Add new endpoint to fetch fork choice context from a client. (#232)

Co-authored-by: Enrico Del Fante <enrico.delfante@consensys.net>
Co-authored-by: Michael Sproul <micsproul@gmail.com>

apis/debug/fork_choice.yaml

@@ -0,0 +1,31 @@
+get:
+  operationId: getDebugForkChoice
+  summary: Get fork choice array
+  description: Retrieves all current fork choice context.
+  tags:
+    - Debug
+  responses:
+    "200":
+      description: Success
+      content:
+        application/json:
+          schema:
+            title: GetForkChoiceResponse
+            type: object
+            description: "Debugging context of fork choice"
+            required: [justified_checkpoint, finalized_checkpoint]
+            properties:
+              justified_checkpoint:
+                $ref: '../../beacon-node-oapi.yaml#/components/schemas/Checkpoint'
+              finalized_checkpoint:
+                $ref: '../../beacon-node-oapi.yaml#/components/schemas/Checkpoint'
+              fork_choice_nodes:
+                type: array
+                description: "Fork choice nodes"
+                minItems: 1
+                items:
+                  $ref: "../../beacon-node-oapi.yaml#/components/schemas/Node"
+              extra_data:
+                $ref: "../../beacon-node-oapi.yaml#/components/schemas/ExtraData"
+    "500":
+      $ref: "../../beacon-node-oapi.yaml#/components/responses/InternalError"

beacon-node-oapi.yaml

@@ -117,6 +117,8 @@ paths:
     $ref: './apis/debug/heads.yaml'
   /eth/v2/debug/beacon/heads:
     $ref: './apis/debug/heads.v2.yaml'
+  /eth/v1/debug/fork_choice:
+    $ref: './apis/debug/fork_choice.yaml'
 
   /eth/v1/node/identity:
     $ref: "./apis/node/identity.yaml"
@@ -292,6 +294,10 @@ components:
       example: "phase0"
     SignedValidatorRegistration:
       $ref: './types/registration.yaml#/SignedValidatorRegistration'
+    Node:
+      $ref: './types/fork_choice.yaml#/Node'
+    ExtraData:
+      $ref: './types/fork_choice.yaml#/ExtraData'
 
   parameters:
     StateId:

types/fork_choice.yaml

@@ -0,0 +1,35 @@
+Node:
+  type: object
+  description: "fork choice node attributes"
+  properties:
+    slot:
+      allOf:
+        - $ref: './primitive.yaml#/Uint64'
+        - description: "The slot to which this block corresponds."
+    block_root:
+      allOf:
+        - $ref: './primitive.yaml#/Root'
+        - description: "The signing merkle root of the `BeaconBlock`."
+    parent_root:
+      allOf:
+        - $ref: './primitive.yaml#/Root'
+        - description: "The signing merkle root of the parent `BeaconBlock`."
+    justified_epoch:
+      $ref: './primitive.yaml#/Uint64'
+    finalized_epoch:
+      $ref: './primitive.yaml#/Uint64'
+    weight:
+      $ref: './primitive.yaml#/Uint64'
+    validity:
+      type: string
+      enum: [VALID, INVALID, OPTIMISTIC]
+    execution_block_hash:
+      allOf:
+        - $ref: './primitive.yaml#/Root'
+        - description: "The `block_hash` from the `execution_payload` of the `BeaconBlock`"
+    extra_data:
+      $ref: '#/ExtraData'
+
+ExtraData:
+  type: object
+  description: 'Optional extra data that clients may provide, which could differ from client to client.'