Oracle: Lightweight Connection Validation

[tsegismont]

See #1450

[tsegismont]

Hi @loiclefevre , I would appreciate your advice on this. Is the SOCKET connection validation level appropriate (non-blocking)? Or should we consider something lower, like INBAND_DOWN or LOCAL?

cc @DavideD

[gvenzl]

Hey @tsegismont,

@loiclefevre is on his well-deserved holiday, hence I'm adding @jeandelavarene to this thread to provide guidance on your question about OracleConnection.ConnectionValidation. and which mode to use.

Meanwhile, according to the JavaDoc it would seems indeed that SOCKET does not involve a network call but just checks whether the socket is still alive.

[jeandelavarene]

Here is a description of the different validation modes in decreasing order of validation strength:

• "SERVER" (or "COMPLETE") makes the driver execute a basic SQL query "SELECT 'x' FROM DUAL",
• "NETWORK" makes the driver issue an OPING TTC function. This is the most lightweight roundtrip to the DB. It's the default validation mode.
• "SOCKET" makes the driver write a zero-length NS data packet on the socket that is ignored by the server. There is no guarantee that this call will always be non-blocking. It should be non-blocking in most of the cases.
• "INBAND_DOWN" makes the driver do a non-blocking socket read call on the socket
• "LOCAL" same as above
• "NONE" just checks the connection's lifecycle (variable check)

Note that, for example, a "SOCKET" validation may return a false positive (it may not always detect all socket defects). On the other hand, a "SOCKET" validation is much faster than "NETWORK". In most cases, we recommend using "SOCKET" validation at connection borrow (in UCP for example). For applications that can't tolerate an error on the connection, turning on "SERVER" or "NETWORK" would be more appropriate.

CC @gvenzl

[tsegismont]

Thank you @gvenzl and @jeandelavarene

In this part of our code we can't tolerate the driver to block (event not every time). And for the other clients (Pg, MySQL, ...etc) where Vert.x manages the connection, we only check the connection's lifecycle (variable check):

vertx-sql-client/vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/SocketConnectionBase.java

Line 160 in ccc784a

return status == Status.CONNECTED;

So I think the appropriate setting is NONE in our case. This will provide the same experience as with other clients.