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Is there any way to connect to perform operation on AWS neptune giving gremlin code in .java file

I tried Connecting the AWS Neptune with this Java code and got the error , NoHostAvailable Exception
approach 1:
public static void main(String[] args) throws Exception {
Cluster.Builder builder = Cluster.build();
builder.addContactPoint("endpoint");
builder.port(8182);
builder.enableSsl(true);
builder.keyStore("pem-file");
Cluster cluster = builder.create();
GraphTraversalSource g = traversal().withRemote(DriverRemoteConnection.using(cluster));
System.out.println(g.V().limit(10).toList());
cluster.close();
}}
approach 2:
Cluster cluster = Cluster.build("endpoint").
enableSsl(true).keyStore("pem").
handshakeInterceptor( r -> {
NeptuneNettyHttpSigV4Signer sigV4Signer = null;
try {
sigV4Signer = new NeptuneNettyHttpSigV4Signer("us-east-2", new
DefaultAWSCredentialsProviderChain());
} catch (NeptuneSigV4SignerException e) {
e.printStackTrace();
}
try {
sigV4Signer.signRequest(r);
} catch (NeptuneSigV4SignerException e) {
e.printStackTrace();
}
return r;
}).create();
Client client=Cluster.open("src\\conf\\remote-objects.yaml").connect();
client.submit("g.V().limit(10).toList()").all().get();
what ever I do, I am getting this error:
Sep 02, 2021 3:18:34 PM io.netty.channel.ChannelInitializer exceptionCaught
WARNING: Failed to initialize a channel. Closing:
java.lang.RuntimeException: java.lang.NullPointerException
org.apache.tinkerpop.gremlin.driver.Channelizer$AbstractChannelizer.initChannel(Channelizer.java:117)
Caused by: org.apache.tinkerpop.gremlin.driver.exception.NoHostAvailableException: All hosts
are considered unavailable due to previous exceptions. Check the error log to find the actual
reason.
I need the code or the document to connect my Gremlin code in .java file to AWS neptune. I am struggling and tried various number of ways,
1.created EC2 instance and did installed maven and apache still got error and code is running in Server(EC2), i want code to present in IntelliJ
it would be more helpful, if I get the Exact Code any way. what should be added in remote-objects.yaml.
if we require Pem-file to access Amazon Neptune, please help with the creation of it.

Assuming SSL is enabled but IAM is not, in terms of Java code, this is all you need to create the connection.
Cluster.Builder builder = Cluster.build();
builder.addContactPoint("localhost");
builder.port(8182);
builder.enableSsl(true);
builder.serializer(Serializers.GRAPHBINARY_V1D0);
cluster = builder.create();
drc = DriverRemoteConnection.using(cluster);
g = traversal().withRemote(drc);
You may need to add an entry to your /etc/hosts file to get the SSL certs to resolve correctly such as:
127.0.0.1 localhost my-neptune-cluster.us-east-1.neptune.amazonaws.com
If you find that using localhost with SSL enabled does not work then use the actual Neptune cluster DNS name and make the edit to your /etc/hosts file.
The last thing you will need to do is create access to the Neptune VPC from your local machine. One way is using an SSH tunnel as explained in this post

Java RMI call slow first time

I'm working on a personal project for school where I have to user RMI to communicate between server and client.
Project info
The goal of my project is to retrieve stock info (from NYSE) for each day on the server at a specific time (after NYSE is closed). Each stock object is saved in a database. The information is retrieved over http and has nothing to do with RMI.
For the client it is also possible to fetch the stocks. When a user wants to fetch the stock object for the current day, it is directly fetched from the 3th party service. When a user, for example, wants to fetch Google's stock from last month, it is requested on the server over RMI. The server will the look for the stock object in the database and retrieve a Stock object and send it to the client.
Problem
When I start the client application, I have to login. The client will create a User object containing the username and password.
When I press the login button, it will take around 2 minutes before the main screen will be shown.
Below the source code where I setup the RMI connection.
Server (main.java)
public static void main(String[] args) throws UnknownHostException {
InetAddress IP= InetAddress.getLocalHost();
System.out.println("IP of my system is := "+IP.getHostAddress());
if(args.length == 1 && args[0].toLowerCase().equals("local")) {
System.out.println("Running on localhost");
System.setProperty("java.rmi.server.hostname", IP.getHostAddress());
} else {
System.out.println("rmi hostname is set to 37.97.223.70");
System.setProperty("java.rmi.server.hostname", "37.97.223.70");
}
try {
Registry reg = LocateRegistry.createRegistry(1099);
StockAppServer server = StockAppServer.getInstance();
reg.rebind("StockApp", server);
System.out.println("StockApp bound for StockAppServer object.");
} catch (RemoteException e) {
e.printStackTrace();
}
}
Based on the arguments that are passed to the application when it starts, I set the RMI hostname to my current IP address, or to the remote server address. The remote server address is a static IP, so this won't change.
Server (StockAppServer.java)
This class implements the interfaces that is used by the client to call methods on the server. So this class extends UnicastRemoteObject. When I start the server, registerStockTask() will be called. This method will fetch the ticker symbols (What are ticker symbols?) and then schedule a task to fetch all stock objects at a specific time.
private static StockAppServer _instance;
private List<User> loggedInUsers;
private List<Group> activeGroups;
private List<Notification> registeredNotifications;
private StockAppServer() throws IOException {
_instance = this;
this.loggedInUsers = new ArrayList<>();
this.activeGroups = new ArrayList<>();
this.registeredNotifications = new ArrayList<>();
this.registerStockTask();
clearActiveGroups();
checkForCompletedNotifications();
// Start the restful framework to allow incoming connections from the NodeJS server to manage new notification
Router.getInstance();
}
public static StockAppServer getInstance() {
try{
return _instance == null ? new StockAppServer() : _instance;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
Client (main.java)
public static void main(String[] arguments) throws Exception {
args = arguments;
Application.launch();
}
#Override
public void start(Stage primaryStage) throws Exception {
InetAddress IP= InetAddress.getLocalHost();
System.out.println("IP of my system is := "+IP.getHostAddress());
if(args.length == 1 && args[0].toLowerCase().equals("local")) {
// Program started with local command, expect that server is running on local host
reg = LocateRegistry.getRegistry(IP.getHostAddress(), 1099);
System.out.println("Attempting to connect to RMI server over 127.0.0.1");
} else {
// Program started without additional commands. Except that "the server" is available;
reg = LocateRegistry.getRegistry("37.97.223.70", 1099);
System.out.println("Attempting to connect to RMI server over 37.97.223.70");
}
try {
StockApp.getInstance().setServerInterfaces((IStockSend) reg.lookup("StockApp"), (IUserHandling) reg.lookup("StockApp"));
} catch(RemoteException e) {
AlertMessage.showException("Unable to connect to server.", e);
} catch (NotBoundException e) {
AlertMessage.showException("No server has been found with the name \"StockApp\" on the remote host.\nPlease try again later", e);
}
LoginController.showMenu();
//FileNotFoundException e = new FileNotFoundException("Couldn't find file blabla.txt");
//AlertMessage.showException("Something went wrong. Please try again later.", e);
}
How I tried to solve my problem
When I test my applications local, there is no problem. The login method will be finished within a few milliseconds and I will be represented the main screen.
I started by turning of my firewall on my macbook. No result, login method still takes around 2 seconds.
I turned off the firewall om my Ubuntu server. No result, both firewalls on server and macbook are turned off. Login method still takes around 2 seconds.
On the server runs (thanks to jenkins) another (unrelated) program. This program uses sockets instead of RMI. When this program is not running, the login method still takes around 2 minutes.
In StockAppServer.java, I called the following method:
super(1099);
This has the same outcome as the above steps I took.
I don't know what else I can try to solve my problem.
I tried to give as much code as possible for the RMI part. I you need any other source code, just ask and I can update this question. Also, the source code is available via github: https://github.com/juleskreutzer/GSO-Maatwerk. Make sure to run the program with -remote param.
Update 1 (9-1-2017)
As yanys requested in the comments, I should run the following command:
dscacheutil -q host -a name localhost
this returns the following output:
Mac:
name: localhost
ip_address: 127.0.0.1
Ubuntu:
dscacheutil: command not found
Update 2 (9-1-2017)
I checked with the provider of my VPS where I run the java server on. On their side everything should be OK. According to them, it shouldn't be a dns problem. After some research, I found out that RMI uses both DNS and reverse DNS. It this case, reverse DNS was the issue. Please see my answer on how I solved my problem.

As EJP pointed out in the comments on the question, it was an DNS problem.
I contacted the support of my hosting provider to see if I had some wrong settings. They helped me a lot in solving this problem.
First we tested the speed of my VPS, this is around 1000mbit download and upload speed. After we checked this, they said there was nothing wrong on their side.
After doing some research, I found out that RMI uses both DNS and Reverse DNS. The problem was that I didn't setup the reverse DNS on my server. I already have a domain name to use for reverse DNS.
I than did the following:
Create a A-record on my website that points to the IP address of the server. I named it vps.mydomain.com
Add the reverse DNS in the control panel of my server
Change the hostname of my server to vps.mydomain.com*
*My server runs Ubuntu 16.04, on ubuntu machines with systemd, you can use the command
sudo hostnamectl set-hostname new-name
to change the hostname

redis.clients.jedis.exceptions.JedisConnectionException: java.net.UnknownHostException

I'm using Jedis to connect to my Redis instance/cluster in AWS, but I kept getting this error, here's the code, I searched extensively on SO, found the closest one is: String hostname from properties file: Java
I tried both ways, neither worked for me.
So please help.
Here's my Java code:
public static void main(String[] args) {
AWSCredentials credentials = null;
try {
credentials = new ProfileCredentialsProvider("default").getCredentials();
} catch (Exception e) {
throw new AmazonClientException("Cannot load the credentials from the credential profiles file. "
+ "Please make sure that your credentials file is at the correct "
+ "location (/Users/USERNAME/.aws/credentials), and is in valid format.", e);
}
AmazonElastiCacheClient client = new AmazonElastiCacheClient(credentials);
client.setRegion(Region.getRegion(Regions.AP_NORTHEAST_2));
DescribeCacheClustersRequest dccRequest = new DescribeCacheClustersRequest();
dccRequest.setShowCacheNodeInfo(true);
DescribeCacheClustersResult clusterResult = client.describeCacheClusters(dccRequest);
List<CacheCluster> cacheClusters = clusterResult.getCacheClusters();
for (CacheCluster cacheCluster : cacheClusters) {
for (CacheNode cacheNode : cacheCluster.getCacheNodes()) {
String addr = cacheNode.getEndpoint().getAddress();
int port = cacheNode.getEndpoint().getPort();
String url = addr + ":" + port;
System.out.println("formed url is: " + url);
Jedis jedis = new Jedis(url);
System.out.println("Connection to server sucessfully");
// check whether server is running or not
System.out.println("Server is running: " + jedis.ping());
}
}
The last line in the above code keeps throwing this error, here's the stacktrace:
Exception in thread "main" redis.clients.jedis.exceptions.JedisConnectionException: java.net.UnknownHostException: REDISNAME.nquffl.0001.apn2.cache.amazonaws.com:6379
at redis.clients.jedis.Connection.connect(Connection.java:207)
at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:93)
at redis.clients.jedis.Connection.sendCommand(Connection.java:126)
at redis.clients.jedis.Connection.sendCommand(Connection.java:121)
at redis.clients.jedis.BinaryClient.ping(BinaryClient.java:106)
at redis.clients.jedis.BinaryJedis.ping(BinaryJedis.java:195)
at sporadic.AmazonElastiCacheClientExample.main(AmazonElastiCacheClientExample.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)Caused by: java.net.UnknownHostException: REDISNAME.nquffl.0001.apn2.cache.amazonaws.com:6379
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at redis.clients.jedis.Connection.connect(Connection.java:184)
... 11 more
What am I doing wrong?
Please point out.

Your setting shoud be this way :
Jedis jedis = new Jedis("REDISNAME.nquffl.0001.apn2.cache.amazonaws.com",6379);
NOT this way :
Jedis jedis = new Jedis("REDISNAME.nquffl.0001.apn2.cache.amazonaws.com:6379");

According to AWS Documentation http://docs.aws.amazon.com/AmazonElastiCache/latest/UserGuide/Access.Outside.html
Amazon ElastiCache is an AWS service that provides cloud-based
in-memory key-value store. On the back end it uses either the
Memcached or Redis engine. The service is designed to be accessed
exclusively from within AWS. However, if the ElastiCache cluster is
hosted inside a VPC, you can use a Network Address Translation (NAT)
instance to provide outside access.
So you have below two options :-
Either you host your app inside the AWS and have proper security group setting to allow access to your elastic-cache cluster from your ec2-instance where your app is deployed.
If you want to run your app outside of AWS then you have to modify the Network Address Translation (NAT) to provide outside access.
IMO, its easy to deploy the code in AWS-Ec2 instance and test it if you are not very familiar with the networking and NAT.
I used to have locally memcache and redis instance where i used to connect for local developement and for other environment like qa,stg,prod used to deploy it in AWS ec2 instance.
Let me know if you any issues.

In my case the 6379 port was not accepting connections, so I changed I configured Redis with different port, and it worked.

ApiDeadlineExceededException using a WebService Client in a GWT WebApp

I've made a WebService Client using the Eclipse Wizard. It works great when i'm using standar java Classes but when I try to use it in a GWT WebApp I get this error:
} catch (ApiProxy.ApiDeadlineExceededException e) {
throw new SocketException("Socket operation timed out: " + e.getMessage());
}
With this message:
java.net.SocketException: Socket operation timed out: The API call remote_socket.Receive() took too long to respond and was cancelled.
Question 1: Is there any form to increase this ApiDeadLine timeout? The thing is that i'm debugging and sadly the connection is slow so the answers will last at least 10-20 seconds.
Question 2: Should I use another form to communicate with the WebService?
Question 3: Should I use some kind of Async threads for this?
Thanks!

It seems that you can increase the timeout with this:
com.google.apphosting.api.ApiProxy.Environment env = ApiProxy.getCurrentEnvironment();
env.getAttributes().put("com.google.apphosting.api.ApiProxy.api_deadline_key", 9999 );

JDBC Example for java

I have downloaded JDK 6 and also I have sqljdb4.jar and I have database.properties file that content the following data
database.driverClassName=com.microsoft.sqlserver.jdbc.SQLServerDriver
database.url=jdbc:sqlserver://.;databaseName=UserInfo;integratedSecurity=true;
database.username=sa
database.password=admin
B.N : I'm installing the server on my machine and the server name = . , also I'm using Windows Authontication
My problem now is when I try to create connection I have the following error
com.microsoft.sqlserver.jdbc.SQLServerException:
The TCP/IP connection to the host
localhost, port 1433 has failed.
Error: Connection refused: connect.
Please verify the connection
properties and check that a SQL Server
instance is running on the host and
accepting TCP/IP connections at the
port, and that no firewall is blocking
TCP connections to the port. at
com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:130)
I don't know what is the exact problem here
If any one can help I will be appreciated
Thanks in Advance

That's caused by many probabilities like
1- IP is worong
2- Port is wrong
3- There is firewall prevent machine to go out and connect to another IP
4- SQL server down .
try to use
public class JdbcSQLServerDriverUrlExample
{
public static void main(String[] args)
{
Connection connection = null;
try
{
// the sql server driver string
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
// the sql server url
String url = "jdbc:microsoft:sqlserver://HOST:1433;DatabaseName=DATABASE";
// get the sql server database connection
connection = DriverManager.getConnection(url,"THE_USER", "THE_PASSWORD");
// now do whatever you want to do with the connection
// ...
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
System.exit(1);
}
catch (SQLException e)
{
e.printStackTrace();
System.exit(2);
}
}
}
What i need to explain is there is very good technology called " Persistence " is better than JDBC and is more than brilliant and easy to use .

The problem is that your SQL server is either
not installed,
not running or
not accepting TCP/IP connections.
Particularly the last one is nasty, as I remember that some versions of SQL Server have not configured the TCP/IP connector to run by default.

Well first and foremost we need to see your code. Second looking at the error message the database is A)not running
B) on a different port
or C) the code is incorrect.