Applies to:
Oracle 11.2.0.4
on Linux Platform
Symptoms:
example 1:
Caused by: java.sql.SQLRecoverableException: Erreur d'E/S: Connection reset
example 2:
ORACLE CONNECTION PROBLEM (Attempt number 1 of 3) MESSAGE:Cannot create PoolableConnectionFactory (Erreur d'E/S: Connection reset)]
example 3:
return jpype.java.sql.DriverManager.getConnection(*driver_args)
jpype._jexception.SQLRecoverableExceptionPyRaisable: java.sql.SQLRecoverableException: Erreur d'E/S: Connection reset
Cause:
java.security.SecureRandom (#5 ) is a standard API provided by sun. Among various methods offered by this class void nextBytes(byte[]) is one. This method is used for generating random bytes. Oracle 11g JDBC drivers use this API to generate random number during login. Users using Linux have been encountering SQLException("Io exception: Connection reset").
The problem is two fold
- The JVM tries to list all the files in the /tmp (or alternate tmp directory set by -Djava.io.tmpdir) when SecureRandom.nextBytes(byte[]) is invoked. If the number of files is large the method takes a long time to respond and hence cause the server to timeout
- The method void nextBytes(byte[]) uses /dev/random on Linux and on some machines which lack the random number generating hardware the operation slows down to the extent of bringing the whole login process to a halt. Ultimately the the user encounters SQLException("Io exception: Connection reset")
Users upgrading to 11g can encounter this issue if the underlying OS is Linux which is running on a faulty hardware.
The cause of this has not yet been determined exactly. It could either be a problem in your hardware or the fact that for some reason the software cannot read from dev/random
Solution:
Change the setup for your application, so you add the next parameter to the java command:
-Djava.security.egd=file:/dev/./urandom
Or edit $JAVA_HOME/jre/lib/security/java.security and add the line : securerandom.source=file:/dev/./urandom
Why not securerandom.source=file/dev/urandom (#4)
Note the "/./" characters in the value. They are needed to work around known Oracle JRE bug #6202721.
See also JDK Enhancement Proposal 123. It is known that implementation of SecureRandom was improved in Java 8 onwards.
Sources: