Openshift System properties and Environment variables

For cloud deployable application, it is advisable to create them as much self-contained as possible. If application allows some configuration, these settings should be packaged inside war file and used as default values, while value override mechanism is provided.

Linux Environment variables

Unfortunately, following (usual) way of setting environment variable will not work on Openshift.

ctl_app stop jbossews
export MY_ENV_VAR="my_env_var_value"
ctl_app start jbossews

To be precise, JAVA_OPTS_EXT variable set like this, will not visible to java process running your application. To set it properly, you have to do it using Openshift rhc tool or using shortcut

echo "my_env_var_value" > ~/.env/user_vars/MY_ENV_VAR

An now you can in your webapp get variable value

  String my_env_var = System.getenv("MY_ENV_VAR"); //"my_env_var_value"
  if (my_env_var == null) {
    my_env_var = "Default value..."; //I told you not to depend on external configuration and provide default values...
  }

Java System Properties

System Properties are most commonly used to pass parameters into Java application. They are specified as java "-D" prefixed command-line parameters:

java -Dmyapp.param=whatever ...

then they can be obtained inside application

String param = System.getProperty("myapp.param"); //"whatever"

But Openshift managed servers are started using ctl_app start ... (or gears start ...) command and we are not directly in control of executing java so we can't add "-D" parameters.

Trick is to use JAVA_OPTS_EXT evironment variable. Since we know how to set Openshift Environment variable, it is just matter of:

echo "-Dmyapp.param=myapp.value" > .env/user_vars/JAVA_OPTS_EXT

...then restart your server...

ctl_app stop jbossews
ctl_app start jbossews

...and enjoy fruits of your effort (look for -Dmyapp.param=myapp.value)...

[wotan-anthavio.rhcloud.com 52d184e45973ca0bc0000088]\> jps -mlv
29444 sun.tools.jps.Jps -mlv -Dapplication.home=/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.45 -Xms8m
24633 org.apache.catalina.startup.Bootstrap start -Xmx256m -XX:MaxPermSize=102m -XX:+AggressiveOpts -DOPENSHIFT_APP_UUID=52d184e45973ca0bc0000088 -Djava.util.logging.config.file=/var/lib/openshift/52d184e45973ca0bc0000088/jbossews//conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.net.preferIPv4Stack=true -Dfile.encoding=UTF-8 -Djava.net.preferIPv4Stack=true -Dmyapp.param=myapp.value -Dcatalina.base=/var/lib/openshift/52d184e45973ca0bc0000088/jbossews/ -Dcatalina.home=/var/lib/openshift/52d184e45973ca0bc0000088/jbossews/ -Djava.endorsed.dirs= -Djava.io.tmpdir=/var/lib/openshift/52d184e45973ca0bc0000088/jbossews//tmp