Add DedicatedExecutor to FlightSQL Server (#247)

Add's a dedicated executor for running CPU bound work on the FlightSQL
server.

There is interest from the [DataFusion
community](apache/datafusion#13274 (comment))
for this, it was already on our
[roadmap](#197)
and I think the DFT FlightSQL server is a great place to have a
reference implementation.

Initial inspiration and context can be found
[here](https://thenewstack.io/using-rustlangs-async-tokio-runtime-for-cpu-bound-tasks/).

Most of the initial implementation was copied from
[here](https://github.com/influxdata/influxdb3_core/blob/6fcbb004232738d55655f32f4ad2385523d10696/executor/src/lib.rs)
with some tweaks for our current setup. In particular we dont have
metrics yet in the FlightSQL server implementation (but it is on the
[roadmap](#210))
- I expect to do a follow on where metrics are integrated.

Cargo.toml

@@ -32,7 +32,9 @@ http-body = {version = "0.4.5" }
 itertools = "0.13.0"
 lazy_static = "1.4.0"
 log = "0.4.22"
+num_cpus = "1.16.0"
 object_store = { version = "0.10.2", features = ["aws"], optional = true }
+parking_lot = "0.12.3"
 pin-project-lite = {version = "0.2.14" }
 prost = "0.12.3"
 ratatui = "0.28.0"

src/args.rs

@@ -91,7 +91,7 @@ pub struct DftArgs {
     #[clap(short = 'n', help = "Set the number of benchmark iterations to run")]
     pub benchmark_iterations: Option<usize>,
 
-    #[cfg(feature = "flightsql")]
+    #[cfg(any(feature = "flightsql", feature = "experimental-flightsql-server"))]
     #[clap(long, help = "Set the host and port to be used for FlightSQL")]
     pub flightsql_host: Option<String>,
 }

src/config.rs

@@ -172,6 +172,10 @@ pub struct ExecutionConfig {
     pub tui_batch_size: usize,
     #[serde(default = "default_flightsql_server_batch_size")]
     pub flightsql_server_batch_size: usize,
+    #[serde(default = "default_dedicated_executor_enabled")]
+    pub dedicated_executor_enabled: bool,
+    #[serde(default = "default_dedicated_executor_threads")]
+    pub dedicated_executor_threads: usize,
 }
 
 fn default_ddl_path() -> Option<PathBuf> {
@@ -204,6 +208,18 @@ fn default_flightsql_server_batch_size() -> usize {
     8092
 }
 
+fn default_dedicated_executor_enabled() -> bool {
+    false
+}
+
+fn default_dedicated_executor_threads() -> usize {
+    // By default we slightly over provision CPUs.  For example, if you have N CPUs available we
+    // have N CPUs for the [`DedicatedExecutor`] and 1 for the main / IO runtime.
+    //
+    // Ref: https://github.com/datafusion-contrib/datafusion-dft/pull/247#discussion_r1848270250
+    num_cpus::get()
+}
+
 impl Default for ExecutionConfig {
     fn default() -> Self {
         Self {
@@ -213,6 +229,8 @@ impl Default for ExecutionConfig {
             cli_batch_size: default_cli_batch_size(),
             tui_batch_size: default_tui_batch_size(),
             flightsql_server_batch_size: default_flightsql_server_batch_size(),
+            dedicated_executor_enabled: default_dedicated_executor_enabled(),
+            dedicated_executor_threads: default_dedicated_executor_threads(),
         }
     }
 }