Configuration error[Application secret not set]

Question

I got this error running Play 2.4 server in production mode:

play.api.UnexpectedException: Unexpected exception[ProvisionException: Unable to provision, see the following errors:

1) Error in custom provider, @6mh5cjo5l: Configuration error
  while locating play.api.libs.CryptoConfigParser
  while locating play.api.libs.CryptoConfig

...

Caused by: play.api.PlayException: Configuration error[Application secret not set]

How to fix?

Answer 1

The default Play template uses the following:

play.crypto.secret="changeme"

in the application.conf which needs to be changed for use in production. Play provides an utility to generate a random secret for you:

./activator playGenerateSecret

with which you can then populate as an environment variable:

APPLICATION_SECRET=...

and in conf/application.conf ensure the following:

play.crypto.secret="changeme"
play.crypto.secret=${?APPLICATION_SECRET}

which as the Play documentation explains:

The second line in that configuration sets the secret to come from an environment variable called APPLICATION_SECRET if such an environment variable is set, otherwise, it leaves the secret unchanged from the previous line.

Then the error will go away.