A good error log should help you to resolve the problem. Or give you enough information to find the cause of the problem.
For the error log of the Lua code, I think it should at least include the filename and line number of the code, the function name trigger the error and the argument trigger the error.
The openresty’s ngx.log will add the file name and the linenumber by default.
For example this is a error log in openresty.
2023/01/04 10:32:20 [error] 5087#5087: *3097 [lua] content_by_lua(nginx.conf:393):3: log message here, client: 127.0.0.1, server: , request: "GET /test-error-log HTTP/1.1", host: "localhost"
But here, my greater concern is how programmers should handle returning error messages when checking function parameters.
This is a error message thrown by the LuaJIT itself.
1
ERROR: gen-test-set.lua:6: bad argument #1 to 'open' (string expected, got nil)
So when writing the error message, we should keepa the same format as the above error message. The message above is short, clear and contains enough message to the end user.
