upstream subset lb: add redundant keys support (#28874)

* upstream subset lb: add redundant keys support

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* add release note

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* fix protobuf format

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update source/extensions/load_balancing_policies/subset/subset_lb.h

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* minor update to address comment

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* fix format

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* minor update

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* update test to address comments

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* enhance test

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* Update api/envoy/extensions/load_balancing_policies/subset/v3/subset.proto

Co-authored-by: Adi (Suissa) Peleg <adip@google.com>
Signed-off-by: code <wangbaiping@corp.netease.com>

* address comment and fix format

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>

---------

Signed-off-by: wbpcode <wangbaiping@corp.netease.com>
Signed-off-by: code <wangbaiping@corp.netease.com>
Co-authored-by: Adi (Suissa) Peleg <adip@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 74bfcb0b591bb692db0b9b0700b4822ef8a6d777

envoy/extensions/load_balancing_policies/subset/v3/subset.proto

@@ -21,7 +21,7 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 
 // Optionally divide the endpoints in this cluster into subsets defined by
 // endpoint metadata and selected by route and weighted cluster metadata.
-// [#next-free-field: 10]
+// [#next-free-field: 11]
 message Subset {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.cluster.v3.LbSubsetConfig";
@@ -171,6 +171,47 @@ message Subset {
   // metadata. The same host may appear in multiple subsets.
   repeated LbSubsetSelector subset_selectors = 3;
 
+  // By default, only when the request metadata has exactly the **same** keys as one of subset selectors and
+  // the values of the related keys are matched, the load balancer will have a valid subset for the request.
+  // For example, given the following subset selectors:
+  //
+  // .. code-block:: json
+  //
+  //   { "subset_selectors": [
+  //       { "keys": [ "version" ] },
+  //       { "keys": [ "stage", "version" ] }
+  //   ]}
+  //
+  // A request with metadata ``{"redundant-key": "redundant-value", "stage": "prod", "version": "v1"}`` or
+  // ``{"redundant-key": "redundant-value", "version": "v1"}`` will not have a valid subset even if the values
+  // of keys ``stage`` and ``version`` are matched because of the redundant key/value pair in the request
+  // metadata.
+  //
+  // By setting this field to true, the most appropriate keys will be filtered out from the request metadata
+  // according to the subset selectors. And then the filtered keys and related values will be matched to find
+  // the valid host subset. By this way, redundant key/value pairs are allowed in the request metadata. The keys
+  // of a request metadata could be superset of the keys of the subset selectors and need not to be exactly the
+  // same as the keys of the subset selectors.
+  //
+  // More specifically, if the keys of a request metadata is a superset of one of the subset selectors, then only
+  // the values of the keys that in the selector keys will be matched. Take the above example, if the request
+  // metadata is ``{"redundant-key": "redundant-value", "stage": "prod", "version": "v1"}``, the load balancer
+  // will only match the values of ``stage`` and ``version`` to find an appropriate subset because ``stage``
+  // ``version`` are contained by the second subset selector and the redundant ``redundant-key`` will be
+  // ignored.
+  //
+  // .. note::
+  //   If the keys of request metadata is superset of multiple different subset selectors keys, the subset
+  //   selector with most keys to win. For example, given subset selectors
+  //   ``{"subset_selectors": ["keys": ["A", "B", "C"], ["A", "B"]]}`` and request metadata ``{"A": "-",
+  //   "B": "-", "C": "-", "D": "-"}``, keys ``A``, ``B``, ``C`` will be evaluated.
+  //   If the keys of request metadata is superset of multiple different subset selectors keys and the number
+  //   of selector keys are same, then the one placed in front to win. For example, given subset selectors
+  //   ``{"subset_selectors": ["keys": ["A", "B"], ["C", "D"]]}`` and request metadata ``{"A": "-", "B": "-",
+  //   "C": "-", "D": "-"}``, keys ``A``, ``B`` will be evaluated.
+  //
+  bool allow_redundant_keys = 10;
+
   // If true, routing to subsets will take into account the localities and locality weights of the
   // endpoints when making the routing decision.
   //