Exception handling
In most applications some errors will get raised that aren't related to possible bugs in your code, they just happen when your app gets into contact with the real world. Bots might drop by and try to automatically post forms, outdated links might direct visitors to content that doesn't exist anymore and so on.
To avoid these errors from being raised as problems in AppSignal it's possible to add exception handling to your code or even let AppSignal completely ignore certain errors.
Ignore errors
The AppSignal configuration makes it possible to ignore errors. By providing a list of specific errors AppSignal will not send alerts when these errors are raised.
Appsignal.set_error/3
If you want to rescue exceptions in your application to prevent crashes, but
still want to track the occurrence you can use
Appsignal.set_error/2
to add the exception to the
current AppSignal transaction:
try do raise "Exception!" rescue exception -> Appsignal.set_error(exception, __STACKTRACE__) end
Erlang
The AppSignal integration tries its best to convert errors raised from Erlang to Elixir exceptions. For example, a :badarg
raised from Erlang is automatically converted to an ArgumentError
. However, sometimes the best it can do is wrapping the error originating from Erlang in an ErlangError
.
Since these don’t give much insight into the underlying issue, we recommend adding information from within your application by catching the error, creating an Elixir exception yourself and adding that to the current span using the set_error/2
function.
On versions before 2.1.0, use catch
and Appsignal.send_error/3
:
try do raise "Exception!" catch kind, reason -> Appsignal.set_error(kind, reason, __STACKTRACE__) end
The exception will be tracked by AppSignal like any other error, and it allows you to provide custom error handling and fallbacks.
If you do not have an error object when calling send_error
, but still want to report the scenario as an error, it's also possible to initialize a custom error struct.
defmodule MyCustomError do defexception message: "default message" # Customize if you call it without a custom message end case Worker.do_something() do :ok -> IO.puts "yay!" {:error, message} -> Appsignal.set_error(:error, %MyCustomError{ message: message }, []) end
Note: This function only works when there is an AppSignal transaction active. Otherwise the error will be ignored.
Please see
Appsignal.send_error/3
for sending errors
without an AppSignal transaction.
Appsignal.send_error/3
AppSignal provides a mechanism to track errors that occur in code that's not in a web or background job context, such as Mix tasks. This is useful for instrumentation that doesn't automatically create AppSignal transactions to profile.
You can use the Appsignal.send_error/3
function to
directly send an exception to AppSignal from any place in your code without
starting an AppSignal transaction first.
try do raise "Exception!" catch kind, reason -> Appsignal.send_error(kind, reason, __STACKTRACE__) end
If you do not have an error object when calling send_error
, but still want to report the scenario as an error, it's also possible to initialize a custom error struct.
defmodule MyCustomError do defexception message: "default message" # Customize if you call it without a custom message end case Worker.do_something() do :ok -> IO.puts "yay!" {:error, message} -> Appsignal.send_error(:error, %MyCustomError{ message: message }, []) end
Additional metadata
To add metadata to the sent error, pass a function as the fourth argument to
Appsignal.send_errror/4
:
try do raise "Exception!" catch kind, reason -> Appsignal.send_error(kind, reason, __STACKTRACE__, fn span -> Appsignal.Span.set_attribute(span, "key", "value") end) end