Merge pull request #232055 from greg-lindsay/update-appgw

update for connection draining

Author: prmerger-automator[bot]

articles/application-gateway/application-gateway-diagnostics.md

@@ -6,7 +6,7 @@ services: application-gateway
 author: greg-lindsay
 ms.service: application-gateway
 ms.topic: article
-ms.date: 03/21/2022
+ms.date: 03/24/2023
 ms.author: greglin 
 ---
 
@@ -18,7 +18,7 @@ You can monitor Azure Application Gateway resources in the following ways:
 
 * [Logs](#diagnostic-logging): Logs allow for performance, access, and other data to be saved or consumed from a resource for monitoring purposes.
 
-* [Metrics](application-gateway-metrics.md): Application Gateway has several metrics which help you verify that your system is performing as expected.
+* [Metrics](application-gateway-metrics.md): Application Gateway has several metrics that help you verify your system is performing as expected.
 
 [!INCLUDE [updated-for-az](../../includes/updated-for-az.md)]
 
@@ -167,7 +167,7 @@ The access log is generated only if you've enabled it on each Application Gatewa
 |httpVersion     | HTTP version of the request.        |
 |receivedBytes     | Size of packet received, in bytes.        |
 |sentBytes| Size of packet sent, in bytes.|
-|clientResponseTime| Length of time (in **seconds**) that it takes for the first byte of a client request to be processed and the first byte sent in the response to the client. |
+|clientResponseTime| Time difference  (in **seconds**) between first byte received from the backend to first byte sent to the client. |
 |timeTaken| Length of time (in **seconds**) that it takes for the first byte of a client request to be processed and its last-byte sent in the response to the client. It's important to note that the Time-Taken field usually includes the time that the request and response packets are traveling over the network. |
 |WAFEvaluationTime| Length of time (in **seconds**) that it takes for the request to be processed by the WAF. |
 |WAFMode| Value can be either Detection or Prevention |
@@ -246,7 +246,7 @@ The access log is generated only if you've enabled it on each Application Gatewa
 |sentBytes| Size of packet sent, in bytes.|
 |timeTaken| Length of time (in milliseconds) that it takes for a request to be processed and its response to be sent. This is calculated as the interval from the time when Application Gateway receives the first byte of an HTTP request to the time when the response send operation finishes. It's important to note that the Time-Taken field usually includes the time that the request and response packets are traveling over the network. |
 |sslEnabled| Whether communication to the backend pools used TLS/SSL. Valid values are on and off.|
-|host| The hostname with which the request has been sent to the backend server. If backend hostname is being overridden, this name will reflect that.|
+|host| The hostname with which the request has been sent to the backend server. If backend hostname is being overridden, this name reflects that.|
 |originalHost| The hostname with which the request was received by the Application Gateway from the client.|
 
 ```json

articles/application-gateway/features.md

@@ -5,7 +5,7 @@ services: application-gateway
 author: greg-lindsay
 ms.service: application-gateway
 ms.topic: conceptual
-ms.date: 03/17/2023
+ms.date: 03/24/2023
 ms.author: greglin
 ---
 
@@ -88,7 +88,7 @@ For more information, see [Application Gateway redirect overview](redirect-overv
 
 ## Session affinity
 
-The cookie-based session affinity feature is useful when you want to keep a user session on the same server. By using gateway-managed cookies, the Application Gateway can direct subsequent traffic from a user session to the same server for processing. This is important in cases where session state is saved locally on the server for a user session.
+The cookie-based session affinity feature is useful when you want to keep a user session on the same server. Using gateway-managed cookies, the Application Gateway can direct subsequent traffic from a user session to the same server for processing. This is important in cases where session state is saved locally on the server for a user session.
 
 For more information, see [How an application gateway works](how-application-gateway-works.md#modifications-to-the-request).
 
@@ -102,14 +102,16 @@ For more information, see [WebSocket support](application-gateway-websocket.md)
 
 ## Connection draining
 
-Connection draining helps you achieve graceful removal of backend pool members during planned service updates or problems with backend health. This setting is enabled via the [Backend Setting](configuration-http-settings.md) and is applied to all backend pool members during rule creation. Once enabled, the aplication gateway ensures all deregistering instances of a backend pool don't receive any new requests while allowing existing requests to complete within a configured time limit. It applies to cases where backend instances are
-- explicitly removed from the backend pool after a configuration change by a user,
+Connection draining helps you achieve graceful removal of backend pool members during planned service updates or problems with backend health. This setting is enabled via the [Backend Setting](configuration-http-settings.md) and is applied to all backend pool members during rule creation. Once enabled, the application gateway ensures all deregistering instances of a backend pool don't receive any new requests while allowing existing requests to complete within a configured time limit. It applies to cases where backend instances are:
+- explicitly removed from the backend pool after a configuration change by a user
 - reported as unhealthy by the health probes, or
-- removed during a scale-in operation.
+- removed during a scale-in operation
 
-The only exception is when requests continue to be proxied to the deregistering instances because of gateway-managed session affinity.
+The only exception is when requests continue to be proxied to the deregistering instances because of gateway-managed session affinity. 
 
-The connection draining is honored for WebSocket connections as well. For information on time limits, see [Backend Settings configuration](configuration-http-settings.md#connection-draining).
+The connection draining is honored for WebSocket connections as well. Connection draining is invoked for every single update to the gateway. To prevent connection loss to existing members of the backend pool, make sure to enable connection draining.
+
+For information on time limits, see [Backend Settings configuration](configuration-http-settings.md#connection-draining).
 
 ## Custom error pages
 
@@ -125,7 +127,7 @@ HTTP headers allow the client and server to pass additional information with the
 - Removing response header fields that can reveal sensitive information.
 - Stripping port information from X-Forwarded-For headers.
 
-Application Gateway and WAF v2 SKU supports the capability to add, remove, or update HTTP request and response headers, while the request and response packets move between the client and backend pools. You can also rewrite URLs, query string parameters and host name. With URL rewrite and URL path-based routing, you can choose to either route requests to one of the backend pools based on the original path or the rewritten path, using the re-evaluate path map option. 
+Application Gateway and WAF v2 SKU supports the capability to add, remove, or update HTTP request and response headers, while the request and response packets move between the client and backend pools. You can also rewrite URLs, query string parameters and host name. With URL rewrite and URL path-based routing, you can choose to either route requests to one of the backend pools based on the original path or the rewritten path, using the reevaluate path map option. 
 
 It also provides you with the capability to add conditions to ensure the specified headers or URL are rewritten only when certain conditions are met. These conditions are based on the request and response information.