proxy-wasm-cpp-sdk

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The file README, line 47 registers the example with no root_id parameter. I assume this picks up the default argument, "", but I couldn't get the example working without a root ID. (I was using Istio EnvoyFilter to configure, perhaps mishandling an empty root_id is an Istio flaw, but it was confusing not to see a root ID in the example.

Consider running the spell checker on the docs (e.g. "from the version of Enovy you are going to deploy")

Empty root id should also be valid. I think it is something else that makes the example not working.. Most likely tool chain. I have a pending https://github.com/proxy-wasm/proxy-wasm-cpp-sdk/pull/71 to update both tool chain and the example to use bazel. Have not yet got time to finish that.

Meanwhile, you can reference this guide: https://github.com/istio-ecosystem/wasm-extensions/blob/master/doc/write-a-wasm-extension-with-cpp.md, which will be blog posted with 1.9.

I'm not trying to get into an argument with you. I have retested it, and can confirm.

Using myproject.cc with static RegisterContextFactory register_ExampleContext(CONTEXT_FACTORY(ExampleContext), "my_root_id"); works; using it with static RegisterContextFactory register_ExampleContext(CONTEXT_FACTORY(ExampleContext)); doesn't.

When using "my_root_id" my Istio EnvoyFilter contained

          value:
            config:
              root_id: "my_root_id"

when using no string parameter to register_ExampleContext() my EnvoyFilter contained

          value:
            config:
              root_id: ""

The logs only appear when I use a non-empty root id. I will try to troubleshoot this to see if it is a problem with Istio, Envoy, or this SDK.

@esnible could you skip adding root_id? Not sure if that makes a difference.

Further investigation. If I use root_id: "my_root_id" vs root_id: "" in my EnvoyFilter Pilot generates six nearly identical type.googleapis.com/envoy.extensions.filters.http.wasm.v3.Wasm and they are ACK'd and make it to Envoy's config_dump.

Istio and Envoy seem to have a disconnect between empty and null root_id. I created https://github.com/istio/istio/issues/30473 to discuss. XDS generates a "" root ID, and Envoy ignores it.

In both cases Envoy's logs show

2021-01-28T16:28:03.570764Z	trace	envoy wasm	[host->vm] proxy_on_context_create(2, 0)
2021-01-28T16:28:03.570848Z	trace	envoy wasm	[vm->host] env.proxy_get_property(2544, 14, 5247632, 5247628)
2021-01-28T16:28:03.571720Z	trace	envoy wasm	[vm<-host] env.proxy_get_property return: 0
2021-01-28T16:28:03.571758Z	trace	envoy wasm	[host<-vm] proxy_on_context_create return: void

with only the context ID varying.

I will do a further experiment trying to put a null value into the root_id.

Further information:

If I don't include a root_id in my EnvoyFilter it works. So you are correct, there is nothing wrong with the lack of one in your README. You can close this issue, although I would recommend putting a root_id into the example as an enhancement to avoid people falling into the same pit I am falling in.

I learned one more weird thing. I also tried root_id: ~ which SHOULD set root_id to the nil pointer rather than the empty string.

When I did that, Envoy logged some unexpected things.

2021-01-28T17:00:01.308172Z	debug	envoy wasm	expr_evaluate value error: No value with name "downstream_peer" found in Activation
2021-01-28T17:00:01.308191Z	trace	envoy wasm	wasm log: [extensions/stats/plugin.cc:607]::report() Failed to evaluate expression: <downstream_peer.cluster_id>

I have no clue if that is a problem with Envoy, or this library, or the config Istio generates. If that log info is troubling please follow-up.