# Start mongo. 
rm -rf  mongo/functions mongo/logs
  # Setup 3 directories:
mkdir -p mongo/functions mongo/logs
  # If not AWS,	  ignore.  Commented out since we probably did this already. 
# sudo  -s -- bash -c   '  echo "127.0.0.1 localhost ">> /etc/hosts '
  # Start once mongo instance
mongod --dbpath mongo/functions --port 4001 --smallfiles --oplogSize 50 --replSet r --bind_ip 127.0.0.1 > mongo/logs/functions.log 2>&1  & 
sleep 2

   # Test mongo, should get backs status.
  # In  the mongo shell
mongo --port 4001 --eval "db.runCommand( { serverStatus: 1, localtime: 1 } )" | grep '"uptime"'

  # Make a client side function. 
echo '
function scheck() {
  s = db.runCommand( { serverStatus: 1 });
  print (s.uptime);
}
' > mongo/sample_functions.js

  # Execute it with eval and it will fail. 
mongo --quiet --port 4001 --eval "scheck()" mongo/sample_functions.js

  # You have to go to shell or put the command in the file. 
echo '
function scheck() {
  s = db.runCommand( { serverStatus: 1 });
  print (s.uptime);
}
scheck()
' > mongo/sample_functions.js
mongo --quiet --port 4001  mongo/sample_functions.js 

  # Or properly use the load command. 
echo '
function scheck() {
  s = db.runCommand( { serverStatus: 1 });
  print (s.uptime);
}
' > mongo/sample_functions2.js
mongo --quiet --port 4001 --eval "load('mongo/sample_functions2.js'); scheck()"  

  # Now create a server side function. 
  # Look at https://docs.mongodb.com/manual/tutorial/store-javascript-function-on-server/

echo '
db.system.js.save(
   {
     _id : "custom_uptime ,
     value : function (){ s = db.runCommand( { serverStatus: 1 }); return s.uptime; }
   }
);' > mongo/server.js
  
  # Load function
mongo --quiet --port 3001 mongo/server.js

  # Execute function, should fail only on 5. 
mongo --quiet --port 3001 test --eval "db.loadServerScripts(); custom_uptime();"
mongo --quiet --port 3002 test --eval "rs.slaveOk(); db.loadServerScripts(); custom_uptime();"
mongo --quiet --port 3003 test --eval "rs.slaveOk(); db.loadServerScripts(); custom_uptime();"
mongo --quiet --port 3004 test --eval "rs.slaveOk(); db.loadServerScripts(); custom_uptime();"
mongo --quiet --port 3005 test --eval "rs.slaveOk(); db.loadServerScripts(); custom_uptime();"
mongo --quiet --port 3006 test --eval "rs.slaveOk(); db.loadServerScripts(); custom_uptime();"