In a recent project I had the need for automatically starting a Datomic transactor when booting a Mac server. On Mac OS systems and some other Linux/BSD systems, starting and stopping programs is handled by the
In this post I will briefly describe the steps needed for setting up a Datomic transactor with
launchd to ensure that it is automatically started when booting the system.
Datomic comes in a free and a commercial version. Here I will assume you have downloaded the free version from http://www.datomic.com into the
~/Downloads folder on your system.
In a terminal, create an appropiate place for your Datomic installation.
sudo mkdir -p /usr/local cd /usr/local sudo unzip ~/Downloads/datomic-free-0.8.3591.zip sudo ln -s datomic-free-0.8.3591 datomic
The Datomic process should run under a restricted privilege user. I recommend creating a dedicated user and group for this purpose. First, check that the group id and user id 109 is free on your system. If it is not, use another free id. You can check the numbers using
dscl . -list /Groups PrimaryGroupID | grep 109 dscl . -list /Users UniqueID | grep 109
The following commands will create the group
_datomic and the user
sudo dscl . -create /Groups/_datomic PrimaryGroupID 109 sudo dscl . -create /Groups/_datomic RealName "Datomic Users" sudo dscl . -create /Groups/_datomic Password \* sudo dscl . -create /Users/_datomic UniqueID 109 sudo dscl . -create /Users/_datomic PrimaryGroupID 109 sudo dscl . -create /Users/_datomic HomeDirectory /usr/local/datomic sudo dscl . -create /Users/_datomic UserShell /usr/bin/false sudo dscl . -create /Users/_datomic RealName "Datomic Administrator" sudo dscl . -create /Users/_datomic Password \*
We need to make sure the user and group of the Datomic installation itself is
wheel. We also need to make sure the
_datomic user which is going to run the process will have a place to write the logs and data from the database. In this tutorial, I have chosen to place the data and logs under
/usr/local/. If you have a dedicated place for data on your system, such as
/opt, you should put it there instead
cd /usr/local/datomic sudo chown -R root:wheel . sudo mkdir data sudo mkdir log sudo chown _datomic:admin data log sudo chmod 2770 data log
You need to set the log and data directory in the transactor properties file. In this tutorial, I’ve used the template file from
config/samples/free-transactor-template.properties in the installed Datomic system. The edited file is placed in
protocol=free host=localhost #free mode will use 3 ports starting with this one: port=4334 ## optional overrides if you don't want ./data and ./log data-dir=/usr/local/datomic/data log-dir=/usr/local/datomic/log #pid-file=<write process pid here on startup>
launchd reads plist files to determine which programs to start when booting the system. Save the following pice of code in the file
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>EnvironmentVariables</key> <dict> <key>JAVA_HOME</key> <string>/System/Library/Frameworks/JavaVM.framework/Home</string> </dict> <key>Label</key> <string>datomic.transactor</string> <key>ServiceDescription</key> <string>Datomic Transactor</string> <key>UserName</key> <string>_datomic</string> <key>GroupName</key> <string>_datomic</string> <key>WorkingDirectory</key> <string>/usr/local/datomic</string> <key>ProgramArguments</key> <array> <string>/usr/local/datomic/bin/transactor</string> <string>/usr/local/datomic/config/free-transactor.properties</string> </array> <key>RunAtLoad</key> <true/> <key>KeepAlive</key> <true/> <key>StandardOutPath</key> <string>/usr/local/datomic/log/launchd-stdout.log</string> <key>StandardErrorPath</key> <string>/usr/local/datomic/log/launchd-stderr.log</string> </dict> </plist>
The configuration will ensure that the transactor is started upon boot, that it is executed as the correct user, and that output will be written to the Datomic log directory. Please make sure that the locations of the Java framework etc. matches your system.
Before the configuration is used by the system, it must be loaded using
sudo launchctl load /Library/LaunchDaemons/datomic.transactor.plist
unload option if you need to remove the datomic transactor.
sudo launchctl unload /Library/LaunchDaemons/datomic.transactor.plist
Since the transactor is configured to be up at all times, you can restart if by asking
launchctl to stop it
sudo launchctl stop datomic.transactor
That should be all that is needed for setting up Datomic on a Mac OS system. Please check the logs to make sure your system is booted. Apart from the log files for standard out and error defined in the plist file,
launchd logs errors to