#Overseer

Overview

Overseer is a small Java application to run tasks periodically while certain conditions are met, and to report the success or failure of those tasks over a WebSocket interface. Some functionality might work on Windows, but I've only tested on Linux.

Specifically I use it to run a couple of different unison synchronization commands periodically while I'm connected to my home network. There is a KDE5 plasmoid I leave in a toolbar to show the time since the last execution and the outcome of that execution, and to trigger a restart if necessary. This makes it easy to keep files synchronized continually, and to verify the age of the last sync.

The invocation I use is as follows

/usr/bin/java -jar /use/local/bin/Overseerbundle.jar \
  --command "unison jody -batch" \
  --command "unison family -batch" \
  --socket 4321 \
  --status_file /home/%u/.overseer.status \
  --log_file /var/log/overseer_unison.log

This starts Overseer to run unison in batch mode on two different configurations, starts the status reporting socket on port 4321, writes a status log (to retain state across restarts) in the user's home directory, and a log file in /var/log.

More invocation details are available using the --help flag.

Components

• src/main/java/com/jsankey contains source files for the Java application, described in more detail below
• src/test/java/com/jsankey contains [partial] unit tests for the Java application
• build.gradle is a gradle build configuration for the project, including a jarBundle task that uses OneJar to compile Overseer and all its dependencies into a single jar at build/libs/OverseerBundle.jar
• overseer_check.html is a web page that uses WebSockets to communicate with Overseer on a [currently hardcoded] port to display status and trigger restarts
• overseer_check.py is a simple python script that communicates with Overseer over a plaintext socket to display status. Since this is the only thing not using websockets it might not be available in the future
• plasmoid contains a KDE5 plasmoid to display status. This has both a compact form suitable for a toolbar and an expanded form showing more details about the outcome of each command and facilitating status. The port is again hardcoded

Package Level Design

• com.jsankey.overser Contains the core of the program, including Configuration to interpret and store command line options and Executive to handle the scheduling.
• com.jsankey.overser.checks contains the gating conditions on execution. Currently the only one of these is to wait for a named Wifi network. The current implementation depends on iwconfig so is not cross platform.
• com.jsankey.overser.history maintains a history of recent executions for each command and handles its serialzation/deserialization to the status file.
• com.jsankey.overser.io handles everything to do with sockets including creation, thread management, WebSocket upgrade and command parsing.
• com.jsankey.overser.runner handles the initiation and termination of the external commands Overseer exists to oversee.
• com.jsankey.overser.util contains a couple of generic utility classes.

Known Issues

• Unit test coverage isn't complete
• Plasmoid makefile isn't complete
• Plasmoid and HTML should have a configuration to set the port
• Proper packaging (e.g. Deb file) would be nice

Future Plans

Right now the project is meeting my needs and I'm not planning on doing a lot of maintenance unless things break for my use case. However, it there is something that you'd like or if you find any bugs let me know. I'd consider adding extra features or taking this further.