8 Recipe Debugging

Some facilities are provided to ease the debugging of recipes and primitives. These are as follows.

• When a recipe will not compile (due to syntax errors, for example) the pipeline aborts and the error message and a listing of relevant recipe lines (the version of the recipe executed internally with all the extra code inserted) is printed to the screen.
• The -w switch should be used during development in order to trap and fix any warnings detected by the Perl interpreter at runtime. In many cases, these warnings are indicative of code that makes assumptions about state (warnings on use of undef) or scope (my declarations masking variables defined in a higher scope).

  If warnings are raised from the orac-dr core please contact the authors and they will be fixed.¹⁰

• The -verbose switch can be used to turn on messages from the algorithm engines. This is sometimes useful to make sure that the external task is doing the expected operation.
• The oracdr_parse_recipe command is provided to translate a recipe into Perl code. It takes a recipe name as argument and sends the translated recipe to standard output. This command can be used to check the syntax of the recipe (by compiling the perl code and exiting immediately) by using the –syntax option.
• The final option is to turn on full debugging with the -debug switch. This creates a file in ORAC_DATA_OUT called ORACDR.DEBUG containing the contents of each message sent to external tasks with an obeyw. This can be used to find out what the final message sent to a task was before the recipe crashed. If a recipe crashes when the debugging is turned on the full contents of the recipe buffer (i.e. the fully parsed recipe) will also be written to a file in ORAC_DATA_OUT called ORACDR_RECIPE.dump. This would be identical to running the oracdr_parse_recipe command.

The Perl debugger should be used with care since it is possible to hang the message bus if the program is frozen during a message transaction and the debugger is not optimized for use with the use of nested eval common in the pipeline internals.