Adding logs to internal shadower to check for failures log

src/main/java/com/uber/cadence/internal/shadowing/ScanWorkflowActivityImpl.java

@@ -42,14 +42,22 @@ public ScanWorkflowActivityImpl(IWorkflowService serviceClient) {
 
   @Override
   public ScanWorkflowActivityResult scan(ScanWorkflowActivityParams params) throws Throwable {
+    log.info("Starting scan with params: {} ", params);
+
     ListWorkflowExecutionsRequest scanRequest =
         new ListWorkflowExecutionsRequest()
             .setDomain(params.getDomain())
             .setNextPageToken(params.getNextPageToken())
             .setPageSize(params.getPageSize())
             .setQuery(params.getWorkflowQuery());
+
+    log.debug("Created ListWorkflowExecutionsRequest: {} ", scanRequest);
+    log.info("Scanning workflows with query: {}", params.getWorkflowQuery());
+
     ListWorkflowExecutionsResponse resp = scanWorkflows(scanRequest);
 
+    log.info("Received response with {} executions", resp.getExecutions().size());
+
     List<WorkflowExecution> executions =
         samplingWorkflows(resp.getExecutions(), params.getSamplingRate());
 
@@ -60,18 +68,26 @@ public ScanWorkflowActivityResult scan(ScanWorkflowActivityParams params) throws
             .map(com.uber.cadence.internal.shadowing.WorkflowExecution::new)
             .collect(Collectors.toList()));
     result.setNextPageToken(resp.getNextPageToken());
+    log.info("Scan completed with {} sampled executions", executions.size());
     return result;
   }
 
   protected ListWorkflowExecutionsResponse scanWorkflows(ListWorkflowExecutionsRequest request)
       throws Throwable {
+    log.info(
+        "Scanning workflows for domain: {} with query: {}",
+        request.getDomain(),
+        request.getQuery());
     try {
-      return RpcRetryer.retryWithResult(
-          RpcRetryer.DEFAULT_RPC_RETRY_OPTIONS,
-          () -> this.serviceClient.ScanWorkflowExecutions(request));
+      ListWorkflowExecutionsResponse response =
+          RpcRetryer.retryWithResult(
+              RpcRetryer.DEFAULT_RPC_RETRY_OPTIONS,
+              () -> this.serviceClient.ScanWorkflowExecutions(request));
+      log.info("Successfully scanned workflows for domain: {}", request.getDomain());
+      return response;
     } catch (BadRequestError | EntityNotExistsError | ClientVersionNotSupportedError e) {
       log.error(
-          "failed to scan workflow records with non-retryable error. domain: "
+          "failed to scan workflow records with non-retryable error. Domain: "
               + request.getDomain()
               + "; query: "
               + request.getQuery(),
@@ -90,13 +106,17 @@ protected ListWorkflowExecutionsResponse scanWorkflows(ListWorkflowExecutionsReq
 
   protected List<WorkflowExecution> samplingWorkflows(
       List<WorkflowExecutionInfo> executionInfoList, double samplingRate) {
+    log.info("Sampling workflows with rate: {}", samplingRate);
     int capacity = (int) (executionInfoList.size() * samplingRate);
     capacity = Math.max(capacity, 1);
-    return executionInfoList
-        .stream()
-        .unordered()
-        .map((executionInfo -> executionInfo.getExecution()))
-        .limit((long) (capacity))
-        .collect(Collectors.toList());
+    List<WorkflowExecution> sampledExecutions =
+        executionInfoList
+            .stream()
+            .unordered()
+            .map((executionInfo -> executionInfo.getExecution()))
+            .limit((long) (capacity))
+            .collect(Collectors.toList());
+    log.info("Sampled {} workflows out of {}", sampledExecutions.size(), executionInfoList.size());
+    return sampledExecutions;
   }
 }