Apache HttpClient 4.5: Connection Resets

I am using httpClient version 4.5 to connect with our external vendor site. We do not need any connection pool or persistent connection, so I am using the BasicHttpClientConnectionManager to create the HttpClient.

This works fine for minimal number of requests, but if I test this for 1TPS for 1 hour, by the end of the test, we start seeing intermittent connection resets. (guessing request count > 100)

I/O exception (java.net.SocketException) caught when processing request to {s}->https://apiURL:443: Connection reset

Please find below the code snippet for making connection.

SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(kmf.getKeyManagers(), new X509TrustManager[] { new DefaultTrustManager() }, new SecureRandom());
SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslContext, new String[] { "TLSv1.2" }, null,SSLConnectionSocketFactory.getDefaultHostnameVerifier());
Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
                .register("https", sslsf).register("http", new PlainConnectionSocketFactory()).build();

HttpClientConnectionManager connectionManager = new BasicHttpClientConnectionManager(socketFactoryRegistry);
HttpRequestRetryHandler retryHandler = new DefaultHttpRequestRetryHandler(1, false);

RequestConfig defaultRequestConfig = RequestConfig.custom().setSocketTimeout(Integer.parseInt(30000)).setConnectTimeout(Integer.parseInt(30000)).setConnectionRequestTimeout(30000).setCookieSpec(CookieSpecs.STANDARD).build();

CloseableHttpClient httpClient = HttpClients.custom().setConnectionManager(connectionManager).setDefaultRequestConfig(defaultRequestConfig).setRetryHandler(retryHandler).evictExpiredConnections().build();

HttpPost httpPost = new HttpPost(<endpoint>);
httpPost.setEntity(new UrlEncodedFormEntity(requestData));
httpResponse = httpClient.execute(httpPost);

I saw that fix for a similar issue reported is already available with version 4.5. (Ref: https://issues.apache.org/jira/browse/HTTPCLIENT-1655) provided by Oleg

If thats the case, not sure why I am still facing this issue. Could someone please help on this.

Thanks!