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// background_load_in_progress used with condition variable
#![allow(clippy::mutex_atomic)]
use std::collections::{HashMap, HashSet};
use std::sync::{Arc, Mutex, Condvar};
use std::collections::VecDeque;
use std_semaphore::Semaphore;
use crate::disk_store::interface::DiskStore;
use crate::disk_store::interface::PartitionID;
use crate::mem_store::*;
use crate::mem_store::partition::ColumnHandle;
use crate::mem_store::partition::Partition;
use crate::scheduler::inner_locustdb::InnerLocustDB;
pub struct DiskReadScheduler {
disk_store: Arc<dyn DiskStore>,
task_queue: Mutex<VecDeque<DiskRun>>,
reader_semaphore: Semaphore,
lru: LRU,
#[allow(dead_code)]
lz4_decode: bool,
background_load_wait_queue: Condvar,
background_load_in_progress: Mutex<bool>,
}
#[derive(Default, Debug)]
struct DiskRun {
start: PartitionID,
end: PartitionID,
columns: HashSet<String>,
bytes: usize,
}
impl DiskReadScheduler {
pub fn new(disk_store: Arc<dyn DiskStore>, lru: LRU, max_readers: usize, lz4_decode: bool) -> DiskReadScheduler {
DiskReadScheduler {
disk_store,
task_queue: Mutex::default(),
reader_semaphore: Semaphore::new(max_readers as isize),
lru,
lz4_decode,
background_load_wait_queue: Condvar::default(),
background_load_in_progress: Mutex::default(),
}
}
pub fn schedule_sequential_read(&self,
snapshot: &mut Vec<Arc<Partition>>,
columns: &HashSet<String>,
readahead: usize) {
let mut task_queue = self.task_queue.lock().unwrap();
snapshot.sort_unstable_by_key(|p| p.id());
let mut current_run = DiskRun::default();
let mut previous_partitionid = 0;
for partition in snapshot {
if current_run.bytes > readahead ||
!partition.nonresidents_match(&current_run.columns, &columns) {
if !current_run.columns.is_empty() {
current_run.end = previous_partitionid;
task_queue.push_back(current_run);
}
let columns = partition.non_residents(columns);
current_run = DiskRun {
start: partition.id(),
end: 0,
bytes: partition.promise_load(&columns),
columns,
};
} else {
current_run.bytes += partition.promise_load(&current_run.columns);
}
previous_partitionid = partition.id();
}
current_run.end = previous_partitionid;
task_queue.push_back(current_run);
debug!("Scheduled sequential reads. Queue: {:#?}", &*task_queue);
}
pub fn schedule_bulk_load(&self,
mut snapshot: Vec<Arc<Partition>>,
chunk_size: usize) {
let mut task_queue = self.task_queue.lock().unwrap();
snapshot.sort_unstable_by_key(|p| p.id());
let mut runs = HashMap::<&str, DiskRun>::default();
for partition in &snapshot {
for col in partition.col_names() {
let reached_chunk_size = {
let mut run = runs.entry(col)
.or_insert(DiskRun {
start: partition.id(),
end: partition.id(),
bytes: 0,
columns: [col.to_string()].iter().cloned().collect(),
});
run.bytes += partition.promise_load(&run.columns);
run.end = partition.id();
run.bytes > chunk_size
};
if reached_chunk_size {
task_queue.push_back(runs.remove(col).unwrap());
}
}
}
for (_, run) in runs {
task_queue.push_back(run);
}
debug!("Scheduled sequential reads. Queue: {:#?}", &*task_queue);
}
pub fn get_or_load(&self, handle: &ColumnHandle) -> Arc<Column> {
loop {
if handle.is_resident() {
let mut maybe_column = handle.try_get();
if let Some(ref mut column) = *maybe_column {
#[cfg(feature = "enable_lz4")] {
if self.lz4_decode {
if let Some(c) = Arc::get_mut(column) { c.lz4_decode() };
handle.update_size_bytes(column.heap_size_of_children());
}
}
self.lru.touch(&handle.key());
return column.clone();
} else {
debug!("{}.{} was not resident!", handle.name(), handle.id());
}
} else if handle.is_load_scheduled() {
let mut is_load_in_progress =
self.background_load_in_progress.lock().unwrap();
while *is_load_in_progress && !handle.is_resident() && handle.is_load_scheduled() {
debug!("Queuing for {}.{}", handle.name(), handle.id());
is_load_in_progress = self.background_load_wait_queue
.wait(is_load_in_progress).unwrap();
}
} else {
debug!("Point lookup for {}.{}", handle.name(), handle.id());
#[allow(unused_mut)]
let mut column = {
let _token = self.reader_semaphore.access();
self.disk_store.load_column(handle.id(), handle.name())
};
// Need to hold lock when we put new value into lru
let mut maybe_column = handle.try_get();
self.lru.put(handle.key().clone());
#[cfg(feature = "enable_lz4")] {
if self.lz4_decode {
column.lz4_decode();
handle.update_size_bytes(column.heap_size_of_children());
}
}
let column = Arc::new(column);
*maybe_column = Some(column.clone());
handle.set_resident();
return column;
}
}
}
pub fn service_reads(&self, ldb: &InnerLocustDB) {
debug!("Waiting to service reads...");
*self.background_load_in_progress.lock().unwrap() = true;
debug!("Started servicing reads...");
loop {
let next_read = {
let mut task_queue = self.task_queue.lock().unwrap();
match task_queue.pop_front() {
Some(read) => read,
None => {
debug!("Stopped servicing reads...");
*self.background_load_in_progress.lock().unwrap() = false;
return;
}
}
};
self.service_sequential_read(&next_read, ldb);
self.background_load_wait_queue.notify_all();
}
}
fn service_sequential_read(&self, run: &DiskRun, ldb: &InnerLocustDB) {
let _token = self.reader_semaphore.access();
debug!("Servicing read: {:?}", &run);
for col in &run.columns {
self.disk_store.load_column_range(run.start, run.end, col, ldb);
}
}
}
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