feat(destination): Add meshed HTTP/2 keep-alive settings

[olix0r]

This commit adds destination controller configuration that enables default
keep-alives for meshed HTTP/2 clients.

This is accomplished by encoding the raw protobuf message structure into the
helm values, and then encoding that as JSON in the destination controller's
command-line options. This allows operators to set any supported HTTP/2 client
configuration without having to modify the destination controller.

[olix0r]

Validated via the diagnostics commands:

:; bin/linkerd diagnostics endpoints web-svc.emojivoto.svc.cluster.local:8080 -o json                                                                 
[
  {
    "namespace": "emojivoto",
    "ip": "10.42.0.103",
    "port": 8080,
    "pod": "web-8d58dcdcd-cp4vv",
    "service": "web-svc.emojivoto",
    "weight": 10000,
    "http2": {
      "keep_alive": {
        "interval": {
          "seconds": 10
        },
        "timeout": {
          "seconds": 3
        },
        "while_idle": true
      }
    },
    "labels": {
      "control_plane_ns": "linkerd",
      "deployment": "web",
      "pod": "web-8d58dcdcd-cp4vv",
      "pod_template_hash": "8d58dcdcd",
      "serviceaccount": "web",
      "zone": ""
    }
  }
]

:; bin/linkerd diagnostics profile 10.42.0.103                                                                                                                                                                       
{
  "retry_budget": {
    "retry_ratio": 0.2,
    "min_retries_per_second": 10,
    "ttl": {
      "seconds": 10
    }
  },
  "endpoint": {
    "addr": {
      "ip": {
        "Ip": {
          "Ipv4": 170524775
        }
      },
      "port": 80
    },
    "weight": 10000,
    "metric_labels": {
      "control_plane_ns": "linkerd",
      "deployment": "web",
      "namespace": "emojivoto",
      "pod": "web-8d58dcdcd-cp4vv",
      "pod_template_hash": "8d58dcdcd",
      "serviceaccount": "web",
      "zone": ""
    },
    "tls_identity": {
      "Strategy": {
        "DnsLikeIdentity": {
          "name": "web.emojivoto.serviceaccount.identity.linkerd.cluster.local"
        }
      },
      "server_name": {
        "name": "web.emojivoto.serviceaccount.identity.linkerd.cluster.local"
      }
    },
    "protocol_hint": {
      "Protocol": {
        "H2": {}
      }
    },
    "http2": {
      "keep_alive": {
        "interval": {
          "seconds": 10
        },
        "timeout": {
          "seconds": 3
        },
        "while_idle": true
      }
    }
  }
}

proxy consuming this:

[     2.100208s] DEBUG ThreadId(01) outbound:accept{client.addr=10.42.0.105:51604 server.addr=10.43.213.5:80}:proxy{addr=10.43.213.5:80}:service{ns=emojivoto name=web-svc port=80}:pool:endpoint{addr=10.42.0.103:8080}:http.endpoint: linkerd_proxy_http::client: Building HTTP client settings=OrigProtoUpgrade(ClientParams { flow_control: Some(Fixed { initial_stream_window_size: 65535, initial_connection_window_size: 1048576 }), keep_alive: Some(ClientKeepAlive { interval: 10s, timeout: 3s, while_idle: true }), max_concurrent_reset_streams: None, max_frame_size: None, max_send_buf_size: None }, PoolSettings { max_idle: 18446744073709551615, idle_timeout: 3s })

[adleong]

since this is in a yaml list of args, does that mean that it will gracefully handle json which contains spaces? or would we need to introduce quoting/escaping?

[olix0r]

toJson (mustToJson): Convert list, slice, array, dict, or object to JSON.
toPrettyJson (mustToPrettyJson): Convert list, slice, array, dict, or object to indented JSON.
toRawJson (mustToRawJson): Convert list, slice, array, dict, or object to JSON with HTML characters unescaped.

toJson gives us a compact, escaped string. Non-newline whitespace is fine in this context.