Fix reconnect to newHeads (#178)

* Fix reconnect to newHeads

src/test/groovy/io/emeraldpay/dshackle/test/EthereumHeadMock.groovy

@@ -77,4 +77,9 @@ class EthereumHeadMock implements Head {
     void stop() {
 
     }
+
+    @Override
+    void onNoHeadUpdates() {
+
+    }
 }

src/test/groovy/io/emeraldpay/dshackle/upstream/AbstractHeadSpec.groovy

@@ -60,7 +60,7 @@ class AbstractHeadSpec extends Specification {
                     head.stop()
                     source.tryEmitComplete()
                 }
-                .expectComplete()
+                .thenCancel()
                 .verify(Duration.ofSeconds(1))
     }
 
@@ -85,7 +85,7 @@ class AbstractHeadSpec extends Specification {
                     head.stop()
                     source.tryEmitComplete()
                 }
-                .expectComplete()
+                .thenCancel()
                 .verify(Duration.ofSeconds(1))
     }
 
@@ -115,7 +115,7 @@ class AbstractHeadSpec extends Specification {
                     head.stop()
                     source.tryEmitComplete()
                 }
-                .expectComplete()
+                .thenCancel()
                 .verify(Duration.ofSeconds(1))
     }
 

src/test/groovy/io/emeraldpay/dshackle/upstream/ethereum/EthereumWsHeadSpec.groovy

@@ -25,8 +25,11 @@ import io.emeraldpay.etherjar.domain.TransactionId
 import io.emeraldpay.etherjar.rpc.json.BlockJson
 import io.emeraldpay.etherjar.rpc.json.TransactionRefJson
 import reactor.core.publisher.Flux
+import reactor.core.publisher.Mono
+import reactor.test.StepVerifier
 import spock.lang.Specification
 
+import java.time.Duration
 import java.time.Instant
 import java.time.temporal.ChronoUnit
 
@@ -71,4 +74,47 @@ class EthereumWsHeadSpec extends Specification {
                 headBlock
         ])
     }
+
+    def "Restart ethereum ws head"() {
+        setup:
+        def block = new BlockJson<TransactionRefJson>()
+        block.timestamp = Instant.now().truncatedTo(ChronoUnit.SECONDS)
+        block.number = 103
+        block.hash = BlockHash.from("0x3ec2ebf5d0ec474d0ac6bc50d2770d8409ad76e119968e7919f85d5ec8915200")
+        def secondBlock = new BlockJson<TransactionRefJson>()
+        secondBlock.timestamp = Instant.now().truncatedTo(ChronoUnit.SECONDS)
+        secondBlock.number = 105
+        secondBlock.hash = BlockHash.from("0x29229361dc5aa1ec66c323dc7a299e2b61a8c8dd2a3522d41255ec10eca25dd8")
+
+        def firstHeadBlock = block.with {
+            Global.objectMapper.writeValueAsBytes(it)
+        }
+        def secondHeadBlock = secondBlock.with {
+            Global.objectMapper.writeValueAsBytes(it)
+        }
+
+        def apiMock = TestingCommons.api()
+        apiMock.answerOnce("eth_getBlockByHash", ["0x3ec2ebf5d0ec474d0ac6bc50d2770d8409ad76e119968e7919f85d5ec8915200", false], null)
+        apiMock.answerOnce("eth_getBlockByHash", ["0x29229361dc5aa1ec66c323dc7a299e2b61a8c8dd2a3522d41255ec10eca25dd8", false], null)
+        apiMock.answerOnce("eth_blockNumber", [], Mono.empty())
+        apiMock.answerOnce("eth_blockNumber", [], Mono.empty())
+
+        def ws = Mock(WsSubscriptions) {
+            2 * subscribe("newHeads") >>> [Flux.fromIterable([firstHeadBlock]), Flux.fromIterable([secondHeadBlock])]
+        }
+
+        def head = new EthereumWsHead("fake", new AlwaysForkChoice(), BlockValidator.ALWAYS_VALID, apiMock, ws, true)
+
+        when:
+        def act = head.getFlux()
+
+        then:
+        StepVerifier.create(act)
+                .then { head.start() }
+                .expectNext(BlockContainer.from(block))
+                .then { head.onNoHeadUpdates() }
+                .expectNext(BlockContainer.from(secondBlock))
+                .thenCancel()
+                .verify(Duration.ofSeconds(1))
+    }
 }