db.rs

/// This code is massively inspired by Tokio mini-redis
use crate::infer::InferError;
use crate::infer::InferStreamResponse;
use crate::validation::ValidGenerateRequest;
use nohash_hasher::{BuildNoHashHasher, IntMap};
use parking_lot::Mutex;
use std::collections::BTreeMap;
use std::sync::Arc;
use text_generation_client::{Batch, Request};
use tokio::sync::mpsc::UnboundedSender;
use tokio::sync::OwnedSemaphorePermit;
use tokio::time::Instant;

/// Database entry
#[derive(Debug)]
pub(crate) struct Entry {
    /// Request
    pub request: ValidGenerateRequest,
    /// Response sender to communicate between the Infer struct and the batching_task
    pub response_tx: UnboundedSender<Result<InferStreamResponse, InferError>>,
    /// Instant when this entry was created
    pub time: Instant,
    /// Instant when this entry was added to a batch
    pub batch_time: Option<Instant>,
    /// Permit
    pub _permit: OwnedSemaphorePermit,
}

/// Request Database
#[derive(Debug, Clone)]
pub(crate) struct Db {
    pub shared: Arc<Shared>,
}

/// Shared state
#[derive(Debug)]
pub struct Shared {
    state: Mutex<State>,
}

/// Database State
#[derive(Debug)]
struct State {
    /// Database entries organized in a BTreeMap to be able to iterate over them in order
    entries: BTreeMap<u64, Entry>,

    /// Id of the next entry
    next_id: u64,

    /// Id of the next batch
    next_batch_id: u64,

    /// Start ID of the next batch. Used to iterate inside the entries BTreeMap
    next_batch_start_id: u64,
}

impl State {
    /// Get the next requests
    fn next_requests(&self, max_size: usize) -> Option<(Vec<u64>, Vec<Request>)> {
        // Iterates for max_size over the BTreemap starting from next_batch_start_id
        let mut requests = Vec::new();
        let mut ids = Vec::new();

        for (id, entry) in self
            .entries
            // Start from next_batch_start_id
            .range(self.next_batch_start_id..)
            // Take max_size
            .take(max_size)
        {
            requests.push(Request {
                id: *id,
                inputs: entry.request.inputs.clone(),
                input_length: entry.request.input_length,
                parameters: Some(entry.request.parameters.clone()),
                stopping_parameters: Some(entry.request.stopping_parameters.clone()),
            });

            ids.push(*id);
        }

        if requests.is_empty() {
            None
        } else {
            Some((ids, requests))
        }
    }
}

impl Db {
    pub(crate) fn new() -> Self {
        // Shared state
        let shared = Arc::new(Shared {
            state: Mutex::new(State {
                entries: BTreeMap::new(),
                next_id: 0,
                next_batch_id: 0,
                next_batch_start_id: 0,
            }),
        });

        Self { shared }
    }

    /// Append an entry to the database
    pub(crate) fn append(&self, entry: Entry) {
        // Acquire lock
        let mut state = self.shared.state.lock();

        // Insert entry
        let id = state.next_id;
        state.next_id += 1;
        state.entries.insert(id, entry);
    }

    // Get the next batch
    pub(crate) fn next_batch(
        &self,
        min_size: Option<usize>,
        max_size: usize,
    ) -> Option<(IntMap<u64, Entry>, Batch)> {
        // Acquire lock
        let mut state = self.shared.state.lock();

        // Get requests from the database
        if let Some((ids, requests)) = state.next_requests(max_size) {
            if let Some(min_size) = min_size {
                // If min_size is set, only return a batch if there are enough requests
                if requests.len() < min_size {
                    return None;
                }
            }
            // Batch size
            let size = requests.len();

            let mut entries = IntMap::with_capacity_and_hasher(size, BuildNoHashHasher::default());
            ids.iter().for_each(|id| {
                // Remove entry from db
                let mut entry = state.entries.remove(id).unwrap();
                // Set batch_time
                entry.batch_time = Some(Instant::now());
                // Insert in entries IntMap
                entries.insert(*id, entry);
            });

            let batch = Batch {
                id: state.next_batch_id,
                requests,
                size: size as u32,
            };
            // Update next_batch_start_id to the last id in the batch + 1
            state.next_batch_start_id = ids.last().unwrap() + 1;
            // Increment batch id
            state.next_batch_id += 1;

            return Some((entries, batch));
        }
        None
    }
}