arcon 0.2.1

A runtime for writing streaming applications
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109

use crate::{
    data::{ArconElement, ArconNever, ArconType},
    error::ArconResult,
    prelude::EmptyState,
    stream::operator::{Operator, OperatorContext},
};
use std::{
    cell::RefCell,
    fs::{File, OpenOptions},
    io::Write,
    marker::PhantomData,
    path::Path,
};

pub struct LocalFileSink<IN>
where
    IN: ArconType,
{
    file: RefCell<File>,
    _marker: PhantomData<IN>,
}

impl<IN> LocalFileSink<IN>
where
    IN: ArconType,
{
    pub fn new(file_path: impl AsRef<Path>) -> Self {
        let file = RefCell::new(
            OpenOptions::new()
                .write(true)
                .create(true)
                .append(true)
                .open(file_path)
                .expect("Failed to open file"),
        );

        LocalFileSink {
            file,
            _marker: PhantomData,
        }
    }
}

impl<IN> Operator for LocalFileSink<IN>
where
    IN: ArconType,
{
    type IN = IN;
    type OUT = ArconNever;
    type TimerState = ArconNever;
    type OperatorState = EmptyState;
    type ElementIterator = std::iter::Empty<ArconElement<Self::OUT>>;

    fn handle_element(
        &mut self,
        element: ArconElement<IN>,
        _ctx: &mut OperatorContext<Self::TimerState, Self::OperatorState>,
    ) -> ArconResult<Self::ElementIterator> {
        if let Err(err) = writeln!(self.file.borrow_mut(), "{:?}", element.data) {
            eprintln!("Error while writing to file sink {}", err);
        }
        Ok(std::iter::empty::<ArconElement<Self::OUT>>())
    }
    crate::ignore_timeout!();
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::prelude::*;
    use std::io::{BufRead, BufReader};
    use tempfile::NamedTempFile;

    #[test]
    fn local_file_sink_test() {
        let file = NamedTempFile::new().unwrap();
        let file_path = file.path().to_string_lossy().into_owned();

        let mut app = vec![6i32, 2i32, 15i32, 30i32]
            .to_stream(|conf| {
                conf.set_arcon_time(ArconTime::Process);
            })
            .operator(OperatorBuilder {
                operator: Arc::new(move || LocalFileSink::new(&file_path)),
                state: Arc::new(|_| EmptyState),
                conf: OperatorConf {
                    parallelism_strategy: ParallelismStrategy::Static(1),
                    ..Default::default()
                },
            })
            .ignore()
            .builder()
            .build();

        app.run();

        std::thread::sleep(std::time::Duration::from_secs(1));

        let file = File::open(file.path()).expect("no such file");
        let buf = BufReader::new(file);
        let result: Vec<i32> = buf
            .lines()
            .map(|l| l.unwrap().parse::<i32>().expect("could not parse line"))
            .collect();

        let expected: Vec<i32> = vec![6, 2, 15, 30];
        assert_eq!(result, expected);
    }
}