Co-authored-by: Ashvitha Sridharan <ashvitha.sridharan@hashicorp.com>
Co-authored-by: Freddy <freddygv@users.noreply.github.com>
Add a new envoy flag: "envoy_hcp_metrics_bind_socket_dir", a directory
where a unix socket will be created with the name
`<namespace>_<proxy_id>.sock` to forward Envoy metrics.
If set, this will configure:
- In bootstrap configuration a local stats_sink and static cluster.
These will forward metrics to a loopback listener sent over xDS.
- A dynamic listener listening at the socket path that the previously
defined static cluster is sending metrics to.
- A dynamic cluster that will forward traffic received at this listener
to the hcp-metrics-collector service.
Reasons for having a static cluster pointing at a dynamic listener:
- We want to secure the metrics stream using TLS, but the stats sink can
only be defined in bootstrap config. With dynamic listeners/clusters
we can use the proxy's leaf certificate issued by the Connect CA,
which isn't available at bootstrap time.
- We want to intelligently route to the HCP collector. Configuring its
addreess at bootstrap time limits our flexibility routing-wise. More
on this below.
Reasons for defining the collector as an upstream in `proxycfg`:
- The HCP collector will be deployed as a mesh service.
- Certificate management is taken care of, as mentioned above.
- Service discovery and routing logic is automatically taken care of,
meaning that no code changes are required in the xds package.
- Custom routing rules can be added for the collector using discovery
chain config entries. Initially the collector is expected to be
deployed to each admin partition, but in the future could be deployed
centrally in the default partition. These config entries could even be
managed by HCP itself.
