Init file for HBase Thrift Server

As part of our HBase setup, we run Thrift servers. This is pretty simple, except for the init files.
Since we’re running Thrift standalone (and not as part of a full HBase server), I couldn’t find a perfect fit from googling.
I eventually settled for this puppet template, but it had a big deficiency - no support for status.

A tiny bit about init

SysVInit is the old-school way of managing services in Linux (and Unix).
Every service has an “init script”, located in /etc/init.d/SERVICENAME, which is in charge of controlling the sevice.
It is called by using service SERVICENAME ACTION, where every script is free to define its own actions, but the standard ones are start,stop,restart,status.

Why status matters

Using status is the best way of checking whether a service is alive.
It could be a sysadmin checking for issues, Nagios making sure the service is OK, or a configuration management tool checking whether it should start the service.
Just for fun, here is how Chef uses it. I quote from the holy repo of Chef, file lib/chef/provider/service/simple.rb, verse 130:

if shell_out("#{default_init_command} status").exitstatus == 0
  @current_resource.running true
  Chef::Log.debug("#{@new_resource} is running")
end

So as long as service SERVICENAME status exits successfully (exit code 0), Chef thinks the service is running.

Implementing status

Since I’m using CentOS 6.5, my common service functions file (/etc/init.d/functions) is old, so it’s not creating new pids (--pidfile only checks for an existing file, not creating a new one) and it can’t rename the process (I’ve heard of a magical --name parameter, but can’t find it in my file).
Because of that, I can’t find the process after starting it, so I can’t make sure it’s still alive. After digging around in the HBase code, I found out that HBase keeps PID files.
bin/hbase-daemon.sh:

(start)
  mkdir -p "$HBASE_PID_DIR"
  if [ -f $pid ]; then
    if kill -0 `cat $pid` > /dev/null 2>&1; then
    echo $command running as process `cat $pid`.  Stop it first.
    exit 1
  fi
fi

All I needed was to use this pidfile in my init script. I accomplished this by replicating the pidfile-building logic in my init script.
It looks something like:

HBASE_PID_DIR=/var/run/
HBASE_IDENT_STRING="$HOSTNAME"
command=thrift
pid=$HBASE_PID_DIR/hbase-$HBASE_IDENT_STRING-$command.pid

Now I can implement the status check like so:

status)
  status -p $pid java
  RETVAL=$?
;;

Note that the process name is java. This is imperfect because the thrift process might die and another java process might take its place, but I don’t find it too much of a risk for now. I might modify it later.

The Result

The full file is stored as a gist, but be warned - it’s a Chef template!
You can probably manually fill it out though.