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https://issues.apache.org/jira/browse/CALCITE-5009?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Istvan Toth updated CALCITE-5009:
---------------------------------
Docs Text:
Avatica will no longer tranparently create a new connection if the proxied
connection object expires from the server side cache.
The transparent reconnection feature can be enabled setting the
"transparent_reconnection" JDBC property to true, but this is only recommended
for connections where losing the connection state, including transactional
state, is not a problem.
However, it is recommended to tune the connection and server side cache
parameters to avoid the cache expiry alltogether.
was:
Avatica will no longer tranparently create a new connection if the proxied
connection object times out from the server side cache.
The transparent reconnection feature can be enabled setting the
"transparent_reconnection" JDBC property to true, but this is only recommended
for connections where losing the connection state, including transactional
state, is not a problem.
However, it is recommended to tune the connection and server side cache
parameters to avoid the cache expiry alltogether.
> 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: 40m
> Remaining Estimate: 0h
>
> Currently, if the server-side JDBC connection goes away because it is expored
> from the server-side connection cache we attempt to transparently 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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