Empty placeholders: Failed to match Route configuration for upstream path

[satano]

Expected Behavior

Match upstream path with empty placeholder and map it correctly to downstream.

Actual Behavior / Motivation for New Feature

Upstream path with placeholder is not working as expected when placeholder is empty. It fails with error:

UnableToFindDownstreamRouteError Message: Failed to match ReRoute configuration for upstream path: /test

Steps to Reproduce the Problem

This special catch all configuration of ReRoute works as expected

"DownstreamPathTemplate": "/api/invoices/{url}"
"UpstreamPathTemplate": "/{url}"

It maps URLs this way:

/ → /api/invoices/
/123 → /api/invoices/123

Now this mapping (downstream is the same):

"DownstreamPathTemplate": "/api/invoices/{url}"
"UpstreamPathTemplate": "/test/{url}"

It works correctly when {url} is specified: /test/123 → /api/invoices/123

But it fails, when {url} is empty. I would expect upstream URL /test/ to reroute to downstream URL /api/invoices/. The error is:

dbug: Ocelot.DownstreamRouteFinder.Middleware.DownstreamRouteFinderMiddleware[0]
      requestId: 0HLJQAG2RQPKO:00000005, previousRequestId: no previous request id, message: Upstream url path is /test/
warn: Ocelot.DownstreamRouteFinder.Middleware.DownstreamRouteFinderMiddleware[0]
      requestId: 0HLJQAG2RQPKO:00000005, previousRequestId: no previous request id, message: DownstreamRouteFinderMiddleware setting pipeline errors. IDownstreamRouteFinder returned Error Code: UnableToFindDownstreamRouteError Message: Failed to match ReRoute configuration for upstream path: /test/, verb: GET.
warn: Ocelot.DownstreamRouteFinder.Middleware.DownstreamRouteFinderMiddleware[0]
      requestId: 0HLJQAG2RQPKO:00000005, previousRequestId: no previous request id, message: Failed to match ReRoute configuration for upstream path: /test/, verb: GET.
warn: Ocelot.Responder.Middleware.ResponderMiddleware[0]
      requestId: 0HLJQAG2RQPKO:00000005, previousRequestId: no previous request id, message: Error Code: UnableToFindDownstreamRouteError Message: Failed to match ReRoute configuration for upstream path: /test/, verb: GET. errors found in ResponderMiddleware. Setting error response for request path:/test/, request method: GET
dbug: Ocelot.Errors.Middleware.ExceptionHandlerMiddleware[0]
      requestId: 0HLJQAG2RQPKO:00000005, previousRequestId: no previous request id, message: ocelot pipeline finished

As a special case of this, I would also expect routing to ignore trailing slash, because from WEB/API wiew, usually the address with the slash at the end is the same as without it. So upstream URL /test would map to downstream URL /api/invoices. Maybe this is not exact from the computers point of view, but for me it makes sense from human point of view of configuration. It does not work this way even if the routing is configured without the slashes:

"DownstreamPathTemplate": "/api/invoices{url}"
"UpstreamPathTemplate": "/test{url}"

It correctly maps non epmty {url} which means, it works with the slash at the end, because the slash is the value of the {url}. But still not without it:

/test/123 → /api/invoices/123
/test/ → /api/invoices/
/test → Failed to match ReRoute configuration for upstream path: /test

To make work everything what I want, I need three reroutes (or at least two, if the first one will be without slashes):

{
    "DownstreamPathTemplate": "/api/invoices/{url}"
    "UpstreamPathTemplate": "/test/{url}"
},
{
    "DownstreamPathTemplate": "/api/invoices/"
    "UpstreamPathTemplate": "/test/"
},
{
    "DownstreamPathTemplate": "/api/invoices"
    "UpstreamPathTemplate": "/test"
}

Specifications

• Version: Ocelot 13.0.0
• Platform: .NET Core 2.2 on Windows

[margaale]

I always thought that it was designed to work this way, let's see if we can get some clarification...

[satano]

New day has come and the new ideas with it. :)

Well. I thought about it and it is not as simple as I wrote in the first post. The problem is, that empty placeholder is not allowed in upstream URLs - special exception is catch all upstream /{everything}. And it really makes sense. But for me, it makes sense only for placeholders in the middle of the path.

So for example, I would not allow empty placeholder in this configuration.

"DownstreamPathTemplate": "/api/{url}/list"
"UpstreamPathTemplate": "/test/v2/{url}/list"

Because the most probably I do not want it to catch upstream URL /test/v2//list. This URL is OK and it is the same as /test/v2/list - the number of consecutive slashes does not matter.

So I would formulate my proposal this way.

If the same placeholder is at the end of both upstream and downstream path after the slash, it should work with empty value. Furthermore, when the placeholder is empty, this upstream route should match URL without the trailing slash.

To clarify this - for me, it is the same as catch all route /{everything}, but with some path prefix. So some examples:

Simple catch all URL

"DownstreamPathTemplate": "/api/test/{url}"
"UpstreamPathTemplate": "/test/{url}"

Will reroute:

/test/123 → /api/test/123
/test/ → /api/test/
/test → /api/test

Multiple placeholders

"DownstreamPathTemplate": "/api/{version}/test/{url}"
"UpstreamPathTemplate": "/test/{version}/{url}"

Will reroute:

/test/v1/123 → /api/v1/test/123
/test/v1/ → /api/v1/test/
/test/v1 → /api/v1/test

Empty value for {version} is not allowed, so upstream URL /test/123 will not match.

Placeholder in the middle of the path

"DownstreamPathTemplate": "/api/{url}/test"
"UpstreamPathTemplate": "/test/{url}"

Or

"DownstreamPathTemplate": "/api/test/{url}"
"UpstreamPathTemplate": "/test/{url}/api"

Empty value for {url} is not allowed. The placeholder must be at the end of both paths.

Different placeholders at the ends

"DownstreamPathTemplate": "/api/{url2}/{url1}"
"UpstreamPathTemplate": "/test/{url1}/{url2}"

Empty value is not allowed for any of the placeholders. The placeholder at the end must be the same.

Conclusion

So what I am thinking about is like extending current behavior of catch all URL /{url}. In mentioned conditions, the catch all will work for any path, not just simple /.

[philproctor]

#737 changes the way the matching templates are created and used, I did not change this behavior as it appeared to be by design. A few days ago I tried having the catch all catch 0 or more if it's the last segment of the pattern, but this caused some acceptance tests to fail which were explicitly verifying that did not happen. As such, I believe this is an intended behavior, but I think as part of #737 we may have some workarounds, particularly, using a grouping match instead of a placeholder. I will discuss with the team.

[upadhyaychandan]

Hi Team,
I want to validate Placeholder value how we can do that
Example:-
Api/test1/{Id}
api/test1/{Id}/test
api/test1/{id}/test/{id2}

Request Url:-
api/test1/{EmptyValue/test
So in Placeholder it is coming {EmptyValue}/test , it should be only {emptyvalue}

[i02coroj]

Hi.
I see this ticket is still open and I would be quite interested to know if there's a plan to get this implemented.
The behavior I see with version 18.0.0 of the package it that it still doesn't match the upstream when the placeholder at the end of the path is empty.
so

[AlyHKafoury]

@raman-m Can I work on this issue ?

[raman-m]

@AlyHKafoury Yes, you can!
With this bug you can go to fix...
Pay attention you need to check a lot of current unit and acceptance tests, and add new ones for "empty placeholder" problem.