Pre-generate the OpenAPI schema

NetBox version

v2.11.3

Feature type

Change to existing functionality

Proposed functionality

A feature like “collectstatic” which builds the openapi schema once in ./upgrade.sh, then serves it as a static file.

Currently it’s served dynamically and is very slow, taking consistently 7-8 seconds on my system:

# time curl -sS localhost:8001/api/docs/?format=openapi | wc
      0   78785  799797

real	0m7.805s
user	0m0.016s
sys	0m0.005s

Alternatively, cache it in redis (it will take nearly a megabyte of RAM, but worth it)

Use case

ansible netbox inventory

The ansible netbox inventory fetches the whole openapi schema each time it runs. When combined with the actual data queries it does for devices, vms etc, this gives around a 10-second lead time to any playbook which is hitting the netbox API.

Whilst this inventory module has a feature to cache the results of the inventory (if you configure a suitable cache plugin), I want to get the “real-time” up-to-the-minute data from Netbox. The plugin can’t be configured to cache the openapi schema only, whilst still making data queries to Netbox.

pynetbox

Any code which uses pynetbox, and calls nb.openapi(), will also benefit.

import pynetbox
nb = pynetbox.api(API_URL, token=API_TOKEN)
nb.openapi()

Database changes

None

External dependencies

None

[candlerb]

There are two ways to bite the cherry.

1. At the server end: pre-generate the spec and serve it statically
2. At the client end: read the spec once and cache it

Whilst both are possible, (1) gives the maximum benefit:

• It only has to be implemented once
• It benefits all clients, even dumb ones
• Clients don’t have to worry about running with a stale copy of the spec when Netbox changes
• TBH, transferring 1MB over the network is cheap these days

Ideally, Netbox would pregenerate the spec and give an ETag - then smart clients can check and don’t have to refetch unless it has changed.

[candlerb]

Given that the solution turns out to be just a case of adding cache_timeout=86400, that seems like a very reasonable cost/benefit tradeoff 😃