Http2 bug workaround (#1060)

* http2 issue workaround

* adding comment

Author: l-trotta

java-client/src/main/java/co/elastic/clients/transport/ElasticsearchTransportBase.java

@@ -243,25 +243,24 @@ private <RequestT, ResponseT, ErrorT> TransportHttpClient.Request prepareTranspo
         Map<String, String> params = endpoint.queryParameters(request);
 
         List<ByteBuffer> bodyBuffers = null;
-        HeaderMap headers = DefaultHeaders;
+        // Setting the Content-type header for all requests, even the ones without body.
+        // This is a workaround for a bug with server version 9.1.2 and http2, where
+        // http2 stream requests are considered not to have a body. So if the client doesn't always send
+        // the Content-type header, empty body requests will fail with the above-described conditions.
+        HeaderMap headers = JsonContentTypeHeaders;
 
         Object body = endpoint.body(request);
         if (body != null) {
             // Request has a body
             if (body instanceof NdJsonpSerializable) {
                 bodyBuffers = new ArrayList<>();
                 collectNdJsonLines(bodyBuffers, (NdJsonpSerializable) request);
-                headers = JsonContentTypeHeaders;
-
             } else if (body instanceof BinaryData) {
                 BinaryData data = (BinaryData) body;
 
                 // ES expects the Accept and Content-Type headers to be consistent.
                 String dataContentType = data.contentType();
-                if (ContentType.APPLICATION_JSON.equals(dataContentType)) {
-                    // Fast path
-                    headers = JsonContentTypeHeaders;
-                } else {
+                if (!ContentType.APPLICATION_JSON.equals(dataContentType)) {
                     headers = new HeaderMap(DefaultHeaders);
                     headers.put(HeaderMap.CONTENT_TYPE, dataContentType);
                 }

java-client/src/main/java/co/elastic/clients/transport/rest5_client/Rest5ClientOptions.java

@@ -238,7 +238,7 @@ private static String getClientMeta() {
         VersionInfo httpClientVersion = null;
         try {
             httpClientVersion = VersionInfo.loadVersionInfo(
-                "org.apache.http.nio.client",
+                "org.apache.hc.core5",
                 HttpAsyncClientBuilder.class.getClassLoader()
             );
         } catch (Exception e) {

java-client/src/main/java/co/elastic/clients/transport/rest5_client/low_level/BufferedByteConsumer.java

@@ -57,7 +57,7 @@ protected int capacityIncrement() {
     protected void data(final ByteBuffer src, final boolean endOfStream) throws ContentTooLongException {
         if (buffer.length() + src.limit() > limit) {
             throw new ContentTooLongException(
-                "entity content is too long [" + src.capacity() + "] for the configured buffer limit [" + limit + "]"
+                "entity content is too long [" + src.limit() + "] for the configured buffer limit [" + limit + "]"
             );
         }
         buffer.append(src);