[
https://issues.apache.org/jira/browse/DERBY-3454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574612#action_12574612
]
Serge Tsv commented on DERBY-3454:
----------------------------------
V.Narayanan, thanks for your comments!
I see the following generic use case for receiver/transmitter classes:
1. A receiver/transmitter instance is created.
2. An initConnection method is called on the created instance
3. sendMessage/readMessage calls are executed on the initialized
receiver/transmitter instance
For the flow above:
* If (3) is executed before (2), then I guess this would be a programmatic
error
and a RE should be called (like IllegalStateException)
* If (2) fails, I do also consider executing (3) after that as a
programmatic error,
because in this case a transmitter/receiver hasn't been properly
initialized.
And there's an attempt to use a transmitter/receiver which has turned up
to
be in an illegal state.
You're right that the transmitter/receiver is an abstraction above the
connection.
But I'm just trying to say that it might be wrong (from a programmatic point of
view)
to try to use them in an illegal state. And might be better to properly process
a (2)
failure and make it so sendMessage/readMessage methods won't be called
afterwards, instead of relying on an IOException been reported to a user.
> If this had been true the NPE (which is also a RuntimeException)
would have resulted in a XRE04 :).
I think that XRE04 is thrown by an initConnection method. The NPE was caused
by a tearDown method, and now it's been fixed, and there're no further calls to
sendMessage/readMessage in case of XRE04.
Thanks!
> 'java.lang.NullPointerException' is thrown when starting a master db before a
> slave one
> ---------------------------------------------------------------------------------------
>
> Key: DERBY-3454
> URL: https://issues.apache.org/jira/browse/DERBY-3454
> Project: Derby
> Issue Type: Bug
> Components: Replication
> Affects Versions: 10.4.0.0
> Reporter: Serge Tsv
> Assignee: V.Narayanan
> Attachments: Derby3454.diff, Derby3454.stat
>
>
> The 'java.lang.NullPointerException' exception is thrown when a database is
> started in a master mode and is trying to establish a connection to an slave
> database socket, which is not available.
> The exception is by the MasterController#startMaster(). First, it tries to
> setup connection with a slave database using a transmitter:
> MasterController#setupConnection
> -> transmitter = new ReplicationMessageTransmit();
> transmitter.initConnection()
> -> new InetSocketAddress() -> createSocket() -> connect()
> The connect() method throws a ConnectException, and so fails to create a
> socketConn instance. The exception is then wrapped several times an
> propagated back to the MasterController#startMaster() method. It's caught
> there and then a MasterController#teardownNetwork() method is called, which
> tries to send a STOP message using the aforementioned transmitter, which
> hasn't been able to init a connection.
> A transmitter simply tries to call socketConn.writeMessage(message), which
> throws NPE because socketConn is null.
> Thanks!
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
