How to change the target API URL in an Edge Microgateway custom plugin?

[francois-xavier]

Depending on the request payload, I want to be able to route the API call to another target API URL (for example to implement data-sharding). Overloading req.url in the original onrequest() does not seem to be working. Do I mis something? Is there a way to implement this manual routing?

[#2]

@Francois-Xavier KOWALSKI I believe you can override req.url for the path and query parameters and override req.headers.host to change the hostname.

EDIT: It looks like the microgateway is using the original target URL, regardless of any changes made to the Host header.

See: https://github.com/apigee/microgateway-core/blob/master/lib/plugins-middleware.js#L186-L193

I haven't tested it out, but you may be able to alter res.proxy.parsedUrl.hostname in a plugin to change the host.

And it looks like you'd have to modify req.reqUrl to change the path.

[francois-xavier]

Hello @kevinswiber, I just tested, but it does not seem to work: when calling next() with a modified re.headers.host & req.url, the target URL that EMG tries to reach is left un-modified. Not using next() & implementing my on routing seems to work... but is it compatible with the EMG design intent?

var targetOptions = {
  method: req.method,
  uri: targetUrl,
  headers: req.headers
};
req.pipe(request(targetOptions)).pipe(res);

[#4]

Hey, @Francois-Xavier KOWALSKI. I found that a little surprising, but it looks like you're correct! I updated my response with another suggestion. Disclaimer: I haven't tried it out myself yet, and I'm aware that it looks like a bit of a hack.

[francois-xavier]

Hi @kevinswiber thanks for the pointer! I would indeed not feel very comfortable in manipulating those fields directly... that looks nowhere close to a public/stable API to play with 😉

Would you see any reason (like "violating the EMG design intent because of blah...") for me to NOT use the double-pipe snippet above?

[#6]

Hello @Francois-Xavier KOWALSKI, We are implementing something similar of modifying the target url in EMG. Did you implement the above in onrequest event handler ?

[francois-xavier]

Yes. I initially thought it would work only in onrequest_end(), but it works in onrequest().

[#8]

@Francois-Xavier KOWALSKI

Microgateway version 2.2.3-beta now supports this.
You may override one or both of

req.targetHostname

req.targetPath

See the release notes for the other changes.

[#9]

hi @mfierro , @Francois-Xavier KOWALSKI

We have a similar requirement where the target url would be sent as a header value.

How do we assign the header value to res.proxy.parsedUrl.hostname? or req.targetHostname?

how are these both different? res.proxy.parsedUrl.hostname and req.targetHostname?

We are running on 2.2.4-beta

[alfredodeolivei]

Hello,

I am running version 3.0.3 and this still doesn't seem to work. In my onend_request function, I override the following variables:

req.targetPath

req.url

req.reqUrl.path

req.reqUrl.pathname

req.reqUrl.href

None of these seem to change the target endpoint. As an aside, I'm also curious about whether it is possible to send out a POST request as a result of a GET request (Required for REST to SOAP). Modifying req.method doesn't work. Anyone had any luck with this (without changing the enderlying plugin routing implementation)?

[dchiesa1]

req.targetHostname is the thing you use to override the target hostname.