feat: Serializer pushes latest data first if configured to do so

configs/config.toml

@@ -20,6 +20,11 @@ default_buf_size = 1024 # 1KB
 # Maximum number of data streams that can be accepted by uplink
 max_stream_count = 10
 
+# All streams will first push the latest packet before pushing historical data in
+# FIFO order, defaults to false. This solves the problem of bad networks leading to
+# data being pushed so slow that it is practically impossible to track the device.
+default_live_data_first = true
+
 # MQTT client configuration
 #
 # Required Parameters
@@ -84,13 +89,19 @@ blacklist = ["cancollector_metrics", "candump_metrics", "pinger"]
 #   used when there is a network/system failure.
 # - priority(optional, u8): Higher prioirity streams get to push their data
 #   onto the network first.
+# - live_data_first(optional, bool): All streams will first push the latest packet
+#   before pushing historical data in FIFO order, defaults to false. This solves the
+#   problem of bad networks leading to data being pushed so slow that it is practically
+#   impossible to track the device.
 #
 # In the following config for the device_shadow stream we set batch_size to 1 and mark
-# it as non-persistent. streams are internally constructed as a map of Name -> Config
+# it as non-persistent, also setting up live_data_first to enable quick delivery of stats.
+# Streams are internally constructed as a map of Name -> Config
 [streams.device_shadow]
 topic = "/tenants/{tenant_id}/devices/{device_id}/events/device_shadow/jsonarray"
 flush_period = 5
 priority = 75
+live_data_first = true
 
 # Example using compression
 [streams.imu]

uplink/src/base/serializer/mod.rs

@@ -8,7 +8,7 @@ use std::{sync::Arc, time::Duration};
 
 use bytes::Bytes;
 use flume::{bounded, Receiver, RecvError, Sender, TrySendError};
-use log::{debug, error, info, trace};
+use log::{debug, error, info, trace, warn};
 use lz4_flex::frame::FrameEncoder;
 use rumqttc::*;
 use thiserror::Error;
@@ -133,11 +133,17 @@ impl MqttClient for AsyncClient {
 
 pub struct Storage {
     inner: storage::Storage,
+    live_data_first: bool,
+    latest_data: Option<Publish>,
 }
 
 impl Storage {
-    pub fn new(name: impl Into<String>, max_file_size: usize) -> Self {
-        Self { inner: storage::Storage::new(name, max_file_size) }
+    pub fn new(name: impl Into<String>, max_file_size: usize, live_data_first: bool) -> Self {
+        Self {
+            inner: storage::Storage::new(name, max_file_size),
+            live_data_first,
+            latest_data: None,
+        }
     }
 
     pub fn set_persistence(
@@ -151,6 +157,13 @@ impl Storage {
     // Stores the provided publish packet by serializing it into storage, after setting its pkid to 1.
     // If the write buffer is full, it is flushed/written onto disk based on config.
     pub fn write(&mut self, mut publish: Publish) -> Result<Option<u64>, storage::Error> {
+        if self.live_data_first {
+            let Some(previous) = self.latest_data.replace(publish) else { return Ok(None) };
+            publish = previous;
+        } else if self.latest_data.is_some() {
+            warn!("Latest data should be unoccupied if not using the live data first scheme");
+        }
+
         publish.pkid = 1;
         if let Err(e) = publish.write(self.inner.writer()) {
             error!("Failed to fill disk buffer. Error = {e}");
@@ -170,6 +183,10 @@ impl Storage {
     // ## Panic
     // When any packet other than a publish is deserialized.
     pub fn read(&mut self, max_packet_size: usize) -> Option<Publish> {
+        if let Some(publish) = self.latest_data.take() {
+            return Some(publish);
+        }
+
         // TODO(RT): This can fail when packet sizes > max_payload_size in config are written to disk.
         // This leads to force switching to normal mode. Increasing max_payload_size to bypass this
         match Packet::read(self.inner.reader(), max_packet_size) {
@@ -184,6 +201,15 @@ impl Storage {
 
     // Ensures all data is written into persistence, when configured.
     pub fn flush(&mut self) -> Result<Option<u64>, storage::Error> {
+        // Write live cache to disk when flushing
+        if let Some(mut publish) = self.latest_data.take() {
+            publish.pkid = 1;
+            if let Err(e) = publish.write(self.inner.writer()) {
+                error!("Failed to fill disk buffer. Error = {e}");
+                return Ok(None);
+            }
+        }
+
         self.inner.flush()
     }
 }
@@ -202,8 +228,11 @@ impl StorageHandler {
         // NOTE: persist action_status if not configured otherwise
         streams.insert("action_status".into(), config.action_status.clone());
         for (stream_name, stream_config) in streams {
-            let mut storage =
-                Storage::new(&stream_config.topic, stream_config.persistence.max_file_size);
+            let mut storage = Storage::new(
+                &stream_config.topic,
+                stream_config.persistence.max_file_size,
+                stream_config.live_data_first,
+            );
             if stream_config.persistence.max_file_count > 0 {
                 let mut path = config.persistence_path.clone();
                 path.push(&stream_name);
@@ -229,7 +258,13 @@ impl StorageHandler {
         match self
             .map
             .entry(stream.to_owned())
-            .or_insert_with(|| Storage::new(&stream.topic, self.config.default_buf_size))
+            .or_insert_with(|| {
+                Storage::new(
+                    &stream.topic,
+                    self.config.default_buf_size,
+                    self.config.default_live_data_first,
+                )
+            })
             .write(publish)
         {
             Ok(Some(deleted)) => {
@@ -907,7 +942,7 @@ pub mod tests {
     fn read_write_storage() {
         let config = Arc::new(default_config());
 
-        let mut storage = Storage::new("hello/world", 1024);
+        let mut storage = Storage::new("hello/world", 1024, false);
         let mut publish = Publish::new(
             "hello/world",
             QoS::AtLeastOnce,
@@ -1024,7 +1059,7 @@ pub mod tests {
             .storage_handler
             .map
             .entry(Arc::new(Default::default()))
-            .or_insert(Storage::new("hello/world", 1024));
+            .or_insert(Storage::new("hello/world", 1024, false));
 
         let (stream_name, stream_config) = (
             "hello",
@@ -1082,7 +1117,7 @@ pub mod tests {
                 topic: "hello/world".to_string(),
                 ..Default::default()
             }))
-            .or_insert(Storage::new("hello/world", 1024));
+            .or_insert(Storage::new("hello/world", 1024, false));
 
         let (stream_name, stream_config) = (
             "hello",
@@ -1194,7 +1229,7 @@ pub mod tests {
                 priority: 0,
                 ..Default::default()
             }))
-            .or_insert(Storage::new("topic/default", 1024));
+            .or_insert(Storage::new("topic/default", 1024, false));
         default.write(publish("topic/default".to_string(), 0)).unwrap();
         default.write(publish("topic/default".to_string(), 2)).unwrap();
 

uplink/src/config.rs

@@ -93,6 +93,8 @@ pub struct StreamConfig {
     pub persistence: Persistence,
     #[serde(default)]
     pub priority: u8,
+    #[serde(default)]
+    pub live_data_first: bool,
 }
 
 impl Default for StreamConfig {
@@ -104,6 +106,7 @@ impl Default for StreamConfig {
             compression: Compression::Disabled,
             persistence: Persistence::default(),
             priority: 0,
+            live_data_first: false,
         }
     }
 }
@@ -536,6 +539,8 @@ pub struct Config {
     pub logging: Option<LogcatConfig>,
     pub precondition_checks: Option<PreconditionCheckerConfig>,
     pub bus: Option<BusConfig>,
+    #[serde(default)]
+    pub default_live_data_first: bool,
 }
 
 impl Config {

uplink/tests/serializer.rs

@@ -4,7 +4,7 @@ use bytes::Bytes;
 use flume::bounded;
 use rumqttc::{Publish, QoS, Request};
 use tempdir::TempDir;
-use tokio::{runtime::Runtime, spawn};
+use tokio::{runtime::Runtime, spawn, time::sleep};
 
 use uplink::{
     base::{bridge::Payload, serializer::Serializer},
@@ -83,18 +83,18 @@ async fn preferential_send_on_network() {
     };
 
     // write packets for one, two and top onto disk
-    let mut one = Storage::new("topic/one", 1024 * 1024);
+    let mut one = Storage::new("topic/one", 1024 * 1024, false);
     one.set_persistence(persistence_path(&config.persistence_path, "one"), 1).unwrap();
     one.write(publish("topic/one".to_string(), 4)).unwrap();
     one.write(publish("topic/one".to_string(), 5)).unwrap();
     one.flush().unwrap();
 
-    let mut two = Storage::new("topic/two", 1024 * 1024);
+    let mut two = Storage::new("topic/two", 1024 * 1024, false);
     two.set_persistence(persistence_path(&config.persistence_path, "two"), 1).unwrap();
     two.write(publish("topic/two".to_string(), 3)).unwrap();
     two.flush().unwrap();
 
-    let mut top = Storage::new("topic/top", 1024 * 1024);
+    let mut top = Storage::new("topic/top", 1024 * 1024, false);
     top.set_persistence(persistence_path(&config.persistence_path, "top"), 1).unwrap();
     top.write(publish("topic/top".to_string(), 1)).unwrap();
     top.write(publish("topic/top".to_string(), 2)).unwrap();
@@ -216,3 +216,55 @@ async fn fifo_data_push() {
     assert_eq!(topic, "topic/default");
     assert_eq!(payload, "[{\"sequence\":2,\"timestamp\":0,\"msg\":\"Hello, World!\"}]");
 }
+
+#[tokio::test]
+// Ensures that live data is pushed first if configured to do so
+async fn prefer_live_data() {
+    let mut config = Config::default();
+    config.default_buf_size = 1024 * 1024;
+    config.mqtt.max_packet_size = 1024 * 1024;
+    config.default_live_data_first = true;
+    let config = Arc::new(config);
+    let (data_tx, data_rx) = bounded(0);
+    let (net_tx, req_rx) = bounded(0);
+    let (metrics_tx, _metrics_rx) = bounded(1);
+    let client = MockClient { net_tx };
+    let serializer = Serializer::new(config, data_rx, client, metrics_tx).unwrap();
+
+    // start serializer in the background
+    thread::spawn(|| _ = Runtime::new().unwrap().block_on(serializer.start()));
+
+    spawn(async {
+        let mut default = MockCollector::new(
+            "default",
+            StreamConfig { topic: "topic/default".to_owned(), batch_size: 1, ..Default::default() },
+            data_tx,
+        );
+        for i in 0.. {
+            default.send(i).await.unwrap();
+            sleep(Duration::from_millis(250)).await;
+        }
+    });
+
+    sleep(Duration::from_millis(750)).await;
+    let Request::Publish(Publish { topic, payload, .. }) = req_rx.recv_async().await.unwrap()
+    else {
+        unreachable!()
+    };
+    assert_eq!(topic, "topic/default");
+    assert_eq!(payload, "[{\"sequence\":0,\"timestamp\":0,\"msg\":\"Hello, World!\"}]");
+
+    let Request::Publish(Publish { topic, payload, .. }) = req_rx.recv_async().await.unwrap()
+    else {
+        unreachable!()
+    };
+    assert_eq!(topic, "topic/default");
+    assert_eq!(payload, "[{\"sequence\":2,\"timestamp\":0,\"msg\":\"Hello, World!\"}]");
+
+    let Request::Publish(Publish { topic, payload, .. }) = req_rx.recv_async().await.unwrap()
+    else {
+        unreachable!()
+    };
+    assert_eq!(topic, "topic/default");
+    assert_eq!(payload, "[{\"sequence\":1,\"timestamp\":0,\"msg\":\"Hello, World!\"}]");
+}