Trying to get logic honor if-statements to control output

[Glowsome (Michael Honkoop)]

Hi all,

As i am quite new to this type of development/fiddling around with check-plugins first of all if i am asking in a wrong wat, please correct me.

Now the case :

I have a client-script that should output updates as found via DND package-manager :

#!/bin/sh

CMK_VERSION="2.0.0p11"

DO_UPDATE=yes

echo '<<<linux_dnf>>>'
function check_dnf_updates {
    if [ "$DO_UPDATE" = yes ] ; then
        /usr/bin/dnf makecache 2> /dev/null
    fi
    /usr/bin/dnf updateinfo
}

#if command -v dnf &> /dev/null; then
#    echo "<<<linux_dnf>>>"
#    echo "5 Security notice(s)"
#    echo "1 Bugfix notice(s)"
#    echo "8 Enhancement notice(s)"
#    echo "3 other notice(s)"
#fi

    output=$(check_dnf_updates)
    if echo $output | grep -q "Updates Information Summary: available"; then
        echo $output | grep -o "[[:digit:]]\+\sBugfix"
        echo $output | grep -o "[[:digit:]]\+\sSecurity"
        echo $output | grep -o "[[:digit:]]\+\sModerate"
        echo $output | grep -o "[[:digit:]]\+\sLow"
        echo $output | grep -o "[[:digit:]]\+\sEnhancement"
        echo $output | grep -o "[[:digit:]]\+\sother"
    else
        echo "No updates found"
    fi

So in essence this should deliver a/the correct format to the CMK server for interpretation.

On the Server i have been struggling to get the plugin to evaluate the offerd data.

from .agent_based_api.v1 import *

def discover_linux_dnf(section):
    yield Service()

def check_linux_dnf(section):
    for line in section:
        if line[0].isdigit():
            if line[0].find('Bugfix'):
                yield Result(state=State.WARN, summary=line[0] + " Bugfix Updates")

            if ("Enhancement" in line[0] != True):
                yield Result(state=State.WARN, summary=line[0] + " Enhancement Updates")

            if "Security" in line[0]:
                yield Result(state=State.CRIT, summary=line[0] + " Security Updates")

        return
    yield Result(state=State.OK, summary="No DNF Updates found.")

register.check_plugin(
    name="linux_dnf",
    service_name="DNF Updates",
    discovery_function=discover_linux_dnf,
    check_function=check_linux_dnf,
)

Now from what i can tell :

• the expected ( if any) numeric will corectly engage the further conditions.
• The further conditions however do NOT honor any means of != -1 ( which should be the output of a find condition.
• Also the (as above) looking for a textual match via the in method does not give expected result conditions.

So what am i missing here ?

i am sort-of stuck in this.

• Glowsome

[robin.gierse]

I cannot help you on the programming part - others might though - but if you only want to get the job done, this plugin from our exchange handles YUM/DNF based systems.
If this is merely a training exercise, I am sure someone can give you pointers.

[Glowsome (Michael Honkoop)]

Well its 2-fold.

On the one end i’d like to get this monitored.
But on the other hand i’m also after learning the way in which plugins are made (correctly).

i’ve been over and over the docs, but i seem to be missing the just that part that makes the whole puzzle fall into place.

• Glowsome

[thl-cmk]

This will not work, see comments inline

if line[0].isdigit():  # this checks for a number
            if line[0].find('Bugfix'):  # if it is a number it can not contain a string
                .....
            if ("Enhancement" in line[0] != True):  # can also not contain a string
               .....
            if "Security" in line[0]:  # and again can not contain a string
               ....

[Glowsome (Michael Honkoop)]

Ok, i’ve been fiddling around a bit as to the feedback/comment @thl-cmk has made.

So i changed the

if line[0].isdigit():  # this checks for a number

to

if (line[0][0].isdigit()): # this should (only) check the _first_character of the line is a number

From my point of view this should be the corect criteria to move further down the logic.
However if i were to make a line after this

yield Result(state=State.WARN, summary=line[0])
return

I only see the digit back … not the entire line - which i would expect.
It is as if the content of line[0] is replaced with the outcome of the evaluation.

• Glowsome

[thl-cmk]

asumming from your output, the check section sould look like this

[
 ['5', 'Security', 'notice(s)'], 
 ['1', 'Bugfix', 'notice(s)'], 
 ['8', 'Enhancement', 'notice(s)'], 
 ['3', 'other', 'notice(s)']
]

if this is correct, there is no real need to first check for a digit at the start of the line, you can easyly check if line[1] contains the string you are looking for, and if so yield your check state with line[0] as the value.

def check_linux_dnf(section):
    for line in section:
        if line[1] == 'Bugfix':
            yield Result(state=State.WARN, summary=line[0] + " Bugfix Updates")
        elif line[1] == "Enhancement":
            yield Result(state=State.WARN, summary=line[0] + " Enhancement Updates")
        elif line[0] == "Security":
            yield Result(state=State.CRIT, summary=line[0] + " Security Updates")
        return
    yield Result(state=State.OK, summary="No DNF Updates found.")

if you still want to check if line[0] is a digit you can do this like so:

def check_linux_dnf(section):
    for line in section:
        if line[0].isdigit:
            if line[1] == 'Bugfix':
                yield Result(state=State.WARN, summary=line[0] + " Bugfix Updates")
            elif line[1] == "Enhancement":
                yield Result(state=State.WARN, summary=line[0] + " Enhancement Updates")
            elif line[1] == "Security":
                yield Result(state=State.CRIT, summary=line[0] + " Security Updates")
            return
    yield Result(state=State.OK, summary="No DNF Updates found.")

btw. have a look at the Writing your own check plug-ins. There you will also find some basic steps on how to debug your checks.

[Glowsome (Michael Honkoop)]

@thl-cmk In reply to your post… for a part you are correct as to the input. ( the client bash script was included in the original post)

However due to the nature of updates i cannot tell in advance if a category is present in the output.

So in this the status would need to reflect OK when there are no numbers present in the output ( the output of the client-script will just read "“No updates found”

So my way of handling this is to report (return) state.OK immediately, not evaluating further logic.

IF however the evaluation does return true on having a number, then further evaluation is needed as to how many, and what type of update is available.

So in your example i cannot tell if line contains either ‘Bugfix, Enhancement, Security’ or even how many lines my output has.
Therefore i am searching for a way to loop over all presented to the server, and in the end have a cumulative state and multiple line summary.

For your insight as to the summary i am looking for as example when multiple categories of updates are available:

3 Bugfix Update(s) [WARN],
2 Enhancement Update(s) [WARN],
1 Security Update(s) [CRIT]

Calculating a total status of the service as [CRIT]

… and yes i have been reading the referenced “Writing your own check plug-ins” over and over again

• Glowsome

[thl-cmk]

You can try it like this

def check_linux_dnf(section):
    update_found=False  # init  update_found marker 
    for line in section:  # loop over the lines
        if line[0].isdigit:  # check if number (update found)
            update_found=True  # set marker
            # check for the update type and output the result
            if line[1] == 'Bugfix':  
                yield Result(state=State.WARN, summary=line[0] + " Bugfix Updates")
            elif line[1] == "Enhancement":
                yield Result(state=State.WARN, summary=line[0] + " Enhancement Updates")
            elif line[1] == "Security":
                yield Result(state=State.CRIT, summary=line[0] + " Security Updates")
    # if no update found, outpout a summary
    if not update_found:  
        yield Result(state=State.OK, summary="No DNF Updates found.")