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use std::cell::UnsafeCell;
use std::cmp;
use std::collections::HashMap;
use std::sync::Arc;
use parking_lot::Mutex;
use scoped_pool::Pool;
use batch::BatchRead;
use cluster::partition::Partition;
use cluster::{Cluster, Node};
use commands::BatchReadCommand;
use errors::*;
use policy::{BatchPolicy, Concurrency};
use Key;
pub struct BatchExecutor {
cluster: Arc<Cluster>,
thread_pool: Pool,
}
impl BatchExecutor {
pub fn new(cluster: Arc<Cluster>, thread_pool: Pool) -> Self {
BatchExecutor {
cluster,
thread_pool,
}
}
pub fn execute_batch_read<'a>(
&self,
policy: &BatchPolicy,
batch_reads: Vec<BatchRead<'a>>,
) -> Result<Vec<BatchRead<'a>>> {
let mut batch_nodes = self.get_batch_nodes(&batch_reads)?;
let batch_reads = SharedSlice::new(batch_reads);
let jobs = batch_nodes
.drain()
.map(|(node, offsets)| {
BatchReadCommand::new(policy, node, batch_reads.clone(), offsets)
})
.collect();
self.execute_batch_jobs(jobs, &policy.concurrency)?;
batch_reads.into_inner()
}
fn execute_batch_jobs(
&self,
mut jobs: Vec<BatchReadCommand>,
concurrency: &Concurrency,
) -> Result<()> {
let threads = match *concurrency {
Concurrency::Sequential => 1,
Concurrency::Parallel => jobs.len(),
Concurrency::MaxThreads(max) => cmp::min(max, jobs.len()),
};
let jobs = Arc::new(Mutex::new(jobs.iter_mut()));
let last_err: Arc<Mutex<Option<Error>>> = Arc::default();
self.thread_pool.scoped(|scope| {
for _ in 0..threads {
let last_err = last_err.clone();
let jobs = jobs.clone();
scope.execute(move || {
let next_job = || jobs.lock().next();
while let Some(cmd) = next_job() {
if let Err(err) = cmd.execute() {
*last_err.lock() = Some(err);
jobs.lock().all(|_| true);
};
}
});
}
});
match Arc::try_unwrap(last_err).unwrap().into_inner() {
None => Ok(()),
Some(err) => Err(err),
}
}
fn get_batch_nodes<'a>(
&self,
batch_reads: &[BatchRead<'a>],
) -> Result<HashMap<Arc<Node>, Vec<usize>>> {
let mut map = HashMap::new();
for (idx, batch_read) in batch_reads.iter().enumerate() {
let node = self.node_for_key(&batch_read.key)?;
map.entry(node).or_insert_with(|| vec![]).push(idx);
}
Ok(map)
}
fn node_for_key(&self, key: &Key) -> Result<Arc<Node>> {
let partition = Partition::new_by_key(key);
let node = self.cluster.get_node(&partition)?;
Ok(node)
}
}
pub struct SharedSlice<T> {
value: Arc<UnsafeCell<Vec<T>>>,
}
unsafe impl<T> Send for SharedSlice<T> {}
unsafe impl<T> Sync for SharedSlice<T> {}
impl<T> Clone for SharedSlice<T> {
fn clone(&self) -> Self {
SharedSlice {
value: self.value.clone(),
}
}
}
impl<T> SharedSlice<T> {
pub fn new(value: Vec<T>) -> Self {
SharedSlice {
value: Arc::new(UnsafeCell::new(value)),
}
}
pub fn get(&self, idx: usize) -> Option<&T> {
unsafe { (*self.value.get()).get(idx) }
}
pub fn get_mut(&self, idx: usize) -> Option<&mut T> {
unsafe { (&mut *self.value.get()).get_mut(idx) }
}
pub fn len(&self) -> usize {
unsafe { (*self.value.get()).len() }
}
pub fn into_inner(self) -> Result<Vec<T>> {
match Arc::try_unwrap(self.value) {
Ok(cell) => Ok(cell.into_inner()),
Err(_) => Err("Unable to process batch request".into()),
}
}
}