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https://issues.apache.org/jira/browse/CALCITE-5009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17515699#comment-17515699
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Istvan Toth commented on CALCITE-5009:
--------------------------------------
Looking at the code some more, we're only retrying if we get a
NoSuchConnectionException exception from the server side.
The text is:
"Connection not found: invalid id, closed, or expired: "
Looking at the code it seems that the connection object is indeed only removed
on close or when the cache decides to remove it (capcity, timeout...), but it
does not get removed on other errors.
This does not affect the patch, but I need to update the description.
> Transparent JDBC connection re-creation may lead to data loss
> -------------------------------------------------------------
>
> Key: CALCITE-5009
> URL: https://issues.apache.org/jira/browse/CALCITE-5009
> Project: Calcite
> Issue Type: Bug
> Components: avatica
> Reporter: Istvan Toth
> Assignee: Istvan Toth
> Priority: Major
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Currently, if the server-side JDBC connection goes away for any reason
> * Avatica connection cache expiry
> * LB/HA Failover
> * Some problem with the "real" connection
> we attempt to create a new "real" JDBC connection, and continue using that
> instead of the original connection
> [https://github.com/apache/calcite-avatica/blob/fbdcc62745a0e8920db759fb6bdce564d854e407/core/src/main/java/org/apache/calcite/avatica/AvaticaConnection.java#L796]
> This is fine for most read-only connections, but it can break transaction
> semantics, which is captured in the "real" connection object.
> {noformat}
> conn.setAutocommit(false)
> stmt = conn.createStatement()
> execute(insert A)
> //Connection lost and object recreated which now proxies a new "real"
> connection
> execute(insert B)
> conn.commit()
> //We have lost "insert A"{noformat}
> I'm not sure if we synchronize autocommit state of the new connection to the
> lost one or not, but it's bad either way.
>
> We should either completely drop this feature, add some logic that avoids it
> if there is an open transaction and/or only allow it for connections that
> have the readOnly flag set.
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