Running Erlang project on Amazon EC2 - amazon-ec2

We have a project with different processes, and run it by calling erl -pa ebin, mymodule_supervisor:start_link().
We have set up an ubuntu instance on Amazon EC2. Being new to this, how can we run the project remotely, so we can close the connection and the project will continue to run?
We can run the Erlang shell in the background, but we can't our project on it. It would be perfect to see an example.

Method 1: You could build a release package from your code. If done right, this will embed a complete Erlang system (along with your application and its dependencies) in an easily distributable tar file. Using an automatically generated script the node can then be started as a daemon, running in the background even after you close your shell.
A good way to get started is to use Rebar, which already supports release handling out of the box.
Method 2: Use tmux or screen (both easily installed on Ubuntu) to start your node and detach the session. If you choose tmux, the following should work:
Start tmux simply by running tmux from a shell.
From within tmux, start your node with the erl command as before.
Detach your session using Ctrl-b followed by d. Exit your shell. The node should still be running.
The "proper" way to start the supervisor is to call its start_link function from within the start function of your Erlang application.

Related

Git bash no longer allows typing into a Minecraft server console

I've recently updated git bash to 2.35.1. I do Minecraft plugin/server development so am often using git bash to start and manage test servers in windows. Unfortunately I do not know what version I was on before.
Now when I started a server using java -Xms4G -Xmx4G -jar server.jar it boots, but I can't type anything into the console. I am completely locked out. Using CTRL+C will shutdown the server but it says "do you want to terminate the batch job" and hangs. I have to force quit the java process.
Before, I could type game console commands in without issue.
I've tried running git bash as administrator, no change. PowerShell doesn't work at all, it won't even show the output of the console after starting the jar.
When I stop the server from in-game, I get this error after it fully stops:
$ stop
bash: stop: command not found

AWS ECS trouble - Running shell script to boot program

I am trying to run a Docker image on amazon ECS. I am using a command that starts a shell script to boot up the program:
CMD ["sh","-c", "app/bin/app start; bash"]
in order to start it because for some reason when I run the app (elixir/phoenix app) in the background it was crashing immediately but if I run it in the foreground it is fine. If I run it this way locally, everything works fine but when I try to run it in my cluster, it shuts down. Please help!!
Docker was supposed to keep track of your running foreground process, if the process stop, the container stop. The reason your container work when you use command with "bash" because bash wasn't stop.
I guess you use she'll script to start an application that serve in background like nginx or a daemon. So try to find an option that make the app running foreground will keep your container alive. I.e nginx has an option while starting "daemon off"
for some reason when I run the app (elixir/phoenix app) in the background it was crashing immediately
So you have a corrupted application and you are looking for a kludge to make it looking like it somewhat works. This is not a reliable approach at all.
Instead you should:
make it working in background
use systemctl or upstart to manage restarts of Erlang VM on crashes
Please note that it matters where you have your application compiled. It must be the exactly same architecture/container as the production one, with same Erlang, Elixir, OS versions, otherwise nobody guarantees it will be robust or even working.

start daemon on remote server via Jenkins SSH shell script exits mysteriously

I have a build job on jenkins that is building my project and after it is done, it opens an ssh shell script on a remote server and transfers files and then stop and starts a daemon.
When I stop and start the daemon from the command line on a RHEL server, it executes just fine. When the job executes in jenkins, there are no errors.
The daemon stops fine and it starts fine. But shortly after starting, the daemon dies suddenly.
sudo service daemonName stop
# transfer files.
sudo service daemonName start
I'm sure that the problem isn't pathing
Does anyone know what could be special about the way Jenkins is executing the ssh shell script that would cause the daemon start to not fully complete?
The problem:
When executing a build through jenkins, the command to start the daemon process was clearly successfully executing, yet after the build job was done, the daemon would suddenly quit.
The solution:
I thought for this whole time that it was jenkins killing the daemon. So I tried many different incarnations and permutations of disabling the ProcessTree module that goes through and cleans up zombie child processes. I tried fooling it by resetting the BUILD_ID environment variable. Nothing worked.
Thanks to this thread I found out that that solution only works for child processes executed on the BUILD machine. I.E. not applicable to my problem.
More searching led me here: Run a persistent process via ssh
The solution? Nohup.
So now the build successfully restarts the daemon by executing the following:
sudo nohup service daemonname start
Jenkins watches for processes spawned by the job and kill them to avoid zombie processes.
See https://wiki.jenkins-ci.org/display/JENKINS/ProcessTreeKiller
The workaround is to override the BUILD_ID environment variable:
BUILD_ID=dontKillMe

Smartfoxserver 2X linux 64 running on EC2 via dotcloud - how to install?

I am currently trying to deploy smartfoxserver 2X on EC2 using dotcloud. I have been able to detect the private ip of the amazon web instance, and using the dotcloud tools I have been able to determine the correct port. However, I have difficulty installing the server proper via the command line so that I can log into it using the AdminTool.
My postinstall is fairly straightforward:
./SFS2X/sfs2x-service start-launchd
I find that on 'dotcloud push' there is a fair amount of promising output in my cygwin terminal, but the push hangs after saying that the sfs2x-service has been launched correctly, until timeout.
Consequently, my question is, has anyone found a way to install SFS2X on EC2 via dotcloud successfully? I managed to have partial success with SFS Pro, with a complete push to dotcloud, by calling ./jre/bin/java -jar installer.jar in my postinstall. Do I need to do extra legwork and build an installer jar for SFS2X? Is there a way that would be best to do this?
I do understand that there is a standard approach to deployment with SFS2X using RightScale on EC2, however I am interested in deployment using the dotcloud platform.
Thanks in advance.
The reason why it is hanging is because you are trying to start your process in the postinstall, and this is not the correct place to do that. The postinstall script is suppose to finish, if it doesn't the deployment will time out, and then get cancelled.
Once the postinstall script is finished, it will then finish the rest of your deployment.
See this page for more information about dotCloud postinstall script:
http://docs.dotcloud.com/0.9/guides/hooks/#post-install
Pay attention to this warning at the end.
Warning:
If your post-install script returns an error (non-zero exit code), or if it runs for more than 10 minutes, the platform will consider that your build has failed, and the new version of your code will not be deployed.
Instead of putting this in the postinstall script, you should add it as a background process, so that it starts up once the deployment process is complete.
See this page for more information on adding background processes to dotCloud services:
http://docs.dotcloud.com/0.9/guides/daemons/
TL;DR: You need to create a supervisord.conf file, and add it to the root of your project, and add your service to that.
Example (you will need to change to fit your situation):
[program:smartfoxserver]
command = /home/dotcloud/current/SFS2X/sfs2x-service start-launchd
Also, make sure you have the correct dotCloud service specified in your dotcloud.yml in order to have the correct binary and libraries installed for what your smartfoxserver application.

Meteor: Debug on server side

Does anyone know a good method to debug server side code?
I tried enable Node.js debug then use node-inspector but it does not show any of my code.
I end up using console.log but this is very inefficient.
Update: I found the following procedure works on my Linux machine:
When you run Meteor, it will spawn two processes
process1: /usr/lib/meteor/bin/node /usr/lib/meteor/app/meteor/meteor.js
process2: /usr/lib/meteor/bin/node /home/paul/codes/bbtest_code/bbtest02/.meteor/local/build/main.js --keepalive
You need to send kill -s USR1 on process2
Run node-inspector and you can see your server code
On my first try, I modify the last line on meteor startup script in /usr/lib/meteor/bin/meteor to
exec "$DEV_BUNDLE/bin/node" $NODE_DEBUG "$METEOR" "$#"
and run NODE_DEBUG=--debug meteor on command prompt. This only put --debug flag on process1 so I only see meteor files on node-inspector and could not find my code.
Can someone check this on Windows and Mac machine?
In Meteor 0.5.4 this has become a lot easier:
First run the following commands from the terminal:
npm install -g node-inspector
node-inspector &
export NODE_OPTIONS='--debug-brk'
meteor
And then open http://localhost:8080 in your browser to view the node-inspector console.
Update
Since Meteor 1.0 you can just type
meteor debug
which is essentially a shortcut for the above commands, and then launch node inspector in your browser as mentioned.
Update
In Meteor 1.0.2 a console or shell has been added. It may come in handy to output variables and run commands on the server:
meteor shell
Meteor apps are Node.js apps. When running a Meteor app with the meteor [run] command, you can configure the NODE_OPTIONS environment variable to start node in debug mode.
Examples of NODE_OPTIONS environment variable values:
--debug
--debug=47977 - specify a port
--debug-brk - break on the first statement
--debug-brk=5858 - specify a port and break on the first statement
If you export NODE_OPTIONS=--debug, all meteor command run from the same shell will inherit the environment variable. Alternatively, you can enable debugging just for one run, with NODE_OPTIONS="--debug=47977" meteor.
To debug, run node-inspector in a different shell, then go to http://localhost:8080/debug?port=<the port you specified in NODE_OPTIONS>, regardless of what node-inspector tells you to run.
To start node.js in debug mode, I did it this way:
open /usr/lib/meteor/app/meteor/run.js
before
nodeOptions.push(path.join(options.bundlePath, 'main.js'));
add
nodeOptions.push('--debug');
Here are additional practical steps for your to attach debugger eclipse:
use '--debug-brk' instead of '--debug' here, because it's easier for me to attach node.js using eclipse as debugger.
add 'debugger;' in the code where you want to debug.(I prefer this way personally)
run meteor in console
attach to node.js in eclipse(V8 tools, attach to localhost:5858)
run, wait for debugger to be hit
when you start meteor in your meteor app folder, you'll see that "debugger listening on port 5858" in console.
On Meteor 1.0.3.1 (update to Sergey.Simonchik answer)
Start your server with meteor run --debug-port=<port-number>
Point browser to http://localhost:6222/debug?port=<port-number>
Where <port-number> is a port you specify.
In your code add a debugger; where you want to set your break point.
Depending on where debugger; is invoked, it will either break on your client or server browser window with inspector opened.
I like to set breakpoints via a GUI. This way I don't have to remember to remove any debugging code from my app.
This is how I managed to do it server side for my local meteor app:
meteor debug
start your app this way.
Open Chrome to the address it gives you. You MAY need to install https://github.com/node-inspector/node-inspector (it might come bundled with Meteor now? not sure)
You'll see some weird internal meteor code (not the app code you wrote). Press play to run the code. This code simply starts up your server to listen for connections.
Only after you press play you'll see a new directory in your debugger folder structure called "app". In there are your meteor project files. Set a breakpoint in there one the line you want.
Open the local address of your app. This will run your server side code and you you should be able to hit your breakpoint!
Note: you have to reopen the inspector and go through this process again each time your app restarts!
As of Meteor 1.0.2 probably the best way for server-side debugging is directly via the new built-in shell: with running server run meteor shell. More info here: https://www.meteor.com/blog/2014/12/19/meteor-102-meteor-shell
I am not sure why it was not working for you.
I am able to use it by following steps on console (Mac).
$ ps
$ kill -s USR1 *meteor_node_process_id*
$ node-inspector &
Above steps are mentioned on https://github.com/dannycoates/node-inspector. It is for attaching node-inspector to running node process.
I wrote a small meteor package called meteor-inspector which simplifies the use of node-inspector to debug meteor apps. It internally manages the lifecycle of node-inspector and hence, the user does not need to restart the debugger manually after some files have changed.
For more details and concrete usage instructions take a look at https://github.com/broth-eu/meteor-inspector.
for meteor 1.3.5.2, run
meteor debug --debug-port 5858+n
n is a non-zero number, this will cause node-inspector use 8080+n as web port.
WebStorm, the powerful IDE free for open source developers, makes it much easier to debug server-side.
I've tested it on Windows, and the configuration was painless - see my answer.
A inspector that solve my issues is meteor server console. Here is the process I followed to install it:
In your project folder, add the smart package server-eval:
mrt add server-eval
For Meteor 1.0:
meteor add gandev:server-eval
Restart meteor.
Download crx Chrome extension file from here.
Open extensions page in Chrome and drag crx file to extensions page.
Restart Chrome.
Check the web inspector out to eval server side code:
In comparison with node-inspector, I have a clearer output.
If you prefer to use nodeJS' official debugger you can call NODE_OPTIONS='--debug' meteor and then (on a different shell) node debug localhost:5858.

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