Added R.I.Pienaar's extlookup.rb to the ext directory

1 files changed, 183 insertions, 0 deletions

diff --git a/ext/extlookup.rb b/ext/extlookup.rb
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+# Puppet External Data Sources 
+#
+# This is a parser function to read data from external files, this version
+# uses CSV files but the concept can easily be adjust for databases, yaml
+# or any other queryable data source.
+#
+# The object of this is to make it obvious when it's being used, rather than 
+# magically loading data in when an module is loaded I prefer to look at the code
+# and see statements like:
+#
+#     $snmp_contact = extlookup("snmp_contact")
+#
+# The above snippet will load the snmp_contact value from CSV files, this in its
+# own is useful but a common construct in puppet manifests is something like this:
+#
+# case $domain {
+#      "myclient.com": { $snmp_contact = "John Doe <john@myclient.com>" }
+#      default:        { $snmp_contact = "My Support <support@my.com>" }
+# }
+#
+# Over time there will be a lot of this kind of thing spread all over your manifests
+# and adding an additional client involves grepping through manifests to find all the
+# places where you have constructs like this.
+#
+# This is a data problem and shouldn't be handled in code, a using this function you
+# can do just that.
+#
+# First you configure it in site.pp:
+# $extlookup_datadir = "/etc/puppet/manifests/extdata"
+# $extlookup_precedence = ["%{fqdn}", "domain_%{domain}", "common"]
+#
+# The array tells the code how to resolve values, first it will try to find it in
+# web1.myclient.com.csv then in domain_myclient.com.csv and finally in common.csv
+#
+# Now create the following data files in /etc/puppet/manifests/extdata
+#
+# domain_myclient.com.csv: 
+#    snmp_contact,John Doe <john@myclient.com>
+#    root_contact,support@%{domain}
+#    client_trusted_ips,192.168.1.130,192.168.10.0/24
+#
+# common.csv:
+#    snmp_contact,My Support <support@my.com>
+#    root_contact,support@my.com
+#
+# Now you can replace the case statement with the simple single line to achieve
+# the exact same outcome:
+#
+#    $snmp_contact = extlookup("snmp_contact")
+#
+# The obove code shows some other features, you can use any fact or variable that 
+# is in scope by simply using %{varname} in your data files, you can return arrays
+# by just having multiple values in the csv after the initial variable name.
+#
+# In the event that a variable is nowhere to be found a critical error will be raised
+# that will prevent your manifest from compiling, this is to avoid accidentally putting
+# in empty values etc.  You can however specify a default value:
+#
+#    $ntp_servers = extlookup("ntp_servers", "1.${country}.pool.ntp.org")
+# 
+# In this case it will default to "1.${country}.pool.ntp.org" if nothing is defined in 
+# any data file.
+#
+# You can also specify an additional data file to search first before any others at use
+# time, for example:
+#
+# $version = extlookup("rsyslog_version", "present", "packages")
+#
+# package{"rsyslog": ensure => $version }
+#
+# This will look for a version configured in packages.csv and then in the rest as configured
+# by $extlookup_precedence if it's not found anywhere it will default to "present", this kind
+# of use case makes puppet a lot nicer for managing large amounts of packages since you do not
+# need to edit a load of manifests to do simple things like adjust a desired version number.
+#
+# For more information on installing and writing your own custom functions see:
+#    http://reductivelabs.com/trac/puppet/wiki/WritingYourOwnFunctions
+#
+# For further help contact Volcane on #puppet
+require 'csv'
+ 
+module Puppet::Parser::Functions
+    newfunction(:extlookup, :type => :rvalue) do |args|
+        key = args[0]
+        default = "_ExtUNSET_"
+        datafile = "_ExtUNSET_"
+
+        default = args[1] if args[1]
+        datafile = args[2] if args[2]
+
+        extlookup_datadir = lookupvar('extlookup_datadir')
+        extlookup_precedence = Array.new
+
+        # precedence values can have variables embedded in them
+        # in the form %{fqdn}, you could for example do
+        #
+        #    $extlookup_precedence = ["hosts/%{fqdn}", "common"]
+        #
+        # this will result in /path/to/extdata/hosts/your.box.com.csv
+        # being searched.
+        #
+        # we parse the precedence here because the best place to specify
+        # it would be in site.pp but site.pp is only evaluated at startup
+        # so $fqdn etc would have no meaning there, this way it gets evaluated
+        # each run and has access to the right variables for that run
+        lookupvar('extlookup_precedence').each do |prec|
+            while prec =~ /%\{(.+?)\}/
+                prec.gsub!(/%\{#{$1}\}/, lookupvar($1))
+            end
+
+            extlookup_precedence << prec
+        end
+    
+
+        datafiles = Array.new
+
+        # if we got a custom data file, put it first in the array of search files
+        if datafile != "" 
+            if File.exists?(extlookup_datadir + "/#{datafile}.csv")
+                datafiles << extlookup_datadir + "/#{datafile}.csv"
+            end
+        end
+
+        extlookup_precedence.each do |d|
+            datafiles << extlookup_datadir + "/#{d}.csv"
+        end
+
+        desired = "_ExtUNSET_"
+
+        datafiles.each do |file|
+            parser.watch_file(file) if File.exists?(file)
+
+            if desired == "_ExtUNSET_"
+                if File.exists?(file)
+                    result = CSV.read(file).find_all do |r|
+                        r[0] == key
+                    end
+    
+
+                    # return just the single result if theres just one,
+                    # else take all the fields in the csv and build an array
+                    if result.length > 0
+                        if result[0].length == 2
+                            val = result[0][1].to_s
+                            
+                            # parse %{}'s in the CSV into local variables using lookupvar()
+                            while val =~ /%\{(.+?)\}/
+                                val.gsub!(/%\{#{$1}\}/, lookupvar($1))
+                            end
+
+                            desired = val
+                        elsif result[0].length > 1
+                            length = result[0].length
+                            cells = result[0][1,length]
+    
+                            # Individual cells in a CSV result are a weird data type and throws
+                            # puppets yaml parsing, so just map it all to plain old strings
+                            desired = cells.map do |c|
+                                # parse %{}'s in the CSV into local variables using lookupvar()
+                                while c =~ /%\{(.+?)\}/
+                                    c.gsub!(/%\{#{$1}\}/, lookupvar($1))
+                                end
+
+                                c.to_s
+                            end
+                        end
+                    end
+                end
+            end
+        end
+
+        # don't accidently return nil's and such rather throw a parse error
+        if desired == "_ExtUNSET_" && default == "_ExtUNSET_"
+            raise Puppet::ParseError, "No match found for '#{key}' in any data file during extlookup()"
+        else 
+            desired = default if desired == "_ExtUNSET_"
+        end
+
+        desired
+    end
+end
+
+# vi:tabstop=4:expandtab:ai