My eureka server is up and running.
I have two copies of the same virtual machine that has my Eureka client in it ready to run.
When one eureka client tries to register at the server, it overrides the other client - registration is 'successful' but I have only one instance of the client instead of two instances.
my clients are registering using the machine name which is obviously the same for the two VMs.
Is there a way make registration based on mac address or IP instead of machine name?
All you need to do is `eureka.instance.preferIpAddress=true'. Check this out
Related
let's take Eureka.
in a normal scenario, A microservice is registered with the Eureka, and we get its information there.
the microservice has multiple backup servers.
the question is, how these servers will be registered in Eureka.
Will all the Backup servers have different IP or same IP!
how the registration for backup servers happen, and how the backup server is chosen.
I have setup ratchet on amazon EC2 instance.
It is running fine, but I am not able to connect with the public IP address of the instance as well as the url.
Following is the screenshot showing ratchet is running.
You need to make sure that the service is running on the right IP address (not only on 127.0.0.1) and that you enabled access in the security group to that particular port.
I had a running instance, and then I became unable to connect to it via http(80) and ssh(22). I tried to reboot the instance, but nothing went up. This has happened to me twice in the past month.
Why does it happen? Can I do anything to fix and/or prevent it from happening?
If I launch a new instance in same region, and it works.
Things to check when trying to connect to an Amazon EC2 instance:
Security Group: Make sure the security group allows inbound access on the desired ports (eg 80, 22) for the appropriate IP address range (eg 0.0.0.0/0). This solves the majority of problems.
Public IP Address: Check that you're using the correct Public IP address for the instance. If the instance is stopped and started, it might receive a new Public IP address (depending on how it has been configured).
VPC Configuration: Accessing an EC2 instance that is launched inside a Virtual Private Cloud (VPC) requires:
An Internet Gateway
A routing table connecting the subnet to the Internet Gateway
NACLs (Network ACLS) that permit through-traffic
If you are able to launch and connect to another instance in the same subnet, then the VPC configuration would appear to be correct.
The other thing to check would be the actual configuration of the operating system on the instance itself. Some software may be affecting the configuration so that the web server / ssh daemon is not working correctly. Of course, that is hard to determine without connecting to the instance.
If you are launching from a standard Amazon Linux AMI, ssh would work correctly anytime. The web server (port 80) would require installation and configuration of software on the instance, which is your responsibility to maintain.
I have a three-tier Windows-based web application bundled into 3 AMIs on Amazon EC2 that I use for load testing.
An ASP.NET web application on IIS
An .NET application server
SQL Server
After I launch them, the config files of each tier needs modifying to update the IP addresses.
At the moment I am doing this manually: I connect to the webserver instance via remote desktop and modify the config file to point to the new IP of the application server instance. Then I do the same with the application server to change the IP in the connection string.
This must be a common requirement and I must be missing something obvious. There must be a better way!
I could use Elastic IP addresses, but these machines are only provisioned for a couple of hours at a time, and I would be charged for the addresses when they were NOT in use (which would be most of the time).
Is there some way of persistently naming the machines? Can I somehow get all the machines on the same network and use machine names instead of IP addresses?
I could write some nifty PowerShell script that would perform the modifications remotely. Is there an example somewhere?
I could use a dynamic IP address service. I'm not sure if this would have any negative effect on performance or availability... Are there any downsides to this approach?
I could install some sort of self-configuring service on each machine (which connects to S3? SNS? SimpleDB?) to publish/retrieve the addresses of the other machines and update the config files automatically. Is there an example somewhere?
What is best practice?
You could use Amazon Virtual Private Cloud (Amazon VPC). You have a private subnet where you can assign an IP address to an instance, but it may require launching an instance from command line to assign IP. VPC is charged the same way as EC2.
I developed a client/server simulation application. I deployed client and server on two different Windows XP machines. Somehow, the client is not able to send requests to the server.
I tried below options:
Pinged server machine successfully from client using ip-address.
Pinged client machine successfully from server using ip-address.
Checked netstat command line tool from both machines. Server is in LISTENING mode and client is in SYS_SENT mode. But the foreign address it is using to send is host name not the ip address.
Pinged server machine unsuccessfully using host name from client.
Pinged client machine successfully using host name from server.
I feel the problem is when the client is trying to connect to the server using the host name.
Could you please let me know how to force an application to use an ip address instead of a host name? Is there any other way to map the host name to an ip address?
Go to your client machine and type in:
nslookup server.company.com
substituting the real host name of your server for server.company.com, of course.
That should tell you which DNS server your client is using (if any) and what it thinks the problem is with the name.
To force an application to use an IP address, generally you just configure it to use the IP address instead of a host name. If the host name is hard-coded, or the application insists on using a host name in preference to an IP address (as one of your other comments seems to indicate), then you're probably out of luck there.
However, you can change the way that most machine resolve the host names, such as with /etc/resolv.conf and /etc/hosts on UNIXy systems and a local hosts file on Windows-y systems.
Try tracert to resolve the hostname. IE you have Ip address 8.8.8.8 so you would use; tracert 8.8.8.8
You could use a C function getaddrinfo() to get the numerical address - both ipv4 and ipv6.
See the example code here
This is hard to answer without more detail about the network architecture. Some things to investigate are:
Is it possible that client and/or server is behind a NAT device, a firewall, or similar?
Is any of the IP addresses involved a "local" address, like 192.168.x.y or 10.x.y.z?
What are the host names, are they "real" DNS:able names or something more local and/or Windows-specific?
How does the client look up the server? There must be a place in code or config data that holds the host name, simply try using the IP there instead if you want to avoid the lookup.
Windows XP has the Windows Firewall which can interfere with network traffic if not configured properly. You can turn off the Windows Firewall, if you have administrator privileges, by accessing the Windows Firewall applet through the Control Panel. If your application works with the Windows Firewall turned off then the problem is probably due to the settings of the firewall.
We have an application which runs on multiple PCs communicating using UDP/IP and we have been doing experiments so that the application can run on a PC with a user who does not have administrator privileges. In order for our application to communicate between multiple PCs we have had to use an administrator account to modify the Windows Firewall settings.
In our application, one PC is designated as the server and the others are clients in a server/client group and there may be several groups on the same subnet.
The first change was to use the functionality of the Exceptions tab of the Windows Firewall applet to create an exception for the port that we use for communication.
We are using host name lookup so that the clients can locate their assigned server by using the computer name which is composed of a mnemonic prefix with a dash followed by an assigned terminal number (for instance SERVER100-1). This allows several servers with their assigned clients to coexist on the same subnet. The client uses its prefix to generate the computer name for the assigned server and to then use host name lookup to discover the IP address of the assigned server.
What we found is that the host name lookup using the computer name (assigned through the Computer Name tab of the System Properties dialog) would not work unless the server PC's Windows Firewall had the File and Printer Sharing Service port enabled.
So we had to make two changes: (1) setup an exception for the port we used for communication and (2) enable File and Printer Service in the Exceptions tab to allow for the host name lookup.
** EDIT **
You may also find this Microsoft Knowledge Base article on helpful on Windows XP networking.
And see this article on NETBIOS name resolution in Windows.