NIFI-12516 Corrected Cluster Replicated Response Headers for HTTP/2

The headers in the map that come back when replicating a request used to be in the case given; however they can be lowercased in the OkHttp Headers object when using HTTP/2 instead of HTTP/1.1. As a result, we need to ensure that we always use lower-case header names or check the map case-insensitive.

This closes #8163

Signed-off-by: David Handermann <exceptionfactory@apache.org>

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-cluster/src/main/java/org/apache/nifi/cluster/coordination/http/replication/okhttp/JacksonResponse.java

@@ -231,7 +231,12 @@ public class JacksonResponse extends Response {
     }
 
     @Override
-    public String getHeaderString(String name) {
-        return responseHeaders.getFirst(name);
+    public String getHeaderString(final String name) {
+        final String headerValue = responseHeaders.getFirst(name);
+        if (headerValue != null) {
+            return headerValue;
+        }
+
+        return responseHeaders.getFirst(name.toLowerCase());
     }
 }

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-web-api/src/main/java/org/apache/nifi/web/StandardNiFiContentAccess.java

@@ -35,6 +35,7 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.regex.Matcher;
@@ -113,11 +114,11 @@ public class StandardNiFiContentAccess implements ContentAccess {
             }
 
             // get the file name
-            final String contentDisposition = responseHeaders.getFirst("Content-Disposition");
+            final String contentDisposition = getHeader(responseHeaders, "content-disposition");
             final String filename = StringUtils.substringBetween(contentDisposition, "filename=\"", "\"");
 
             // get the content type
-            final String contentType = responseHeaders.getFirst("Content-Type");
+            final String contentType = getHeader(responseHeaders, "content-type");
 
             // create the downloadable content
             return new DownloadableContent(filename, contentType, nodeResponse.getInputStream());
@@ -159,6 +160,37 @@ public class StandardNiFiContentAccess implements ContentAccess {
         }
     }
 
+    /**
+     * Returns the value of the first header in the given header map whose name matches the given header name.
+     * In HTTP 2.0, all header names should be lower-case. Before that, they were not necessarily. The spec, however,
+     * indicates that header names are case-insensitive. That said, the code has them stored in a Map, and the keys in Maps
+     * are not case-insensitive. This method allows us to access the value of the first header with the given name,
+     * ignoring case.
+     *
+     * @param headers the map containing all headers
+     * @param headerName the case-insensitive name of the header to retrieve
+     * @return the value of the first header with the given name, or <code>null</code> if the header is not found
+     */
+    private String getHeader(final MultivaluedMap<String, String> headers, final String headerName) {
+        if (headers == null || headers.isEmpty() || headerName == null || headerName.isBlank()) {
+            return null;
+        }
+
+        final String exactMatch = headers.getFirst(headerName);
+        if (exactMatch != null) {
+            return exactMatch;
+        }
+
+        for (final Map.Entry<String, List<String>> entry : headers.entrySet()) {
+            if (entry.getKey().equalsIgnoreCase(headerName)) {
+                final List<String> values = entry.getValue();
+                return values == null || values.isEmpty() ? null : values.get(0);
+            }
+        }
+
+        return null;
+    }
+
     private DownloadableContent getFlowFileContent(final String connectionId, final String flowfileId, final String dataUri) {
         // user authorization is handled once we have the actual content so we can utilize the flow file attributes in the resource context
         return serviceFacade.getContent(connectionId, flowfileId, dataUri);