I am using Apache-JMeter for distributed performance testing.
The master & slave communicate via Java RMI. It works fine so far. I do not see any issues.
But in some forums/blog, I see people use SSH Tunneling/Port forwarding for communication between master & slave.
I tried to google to find the advantages of SSH tunneling over RMI. I could not find any.
Is the communication via SSH is faster than RMI? Could someone please clarify?
NOTE:
I am trying to find the advantages of using SSH tunneling for JMeter distributed testing over RMI. In which case we will prefer SSH tunneling ?
The standard arrangement is based on RMI and works fine if all the systems are in the same network.
If you need to put the systems on different networks, the you have to set up some kind of VPN between them and in that case SSH tunneling can do the trick.
It makes sense only in case when jmeter master and slave cannot communicate directly and connection needs to be done via hopoff node or in secure environments where only one SSH port is open and you need to establish connectivity.
You're comparing apples and oranges. RMI is an application protocol and API. SSH tunneling is a system utility. They're not interchangeable or comparable.
Related
I've set up tailscale and connected to an exit node on my VPS on vultr.com. Predictably, I was kicked out and couldn't reconnect, as the VPS's public IP address has changed.
I can reboot the VPS and try again. What steps will I need to take? Does my VPS running behind an exit node even have a unique public address (which?), or does it need to be set up for something like port forwarding?
From looking at tailscale documentation, it looks like they came up with their own ssh, why? Why is the standard ssh inadequate for the purpose? I am not the admin of my tailscale network, and the admin is swamped right now. What can I do?
SSH uses TCP as transport and therefore requires the (srcaddr, srcport, dstaddr, dstport) tuple to be constant over the connection's lifetime.
I believe that since tailscale rotates connections dynamically, it is more suitable for use by clients than servers in a traditional client-server model, unless it provides an 'internal' virtual network over the distributed transport (which would kind of defeat the purpose of covering your tracks).
If you want to connect to your VPS over tailscale, you need to use their tools probably because of that. You can still connect directly to your VPS, though, through plain Internet, if it has any address of its own, and is not firewalled away (or similarly, NATed away). Your provider should either show you the address, or even better, provide access to out-of-band (like serial-port) command line access, where you can query the current addresses using commands like ip addr show.
In your Tailscale Admin console you should be able to see the machine's IP. Just use normal ssh and login that way.
So instead of ssh user#8.8.8.8 you'd do ssh user#100.64.0.1. Tailscale's own ssh client is useful if you want to hook deeper into their MagicDNS stuff, but it's not meant to be the only way to ssh into your machine.
If you run into errors, ping the machine you want to connect to (tailscale ping vps-machine-name). That should help you debug any tailscale client connection problems.
I have a raspi machine behind NAT in my room, and I want to access it from the interenet using the URL.I found this article.
https://developers.cloudflare.com/cloudflare-one/tutorials/ssh
However, it required me to run the cloudflared program on the connecting client. I understand that this is for the security purpose. Does it possible to make the connect without running the cloudflared program on the client machine.
A follow-up question would be is it possible to ssh into ipv6 machine that using the same technique.
There are various options when it comes to connecting to a machine running on a private network:
Running cloudflared on the client (which you already found)
Installing the WARP client on the user side, then using cloudflared on the server side to expose the service securely. Finally, route the network traffic for the private network on the tunnel via WARP. This approach is described in a tutorial here
Cloudflare started also supporting in browser rendering of an SSH session. I have wrote a tutorial describing how to set it up here.
Approach (3) would do away with the need of running a client since it relies on a simple browser.
I have a problem setting up a ipython cluster on a Windows server and connecting to this ipcluster using a ssh connection. I tried following the tutorial on https://ipython.org/ipython/doc/dev/parallel/parallel_process.html#ssh, but I have problems to understand what the options mean exactly and what parameters are to use exactly...
Could anyone help a total noob to set up an ipcluster? (Let's say the remote machine has ip 192.168.0.1 and the local machine has 192.168.0.2)
If you scroll roughly to the middle of the page https://ipython.org/ipython-doc/dev/parallel/parallel_process.html#ssh you will find this:
Current limitations of the SSH mode of ipcluster are:
Untested and unsupported on Windows. Would require a working ssh on Windows. Also, we are using shell scripts to setup and execute
commands on remote hosts.
That means, there is no easy way to build an ipcluster with ssh connection on windows (if it works at all).
Do you really need to connect the machines with an ssh connection? I guess it's possible with a ssh client on each windows machine, but if you are in a trusted local network you can also decide not to use the loopback interface and just expose the ports...
Sure you can start controller and engine separately! For further examples about ports (if you have problems with firewalls) see also How to setup ssh tunnel for ipython cluster (ipcluster)
I want to install a number of raspberry pis at remote locations and be able to log in to them remotely. (Will begin with 30-40 boxes and hopefully grow to 1000 individual raspberry pis soon.)
I need to be able to remotely manage these boxes. Going the easier route, forwarding a port on the router and setting a DHCP reservation, requires either IT support from the company we'll be doing the install for (many of which don't have IT), or it will require one of our IT people physically installing each box.
My tentative solution is to have each box create a reverse SSH tunnel to our server. My question is: How feasible would this be? How easy would it be to manage that many connections? Would it be an issue for a small local server to have 1000+ concurrent SSH connections? Is there an easier solution to this problem?
My end goal is to be able to ship someone a box, have them plug it in, and be able to access it.
Thanks,
w
An alternate solution would be to:
Install OpenVPN server on your server machine. How to install OpenVPN Server on the PI. Additionally, add firewall rules that block everything but traffic directed for the client's ssh and other services ports (if desired), from administrating machine(s).
Run OpenVPN clients on your Raspberry PI client machines. They will connect back to your VPN server. On a side note, the VPN server and administrating machine(s) need not be the same machine if resources are limited on the VPN server. How to install OpenVPN on the client Raspberry PIs.
SSH from administrating machine(s) to each client machine. Optionally, you could use RSA authentication to simplify authentication.
Benefits include encryption for the tunnel including ssh encryption for administrating, as well as being able to monitor other services on their respective ports.
I made a WebApp to manage this exact same setting in about 60 minutes with my java web template. All I can share are some scripts that I use to list the connection and info about them. You can use those to build your own app, it is really simple to display this in some fancy way in a fast web.
Take a look at my scripts: https://unix.stackexchange.com/a/625771/332669
Those will allow you to get the listening port, as well as the public IPs they're binded from. With that you can easilly plan a system where everything is easilly identificable with a simple BBDD.
You might find this docker container useful https://hub.docker.com/r/logicethos/revssh/
I'd like to use a server between two machines (with no static IP). The only IP known to me is the server's IP address. I'd like to build/use a system that listens to 2 different ports within the server and whatever is received from localhost:portA is sent to localhost:portB and vise versa. Consequently, both machines (with java apps) can communicate through the server in the middle.
Please what is the best solution to do this. I'm working on linux system and I thought of using an SSH java API (hudson / ganymed-ssh-2) to build a port forwarding server application.
Some issue:
1) determining the size of the data transmitted to buffer read or not to forward it to the other port.
2)The speed of reading/writing bytes.
If you can use ssh protocol you can tunnel local or remote ports (this need support on server side). You can also think about an OpenSSH VPN (take a look on ssh -w option, this will create a real VPN (TUN/TAP device is required). ).
You can use the the ssh program. Take a look at the -L and -R options specifically.