Backend Server Parameterization
Backend configuration establishes several key aspects of MythTV's operation from declaring master and slave servers to defining service addresses, ports, storage directories and a number of features that pertain to shutdown and wakeup options on a per server basis. Each backend also has its own scheduled job queue, wherein any task may be described and instructed to execute at some predetermined time in the future (on each backend, the job queue is local, and is regularly polled to make sure all pending tasks execute at their scheduled start times).
Backend operation concerns itself primarily with capture cards and storage volumes. As such, each backend contains at least one capture card and the means to store captured video, either locally or onto a shared, attached drive. For that matter, central storage volumes (shared among many slave backends) may be groomed and managed by the master backend when the central storage volume is configured to work in that way.
Region-specific television formats (default: NTSC in North America, PAL in Europe), channel frequency tables and time offsets for XMLTV listings (provided by Zap2It Labs DataDirect service) are also configured on the backend. Several time-related settings are also available, from idle timeouts to maximum wait values, startup intervals prior to scheduled recordings and so forth. There is even a wake-up time format.
By introducing scripted commands designed to execute at startup, immediately before shutdown or during shutdown periods, you can create a network of autonomous slave backend servers. That way, any active server with ongoing processes unrelated to MythTV may gracefully exit and its resources be freed or properly closed - all part of being good network neighbors. Samba shares can be appropriately disconnected; streaming content properly disengaged and other applications or services may be notified to terminate cleanly before shutdown. Thus, if a server is configured to respond to wake-up calls, you can even use one of the backend servers (perhaps the master backend) to remain eternally vigilant, and then to issue wake-up calls to other backend servers so that they will be up and going when their next scheduled recordings get underway. This explains why MythTV also supports a wake-up time format, in case you hadn't already guessed.
