SpringBoot: Flow Polling

backend/src/main/java/djmil/cordacheckers/cordaclient/CordaClient.java

@@ -3,6 +3,8 @@ package djmil.cordacheckers.cordaclient;
 import static java.util.Objects.requireNonNull;
 
 import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
 
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
@@ -12,25 +14,27 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Service;
 import org.springframework.web.client.RestTemplate;
 
-import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import djmil.cordacheckers.cordaclient.dao.HoldingIdentity;
 import djmil.cordacheckers.cordaclient.dao.VirtualNode;
 import djmil.cordacheckers.cordaclient.dao.VirtualNodeList;
 import djmil.cordacheckers.cordaclient.dao.flow.RequestBody;
+import djmil.cordacheckers.cordaclient.dao.flow.ResponseBody;
 import djmil.cordacheckers.cordaclient.dao.flow.arguments.Empty;
 
 @Service
 public class CordaClient {
     private final RestTemplate restTemplate;
+    private final ObjectMapper jsonMapper;
 
-    public CordaClient(RestTemplate restTemplate) {
+    public CordaClient(RestTemplate restTemplate, ObjectMapper jsonMapper) {
         //System.out.println("Creating REST Service");
         // this.restTemplate = restTemplateBuilder
         //     .basicAuthentication("admin", "admin")
         //     .build();
         this.restTemplate = restTemplate;
+        this.jsonMapper = jsonMapper;
     }
 
     public List<VirtualNode> getVirtualNodeList() {
@@ -59,41 +63,121 @@ public class CordaClient {
      * Obtain list of unconsumed (active) GameProposals 
      * @param holdingIdentity
      * @return GameProposals list in JSON form
-     * @throws JsonProcessingException
      */
-    public String listGameProposals(HoldingIdentity holdingIdentity) throws JsonProcessingException {
-        // Request authorization header
-		HttpHeaders headers = basicAuthorizationHeader();
+    public String listGameProposals(HoldingIdentity holdingIdentity) {
 
+        final RequestBody requestBody = new RequestBody(
+            "list-" + UUID.randomUUID(),
+            "djmil.cordacheckers.gameproposal.ListFlow",
+            new Empty()
+        );
 
+        final String gameProposalsJsonString = cordaFlowExecute(
+            holdingIdentity,
+            requestBody
+        );
 
-        RequestBody body = new RequestBody("list-2", "djmil.cordacheckers.gameproposal.ListFlow", new Empty());
+        return gameProposalsJsonString;
+    }
 
-        ObjectMapper mapper = new ObjectMapper();
+    private String cordaFlowExecute(HoldingIdentity holdingIdentity, RequestBody requestBody) {
 
-        String json =  mapper.writeValueAsString(body);
+        try {
+            final String requestBodyJson = this.jsonMapper.writeValueAsString(requestBody);
 
-        if (json != null)
-            return json;
-        // new String("{\n" + //
-        //         "  \"clientRequestId\": \"list-1\",\n" + //
-        //         "  \"flowClassName\": \"djmil.cordacheckers.gameproposal.ListFlow\",\n" + //
-        //         "  \"requestBody\": {}\n" + //
-        //         "}");
+            final ResponseBody startedFlow = cordaFlowPost(
+                holdingIdentity,
+                requestBodyJson
+            );
 
-		System.out.println("HiH "+holdingIdentity.shortHash()+"\nRequst JSON = "+json);
+            final String flowExecutionResult = cordaFlowPoll(startedFlow);
 
+            // NOTE:
+            // At this point, real production code, probably should convert data between CordaFlow
+            // abstarction into ReactApp abstraction. Instead, to limit boring json shuffling, all
+            // family of Corda.List flows were deliberatly designed to return frontend frendly JSONs.
+            // At the same time, all other Corda flows, simply return plain text string with
+            // operation result.
+            return flowExecutionResult;
+        } 
+        catch (Exception e) {
+            throw new RuntimeException("Unable to perform "+requestBody.flowClassName()
+                                        +". Reason "+e.getMessage());
+        }
+    }
 
-		// Request
-		final HttpEntity<String> request = new HttpEntity<>(json, headers);
+    private ResponseBody cordaFlowPost(HoldingIdentity holdingIdentity, String requestBodyJson) {
+		final HttpHeaders requestHeaders = basicAuthorizationHeader();
  
-        ResponseEntity<String> resp = this.restTemplate.exchange(
-            "https://localhost:8888/api/v1/flow/"+holdingIdentity.shortHash(),
+		final HttpEntity<String> request = new HttpEntity<>(requestBodyJson, requestHeaders);
+
+        final ResponseEntity<ResponseBody> responce = this.restTemplate.exchange(
+            "https://localhost:8888/api/v1/flow/" + holdingIdentity.shortHash(),
             HttpMethod.POST,
             request, 
-            String.class);
+            ResponseBody.class
+        );
         
-        return resp.getBody();
+        if (!responce.getStatusCode().is2xxSuccessful()) {
+            throw new RuntimeException("CordaClient.startCordaFlow: unexpected request status "
+                                        +responce.getStatusCode()) ;
+        }
+
+        final ResponseBody responseBody = requireNonNull(
+            responce.getBody(),
+            "CordaClient.startCordaFlow: empty getBody()"
+        );
+
+        if (!responseBody.isFlowStarted()) {
+            throw new RuntimeException("CordaClient.startCordaFlow: Unexpected status: "
+                +responseBody.flowStatus() + ": " 
+                +responseBody.flowError());
+        }
+
+        return responseBody;
+    }
+
+    private String cordaFlowPoll(ResponseBody startedFlow) throws InterruptedException {
+        final HttpHeaders requestHeaders = basicAuthorizationHeader();
+ 
+		final HttpEntity<String> request = new HttpEntity<>(requestHeaders);
+
+        for (int retry = 0; retry < 6; retry++) {
+            // Give Corda cluster some time to process our request
+            TimeUnit.SECONDS.sleep(retry*retry +1); // 1 2 5 8 17 33 sec
+
+            final ResponseEntity<ResponseBody> responce = this.restTemplate.exchange(
+                "https://localhost:8888/api/v1/flow/" 
+                    + startedFlow.holdingIdentityShortHash()+"/"
+                    + startedFlow.clientRequestId(),
+                HttpMethod.GET,
+                request, 
+                ResponseBody.class
+            );
+          
+            if (responce.getStatusCode() != HttpStatus.OK) {
+                throw new RuntimeException("CordaClient.cordaFlowPoll: unexpected request status "
+                                            +responce.getStatusCode()) ;
+            }
+
+            final ResponseBody responseBody = requireNonNull(
+                responce.getBody(),
+                "CordaClient.cordaFlowPoll: empty getBody()"
+            );
+
+            if (responseBody.isFlowCompleted() && responseBody.flowResult() != null) {
+                System.out.println("Completed "+responseBody.flowResult());
+                return responseBody.flowResult();
+            } else
+            if (responseBody.flowError() != null) {
+                return "Flow execution error: " +responseBody.flowError();
+            } else
+            if (!responseBody.isFlowRunning()) {
+                return "Unexpect ResponseBody status: " +responseBody.flowStatus();
+            } 
+        }
+
+        return "CordaClient.cordaFlowPoll: retry limit";
     }
 
     private HttpHeaders basicAuthorizationHeader() {

backend/src/main/java/djmil/cordacheckers/cordaclient/dao/flow/ResponseBody.java

@@ -8,4 +8,18 @@ public record ResponseBody(
     String flowResult,
     String flowError,
     String timestamp
-) { }
+) { 
+
+    public boolean isFlowStarted() {
+        return this.flowStatus.equals("START_REQUESTED");
+    }
+
+    public boolean isFlowRunning() {
+        return this.flowStatus.equals("RUNNING");
+    }
+
+    public boolean isFlowCompleted() {
+        return this.flowStatus.equals("COMPLETED");
+    }
+
+}

backend/src/test/java/djmil/cordacheckers/cordaclient/CordaClientTest.java

@@ -32,7 +32,8 @@ public class CordaClientTest {
 
     @Test
     void testListGameProposals() throws JsonProcessingException {
-        String resp = cordaClient.listGameProposals(holdingIdentityResolver.getByCommonName("alice"));
+        String resp = cordaClient.listGameProposals(
+            holdingIdentityResolver.getByCommonName("alice"));
 
         System.out.println("testListGameProposals "+ resp);
     }