Add framed json stream

apidoc/src/events.md

@@ -48,6 +48,9 @@ where each `[JSON-frame]` looks like:
 [padding: P zero-bytes, 0 <= P <= 7, such that (N + P) mod 8 = 0]
 ```
 
+Note: "data" objects are currently identified by the presence of the `tss` key.
+There can be other types of objects, like keepalive, log or statistics.
+
 
 ## Events as framed CBOR stream
 
@@ -81,6 +84,5 @@ Most returned CBOR objects are data objects and look like this in equivalent jso
 ```
 where `tss` is the array of timestamps and `values` the corresponding array of values.
 
-Note: "data" CBOR objects are currently identified by the presence of the `tss` key. There can be
-other types of CBOR objects, like log or statistics.
-The next update will add a type-tag to discriminate them, but for now, look for the key `tss`.
+Note: "data" objects are currently identified by the presence of the `tss` key.
+There can be other types of objects, like keepalive, log or statistics.

crates/items_2/src/eventsdim0.rs

@@ -966,17 +966,31 @@ impl<STY: ScalarOps> Events for EventsDim0<STY> {
     }
 
     fn to_json_vec_u8(&self) -> Vec<u8> {
-        let ret = EventsDim0ChunkOutput {
-            // TODO use &mut to swap the content
-            tss: self.tss.clone(),
-            pulses: self.pulses.clone(),
-            values: self.values.clone(),
-            scalar_type: STY::scalar_type_name().into(),
+        // TODO redesign with mut access, rename to `into_` and take the values out.
+        let mut tss = self.tss.clone();
+        let mut pulses = self.pulses.clone();
+        let mut values = self.values.clone();
+        let tss_sl = tss.make_contiguous();
+        let pulses_sl = pulses.make_contiguous();
+        let (ts_anchor_sec, ts_off_ms, ts_off_ns) = crate::ts_offs_from_abs(tss_sl);
+        let (pulse_anchor, pulse_off) = crate::pulse_offs_from_abs(pulses_sl);
+        let values = mem::replace(&mut values, VecDeque::new());
+        let ret = EventsDim0CollectorOutput {
+            ts_anchor_sec,
+            ts_off_ms,
+            ts_off_ns,
+            pulse_anchor,
+            pulse_off,
+            values,
+            range_final: false,
+            timed_out: false,
+            continue_at: None,
         };
         serde_json::to_vec(&ret).unwrap()
     }
 
     fn to_cbor_vec_u8(&self) -> Vec<u8> {
+        // TODO redesign with mut access, rename to `into_` and take the values out.
         let ret = EventsDim0ChunkOutput {
             // TODO use &mut to swap the content
             tss: self.tss.clone(),

crates/streams/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2021"
 tokio = { version = "1.34", features = ["io-util", "net", "time", "sync", "fs"] }
 futures-util = "0.3.15"
 pin-project = "1.0.12"
+tokio-stream = "0.1"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 serde_cbor = "0.11.1"

crates/streams/src/cbor_stream.rs

@@ -22,6 +22,7 @@ use std::io::Cursor;
 use std::pin::Pin;
 use std::task::Context;
 use std::task::Poll;
+use std::time::Duration;
 
 const FRAME_HEAD_LEN: usize = 16;
 const FRAME_PAYLOAD_MAX: u32 = 1024 * 1024 * 80;
@@ -70,7 +71,20 @@ pub type SitemtyDynEventsStream =
     Pin<Box<dyn Stream<Item = Result<StreamItem<RangeCompletableItem<Box<dyn Events>>>, Error>> + Send>>;
 
 pub fn events_stream_to_cbor_stream(stream: SitemtyDynEventsStream) -> impl Stream<Item = Result<CborBytes, Error>> {
-    let stream = stream.map(|x| match x {
+    let interval = tokio::time::interval(Duration::from_millis(4000));
+    let stream = tokio_stream::StreamExt::timeout_repeating(stream, interval).map(|x| match x {
+        Ok(x) => map_events(x),
+        Err(_) => make_keepalive(),
+    });
+    let prepend = {
+        let item = make_keepalive();
+        futures_util::stream::iter([item])
+    };
+    prepend.chain(stream)
+}
+
+fn map_events(x: Result<StreamItem<RangeCompletableItem<Box<dyn Events>>>, Error>) -> Result<CborBytes, Error> {
+    match x {
         Ok(x) => match x {
             StreamItem::DataItem(x) => match x {
                 RangeCompletableItem::Data(evs) => {
@@ -130,8 +144,20 @@ pub fn events_stream_to_cbor_stream(stream: SitemtyDynEventsStream) -> impl Stre
             let item = CborBytes(bytes);
             Ok(item)
         }
-    });
-    stream
+    }
+}
+
+fn make_keepalive() -> Result<CborBytes, Error> {
+    use ciborium::cbor;
+    let item = cbor!({
+        "type" => "keepalive",
+    })
+    .map_err(Error::from_string)?;
+    let mut buf = Vec::with_capacity(64);
+    ciborium::into_writer(&item, &mut buf).map_err(Error::from_string)?;
+    let bytes = Bytes::from(buf);
+    let item = Ok(CborBytes(bytes));
+    item
 }
 
 pub struct FramedBytesToSitemtyDynEventsStream<S> {

crates/streams/src/json_stream.rs

@@ -5,9 +5,11 @@ use futures_util::Stream;
 use futures_util::StreamExt;
 use items_0::streamitem::RangeCompletableItem;
 use items_0::streamitem::StreamItem;
+use items_0::Events;
 use items_0::WithLen;
 use netpod::log::*;
 use std::pin::Pin;
+use std::time::Duration;
 
 pub struct JsonBytes(Bytes);
 
@@ -36,7 +38,20 @@ impl From<JsonBytes> for Bytes {
 pub type JsonStream = Pin<Box<dyn Stream<Item = Result<JsonBytes, Error>> + Send>>;
 
 pub fn events_stream_to_json_stream(stream: SitemtyDynEventsStream) -> impl Stream<Item = Result<JsonBytes, Error>> {
-    let stream = stream.map(|x| match x {
+    let interval = tokio::time::interval(Duration::from_millis(4000));
+    let stream = tokio_stream::StreamExt::timeout_repeating(stream, interval).map(|x| match x {
+        Ok(x) => map_events(x),
+        Err(_) => make_keepalive(),
+    });
+    let prepend = {
+        let item = make_keepalive();
+        futures_util::stream::iter([item])
+    };
+    prepend.chain(stream)
+}
+
+fn map_events(x: Result<StreamItem<RangeCompletableItem<Box<dyn Events>>>, Error>) -> Result<JsonBytes, Error> {
+    match x {
         Ok(x) => match x {
             StreamItem::DataItem(x) => match x {
                 RangeCompletableItem::Data(evs) => {
@@ -75,6 +90,15 @@ pub fn events_stream_to_json_stream(stream: SitemtyDynEventsStream) -> impl Stre
             let item = JsonBytes(bytes);
             Ok(item)
         }
-    });
-    stream
+    }
+}
+
+fn make_keepalive() -> Result<JsonBytes, Error> {
+    let item = serde_json::json!({
+        "type": "keepalive",
+    });
+    let buf = serde_json::to_vec(&item).unwrap();
+    let bytes = Bytes::from(buf);
+    let item = Ok(JsonBytes(bytes));
+    item
 }