write xml format log file

Question

Our customized logging sysem saves info into a xml file, like this:

<?xml version="1.0" standalone="yes"?>
<log>
<entry> msg </entry>
<entry> msg </entry>
.
.
.
</log>

Right now we are using StreamWriter to write. If the system crashes (we are in the middle of the development), the end tag/element, </log>, will not be written to the file so the xml file cannot be opened correct with IE. I found there are two possible options to correct this:

Option A: write the end tag at very beginning when file is initialized and then do "insert" for each new entry. right now we are doing "append".

Option B: change to XmlDocument or XmlWriter.

In option A, change "append" to "insert", we need to keep the current location, which is right before the end tag, </log>,. And write from that current location. I didn't find a good way to do this.

In option B, the XmlWriter is almost the same as other stream/writer. No easy way to "insert". The XmlDocument is easy to "insert", but there is no Flush() method to call. we have to Save() to make it write to file. If the Save() means close the stream/file, I don't want to do Load() and Save() for each entry. that will be too expensive, I think.

do you have any good idea about this?

Can you write just the <entry> elements? That will always be a well-formed document fragment, which your system could splice in between <log> tags before you view it. — Chris Nash
– Chris Nash, Commented Feb 24, 2011 at 19:28

Francesco De Vittori · Accepted Answer · 2011-02-24 19:37:37Z

2

I would set a global exception handler: that way you could finalize the log, but most important you can collect details relevant to the failure (a stacktrace but also memory state, etc.). In my experience this has always been very effective to understand crashes later on when the system is running "in the wild".

answered Feb 24, 2011 at 19:37

Francesco De Vittori

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2 Comments

5YrsLaterDBA Over a year ago

I cannot understand the "global exception handler". It will catch ALL exceptions? We do have handler for unhandled exception.

Francesco De Vittori Over a year ago

I mean an handler for unhandled exceptions. If the whole system crashes and shutdowns it must be because an unhandled exception -except it's an hardware failure or something external to your process.

GRGodoi · Accepted Answer · 2011-02-24 19:36:00Z

1

You can use the Enterprise Library that allow you to log to a XML file and much much more. I strongly recomend that you, at least, take a look at that. But if you just want to write a XML log without the other goods from EntLib you can try log4Net for example.

answered Feb 24, 2011 at 19:36

GRGodoi

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Tony Abrams · Accepted Answer · 2011-02-24 21:37:04Z

1

You might want to think about using try ... catch ... finally when writing the log file(s). Then if the main method (for writing the logs) fails, inside of the finally switch to a different method and/or location (if needed) and continue writing the log.

edited Feb 24, 2011 at 21:37

answered Feb 24, 2011 at 19:31

Tony Abrams

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1 Comment

5YrsLaterDBA Over a year ago

are you saying in the main method catch Exception and UnhandledException and always write the end tag in the Finally block? But is it a good idea to put entry application into a try-catch block?

Just Do It · Accepted Answer · 2015-12-17 23:43:15Z

1

You may want to consider implementing an unhandled exception filter in your application and take care of cleanly flushing your logs there. Take a look at this blog post for information.

edited Dec 17, 2015 at 23:43

Just Do It

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answered Feb 24, 2011 at 19:39

nithins

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Evgeny Gavrin · Accepted Answer · 2011-02-24 23:19:01Z

0

Are you sure about using xml for logging? You can try html for you purposes.

<title>Cool log</title>
<pre>Started</pre>
<pre>Finished</pre>

edited Feb 24, 2011 at 23:19

answered Feb 24, 2011 at 19:49

Evgeny Gavrin

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2 Comments

xtofl Over a year ago

same problem here... <pre class="sy crash.

Evgeny Gavrin Over a year ago

Try to remove class="sys" - is not defined.

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