Clarify when rpc/http tags are added (#96)

Author: Bogdan Drutu

stats/HTTP.md

@@ -41,6 +41,12 @@ All client metrics should be tagged with the following.
 | http_client_status | HTTP status code as an integer (e.g. 200, 404, 500.), or "error" if no response status line was received |
 | http_client_host   | Value of the request Host header                                                                         |
 
+`http_client_method`, `http_client_path`, `http_client_host` are set when an outgoing request 
+starts and are available in the context for the entire outgoing request processing.
+`http_client_status` is set when an outgoing request finishes and is only available around the 
+stats recorded at the end of request processing.
+
+
 ### Default views
 
 The following set of views are considered minimum required to monitor client side performance:
@@ -69,8 +75,6 @@ Server stats are recorded for each individual HTTP request, including for each r
 ### Tags
 
 All server metrics should be tagged with the following. 
-`http_server_method`, `http_server_path`, `http_server_host` are available in the context for the entire request processing.
-`http_server_status` is only available around the stats recorded at the end of request processing.
 
 | Tag suffix         | Description                                                         |
 |--------------------|---------------------------------------------------------------------|
@@ -79,6 +83,11 @@ All server metrics should be tagged with the following.
 | http_server_status | HTTP server status code returned, as an integer e.g. 200, 404, 500. |
 | http_server_host   | Value of the request Host header                                    |
 
+`http_server_method`, `http_server_path`, `http_server_host` are set when an incoming request 
+starts and are available in the context for the entire incoming request processing.
+`http_server_status` is set when an incoming request finishes and is only available around the stats
+recorded at the end of request processing.
+
 ### Default views
 
 The following set of views are considered minimum required to monitor server side performance:

stats/gRPC.md

@@ -47,6 +47,11 @@ All client metrics should be tagged with the following.
 | grpc_client_method | Full gRPC method name, including package, service and method, e.g. google.bigtable.v2.Bigtable/CheckAndMutateRow |
 | grpc_client_status | gRPC server status code received, e.g. OK, CANCELLED, DEADLINE_EXCEEDED                                          |
 
+`grpc_client_method` is set when an outgoing request starts and is available in all the recorded
+metrics. 
+`grpc_client_status` is set when an outgoing request finishes and is only available around metrics
+recorded at the end of the outgoing request.
+
 ### Default views
 
 The following set of views are considered minimum required to monitor client-side performance:
@@ -89,8 +94,10 @@ All server metrics should be tagged with the following.
 | grpc_server_method | Full gRPC method name, including package, service and method, e.g. com.exampleapi.v4.BookshelfService/Checkout |
 | grpc_server_status | gRPC server status code returned, e.g. OK, CANCELLED, DEADLINE_EXCEEDED                                        |
 
-`grpc_server_method` is available in the context for the entire RPC call handling. 
-`grpc_server_status` is only available around metrics recorded at the end of the request.
+`grpc_server_method` is set when an incoming request starts and is available in the context for
+the entire RPC call handling. 
+`grpc_server_status` is set when an incoming request finishes and is only available around metrics
+recorded at the end of the incoming request.
 
 ### Default views