problem: single invalid response from upstream breaks whole batch

solution: handle http and json errors and convert to RPC errors

src/test/groovy/io/emeraldpay/dshackle/upstream/rpcclient/JsonRpcHttpClientSpec.groovy

@@ -17,6 +17,8 @@ package io.emeraldpay.dshackle.upstream.rpcclient
 
 import io.emeraldpay.dshackle.config.AuthConfig
 import io.emeraldpay.dshackle.test.TestingCommons
+import io.infinitape.etherjar.rpc.RpcException
+import io.infinitape.etherjar.rpc.RpcResponseError
 import org.mockserver.integration.ClientAndServer
 import org.mockserver.model.HttpRequest
 import org.mockserver.model.HttpResponse
@@ -88,4 +90,25 @@ class JsonRpcHttpClientSpec extends Specification {
         )
     }
 
+    def "Produces RPC Exception on error status code"() {
+        setup:
+        def client = new JsonRpcHttpClient("localhost:18332", null, null)
+
+        mockServer.when(
+                HttpRequest.request()
+        ).respond(
+                HttpResponse.response()
+                        .withStatusCode(500)
+                        .withBody("pong")
+        )
+        when:
+        def act = client.execute("ping".bytes).map { new String(it) }
+        then:
+        StepVerifier.create(act)
+                .expectErrorMatches { t ->
+                    t instanceof RpcException && t.code == RpcResponseError.CODE_UPSTREAM_INVALID_RESPONSE
+                }
+                .verify(Duration.ofSeconds(1))
+    }
+
 }

src/test/groovy/io/emeraldpay/dshackle/upstream/rpcclient/JsonRpcParserSpec.groovy

@@ -15,6 +15,7 @@
  */
 package io.emeraldpay.dshackle.upstream.rpcclient
 
+import io.infinitape.etherjar.rpc.RpcResponseError
 import spock.lang.Specification
 
 class JsonRpcParserSpec extends Specification {
@@ -177,4 +178,16 @@ class JsonRpcParserSpec extends Specification {
         !act.hasResult()
     }
 
+    def "Handle non-json with producing an error response"() {
+        setup:
+        def json = 'NOT JSON'
+        when:
+        def act = parser.parse(json.getBytes())
+        then:
+        act.error != null
+        act.error.code == RpcResponseError.CODE_UPSTREAM_INVALID_RESPONSE
+        act.hasError()
+        !act.hasResult()
+    }
+
 }