Running python app in the background on linux

Question

so I have an Action, which fetches some data from rest. In a component, i need this data from the fetch, which is set in store. I use this data then like someFunc(this.props.data) in componentDidMount(). Afterwards i give the return value of someFunc an another Action, which does something with this data and also sets it in store.

My only idea is, to give someFunc to the Action as a callback and call this right after the first data is fetched. So i have 2 dispatched in one action.

I hope you guys understand what i mean. Is there a better way to do this?

Edit

In Component1 i dispatch an Action, which loads data i need to the store. In Component2 i dispatch another Action, which gets his value from someFunc function. But someFunc gets the data from the first Action, so the data is undefined when i call someFunc, because the data isn't set in the store yet.

More clear yet?

Component1

componentDidMount(){
        this.props.dataLoadAction()   //action for the fetch i told
}

const mapDispatchToProps = (dispatch) => {

    return {
        dataLoadAction: () => {
            dispatch(dataLoadAction())
        }
    }
};

export default connect(null, mapDispatchToProps)(Component1);

Component2

componentDidMount(){
        this.props.changeDataAction(this.someFunc(this.props.data))
}

render(){
        return (
            <div>
                {this.props.otherData}
            </div>
        )
    }

const mapStateToProps = (state) => {

    return {
        otherData: state.someReducer.otherData,
        data: state.someReducer.data,
    }
};

const mapDispatchToProps = (dispatch) => {

    return {
        changeDataAction: (changedData) => {
            dispatch(changeDataAction(changedData))
        }
    }
};

export default connect(mapStateToProps, mapDispatchToProps)(Component2);

Actions

export function dataLoadAction(){
    return dispatch => {

    HttpRequest.getJson("some url", json => {

            dispatch(
                {
                    type: 'DATA_LOADED',
                    payload: {
                        data: json
                    }
                }
            )
        });
    });
};

}

export function changeDataAction(changedData){
    return dispatch => {

        dispatch(
            {
                type: 'LOAD_CHANGEDDATA',
                payload: mappedVis
            }
        )

    };
}

Solution 1

You can use nohup python ChatServer_Listen.py &

nohup will log your program output to nohup.out file.

To stop your program you have to use kill your_pid command.

Solution 2

Like explained here :

https://stackoverflow.com/questions/625409/how-do-i-put-an-already-running-process-under-nohup

"

Using the Job Control of bash to send the process into the background:

[crtl]+z

bg

And as Sam/Jan mentioned you have to execute disown to avoid killing the process after you close the terminal.

disown -h

"

Solution 3

The right way to do this is to change the code to daemonize the process correctly. One way to do this is to use the daeminize module.

The expedient way to do this, which also works with software that you cannot modify, is to start it like this

nohup python ChatServer_Listen.py >logfile.txt 2>&1 </dev/null &

Note that I didn't use sudo. That is because you should put the above line in a shell script and run the shell script with sudo.

Solution 4

You want to use Supervisor. It's made exactly for this purpose, plus it will do things like restart the process if it dies, provide a web-based GUI to control it, etc.

Solution 5

An easy way to keep a process alive after you log off is to use screen.

View more solutions

Comments

[Manula Waidyanatha]

Did you try nohup python ChatServer_Listen.py & ? It should work.

[SilverbackNet]

Same as any other *nix: stackoverflow.com/questions/4525188/… The & is the most important part.

[EEAA]

This really has nothing to do with EC2.

[Daddy]

It worked, gents, someone please make an official answer =) Follow up, with the process detached, how do I kill/stop or restart?

[Daddy]

When I try this, sudo screen python Chatserver_Listen.py, the next line says "[screen is terminating]". The python app begins as normal, but using another terminal instance and "sudo screen -r python" returns "There is no screen to be resumed matching python."

[Daddy]

This is what works for me. Can you explain the disown -h command and what it actually does? My flowchart was like this: 1) run python app, 2) press ctrl+z [app is suspended?],3) type bg [console prints something regarding python], 4) type disown -h [console prints nothing]. It seems to be working though, I closed the terminal window and the server is still listening and accepting clients

[Daddy]

This works for me, I thought it didn't but then I realized that I wasn't including the & character. Will this keep the program running indefinitely (until a reboot, crash or explicit kill of course)

[Manula Waidyanatha]

@JustinXXVII Yes of course