> Fix For: 0.8.0
>
> Attachments: api-without-thrift.patch
>
>
> This is follow-up work on HIVE-2038.
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