Allow paging on TOP-N queries

Change BusRequest::GetTopNDownloaders and GetWorstRtt to accept
a start and end field, rather than just "n_rows".

src/rust/lqos_bus/src/bus/request.rs

@@ -15,10 +15,20 @@ pub enum BusRequest {
     GetCurrentThroughput,
 
     /// Retrieve the top N downloads by bandwidth use.
-    GetTopNDownloaders(u32),
+    GetTopNDownloaders{
+        /// First row to retrieve (usually 0 unless you are paging)
+        start: u32, 
+        /// Last row to retrieve (10 for top-10 starting at 0)
+        end: u32
+    },
 
     /// Retrieves the TopN hosts with the worst RTT, sorted by RTT descending.
-    GetWorstRtt(u32),
+    GetWorstRtt{
+        /// First row to retrieve (usually 0 unless you are paging)
+        start: u32,
+        /// Last row to retrieve (10 for top-10 starting at 0)
+        end: u32
+    },
 
     /// Retrieves current byte counters for all hosts.
     GetHostCounter,

src/rust/lqos_node_manager/src/tracker/cache_manager.rs

@@ -71,8 +71,8 @@ async fn get_data_from_server(bus_client: &mut BusClient) -> Result<()> {
     // Send request to lqosd
     let requests = vec![
         BusRequest::GetCurrentThroughput,
-        BusRequest::GetTopNDownloaders(10),
+        BusRequest::GetTopNDownloaders{start: 0, end: 10},
-        BusRequest::GetWorstRtt(10),
+        BusRequest::GetWorstRtt{start: 0, end: 10},
         BusRequest::RttHistogram,
         BusRequest::AllUnknownIps,
     ];

src/rust/lqosd/src/main.rs

@@ -118,8 +118,8 @@ fn handle_bus_requests(requests: &[BusRequest], responses: &mut Vec<BusResponse>
                 throughput_tracker::current_throughput()
             }
             BusRequest::GetHostCounter => throughput_tracker::host_counters(),
-            BusRequest::GetTopNDownloaders(n) => throughput_tracker::top_n(*n),
+            BusRequest::GetTopNDownloaders{start, end} => throughput_tracker::top_n(*start, *end),
-            BusRequest::GetWorstRtt(n) => throughput_tracker::worst_n(*n),
+            BusRequest::GetWorstRtt{start, end} => throughput_tracker::worst_n(*start, *end),
             BusRequest::MapIpToFlow {
                 ip_address,
                 tc_handle,

src/rust/lqosd/src/throughput_tracker/mod.rs

@@ -75,7 +75,7 @@ fn retire_check(cycle: u64, recent_cycle: u64) -> bool {
     cycle < recent_cycle + RETIRE_AFTER_SECONDS
 }
 
-pub fn top_n(n: u32) -> BusResponse {
+pub fn top_n(start: u32, end: u32) -> BusResponse {
     let mut full_list: Vec<(XdpIpAddress, (u64, u64), (u64, u64), f32, TcHandle)> = {
         let tp = THROUGHPUT_TRACKER.read();
         tp.raw_data
@@ -96,7 +96,8 @@ pub fn top_n(n: u32) -> BusResponse {
     full_list.sort_by(|a, b| b.1 .0.cmp(&a.1 .0));
     let result = full_list
         .iter()
-        .take(n as usize)
+        .skip(start as usize)
+        .take((end as usize) - (start as usize))
         .map(
             |(ip, (bytes_dn, bytes_up), (packets_dn, packets_up), median_rtt, tc_handle)| IpStats {
                 ip_address: ip.as_ip().to_string(),
@@ -110,7 +111,7 @@ pub fn top_n(n: u32) -> BusResponse {
     BusResponse::TopDownloaders(result)
 }
 
-pub fn worst_n(n: u32) -> BusResponse {
+pub fn worst_n(start: u32, end: u32) -> BusResponse {
     let mut full_list: Vec<(XdpIpAddress, (u64, u64), (u64, u64), f32, TcHandle)> = {
         let tp = THROUGHPUT_TRACKER.read();
         tp.raw_data
@@ -131,7 +132,8 @@ pub fn worst_n(n: u32) -> BusResponse {
     full_list.sort_by(|a, b| b.3.partial_cmp(&a.3).unwrap());
     let result = full_list
         .iter()
-        .take(n as usize)
+        .skip(start as usize)
+        .take((end as usize) - (start as usize))
         .map(
             |(ip, (bytes_dn, bytes_up), (packets_dn, packets_up), median_rtt, tc_handle)| IpStats {
                 ip_address: ip.as_ip().to_string(),

src/rust/lqtop/src/main.rs

@@ -23,7 +23,7 @@ async fn get_data(client: &mut BusClient, n_rows: u16) -> Result<DataResult> {
   let mut result = DataResult { totals: (0, 0, 0, 0), top: Vec::new() };
   let requests = vec![
     BusRequest::GetCurrentThroughput,
-    BusRequest::GetTopNDownloaders(n_rows as u32),
+    BusRequest::GetTopNDownloaders{start: 0, end: n_rows as u32},
   ];
   for r in client.request(requests).await? {
     match r {