* Expand 'linkerd edges' to work with TCP connections
Fixes#4999
Before:
```
$ bin/linkerd edges po -owide
SRC DST SRC_NS DST_NS CLIENT_ID SERVER_ID SECURED
linkerd-prometheus-764ddd4f88-t6c2j rabbitmq-controller-5c6cf7cc6d-8lxp2 linkerd default √
linkerd-prometheus-764ddd4f88-t6c2j temp linkerd default √
```
After:
```
$ bin/linkerd edges po -owide
SRC DST SRC_NS DST_NS CLIENT_ID SERVER_ID SECURED
temp rabbitmq-controller-5c6cf7cc6d-5fpsc default default default.default default.default √
linkerd-prometheus-66fb97b7fc-vpnxf rabbitmq-controller-5c6cf7cc6d-5fpsc linkerd default √
linkerd-prometheus-66fb97b7fc-vpnxf temp linkerd default √
```
With the latest proxy upgrade to v2.113.0 (#5037), the `tcp_open_total` metric now contains the `client_id` label so that we can replace the http-only metric `response_total` with this one to determine edges for TCP-only connections.
This change basically performs the same query as before, but two times, one for `response_total` and another for `tcp_open_total`. For each resulting entry, the latter is kept if `client_id` is present, otherwise the former is used (if present at all). That way things keep on working for older proxies.
Disclaimers:
- This doesn't fix#3706: if two sources connect to the same destination there's no way to tell them appart from the metrics perspective and their edges can get mangled. To fix that, the proxy would have to expose `src_resource` labels in the `tcp_open_total` total inbound metric.
- Note connections coming from prometheus are still unidentified. The reason is those hit the proxy's admin server (instead of the main container) which doesn't expose metrics.
Fixes#3052.
Adds a unit test for the edges API endpoint. To maintain a consistent order for
testing, the returned rows in api/public/edges.go are now sorted.
This PR fixes a bug in the edges command where if src_resources from two
different namespaces sent requests to the same dst_resource, the original
src_identity was overwritten.
Adds a check to Prometheus `edges` queries to verify that data for the requested
resource type exists. Previously, if Prometheus could not find request data for the
requested resource type, it would skip that label and still return data for
other labels in the `by` clause, leading to an incorrect response.
This change adds an endpoint to the public API to allow us to query Prometheus for edge data, in order to display identity information for connections between Linkerd proxies. This PR only includes changes to the controller and protobuf.
Alejandro Pedraza
Carol A. Scott