Initial Logwatch integration readme

etc/logwatch/README.md

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+# Using Logwatch to monitor Cloudflare DDNS updater script
+
+The Cloudflare DDNS update script's log file has been setup so that utilities
+like Logwatch can easily parse it.  In order to make that happen, a LogFile
+group file, service and script have to be created for Logwatch to generate
+reports.  The correct (general) directory structure has been created in this git
+archive already.  Below are the details of each file.
+
+## LogFile Group file (/etc/logwatch/conf/logfiles/cfddns.conf)
+
+### Log file location
+
+This file is commented so you can update it as necessary for your environment
+(i.e. you've changed the name of the log file generated by the script via the -l
+parameter).
+
+```Ini
+LogFile = /path/to/your/cfddns.log
+...
+```
+
+Update this needed to point to the location and name of the log file generated
+by the updater script.  Remember, by default, the log file is created in the
+same directory as the script itself.  Best practices suggest you use the *-l*
+flag to change this location to something like */var/log/cfddns.log*, for
+example.  In that case, the entry would look like:
+
+```Ini
+LogFile = /var/log/cfddns.log
+...
+```
+
+### Archive location and name format
+
+If you want Logwatch to process old (archived) log files generated by something
+like *Logrotate*, then you have to specify that location and file name format of
+those files.  I've included the generalized compressed format of such rotated
+files as the default in the script.  Suppose you store your log files in the
+recommended location (*/var/log/*) and are using *Logrotate* with compression
+enabled, the archive line would look like:
+
+```Ini
+...
+Archive = /var/log/cfddns.log.?.gz
+...
+```
+
+This would tell Logwatch, when the archive option is set to true, that your
+*cfddns.log* files are archived as: *cfddns.log.1.gz*, *cfddns.log.2.gz*, etc.
+and are all located in */var/log/*.
+
+**Note: This line is totally optional and only used if you set the archive
+option in Logwatch to true.  You can comment/delete this line if you wish.**
+
+### External script for timestamp processing
+
+Since the log file uses a non-standard (according to Logwatch) method of
+time-stamping, a custom filter had to be created.  See the relevant section of
+this document for more information.
+
+The script file is called with an *\** before the filename.
+
+```Ini
+...
+*sqFullStampAnywhere
+...
+```
+
+If you change the name of this file, you will have to change this line.
+Remember that whatever you type here as a name is converted to all-lowercase
+so your filename should be all lowercase also.
+
+## Service definition file (/etc/logwatch/conf/services/cfddns.conf)
+
+### LogFile group definition
+The service file needs to know what group of log file it is responsible for
+processing.  This MUST match the name of your *LogFile Group file*:
+
+```Ini
+LogFile = cfddns
+...
+```
+
+If you change your LogFile Group filename, then update it here too without the
+*.conf* extension.
+
+### Report title
+The Logwatch output file (html or text) is divided into sections.  You can
+define the title to be anything that has meaning for you.  I have arbitrarily
+chosen *"CloudFlare DDNS update"* but you can change it to anything you want by
+modifying the line:
+
+```Ini
+...
+Title = "CloudFlare DDNS update"
+```
+
+## Service script (/etc/logwatch/scripts/services/cfddns)
+
+Logwatch calls any script with a name that **matches the service name**.  You'll
+notice that I just named everything *cfddns* to keep things simple.  You can
+change this to whatever you want, however.  If you changed the service name to
+*"cloudflare*.conf", for example, you would have to rename this script file to
+"*cloudflare*" with no extension.  Note: The script is a PERL file.
+
+In essence, Logwatch just spits out the log file(s) defined in the LogFile Group
+file as standard input (STDIN) and then takes whatever is output (STDOUT) and
+assembles that into it's report.
+
+### Detail levels
+
+The script supports four (4) detail levels as follows:
+
+-  **Level 0: Summary output only**
+    -  This will display an aggregate total of certain logged elements.  It will
+       display the total number of hostnames (A and AAAA) that are already
+       up-to-date, those that needed updated, those successfully updated and the
+       total number of errors (or any type) encountered by the script.  All
+       totals are relative to the reporting period Logwatch is using (--range
+       parameter).  **This is the recommended reporting level.**  It does not
+       take up much space and is quick to read.  If you see successful updates
+       match the number of needed updates and no errors logged, then things are
+       working properly.  If you notice errors, you should consult the full
+       logs.
+-  **Levels 1-4: Critical messages**
+    -  This uses the data which is summarized by Level 0 but outputs the actual
+       messages in the log file.  For example, you will see the actual text of
+       the errors logged instead of just a total number of errors.  This level
+       of reporting is useful when *initially* monitoring the script's
+       operation since you can see the actual text of any generated errors.
+-  **Level 5: Verbose (debugging) output**
+    -  Like the previous level, this outputs the actual messages found in the
+       log file.  However, it also includes *[INFO] tags* which contain logged
+       messages such as the detected IP address and the specific names of any
+       hostnames not found in your Cloudflare account, etc.  This level of
+       reporting is useful in diagnosing why errors are occurring or if you just
+       want more insight into how the script works.  **This level of output will
+       make your Logwatch reports longer and consume more of your time to
+       review. You should not use this level day-to-day.**
+- **Levels 6+: Complete log file dump**
+    -  Any number greater than 5 passed as a detail level will trigger the
+       script to dump the entire log file out to Logwatch line-by-line.  This is
+       useful only if you are debugging an issue and cannot get access to the
+       actual raw log file itself.  The actual log file is colour-coded which
+       makes it much easier to read.  **Use this detail level only when you need
+       to see the entire log file and cannot otherwise access the log file.**
+
+## Timestamp processing script (/etc/logwatch/scripts/shared/sqfullstampanywhere)
+
+This is basically a modified version of the '*applyeurodate*' script that comes
+with Logwatch.  It had to be modified to search within [square brackets] and to
+accept characters coming before the stamp (i.e. ANSI colour codes).  If you
+change '**stamp**' variable in the updater script to update the timestamp to
+your liking (which to totally fine!) then you'll probably have to update this
+file.  There are two lines you need to modify to suit your new '**stamp**'
+variable.
+
+### The time format specification
+
+SearchDate is the variable used in the PERL script to do exactly what it says,
+search for the date stamp.  I have it set up to look for the format
+'*year-month-date hour:minute:second*'.  Note, we don't care about brackets or
+anything here, we're just defining the format of the date/time stamp.
+
+```Perl
+...
+$SearchDate = TimeFilter('%Y-%m-%d %H:%M:%S');
+...
+```
+
+If you changed the '**stamp**' variable so it was formatted as '*month/day/year
+hour:minute*' (ex: '*[09/27/2018 18:38]*') then you'd update the **$SearchDate**
+variable as follows:
+
+```Perl
+...
+$SearchDate = TimeFilter('%m/%d/%Y %H:%M');
+...
+```
+
+### The search REGEX
+
+The PERL script uses a '*regular expression*' (REGEX) to search within the log file for
+'*$SearchDate*'.  For the default datestamp, this specification looks like:
+
+```Perl
+...
+if ($ThisLine =~ m/\[$SearchDate\] /o) {
+...
+```
+
+The REGEX appears between '*m/*' and '*/o*'.  In this case, it searches for
+'*$SearchDate*' inside [square brackets] appearing anywhere on the line.  This
+is because ANSI colour-codes often appear before the datestamp in the default
+log file.  If you have modified this so that your datestamp appears at the
+beginning of the line and in the example format in the section above (using
+slashes instead of dashes) then you'd rewrite this REGEX as follows:
+
+```Perl
+...
+if ($ThisLine =~ m/^\[$SearchDate\] /o) {
+...
+```
+
+or using regular brackets anywhere on the line:
+
+```Perl
+...
+if ($ThisLine =~ m/\($SearchDate\) /o) {
+...
+```
+
+or without any brackets but appearing at the beginning of the line:
+
+```Perl
+...
+if ($ThisLine =~ m/^$SearchDate /o) {
+...
+```
+
+## Testing
+
+Run *logwatch --help* and note the options.  You can test just this service
+locally on your screen with the following command (assuming you kept default
+names for everything):
+
+```Bash
+# Summary output entire duration of log file
+logwatch --service cfddns --output stdout --format text --range all --detail 0
+
+# Minimal detail yesterday only
+logwatch --service cfddns --output stdout --format text --range yesterday --detail 1
+
+# Verbose output today only
+logwatch --service cfddns --output stdout --format text --range today --detail 5
+```
+
+## Final thoughts
+
+That's it!  I'm a horrible PERL programmer so if anyone can optimize/improve the
+script file used for Logwatch then please do it!  Otherwise, I hope this made
+sense and helped you out integrating the updater script with Logwatch for easy
+monitoring :-)