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
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270

use crate::{
    build_event_error_request, deserializer, incoming, type_name_of_val, Config, Context, Error, EventErrorRequest,
    IntoRequest, LambdaEvent, Runtime,
};
use bytes::Bytes;
use futures::FutureExt;
use http::header::{CONTENT_TYPE, SET_COOKIE};
use http::{Method, Request, Response, Uri};
use hyper::body::HttpBody;
use hyper::{client::connect::Connection, Body};
use lambda_runtime_api_client::{build_request, Client};
use serde::Deserialize;
use serde_json::json;
use std::collections::HashMap;
use std::str::FromStr;
use std::{
    env,
    fmt::{self, Debug, Display},
    future::Future,
    panic,
};
use tokio::io::{AsyncRead, AsyncWrite};
use tokio_stream::{Stream, StreamExt};
use tower::{Service, ServiceExt};
use tracing::{error, trace, Instrument};

/// Starts the Lambda Rust runtime and stream response back [Configure Lambda
/// Streaming Response](https://docs.aws.amazon.com/lambda/latest/dg/configuration-response-streaming.html).
///
/// # Example
/// ```no_run
/// use hyper::{body::Body, Response};
/// use lambda_runtime::{service_fn, Error, LambdaEvent};
/// use std::{thread, time::Duration};
/// use serde_json::Value;
///
/// #[tokio::main]
/// async fn main() -> Result<(), Error> {
///     lambda_runtime::run_with_streaming_response(service_fn(func)).await?;
///     Ok(())
/// }
/// async fn func(_event: LambdaEvent<Value>) -> Result<Response<Body>, Error> {
///     let messages = vec!["Hello ", "world ", "from ", "Lambda!"];
///
///     let (mut tx, rx) = Body::channel();
///
///     tokio::spawn(async move {
///         for message in messages.iter() {
///             tx.send_data((*message).into()).await.unwrap();
///             thread::sleep(Duration::from_millis(500));
///         }
///     });
///
///     let resp = Response::builder()
///         .header("content-type", "text/plain")
///         .header("CustomHeader", "outerspace")
///         .body(rx)?;
///     
///     Ok(resp)
/// }
/// ```
pub async fn run_with_streaming_response<A, B, F>(handler: F) -> Result<(), Error>
where
    F: Service<LambdaEvent<A>>,
    F::Future: Future<Output = Result<http::Response<B>, F::Error>>,
    F::Error: Debug + Display,
    A: for<'de> Deserialize<'de>,
    B: HttpBody + Unpin + Send + 'static,
    B::Data: Into<Bytes> + Send,
    B::Error: Into<Error> + Send + Debug,
{
    trace!("Loading config from env");
    let config = Config::from_env()?;
    let client = Client::builder().build().expect("Unable to create a runtime client");
    let runtime = Runtime { client, config };

    let client = &runtime.client;
    let incoming = incoming(client);
    runtime.run_with_streaming_response(incoming, handler).await
}

impl<C> Runtime<C>
where
    C: Service<http::Uri> + Clone + Send + Sync + Unpin + 'static,
    C::Future: Unpin + Send,
    C::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    C::Response: AsyncRead + AsyncWrite + Connection + Unpin + Send + 'static,
{
    async fn run_with_streaming_response<F, A, B>(
        &self,
        incoming: impl Stream<Item = Result<Response<Body>, Error>> + Send,
        mut handler: F,
    ) -> Result<(), Error>
    where
        F: Service<LambdaEvent<A>>,
        F::Future: Future<Output = Result<Response<B>, F::Error>>,
        F::Error: fmt::Debug + fmt::Display,
        A: for<'de> Deserialize<'de>,
        B: HttpBody + Unpin + Send + 'static,
        B::Data: Into<Bytes> + Send,
        B::Error: Into<Error> + Send + Debug,
    {
        let client = &self.client;
        tokio::pin!(incoming);
        while let Some(next_event_response) = incoming.next().await {
            trace!("New event arrived (run loop)");
            let event = next_event_response?;
            let (parts, body) = event.into_parts();

            #[cfg(debug_assertions)]
            if parts.status == http::StatusCode::NO_CONTENT {
                // Ignore the event if the status code is 204.
                // This is a way to keep the runtime alive when
                // there are no events pending to be processed.
                continue;
            }

            let ctx: Context = Context::try_from(parts.headers)?;
            let ctx: Context = ctx.with_config(&self.config);
            let request_id = &ctx.request_id.clone();

            let request_span = match &ctx.xray_trace_id {
                Some(trace_id) => {
                    env::set_var("_X_AMZN_TRACE_ID", trace_id);
                    tracing::info_span!("Lambda runtime invoke", requestId = request_id, xrayTraceId = trace_id)
                }
                None => {
                    env::remove_var("_X_AMZN_TRACE_ID");
                    tracing::info_span!("Lambda runtime invoke", requestId = request_id)
                }
            };

            // Group the handling in one future and instrument it with the span
            async {
                let body = hyper::body::to_bytes(body).await?;
                trace!("incoming request payload - {}", std::str::from_utf8(&body)?);

                #[cfg(debug_assertions)]
                if parts.status.is_server_error() {
                    error!("Lambda Runtime server returned an unexpected error");
                    return Err(parts.status.to_string().into());
                }

                let lambda_event = match deserializer::deserialize(&body, ctx) {
                    Ok(lambda_event) => lambda_event,
                    Err(err) => {
                        let req = build_event_error_request(request_id, err)?;
                        client.call(req).await.expect("Unable to send response to Runtime APIs");
                        return Ok(());
                    }
                };

                let req = match handler.ready().await {
                    Ok(handler) => {
                        // Catches panics outside of a `Future`
                        let task = panic::catch_unwind(panic::AssertUnwindSafe(|| handler.call(lambda_event)));

                        let task = match task {
                            // Catches panics inside of the `Future`
                            Ok(task) => panic::AssertUnwindSafe(task).catch_unwind().await,
                            Err(err) => Err(err),
                        };

                        match task {
                            Ok(response) => match response {
                                Ok(response) => {
                                    trace!("Ok response from handler (run loop)");
                                    EventCompletionStreamingRequest {
                                        request_id,
                                        body: response,
                                    }
                                    .into_req()
                                }
                                Err(err) => build_event_error_request(request_id, err),
                            },
                            Err(err) => {
                                error!("{:?}", err);
                                let error_type = type_name_of_val(&err);
                                let msg = if let Some(msg) = err.downcast_ref::<&str>() {
                                    format!("Lambda panicked: {msg}")
                                } else {
                                    "Lambda panicked".to_string()
                                };
                                EventErrorRequest::new(request_id, error_type, &msg).into_req()
                            }
                        }
                    }
                    Err(err) => build_event_error_request(request_id, err),
                }?;

                client.call(req).await.expect("Unable to send response to Runtime APIs");
                Ok::<(), Error>(())
            }
            .instrument(request_span)
            .await?;
        }
        Ok(())
    }
}

pub(crate) struct EventCompletionStreamingRequest<'a, B> {
    pub(crate) request_id: &'a str,
    pub(crate) body: Response<B>,
}

impl<'a, B> IntoRequest for EventCompletionStreamingRequest<'a, B>
where
    B: HttpBody + Unpin + Send + 'static,
    B::Data: Into<Bytes> + Send,
    B::Error: Into<Error> + Send + Debug,
{
    fn into_req(self) -> Result<Request<Body>, Error> {
        let uri = format!("/2018-06-01/runtime/invocation/{}/response", self.request_id);
        let uri = Uri::from_str(&uri)?;

        let (parts, mut body) = self.body.into_parts();

        let mut builder = build_request().method(Method::POST).uri(uri);
        let headers = builder.headers_mut().unwrap();

        headers.insert("Transfer-Encoding", "chunked".parse()?);
        headers.insert("Lambda-Runtime-Function-Response-Mode", "streaming".parse()?);
        headers.insert(
            "Content-Type",
            "application/vnd.awslambda.http-integration-response".parse()?,
        );

        let (mut tx, rx) = Body::channel();

        tokio::spawn(async move {
            let mut header_map = parts.headers;
            // default Content-Type
            header_map
                .entry(CONTENT_TYPE)
                .or_insert("application/octet-stream".parse().unwrap());

            let cookies = header_map.get_all(SET_COOKIE);
            let cookies = cookies
                .iter()
                .map(|c| String::from_utf8_lossy(c.as_bytes()).to_string())
                .collect::<Vec<String>>();

            let headers = header_map
                .iter()
                .filter(|(k, _)| *k != SET_COOKIE)
                .map(|(k, v)| (k.as_str(), String::from_utf8_lossy(v.as_bytes()).to_string()))
                .collect::<HashMap<&str, String>>();

            let metadata_prelude = json!({
                "statusCode": parts.status.as_u16(),
                "headers": headers,
                "cookies": cookies,
            })
            .to_string();

            trace!("metadata_prelude: {}", metadata_prelude);

            tx.send_data(metadata_prelude.into()).await.unwrap();
            tx.send_data("\u{0}".repeat(8).into()).await.unwrap();

            while let Some(chunk) = body.data().await {
                let chunk = chunk.unwrap();
                tx.send_data(chunk.into()).await.unwrap();
            }
        });

        let req = builder.body(rx)?;
        Ok(req)
    }
}