Hot code reloading is really amazing in Erlang. We use it to patch a method without restarting on a regular basis. Getting reltool properly configured to deploy the new version of your application though is a MAJOR pain in the ass.
for the non-erlangers:
the 'simple' way (ie i have a tiny change i want to make, so i'll just ssh in and do it) is to just edit your code, then attach to an existing node, and do make:all([load]) to pick up the code changes. we added a makefile "make attach" that does this for us.
the 'reltool' way is you package your application into releases. We use jenkins build numbers as the third digit in our releases, so each one is packaged into a zip, encrypted, and then is ready to deploy. at deploy time, the zip is copied to all machines, then we use some escript to attach to the running nodes, and use the 'release_handler' bring up the N+1 version of our app. it's a pain but once it's configured it's amazing...
for the non-erlangers:
the 'simple' way (ie i have a tiny change i want to make, so i'll just ssh in and do it) is to just edit your code, then attach to an existing node, and do make:all([load]) to pick up the code changes. we added a makefile "make attach" that does this for us.
the 'reltool' way is you package your application into releases. We use jenkins build numbers as the third digit in our releases, so each one is packaged into a zip, encrypted, and then is ready to deploy. at deploy time, the zip is copied to all machines, then we use some escript to attach to the running nodes, and use the 'release_handler' bring up the N+1 version of our app. it's a pain but once it's configured it's amazing...