Relevant telegraf.conf:

############################################################################
#                          INPUT PLUGINS                                   #
############################################################################

#HIKVISION IP Camera telegraf snmp collector
#Uses the HIK-DEVICE-MIB


[[inputs.snmp]]
  agents = [ "IP-ADDRESS" ]
  version = 2
  community = "public"
  interval = "60s"
  timeout = "10s"
  retries = 3

  [[inputs.snmp.field]]
    name = "manufacturer"
    oid = "HIK-DEVICE-MIB::manufacturer.0"

  [[inputs.snmp.field]]
    name = "deviceModel"
    oid = "HIK-DEVICE-MIB::deviceType.0"

  [[inputs.snmp.field]]
    name="cpuPercent"
    oid = "HIK-DEVICE-MIB::cpuPercent.0"

  [[processors.regex]]
    order = 1
    namepass = "cpuPercent"
    [[processors.regex.fields]]
      pattern = "([^0-9]+)"
      replacement = "${1}"

  [[processors.converter]]
    order = 2
    [processors.converter.fields]
      integer = ["cpuPercent"]

  [[inputs.snmp.field]]
    name="memUsed"
    oid = "HIK-DEVICE-MIB::memUsed.0"

  [[inputs.snmp.field]]
    name="memUsed"
    oid = "HIK-DEVICE-MIB::memUsed.0"

  [[inputs.snmp.field]]
    name="staticIp"
    oid = "HIK-DEVICE-MIB::staticIpAddr.0"

  [[inputs.snmp.field]]
    name="vidEncode"
    oid = "HIK-DEVICE-MIB::videoEncode.0"

System info:

Ubuntu 20.04.1 LTS (GNU/Linux 5.4.0-47-generic x86_64)
Telegraf 1.15.3

Steps to reproduce:

When running the test config command against the file containing the above configuration, I receive a panic: runtime error

Expected behavior:

When running the config test command: sudo telegraf --test --config /etc/telegraf/telegraf.d/hiktest.conf

Actual behavior:

The script panics:

2020-09-23T13:28:10Z I! Starting Telegraf 1.15.3
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x1f94624]

goroutine 32 [running]:
github.com/influxdata/telegraf/plugins/processors/converter.(*Converter).convertFields(0xc000545470, 0x2f59f00, 0xc0004fe8c0)
/go/src/github.com/influxdata/telegraf/plugins/processors/converter/converter.go:278 +0x8c4
github.com/influxdata/telegraf/plugins/processors/converter.(*Converter).Apply(0xc000545470, 0xc0001fa180, 0x1, 0x1, 0xc00007ca20, 0x0, 0xc000554d80)
/go/src/github.com/influxdata/telegraf/plugins/processors/converter/converter.go:86 +0x9c
github.com/influxdata/telegraf/plugins/processors.(*streamingProcessor).Add(0xc00000efa0, 0x2f59f00, 0xc0004fe8c0, 0x2f4aea0, 0xc00000f560, 0x2e53201, 0x101)
/go/src/github.com/influxdata/telegraf/plugins/processors/streamingprocessor.go:35 +0x81
github.com/influxdata/telegraf/models.(*RunningProcessor).Add(0xc0005455f0, 0x2f59f00, 0xc0004fe8c0, 0x2f4aea0, 0xc00000f560, 0x0, 0x0)
/go/src/github.com/influxdata/telegraf/models/running_processor.go:95 +0x106
github.com/influxdata/telegraf/agent.(*Agent).runProcessors.func1(0xc000053730, 0xc00000f3e0)
/go/src/github.com/influxdata/telegraf/agent/agent.go:559 +0x156
created by github.com/influxdata/telegraf/agent.(*Agent).runProcessors
/go/src/github.com/influxdata/telegraf/agent/agent.go:554 +0x90

Additional info:

The important portion of the config is:

[[inputs.snmp.field]]
    name="cpuPercent"
    oid = "HIK-DEVICE-MIB::cpuPercent.0"

  [[processors.regex]]
    order = 1
    namepass = "cpuPercent"
    [[processors.regex.fields]]
      pattern = "([^0-9]+)"
      replacement = "${1}"

  [[processors.converter]]
    order = 2
    [processors.converter.fields]
      integer = ["cpuPercent"]

The snmp pull of oid = "HIK-DEVICE-MIB::cpuPercent.0" returns a result of "10 PERCENT" without the quotes. I was attempting to use regex/converter plugin to remove the " PERCENT" portion of the result.

To go from:

name: snmp
time                agent_host cpuPercent 
----                ---------- ---------- 
1600392300000000000 IP-ADDRESS 10 PERCENT 

To:

name: snmp
time                agent_host cpuPercent 
----                ---------- ---------- 
1600392300000000000 IP-ADDRESS 10

I have tried additional regex patterns as well with the same results. Additional information info/testing can be seen on the influx community site here https://community.influxdata.com/t/changing-snmp-input-with-regex-using-telegraf-pulls-before-influxdb/16021