Alfred - General Limitations

The following list of general limitations is intended to help system administrators plan for resources required to support Alfred, as well as to help them understand potential sources of problems. These issues are unlikely to have an impact on people using Alfred in its typical role as the rendering dispatcher for the RenderMan Artist Tools.

Alfred consumes a process table slot and two file descriptors (three for expand commands) for each task that it launches. There are shell and kernel limits on these resources (for a given parent process). Note: these limits are only likely to be an issue for sites running alfred in -power mode, a licensed feature which uses a modified dispatching algorithm; this feature assumes a large clienting system which can handle a virtually unlimited number of parallel client launches. Most shells report their current limit settings when "limit" is typed. Each invocation of a shell can usually increase certain limit values up to the kernel maximum using a command like "limit descriptors 200". Use sysconf(1) to obtain the current kernel max values (specifically, look for CHILD_MAX and OPEN_MAX). See systune(1) for information on changing the system-wide kernel values.

Both stdout and stderr of launched commands are merged into the log file. Normally this results in reasonable log messages, however under some circumstances stdout text can be interleaved with stderr text. This can happen if a process uses both buffered and unbuffered writes (i.e. write(2) and printf(3)) or if system errors are generated between user buffer flushes. Even so, this intermixing usually just results in a somewhat confusing task log. If, however, the executed command is using the ALF_PROGRESS or ALF_EXIT_STATUS feedback mechanism, it is important to make sure that these tokens appear "at the beginning of a line". If intermixing of output causes these messages to be missed, things can be somewhat improved by atomically printing the message to stderr with an embedded leading newline.