fix: additional logging (#162)

* fix: Adding a call to shutdown() to avoid the consequences of Executor errors

* fix: Adding additional DEBUG Level logs in NvdApiRetryStrategy.

open-vulnerability-clients/src/main/java/io/github/jeremylong/openvulnerability/client/nvd/NvdApiRetryStrategy.java

@@ -27,6 +27,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.time.Instant;
 import java.util.ArrayList;
@@ -53,33 +54,45 @@ public class NvdApiRetryStrategy extends DefaultHttpRequestRetryStrategy {
      */
     private final long delay;
 
+    private static final String RETRY_MESSAGE_TEMPLATE = "NVD API request failures are occurring; retrying request for the {} time";
+
     public NvdApiRetryStrategy(int maxRetries, long delay) {
-        super(maxRetries, TimeValue.of(delay, TimeUnit.MILLISECONDS), new ArrayList<Class<? extends IOException>>(),
+        super(maxRetries, TimeValue.of(delay, TimeUnit.MILLISECONDS), new ArrayList<>(),
                 Arrays.asList(429, 502, 503, 504));
         this.maxRetries = maxRetries;
         this.delay = delay;
     }
 
     @Override
-    public boolean retryRequest(HttpRequest request, IOException exception, int execCount, HttpContext context) {
-        if (execCount >= (maxRetries / 2)) {
-            LOG.warn("NVD API request failures are occurring; retrying request for the {} time", execCount);
-        } else if (execCount > 1) {
-            LOG.debug("Retrying request {} : {} time", request.getRequestUri(), execCount);
-        }
+    public boolean retryRequest(@Nonnull HttpRequest request, @Nonnull IOException exception, int execCount, HttpContext context) {
+        logRetryState(request, exception, execCount);
         return super.retryRequest(request, exception, execCount, context);
     }
 
     @Override
     public boolean retryRequest(HttpResponse response, int execCount, HttpContext context) {
         if (execCount >= (maxRetries / 2)) {
-            LOG.warn("NVD API request failures are occurring; retrying request for the {} time", execCount);
+            LOG.warn(RETRY_MESSAGE_TEMPLATE, execCount);
         } else if (execCount > 1) {
             LOG.debug("Retrying request {} time", execCount);
         }
         return super.retryRequest(response, execCount, context);
     }
 
+    private void logRetryState(@Nonnull HttpRequest request, @Nonnull IOException exception, int execCount) {
+        if (execCount >= (maxRetries / 2)) {
+            LOG.warn(RETRY_MESSAGE_TEMPLATE, execCount);
+            if (LOG.isDebugEnabled()) {
+                LOG.debug("NVD API request failures with exception : {}. Message: {}", exception.getClass().getName(), exception.getMessage());
+            }
+        } else if (execCount > 1) {
+            LOG.warn("Retrying request {} : {} time", request.getRequestUri(), execCount);
+            if (LOG.isDebugEnabled()) {
+                LOG.debug("Retrying request with exception {}. Message: {}", exception.getClass().getName(), exception.getMessage());
+            }
+        }
+    }
+
     @Override
     public TimeValue getRetryInterval(final HttpResponse response, final int execCount, final HttpContext context) {
         TimeValue value;