holdApplicationUntilProxyStarts like configuration in Linkerd2 ?

[BlackRider97]

Istio has added supported for holdApplicationUntilProxyStarts, which causes the sidecar injector to inject the sidecar at the start of the pod’s container list and configures it to block the start of all other containers until the proxy is ready.

I am using Argo workload pods along with Linkerd2 as Service Mesh technology. I don't want to start main processing logic unless Linkerd proxy is ready to accept connection which takes few seconds only.

Another way to solve this problem is wait until proxy port is not open but this requires some Init container definition which I wanted to avoid.

Is there any configuration to hold application until proxy is not ready ?

[kleimkuhler]

Hey @BlackRider97 it may be worth checking out linkerd-await. There is not a similarly convenient config option for setting this, but it should take care of your issue.

#3450 which has been open for a while and would help make this easier to find; it may be worth coming back around to that. Let me know if this solves your issue and if you have any questions about using it.

[nesl247]

@kleimkuhler As mentioned, it's not possible (without significant work) to use linkerd-await. We'd be happy to use the pod order, but I am not aware of any way to tell linkerd to inject the container in the first position.

[kleimkuhler]

Yep I understand the issue with linkerd-await. And the solution for container order would probably have to be built into Linkerd.

Unfortunately there is not that much I can suggest right now to fix this, but as I said I think a solution similar to the wait container is worth exploring more.

[wmorgan]

Could Linkerd implement something similar to Istio's holdApplicationUntilProxyStarts behavior?

[kleimkuhler]

@wmorgan Yep I got something working over the weekend and just posted #5967! It introduces a config.linkerd.io/await-proxy annotation which forces the container to wait for proxy-readiness.

[wmorgan]

@kleimkuhler Nice! We're on the same page :)