problem: suboptimal routing for upstreams in different datacenters

solution: additional role to separate primary and secondary upstreams
fix: #141

src/test/resources/upstreams-roles-2.yaml

@@ -0,0 +1,44 @@
+version: v1
+
+defaults:
+  - chains:
+      - ethereum
+    options:
+      min-peers: 3
+
+upstreams:
+  - id: local
+    chain: ethereum
+    connection:
+      ethereum:
+        rpc:
+          url: "http://localhost:8545"
+        ws:
+          url: "ws://localhost:8546"
+          origin: "http://localhost"
+          basic-auth:
+            username: 9c199ad8f281f20154fc258fe41a6814
+            password: 258fe4149c199ad8f2811a68f20154fc
+  - id: closeby
+    chain: ethereum
+    role: secondary
+    connection:
+      ethereum:
+        rpc:
+          url: "http://localhost:8545"
+        ws:
+          url: "ws://localhost:8546"
+          origin: "http://localhost"
+          basic-auth:
+            username: 9c199ad8f281f20154fc258fe41a6814
+            password: 258fe4149c199ad8f2811a68f20154fc
+  - id: infura
+    chain: ethereum
+    role: fallback
+    connection:
+      ethereum:
+        rpc:
+          url: "https://mainnet.infura.io/v3/fa28c968191849c1aff541ad1d8511f2"
+          basic-auth:
+            username: 4fc258fe41a68149c199ad8f281f2015
+            password: 1a68f20154fc258fe4149c199ad8f281