ISTIO_DELTA_XDS is not a pilot-discovery env var

[spacewander]

Is this the right place to submit this?

• This is not a security vulnerability or a crashing bug
• This is not a question about how to use Istio

Bug Description

(This is trivial nowadays as ISTIO_DELTA_XDS is defaulted to true since istio 1.22)

Although ISTIO_DELTA_XDS is listed as a pilot-discovery env var in https://istio.io/latest/docs/reference/commands/pilot-discovery/#envvars, in fact, it's only used in the pilot-agent.

Therefore setting ISTIO_DELTA_XDS like other pilot discovery env var doesn't take effect. We need to set it as a pilot agent env var with something like meshConfig.defaultConfig.proxyMetadata.ISTIO_DELTA_XDS=true.

Version

$ istioctl version                                                                          
client version: 1.21.0
control plane version: unknown
data plane version: 1.21.0 (2 proxies)
$ kubectl version --short
Client Version: v1.25.11
Kustomize Version: v4.5.7
Server Version: v1.25.11

Additional Information

No response

[zirain]

it's a known issue #47925

[hzxuzhonghu]

Currently not only this one, but also other envs, like ISTIO_AGENT_ENABLE_WASM_REMOTE_LOAD_CONVERSION