fix(mock): add channel bound to avoid io bottleneck (#27)

src/mock.rs

@@ -37,9 +37,15 @@ use std::sync::Arc;
 use std::thread::JoinHandle;
 use std::{thread, usize};
 
-pub(crate) static MINIMUM_N_ROWS_FOR_MULTITHREADING: usize = 1000;
+// This default value should depend on the memory capacity of the system
+// running the program. Because the workers produce buffers faster than
+// the master can write them to disk we need to bound the worker/master
+// channel. If you have a lot of system memory, you can increase this value,
+// but if you increase it too much the program will run out of system memory.
+pub(crate) static DEFAULT_THREAD_CHANNEL_CAPACITY: usize = 128;
+pub(crate) static DEFAULT_MIN_N_ROWS_FOR_MULTITHREADING: usize = 1000;
 pub(crate) static DEFAULT_MOCKED_FILENAME_LEN: usize = 8;
-pub(crate) static DEFAULT_ROW_BUFFER_LEN: usize = 1024 * 1024;
+pub(crate) static DEFAULT_ROW_BUFFER_LEN: usize = 1048 * 1024;
 
 ///
 pub struct Mocker {
@@ -67,7 +73,7 @@ impl Mocker {
 
     ///
     pub fn generate(&self, n_rows: usize) {
-        if self.multithreaded && n_rows > MINIMUM_N_ROWS_FOR_MULTITHREADING {
+        if self.multithreaded && n_rows > DEFAULT_MIN_N_ROWS_FOR_MULTITHREADING {
             self.generate_multithreaded(n_rows);
         } else {
             if self.multithreaded {
@@ -221,7 +227,7 @@ pub fn spawn_workers(
     info!("Remaining rows to handle: {}", remaining_rows);
 
     let arc_schema = Arc::new(schema);
-    let (sender, receiver) = channel::unbounded();
+    let (sender, receiver) = channel::bounded(DEFAULT_THREAD_CHANNEL_CAPACITY);
 
     let threads: Vec<JoinHandle<()>> = (0..n_threads)
         .map(|t| {