Propagate opentelemetry tracing headers in requests to limitador

[adam-cattermole]

Propagates the following three headers to limitador:

• Traceparent
• Tracestate
• Baggage

Example curl:

curl -H 'Authorization: APIKEY IAMALICE' -H 'Host: api.toystore.com' -H 'Traceparent: 00-80e1afed08e019fc1110464cfa66635c-7a085853722dc6d2-01' -H 'Tracestate: rojo=00f067aa0ba902b7' -H 'Baggage: key1=value1;property1;property2, key2 = value2, key3=value3; propertyKey=propertyValue' http://$GATEWAY_URL/cars

Limitador:

2024-03-19T16:32:39.529787Z DEBUG should_rate_limit: limitador_server::envoy_rls::server: Request received: Request { metadata: MetadataMap { headers: {"te": "trailers", "grpc-timeout": "5000m", "content-type": "application/grpc", "traceparent": "00-80e1afed08e019fc1110464cfa66635c-7a085853722dc6d2-01", "tracestate": "rojo=00f067aa0ba902b7", "baggage": "key1=value1;property1;property2, key2 = value2, key3=value3; propertyKey=propertyValue", "x-envoy-internal": "true", "x-envoy-expected-rq-timeout-ms": "5000"} }, message: RateLimitRequest { domain: "default/toystore", descriptors: [RateLimitDescriptor { entries: [Entry { key: "limit.alice_limit__f994feea", value: "1" }], limit: None }], hits_addend: 1 }, extensions: Extensions 

Resolves #48

[eguzki]

self.get_http_request_headers returns lowercase header names? in other words, if the header is TraceParent, is the value captured? According to https://w3c.github.io/trace-context/#traceparent-header

The header name is [ASCII case-insensitive](https://infra.spec.whatwg.org/#ascii-case-insensitive). That is, TRACEPARENT, TraceParent, and traceparent are considered the same header. The header name is a single word; it does not contain any delimiters such as a hyphen.

[adam-cattermole]

Yep from what I could tell no matter the provided format the headers were retrieved in lowercase - perhaps due to this https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/header_casing

I could add a .to_lowercase() before the match for safety in case though (perhaps this preserve case formatter causes the headers to no longer be lowercase when received by wasm shim). Also considering moving the three header strings out to constants

[eguzki]

if it's only used there, no need for a constant.

[eguzki]

verification steps

• Run devel env

make development

This is currently failing but easily fixed with

diff --git a/Makefile b/Makefile
index 7808041..5362a26 100644
--- a/Makefile
+++ b/Makefile
@@ -61,10 +61,10 @@ $(WASM_RELEASE_PATH): $(RUST_SOURCES)
        make -C $(PROJECT_PATH) -f $(MKFILE_PATH) build
 
 development: $(WASM_RELEASE_PATH)
-       docker-compose up
+       docker compose up
 
 stop-development:
-       docker-compose down
+       docker compose down
 
 # get-protoc will download zip from $2 and install it to $1.
 define get-protoc

• Send a request that will hit limitador with a Traceparent header (upper case T used on purpose)

curl -H "Host: test.c.com" -H "x-forwarded-for: 127.0.0.1" -H "My-Custom-Header-01: my-custom-header-value-01" -H 'Traceparent: 00-80e1afed08e019fc1110464cfa66635c-7a085853722dc6d2-01' -H "x-dyn-user-id: bob" http://127.0.0.1:18000/get

Expected to see in limitador's logs the traceparent

limitador-1  | 2024-03-21T16:28:47.739377Z DEBUG should_rate_limit: limitador_server::envoy_rls::server: Request received: Request { metadata: MetadataMap { headers: {"te": "trailers", "grpc-timeout": "5000m", "content-type": "application/grpc", "traceparent": "00-80e1afed08e019fc1110464cfa66635c-7a085853722dc6d2-01", "x-envoy-internal": "true", "x-forwarded-for": "172.21.0.4", "x-envoy-expected-rq-timeout-ms": "5000"} }, message: RateLimitRequest { domain: "rlp-ns-C/rlp-name-C", descriptors: [RateLimitDescriptor { entries: [Entry { key: "limit_to_be_activated", value: "1" }], limit: None }, RateLimitDescriptor { entries: [Entry { key: "source.address", value: "127.0.0.1:0" }], limit: None }, RateLimitDescriptor { entries: [Entry { key: "request.headers.My-Custom-Header-01", value: "my-custom-header-value-01" }], limit: None }, RateLimitDescriptor { entries: [Entry { key: "user_id", value: "bob" }], limit: None }], hits_addend: 1 }, extensions: Extensions }

[eguzki]

@adam-cattermole nitpick: does it makes sense to use some external library, as a new dep strum, for such a simple thing as to iterate few values?

[adam-cattermole]

@adam-cattermole nitpick: does it makes sense to use some external library, as a new dep strum, for such a simple thing as to iterate few values?

I had the same thought on this - I'm wondering if there's a nice alternative that would allow us to simply add/remove from the TracingHeader enum without changing anything else - it didn't seem very straightforward to write the iter() method myself.

[alexsnaps]

Not hurtful, but I don't know we clone that anywhere...

[adam-cattermole]

Woops, remnant from an earlier change - removed it now.