How to get custom couchdb to run as upstart job?

I built a recent version of CouchDB with the excellent iriscouch/build-couchdb repo, and now I want to create an upstart job on my Ubuntu 12.04 server.

However, the upstart job fails with:

kernel: [265024.963594] init: couchdb_a main process (5341) terminated with status 1

The upstart conf file (/etc/init/couchdb_a.conf):

description     "CouchDB v1.2.0"
console output

start on (local-filesystems and net-device-up IFACE!=lo)
stop on runlevel [!2345]

pre-start script
  logger -t "$0" "pre-start"
  export PATH="/path/to/build-couchdb/build/bin:$PATH"
  logger -t "$0" "DEBUG (pre-start): `set`"
end script

exec /path/to/build-couchdb/build/bin/couchdb

From what I can tell, the custom couchdb simply needs its PATH adjusted to the location of the couchdb binary (that's what iriscouch's env.sh does).

But whether I update the PATH or not, the custom couchdb will not launch in this upstart job (it works perfectly from a shell).

Solution

This upstart configuration successfully handles a custom install of CouchDB:

# couchdb v1.2.0
#
# Custom installation of CouchDB

description     "CouchDB v1.2.0, local"
console output

# start after all filesystems & network interfae are available
start on (local-filesystems and net-device-up IFACE!=lo)
stop on runlevel [!2345]

# set working directory
env COUCHDB_WD="/path/to/build-couchdb/build/bin"
export COUCHDB_WD

# required for erlang
env HOME="/home/user"
export HOME

script
  # modify PATH to hit local couchdb's working directory first
  PATH="$COUCHDB_WD:$PATH"
  #export PATH # not necessary inside script block
  #logger -t $0 "HOME='$HOME'"
  #logger -t $0 "PATH='$PATH'"
  # output couchdb logs to custom location
  #exec >>/home/user/couchdb_local.log 2>&1
  exec couchdb
end script

This helped, but only partially:

# change working directory: not effective with env variable
chdir /path/to/build-couchdb/build/bin

chdir works if just the executable needs to be run from a directory, but doesn't modify PATH, and does not accept env variables.

The commented lines in the script block helped me ensure that HOME and PATH were properly updated. The exec >> line outputs all couchdb logging to a custom file, which helped me find the root cause: Erlang.

Specifically, the erlexec: HOME must be set error. HOME can be apparently any value (not sure if it must exist, but I set it to my user account's home directory).