Logging exception details in try finally block

Question

I have a small section of code invoking a webservice client method.

The method returns an array of messages as an out parameter. Often these messages contain details of any errors that have occured. When an error does occur an exception is also thrown.

I want to log the messages regardless of whether an exception is thrown or the type of the exception. Is logging in the finally block acceptable practice?

WebServiceClient client = GetWebServiceClient();
Console.WriteLine("Calling getUpdates...");
ItemStatus[] itemStatuses;
Message[] messages = null;
string outToken;
try
{
     outToken = client.getUpdates(inToken, out itemStatuses, out messages);
}
finally
{
     LogMessages(messages);
}

The arrangement is somewhat unusual, but given that it's not up for discussion what argument could there be against logging like this? It's natural and good. — Jon, Jul 02 '13 at 08:52
What if `getUpdates` throws an exception (webservice call timed out, ...), before `messages` is assigned a useful value? — Hans Keﬆing, Jul 02 '13 at 08:55
Yes, there are some circumstances where messages will be null or empty and these are checked for. I just want to be sure if messages contains anything useful it gets logged. — TonE, Jul 02 '13 at 10:07

score 6 · Accepted Answer · answered Jul 02 '13 at 08:51

6

Yes, a finally block will always be executed (Even if an exception is not thrown). So it kinda makes sense to put the Logging there in this context.

answered Jul 02 '13 at 08:51

Darren

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Thanks - I wanted a second opinion that this is an acceptable approach. – TonE Jul 02 '13 at 10:08

score 2 · Answer 2 · edited May 23 '17 at 11:59

2

I finally block will always be executed, regardless of any exception that is thrown or not.

If this is your complete code, then it's fine. If not, I recommend some null checking before logging messages variable, since it may not be initialized when exception is thrown.

I think logging like this is perfectly fair.

EDIT:

I forgot to mention that there are some corner cases that will prevent finally from executing - which I don't believe that is your case, but it is worth mentioning (thanks Simon for pointing it out!).

Also, I like the finally approach if you want your method to log even if your method returns.

edited May 23 '17 at 11:59

Community

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answered Jul 02 '13 at 08:59

Joel

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This isn't entirely accurate. There are indeed exceptions that cause a finally block not to execute. – Simon Whitehead Jul 02 '13 at 09:20
Thanks for pointing it out! Edited my answer to reflect that. – Joel Jul 02 '13 at 09:39
No worries. I wouldn't have mentioned it except the way you worded it sounded so definitive :) – Simon Whitehead Jul 02 '13 at 10:04

Logging exception details in try finally block

2 Answers2