Customize request headers and response headers by using the VirtualService CRD - Alibaba Cloud Service Mesh

Service Mesh (ASM) allows you to customize request headers and response headers by using the headers field of the VirtualService CustomResourceDefinition (CRD). The VirtualService CRD allows you to add, modify, or delete HTTP headers at the route level. This way, customized processing of header information is implemented.

Prerequisites

The HTTPBin application is deployed. For more information, see Deploy the HTTPBin application.

Step 1: Define the VirtualService CRD

VirtualService can meet most common header operation requirements, such as simple addition, modification, or deletion of request headers and response headers. For example, it can set header values to fixed static strings. In addition, it can dynamically generate request and response header values by using built-in expressions. These expressions are usually enclosed in the % symbol and can reference different dynamic content such as request attributes. All HTTP command operators used to access logs can be specified in custom request or response headers. For example, %UPSTREAM_CLUSTER% indicates the name of a service provider. For more information, see Command Operators.

You can customize the HTTP headers of requests and responses based on routing rules. This is useful in scenarios such as tracing, logging, adding security headers, or implementing specific service logic. The following section provides a configuration example of VirtualService. This example demonstrates how to customize request headers and response headers.

Type

Description

Request headers

Add the x-custom-request-header request header and set the value to "custom-value".
Set the x-another-request-header request header to "another-value". If this request header already exists, its value will be overwritten. If this request header does not exist, it will be added.
Remove the x-unwanted-header request header.

Response headers

Add the x-custom-response-header response header and set the value to "custom-response-value".
Set x-another-response-header response header to "another-response-value". If this response header already exists, its value will be overwritten. If this response header does not exist, it will be added.
Remove the x-unwanted-response-heade response header.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: httpbin-vs
spec:
  gateways:
    - httpbin
  hosts:
    - '*'
  http:
  - route:
    - destination:
        host: httpbin
        port:
          number: 8000
      weight: 100
    headers:
      request:
        add:
          x-custom-request-header: "custom-value" # Add a custom request header. 
          x-dynamic-request-header: "%START_TIME%" # Add a custom request header. 
        set:
          x-another-request-header: "another-value" # Modify or set the request header. 
        remove:
        -x-unwanted-header # Remove the request header. 
      response:
        add:
          x-custom-response-header: "custom-response-value" # Add a custom response header. 
        set:
          x-another-response-header: "another-response-value" # Modify or set the response header. 
        remove:
        -x-unwanted-response-header # Remove the response header.

Note

The VirtualService CRD can be used to set and modify HTTP headers. However, Envoy access logs do not record these changes if Envoy retains the default configurations of access logs. If you want to record custom headers in Envoy access logs, you must modify the log format of Envoy.

Step 2: View custom request headers and response headers in access logs

ASM allows you to customize log formats. The custom expressions of access logs can obtain values from request headers, response headers, and Envoy built-in values. For more information, see Customize the format of access logs.

The following table lists three new fields, which are used to display content in access logs.

Field	Type	Value
my-x-custom-request-header	Request attribute	%REQ(x-custom-request-header)%
my-x-dynamic-request-header	Request attribute	%REQ(x-dynamic-request-header)%
my-x-custom-response-header	Response attribute	%RESP(x-custom-response-header)%

Note

In VirtualService, if the modification of response headers takes effect after logging, these modified response headers are not recorded in access logs.

Check the access logs of the gateway pod and you can see content similar to the following:

{
    "bytes_received": "9",
    "bytes_sent": "33",
    "response_code": "200",
    "my-x-custom-request-header": "custom-value",
    "my-x-dynamic-request-header":"2024-01-16T14:49:21.187Z"
    "my-x-custom-response-header": "custom-response-value"
}

Check the access logs of the HTTPBin pod and you can see content similar to the following:

{
    "bytes_received": "9",
    "bytes_sent": "33",
    "response_code": "200",
    "my-x-custom-request-header": "custom-value",
    "my-x-dynamic-request-header": "2024-01-16T14:49:21.187Z"
    "my-x-custom-response-header": "-"
}