Auto increment asset tag?

[sliddjur]

#7501

I saw this was discussed in this issue, and I am wondering now with version 3.2.1, is this easily achievable without a plugin, or if someone already has developed a plugin? @PieterL75 ? :)

[kkthxbye-code]

You could do it with custom validators which would save you creating a plugin. If you provide your exact usecase, I can give you an example if you are not comfortable in python.

[sliddjur]

Thanks!
I created one device without asset-tag, and I got the asset-tag datacenter-00001
The second device without asset-tag I created gave me this error

Server Error
There was a problem with your request. Please contact an administrator.

The complete exception is provided below:

<class 'AttributeError'>

'str' object has no attribute 'removeprefix'

Python version: 3.8.10
NetBox version: 3.2.1
If further assistance is required, please post to the [NetBox discussion forum](https://github.com/netbox-community/netbox/discussions) on GitHub.

[kkthxbye-code]

I'm on python 3.9 so I used the removeprefix method. Here's a version that should work on python 3.8:

from extras.validators import CustomValidator

class MyValidator(CustomValidator):

    def validate(self, instance):
        from dcim.models import Device
        prefix = "datacenter-"
        max_digits = 5

        if not instance.asset_tag:
            device = Device.objects.filter(asset_tag__startswith=prefix).order_by("-asset_tag").first()

            if not device:
                # Return 1 if no device has an asset tag yet.
                instance.asset_tag = prefix + "1".zfill(max_digits)
                return

            try:
                next_id = int(device.asset_tag[len(prefix):]) + 1
                instance.asset_tag = prefix + str(next_id).zfill(max_digits)
            except ValueError:
                # If we fail to parse the id do nothing (proper error handling can be added)
                return

CUSTOM_VALIDATORS = {
    'dcim.device': (
        MyValidator(),
    )
}

[jeremystretch]

This is a really interesting use for custom validators that I hadn't considered: Using them to automatically set undefined instance attributes. Might be worth calling out as an example in the docs.

[sliddjur]

Thanks, now the second device works.

But one issue is that when I edit an already existing device without an asset tag, and press save, I get this error.

Errors
Asset tag
Device with this Asset tag already exists.

Also, it kind of breaks my scripts that runs to update and create some devices. Is it perhaps possible to make a checkbox in the GUI "generate asset tag" on the "create device" screen that will call this script?

Again, thanks for your time.

[kkthxbye-code]

But one issue is that when I edit an already existing device without an asset tag, and press save, I get this error.

Sorry, that was a typo from my end, sorting by device name instead of asset_tag. I have edited the second version.

Also, it kind of breaks my scripts that runs to update and create some devices.

Should also be fixed by my new version I guess.

@jeremystretch - Yeah, it's like a light version of post_save signals.

[LHBL2003]

We have inventory numbers starting from SP0001 to SP4300 something. Of course I don't want any problems when it gets to 5 digits. Therefore, I have adapted it a little so that it also works with a number caos.

Example alphabetical sorting:

• SP4348
• SP4338
• SP40002
• SP40001
• SP40000
• SP1000
• SP0303
• SP03001
• SP0001

Next Result: SP40003

###################################
# DE: Ist kein Asset-Tag angegeben, wird das höchste Asset-Tag beginnend mit SP gesucht und um 1 erhöht. Gibt es noch kein Asset Tag so wird mit 1 gestartet.
# EN: If no asset tag is specified, the highest asset tag starting with SP is searched for and incremented by 1. If there is no asset tag yet, it is started with 1.

# THX: https://github.com/netbox-community/netbox/discussions/9226
#      https://stackoverflow.com/a/70153906/27018495
class CreateAssetTag(CustomValidator):

    def validate(self, obj):        
        from django.db.models.expressions import RawSQL
        from operator import attrgetter
        
        prefix = "SP" # Text that should appear in the asset name on the left
        max_digits = 0 # Number of leading zeros in the count
       
        if not obj.asset_tag:
            compareObj = obj.__class__.objects.filter(asset_tag__iregex=r'^' + prefix + r'(\d+)$')\
                        .all().annotate(theLastAssetId=RawSQL("CAST(regexp_replace(asset_tag, '[^0-9]+', '', 'g') AS INTEGER)", '')) #.order_by('-theLastAssetId').first() # *Alternative to the max function
               
            maxObj = max(compareObj, key=attrgetter('theLastAssetId')) # Entry with the highest asset value
               
            if not compareObj:
                # Returns 1 if no comparison object has an asset tag yet.
                obj.asset_tag = prefix + "1".zfill(max_digits)
                return

            try:
                next_id = maxObj.theLastAssetId + 1
                #next_id = compareObj.theLastAssetId + 1 # *Alternative to the max function
                obj.asset_tag = prefix + str(next_id).zfill(max_digits)
                
            except ValueError:
                # If the ID cannot be parsed, nothing happens (appropriate error handling can be added)
                return

It can certainly be optimized. :)
But I'm glad that it worked out on Friday.
I wanted to see if you can replace Order by with Max. It's certainly quicker than sorting.
Addendum: order_by has been replaced by the max function. But left as a comment as a teaching factor.