aerro 0.5.0

Cross-service gRPC error framework for Rust.
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

//! `tonic::Status` → `ServiceFailure<E>` decoding — the client-side counterpart to
//! [`encode`](crate::wire::encode::encode).

use bytes::Bytes;
use prost::Message;
use smallvec::SmallVec;
use tonic::{Code, Status};

use crate::{Aerro, Category, Frame, RemoteError, ServiceFailure, trace::TraceContext};

use super::envelope::from_proto;
use super::raw;

/// Decode a `tonic::Status` into a [`ServiceFailure<E>`](crate::ServiceFailure).
///
/// Returns `Err(RemoteError)` when the envelope's type ID is not in `E::TYPE_IDS`.
/// The returned `RemoteError` still carries the wire envelope so it can be re-encoded
/// or forwarded without data loss.
pub fn decode<E: Aerro>(status: Status) -> Result<ServiceFailure<E>, RemoteError> {
    let details = status.details();
    if details.is_empty() {
        return Err(transport_remote_error(&status));
    }
    let env = match raw::Envelope::decode(details) {
        Ok(e) => e,
        Err(_) => return Err(transport_remote_error(&status)),
    };

    if !E::TYPE_IDS.contains(&env.type_id.as_str()) {
        return Err(into_remote_error(env, &status));
    }

    let inner = match E::decode_payload(&env.type_id, &env.payload) {
        Ok(v) => v,
        Err(_) => return Err(into_remote_error(env, &status)),
    };
    let frames = decode_frames(&env.frames);
    let trace = decode_trace(&env.trace_id, &env.span_id);
    Ok(ServiceFailure::from_parts(inner, frames, trace))
}

fn into_remote_error(env: raw::Envelope, status: &Status) -> RemoteError {
    let category =
        from_proto(raw::Category::try_from(env.category).unwrap_or(raw::Category::System));
    let trace = decode_trace(&env.trace_id, &env.span_id);
    let frames = decode_frames(&env.frames);
    RemoteError::from_parts(crate::remote::RemoteErrorParts {
        category,
        type_id: env.type_id,
        frames,
        trace,
        outer_code: status.code(),
        outer_message: status.message().to_string(),
        payload_bytes: Bytes::from(env.payload.to_vec()),
    })
}

fn transport_remote_error(status: &Status) -> RemoteError {
    RemoteError::from_parts(crate::remote::RemoteErrorParts {
        category: Category::Transport,
        type_id: "aerro.transport".into(),
        frames: SmallVec::new(),
        trace: TraceContext::default(),
        outer_code: status.code(),
        outer_message: status.message().to_string(),
        payload_bytes: Bytes::new(),
    })
}

fn decode_frames(frames: &[raw::Frame]) -> SmallVec<[Frame; 4]> {
    let mut out = SmallVec::new();
    for f in frames {
        let cat = from_proto(raw::Category::try_from(f.category).unwrap_or(raw::Category::System));
        let code = code_from_u32(f.code);
        let loc = if f.location.is_empty() {
            None
        } else {
            Some(f.location.clone())
        };
        out.push(Frame::received(
            f.service.clone(),
            f.rpc.clone(),
            code,
            f.message.clone(),
            loc,
            cat,
        ));
    }
    out
}

fn code_from_u32(c: u32) -> Code {
    // tonic::Code is `#[repr(i32)]` over the gRPC code numbers 0..=16.
    Code::from(c as i32)
}

fn decode_trace(trace_id: &[u8], span_id: &[u8]) -> TraceContext {
    let mut t = TraceContext::default();
    if trace_id.len() == 16 {
        t.trace_id.copy_from_slice(trace_id);
    }
    if span_id.len() == 8 {
        t.span_id.copy_from_slice(span_id);
    }
    t
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test_support::Boom;
    use crate::wire::encode::{EncodeOptions, encode};

    #[test]
    fn roundtrip_known_type() {
        let sf: ServiceFailure<Boom> = Boom { x: 13 }.into();
        let st = encode(&sf, &EncodeOptions::default());
        let back = decode::<Boom>(st).expect("known type round-trips");
        assert_eq!(back.inner.x, 13);
    }

    #[test]
    fn unknown_type_falls_back_to_remote_error() {
        let sf: ServiceFailure<Boom> = Boom { x: 5 }.into();
        let st = encode(&sf, &EncodeOptions::default());

        #[derive(Debug, thiserror::Error)]
        #[error("other")]
        struct Other;
        impl Aerro for Other {
            const TYPE_IDS: &'static [&'static str] = &["other.thing"];
            fn type_id(&self) -> &'static str {
                "other.thing"
            }
            fn category(&self) -> Category {
                Category::Business
            }
            fn code(&self) -> Code {
                Code::NotFound
            }
            fn encode_payload(&self, _: crate::Exposure, _: &mut Vec<u8>) {}
            fn decode_payload(_: &str, _: &[u8]) -> Result<Self, crate::DecodeError> {
                Err(crate::DecodeError::Missing)
            }
        }
        let r = decode::<Other>(st).expect_err("type_id mismatch");
        assert_eq!(r.type_id, "toy.boom");
        assert_eq!(r.downcast::<Boom>().unwrap().x, 5);
    }

    #[test]
    fn bare_status_becomes_transport_remote_error() {
        let st = Status::unavailable("backend down");
        let r = decode::<Boom>(st).err().unwrap();
        assert_eq!(r.category, Category::Transport);
        assert_eq!(r.outer_code, Code::Unavailable);
    }
}