Javascript set Host header policy works fine in APIGee SaaS but not in edge micro-gateway local

[PradeepMathada]

Hi,

I have a requirement to deploy APIGee micro-gateway on a cloud and make internal URLs accessible through micro-gateway URL+Proxy

Internal URL can be accessed through a NGINX load balancer as below.

curl -H "Host: nginx.local" http://istio-ingressgateway.gvillain-istio.svc.cluster.local

As the host and target URL are different, I have set Host Header JS policy for one of my proxies, works absolutely fine in APIGee SaaS when I trace. I can see host set to the value (nginx.local) set in my JS file

Host->nginx.local 
URL->http://mocktarget.apigee.net/echo {changed URL for testing purpose}


https://apigee.com/platform/amadeus-dev/proxies/edgemicro_hello/develop/9 
Response

{"headers":{"x-forwarded-proto":"http","x-cloud-trace-context":"b55b97afda65f1a2741df7a8686aea37\/12906793859235135570","host":"nginx.local","connection":"Keep-Alive","via":"1.1 google"},"method":"GET","body":"","url":"\/"}

I have APIGee micro-gateway POD running on local setup where it downloads products and accessed micro-gateway proxy URL. Surprisingly Host header is set to mocktarget.apigee.net instead of  nginx.local 

Can you please help me resolving the issue?

[tapasthakkar · Accepted solution]

Yes, your observation is accurate. Apigee Edge Microgateway, unlike Apigee Edge, doesn't execute standard Apigee policies. This is because Edge Microgateway is designed as a standalone, lightweight component focusing primarily on product management and security.

In your situation, you're trying to alter the 'Host' header via a JavaScript policy which works on Apigee Edge but not on Edge Microgateway due to the above-mentioned constraint.

To achieve similar functionality in Edge Microgateway, you'll need to create a custom plugin. Through this plugin, you can directly inspect and modify the request and response objects, including the 'Host' header.

In summary, Edge Microgateway requires a programmatic approach for tasks requiring a level of customization typically provided by Apigee Edge's policies.

[PradeepMathada]

You have github repo of sample custom plugins?

[dchiesa1]

Let me Google that for you. 

[PradeepMathada]

Thanks.

I have added custom plugin, below code sets host.

module.exports.init = function(config, logger, stats) {

  return {

onrequest: function(req, res, data, next) {

      req.headers['host'] = 'nginx.amadeus.local';

      next();

    }

  };

}

In the response, host is not modified, instead it is assigned to 'x-forwarded-host'. Host is still assigned to target endpoint host "mocktarget.apigee.net".

Is there any other workaround to fix this issue ?

[dchiesa1]

I think so. In your plugin can you try this:? 

    // req.headers['host'] = 'nginx.amadeus.local';
    req.targetHostname = 'nginx.amadeus.local';

reference: [Apigee community post from 2016]