Low-Level Discovery preprocessing questions

[TomasC]

Hello,

I am creating a Zabbix template to monitor a commercial software package.
I am using a lot of Low-Level Discovery (LLD) and it works.
However, some of the preprocessing rules seem redundant, so I am wondering if I am perhaps not using the most effective/efficient way of monitoring.

The application is connected to cameras. For each camera, I would like to monitor the processing lag, and also run some checks on the camera itself. This seems to me to mean a discovery rule with an item prototype and a host prototype.

On the system with the zabbix-agent, I've created a script that produces the output for Zabbix to consume, /usr/local/bin/zabbixscripts/cameras.sh. It produces output like this:

[
  {
    "id": "camera001",
    "version": 1,
    "ip": "10.3.0.7",
    "lag": 83
  },
  {
    "id": "camera002",
    "version": 2,
    "ip": "10.3.0.8",
    "lag": 116
  },
  {
    "id": "camera003",
    "version": 2,
    "ip": "10.3.0.9",
    "lag": 97
  }
]​

This is how I configure this in Zabbix:

1. In the Zabbix agent configuration, add

   UserParameter=cameras.get,/usr/local/bin/zabbixscripts/cameras.sh

2. In Zabbix server, in the template, create a new item and in Tab Item:
   1. Name: cameras information
   2. Type Zabbix agent (active)
   3. Key "cameras.get"
   4. Type of information: Text
   5. Update interval 10m
3. Click the three dots next to the new item and choose "Create dependent discovery rule"
   1. Tab Discovery rule:
      1. Name: Discovery rule for cameras
      2. Type: Dependent item
      3. Key: cameras.discovery
      4. Master item: template: cameras.get
   2. Tab LLD macros
      1. {#ID}: $.id
      2. {#VERSION}: $.version
      3. {#IP}: $.ip
      4. {#LAG}: $.lag
4. In the discovery rule list, click item prototypes and Create item prototype
   1. Tab Item prototype
      1. Name: Camera {#ID} lag
      2. Type: Dependent item
      3. Key: camera.lag[{#ID}]
      4. Type: Numeric (unsigned)
      5. Master item: template: cameras.get
   2. Tab Preprocessing
      1. JSONPath: $.[?(@.id=='{#ID}')].lag.first()
5. In the discovery rule list, click host prototypes and Create host prototype
   1. Host tab:
      1. Host name: camera {#ID}
      2. Templates: camera_test_template
      3. Groups: cameras
      4. Interfaces: SNMP, {#IP}

This works, I get for each camera an item showing the lag, and also each camera is discovered as its own host with template camera_test_template applied.

Questions:

• Is the item prototype preprocessing required? It seems it already knows which item of the array it is working with (#ID is already set to one specific camera), but at the same time it needs a JSONPath to select the specific camera from the array? For the host prototype, the preprocessing doesn't seem to be required?
• Can I skip the creation of the item (step 2 above) and just create a discovery rule of type Zabbix agent (active) and key "cameras.get"? I have tried, but can't get it to work.
  • Would this impact performance?
• The LLD macros seem superfluous: can I skip these macros if I change the output of the script from

  {"id": "x", "ip": "127.0.0.1", ...}

  to

  {"{#ID}": "x", "{#IP}": "127.0.0.1", ...}

  ?