better example chart for generic use

diff --git a/charts.d/example.chart.sh b/charts.d/example.chart.sh
index b20740e862ef67180f1e798d9103e7a95196bfa2..df6c3a3eeea91a6f129feeafc89a507297b41f83 100755 (executable)
--- a/charts.d/example.chart.sh
+++ b/charts.d/example.chart.sh
@@ -15,13 +15,63 @@ example_priority=150000
 # (just a demonstration for something that needs to be checked)
 example_magic_number=
 
+# global variables to store our collected data
+# remember: they need to start with the module name example_
+example_value1=
+example_value2=
+example_value3=
+example_value4=
+example_last=0
+example_count=0
+
+example_get() {
+       # do all the work to collect / calculate the values
+       # for each dimension
+       #
+       # Remember:
+       # 1. KEEP IT SIMPLE AND SHORT
+       # 2. AVOID FORKS (avoid piping commands)
+       # 3. AVOID CALLING TOO MANY EXTERNAL PROGRAMS
+       # 4. USE LOCAL VARIABLES (global variables may overlap with other modules)
+
+       example_value1=$RANDOM
+       example_value2=$RANDOM
+       example_value3=$RANDOM
+       example_value4=$((8192 + (RANDOM * 16383 / 32767) ))
+
+       if [ $example_count -gt 0 ]
+               then
+               example_count=$((example_count - 1))
+
+               [ $example_last -gt 16383 ] && example_value4=$((example_last + (RANDOM * ( (32767 - example_last) / 2) / 32767)))
+               [ $example_last -le 16383 ] && example_value4=$((example_last - (RANDOM * (example_last / 2) / 32767)))
+       else
+               example_count=$((1 + (RANDOM * 5 / 32767) ))
+
+               [ $example_last -gt 16383 -a $value4 -gt 16383 ] && example_value4=$((value4 - 16383))
+               [ $example_last -le 16383 -a $value4 -lt 16383 ] && example_value4=$((value4 + 16383))
+       fi
+       example_last=$example_value4
+
+       # this should return:
+       #  - 0 to send the data to netdata
+       #  - 1 to report a failure to collect the data
+
+       return 0
+}
+
 # _check is called once, to find out if this chart should be enabled or not
 example_check() {
        # this should return:
        #  - 0 to enable the chart
        #  - 1 to disable the chart
 
-       [ "${example_magic_number}" != "12345" ] && return 1
+       # check something
+       [ "${example_magic_number}" != "12345" ] && echo >&2 "example: you have to set example_magic_number=$example_magic_number in example.conf to start example chart." && return 1
+
+       # check that we can collect data
+       example_get || return 1
+
        return 0
 }
 
@@ -41,46 +91,21 @@ EOF
 }
 
 # _update is called continiously, to collect the values
-example_last=0
-example_count=0
 example_update() {
-       local value1 value2 value3 value4 mode
-
        # the first argument to this function is the microseconds since last update
        # pass this parameter to the BEGIN statement (see bellow).
 
-       # do all the work to collect / calculate the values
-       # for each dimension
-       # remember: KEEP IT SIMPLE AND SHORT
-
-       value1=$RANDOM
-       value2=$RANDOM
-       value3=$RANDOM
-       value4=$((8192 + (RANDOM * 16383 / 32767) ))
-
-       if [ $example_count -gt 0 ]
-               then
-               example_count=$((example_count - 1))
-
-               [ $example_last -gt 16383 ] && value4=$((example_last + (RANDOM * ( (32767 - example_last) / 2) / 32767)))
-               [ $example_last -le 16383 ] && value4=$((example_last - (RANDOM * (example_last / 2) / 32767)))
-       else
-               example_count=$((1 + (RANDOM * 5 / 32767) ))
-
-               [ $example_last -gt 16383 -a $value4 -gt 16383 ] && value4=$((value4 - 16383))
-               [ $example_last -le 16383 -a $value4 -lt 16383 ] && value4=$((value4 + 16383))
-       fi
-       example_last=$value4
+       example_get || return 1
 
        # write the result of the work.
        cat <<VALUESEOF
 BEGIN example.random $1
-SET random1 = $value1
-SET random2 = $value2
-SET random3 = $value3
+SET random1 = $example_value1
+SET random2 = $example_value2
+SET random3 = $example_value3
 END
 BEGIN example.random2 $1
-SET random = $value4
+SET random = $example_value4
 END
 VALUESEOF
        # echo >&2 "example_count = $example_count value = $value4"