Java Web Applications Start Slow or are Failing

Products

• Services Suite

Issue/Introduction

You have a Java web application (Java Web, Grails, Spring, etc...) which starts up very slowly or fails indicating that it did not begin accepting for connections.

Cause

When a Java web application is deployed to PWS, the Java buildpack configures an instance of Apache Tomcat where the Java web application will be deployed. Recent versions of Tomcat (7 and 8) rely on Java's SecureRandom class to provide random values for things like session ids.  Depending on the JVM and environment, the startup of Tomcat can be delayed if SecureRandom does not have access to sufficient entropy.  This will, in turn, cause your application to start slow and, if it's slow enough, fail with:

Error Message:

instance failed to start accepting connections.

Resolution

The recommended workaround to this problem is to add -Djava.security.egd=file:/dev/./urandom to your list of JVM options.  This instructs the JVM to use a non-blocking entropy source (i.e./dev/urandom) instead of the default blocking entropy source (i.e. /dev/random).

This can be done in your application by setting the JAVA_OPTS environment variable either via your application's manifest.yml file or with the cf set-env command.

Ex:  manifest.yml
 

---
applications:
- name: <your-app>
  memory: 512M
  instances: 1
  path: <path-to-your-app>
  env:
    JAVA_OPTS: -Djava.security.egd=file:///dev/urandom

Ex: cf set-env

 $ cf set-env <your-app> JAVA_OPTS "-Djava.security.egd=file:///dev/urandom"

It is worth mentioning that some believe that this workaround can result in your application receiving data that is less random.  There are varying opinions on this matter and how it might affect an application.  For the purposes that Tomcat needs this random data (session id generation), we do not believe that this will weaken the security of your application.