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
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160

use crate::data::ArconType;
use crate::stream::operator::window::WindowContext;
use crate::{
    error::ArconResult,
    index::{IndexOps, WindowIndex},
    prelude::*,
    table::ImmutableTable,
    util::{prost_helpers::ProstOption, ArconFnBounds},
};
use arcon_state::{backend::handles::ActiveHandle, Aggregator, AggregatorState, Backend};

#[derive(Clone)]
pub struct IncrementalWindowAggregator<IN, OUT, INIT, AGG>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
{
    init: INIT,
    agg: AGG,
    _marker: std::marker::PhantomData<(IN, OUT)>,
}

impl<IN, OUT, INIT, AGG> Aggregator for IncrementalWindowAggregator<IN, OUT, INIT, AGG>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
{
    type Input = IN;
    type Accumulator = ProstOption<OUT>; // this should be an option, but prost
    type Result = OUT;

    fn create_accumulator(&self) -> Self::Accumulator {
        None.into()
    }

    fn add(&self, acc: &mut Self::Accumulator, value: IN) {
        match &mut acc.inner {
            None => {
                *acc = Some((self.init)(value)).into();
            }
            Some(inner) => *acc = Some((self.agg)(value, inner)).into(),
        }
    }

    fn merge_accumulators(
        &self,
        _fst: Self::Accumulator,
        _snd: Self::Accumulator,
    ) -> Self::Accumulator {
        unimplemented!()
    }

    fn accumulator_into_result(&self, acc: Self::Accumulator) -> Self::Result {
        let opt: Option<_> = acc.into();
        opt.expect("uninitialized incremental window")
    }
}

// Alias around AggregatorState for IncrementalWindowFn
type AggState<IN, OUT, INIT, AGG> =
    AggregatorState<IncrementalWindowAggregator<IN, OUT, INIT, AGG>>;

/// A window index that incrementally aggregates elements
///
/// Used for associative and commutative operations
///
pub struct IncrementalWindow<IN, OUT, INIT, AGG, B>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
    B: Backend,
{
    aggregator: ActiveHandle<B, AggState<IN, OUT, INIT, AGG>, u64, u64>,
}

impl<IN, OUT, INIT, AGG, B> IncrementalWindow<IN, OUT, INIT, AGG, B>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
    B: Backend,
{
    pub fn new(backend: Arc<B>, init: INIT, agg: AGG) -> Self {
        let mut aggregator = Handle::aggregator(
            "incremental_window_aggregating_state",
            IncrementalWindowAggregator {
                init,
                agg,
                _marker: std::marker::PhantomData,
            },
        )
        .with_item_key(0)
        .with_namespace(0);

        backend.register_aggregator_handle(&mut aggregator);

        let aggregator = aggregator.activate(backend);

        Self { aggregator }
    }
}

impl<IN, OUT, INIT, AGG, B> WindowIndex for IncrementalWindow<IN, OUT, INIT, AGG, B>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
    B: Backend,
{
    type IN = IN;
    type OUT = OUT;
    fn on_element(&mut self, element: Self::IN, ctx: WindowContext) -> ArconResult<()> {
        self.aggregator.set_item_key(ctx.key);
        self.aggregator.set_namespace(ctx.index);

        self.aggregator.aggregate(element)?;

        Ok(())
    }

    fn result(&mut self, ctx: WindowContext) -> ArconResult<Self::OUT> {
        self.aggregator.set_item_key(ctx.key);
        self.aggregator.set_namespace(ctx.index);

        let result = self.aggregator.get()?;
        Ok(result)
    }

    fn clear(&mut self, ctx: WindowContext) -> ArconResult<()> {
        self.aggregator.set_item_key(ctx.key);
        self.aggregator.set_namespace(ctx.index);

        let _ = self.aggregator.clear()?;
        Ok(())
    }
}
impl<IN, OUT, INIT, AGG, B> IndexOps for IncrementalWindow<IN, OUT, INIT, AGG, B>
where
    IN: ArconType,
    OUT: ArconType,
    INIT: Fn(IN) -> OUT + ArconFnBounds,
    AGG: Fn(IN, &OUT) -> OUT + ArconFnBounds,
    B: Backend,
{
    fn persist(&mut self) -> ArconResult<()> {
        Ok(())
    }
    fn set_key(&mut self, _: u64) {}
    fn table(&mut self) -> ArconResult<Option<ImmutableTable>> {
        Ok(None)
    }
}