Database error codes

The table below lists some popular errors that can be raised by Tarantool in case of various issues. You can find a complete list of errors in the errcode.h file.

Here are some procedures that can make Lua functions more robust when there are errors, particularly database errors.

1. Invoke a function using pcall.

   Take advantage of Lua's mechanisms for Error handling and exceptions, particularly pcall. That is, instead of invoking with ...

    
   box.space.{space-name}:{function-name}()

   ... call the function as follows:

    
   if pcall(box.space.{space-name}.{function-name}, box.space.{space-name}) ...

   For some Tarantool box functions, pcall also returns error details, including a file-name and line-number within Tarantool's source code. This can be seen by unpacking, for example:

    
   status, error = pcall(function() box.schema.space.create('') end)error:unpack()

   See the tutorial Sum a JSON field for all tuples to see how pcall can fit in an application.

2. Examine errors and raise new errors using box.error.

   To make a new error and pass it on, the box.error module provides box.error().

   To find the last error, the box.error submodule provides box.error.last(). There is also a way to find the text of the last operating-system error for certain functions – errno.strerror([code]).

3. Log.

   Put messages in a log using the log module.

   Filter automatically generated messages using the log configuration parameter.

Generally, for Tarantool built-in functions which are designed to return objects: the result is an object, or nil, or a Lua error. For example consider the fio_read.lua program in a cookbook:

 
#!/usr/bin/env tarantoollocal fio = require('fio')local errno = require('errno')local f = fio.open('/tmp/xxxx.txt', {'O_RDONLY' })if not f then    error("Failed to open file: "..errno.strerror())endlocal data = f:read(4096)f:close()print(data)

After a function call that might fail, like fio.open() above, it is common to see syntax like if not f then ... or if f == nil then ..., which check for common failures. But if there had been a syntax error, for example fio.opex instead of fio.open, then there would have been a Lua error and f would not have been changed. If checking for such an obvious error had been a concern, the programmer would probably have used pcall().

All functions in Tarantool modules should work this way, unless the manual explicitly says otherwise.