App powerdns-recursor missing "answers" graph


[email protected]:~$ ./validate.php 
Component | Version
--------- | -------
LibreNMS  | 22.8.0-6-g1dbab5ac7
DB Schema | 2022_07_03_1947_add_app_data (244)
PHP       | 8.1.9
Python    | 3.9.2
Database  | MariaDB 10.5.15-MariaDB-0+deb11u1
RRDTool   | 1.7.2
SNMP      | 5.9

[OK]    Composer Version: 2.4.0
[OK]    Dependencies up-to-date.
[OK]    Database connection successful
[OK]    Database Schema is current
[OK]    SQL Server meets minimum requirements
[OK]    lower_case_table_names is enabled
[OK]    MySQL engine is optimal
[OK]    Database schema correct
[OK]    MySQl and PHP time match
[OK]    Active pollers found
[OK]    Dispatcher Service not detected
[OK]    Locks are functional
[OK]    Python poller wrapper is polling
[OK]    Redis is unavailable
[OK]    rrdtool version ok
[OK]    Connected to rrdcached
[email protected]:~$ 

It seems that there is a problem with the powerdns-recursor application. It’s missing the “answers” graphs.

I made sure that /etc/snmp/powerdns-recursor is current, readable and executable. The values for answers-slow, answers0-1, answers1-10, answers10-100 and answers100-1000 are valid and reasonable, the resulting json result is valid and accessible via snmp. I even removed the whole rrd/hostname/app-powerdns-recursor-38.rrd on one host for testing purposes, but with no difference.

As below example shows, all hosts with enabled powerdns-recursor display three graphs instead of four, while Answers/sec is missing:

(This is one host from librenms/apps/app=powerdns-recursor overview where usually Questions/sec, Answers/sec, Packets/sec and Queries/sec are displayed)

When setting APP_DEBUG=true in .env and opening one of these broken graphs the error message reads:

    "message": "implode(): Argument #2 ($array) must be of type ?array, string given",
    "exception": "TypeError",
    "file": "/opt/librenms/includes/html/graphs/",
    "line": 96,
    "trace": [
            "file": "/opt/librenms/includes/html/graphs/",
            "line": 96,
            "function": "implode"
            "file": "/opt/librenms/includes/html/graphs/application/",
            "line": 63,
            "function": "require"
            "file": "/opt/librenms/includes/html/graphs/",
            "line": 44,
            "function": "include"
            "file": "/opt/librenms/html/graph.php",
            "line": 29,
            "function": "require"

Unfortunately, I have no clue since when this error occurs, but I’m quite sure that this worked fine some day. It’s possible that this is the case since Sep 11 2021 (last update on the application’s files) since I usually don’t pay that much attention to these graphs as long as the graphed service is running fine :slight_smile:

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