Introduction

If you face the error

 Exception in thread "main" java.lang.Exception: connect to database failed: Io exception: Connection reset

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The article explains why this happens and what you can do about it.

Entropy Pool Issues

The JDBC interface requires random numbers to encrypt the connection. Java releases before 1.12 use the /dev/random file for high quality of randomness. However, when the entropy pool is is falling below the number of 64 units then /dev/random will block while reading random numbers.

The JDBC interface might be configured to read from the file /dev/random to get random numbers. The difference with the /dev/urandom file is, that /dev/urandom does not block if no random numbers are available.

Check Entropy Pool Issues (Unix)

Check Entropy Pool Configuration

You can check available entropy pool units with the command:

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The /dev/random file will deliver the next random number when the pool has reached more than 64 entropy units and otherwise blocks any application accessing the entropy pool. Such blocks can delay e.g. a JDBC connection to a database and may result in timeouts being exceeded.

Check Temporary Resolution

To verify the entropy pool being the root cause of this issue try this (requires root permission):

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If this solves your problem then the JDBC interface was not able to get random numbers from the OS in good time. Please note that the effect of the given commands is reverted on reboot.

Monitor Entropy Pool Use

You can check use of random numbers by running the following commands in two separate console windows:

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# initial test
dd if=/dev/random of=/dev/null bs=1024 count=1 iflag=fullblock 

# full test (should rngtest be available)
rngtest -c 100 </dev/random

Resolve Entropy Pool Issues

There are two alternative solutions: modify the Java security settings or modify the JOC Cockpit settings.

Both solutions apply to Unix and Windows operating systems.

Modify Java Security Configuration

Java holds the security configuration with the ./jre/lib/security/java.security or ./conf/security/java.security files. You can modify this file to point to /dev/urandom instead of /dev/random like this:

# original configuration
# securerandom.source=file:/dev/random

# updated configuration
securerandom.source=file:/dev/urandom

Modify JOC Cockpit Configuration

Installation

Should the entropy issue have occurred during installation then create or update the JAVA_OPTIONS environment variable like this:

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set JAVA_OPTIONS="-Djava.security.egd=file:///dev/urandom"

Operation

For permanent operation of JOC Cockpit on Unix add the following setting to your /home/<user-account>/.jocrc file:

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• for JOC Cockpit: js7_jocw.exe
  
  • Example: C:\Program Files\sos-berlin.com\js7\joc\service\js7_jocw.exe
• This brings up a utility that allows Java options to be specified:
  
  
  
  

Network Issues

A wrong network configuration can cause delays when executing Java and when accessing a database, e.g. if host name resolution takes too long. 

For Unix check the /etc/resolve.conf configuration file if entries for name servers and host name resolution are correct.

Other Root Causes

Another possible reason for delays could be a huge number of files in /tmp as the JDBC interface tries to list files in the /tmp directory when SecureRandom.nextBytes(byte[]) is invoked.

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