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92 lines
3.2 KiB
Rust
92 lines
3.2 KiB
Rust
use failure::{format_err, Fallible};
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use std::sync::{Arc, RwLock};
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pub fn open() -> Fallible<Arc<RwLock<dyn PreprocCache>>> {
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Ok(Arc::new(RwLock::new(LmdbCache::open()?)))
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}
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pub trait PreprocCache {
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// possible without second lambda?
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fn get_or_run<'a>(
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&mut self,
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db_name: &str,
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key: &[u8],
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runner: Box<dyn FnOnce() -> Fallible<Option<Vec<u8>>> + 'a>,
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callback: Box<dyn FnOnce(&[u8]) -> Fallible<()> + 'a>,
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) -> Fallible<()>;
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}
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/// opens a LMDB cache
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fn open_cache_db() -> Fallible<std::sync::Arc<std::sync::RwLock<rkv::Rkv>>> {
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let app_cache = cachedir::CacheDirConfig::new("rga").get_cache_dir()?;
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let db_arc = rkv::Manager::singleton()
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.write()
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.expect("could not write db manager")
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.get_or_create(app_cache.as_path(), |p| {
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let mut builder = rkv::Rkv::environment_builder();
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builder
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.set_flags(rkv::EnvironmentFlags::NO_SYNC | rkv::EnvironmentFlags::WRITE_MAP) // not durable cuz it's a cache
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// i'm not sure why NO_TLS is needed. otherwise LMDB transactions (open readers) will keep piling up until it fails with
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// LmdbError(ReadersFull)
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// hope it doesn't break integrity
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.set_flags(rkv::EnvironmentFlags::NO_TLS)
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.set_map_size(2 * 1024 * 1024 * 1024)
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.set_max_dbs(100)
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.set_max_readers(128);
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rkv::Rkv::from_env(p, builder)
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})
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.expect("could not get/create db");
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Ok(db_arc)
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}
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pub struct LmdbCache {
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db_arc: std::sync::Arc<std::sync::RwLock<rkv::Rkv>>,
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}
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impl LmdbCache {
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pub fn open() -> Fallible<LmdbCache> {
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Ok(LmdbCache {
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db_arc: open_cache_db()?,
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})
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}
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}
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impl PreprocCache for LmdbCache {
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// possible without second lambda?
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fn get_or_run<'a>(
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&mut self,
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db_name: &str,
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key: &[u8],
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runner: Box<dyn FnOnce() -> Fallible<Option<Vec<u8>>> + 'a>,
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callback: Box<dyn FnOnce(&[u8]) -> Fallible<()> + 'a>,
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) -> Fallible<()> {
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let db_env = self.db_arc.read().unwrap();
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let db = db_env
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.open_single(db_name, rkv::store::Options::create())
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.map_err(|p| format_err!("could not open db store: {:?}", p))?;
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let reader = db_env.read().expect("could not get reader");
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let cached = db
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.get(&reader, &key)
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.map_err(|p| format_err!("could not read from db: {:?}", p))?;
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match cached {
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Some(rkv::Value::Blob(cached)) => {
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callback(cached)?;
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}
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Some(_) => Err(format_err!("Integrity: value not blob"))?,
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None => {
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drop(reader);
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if let Some(got) = runner()? {
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let mut writer = db_env.write().map_err(|p| {
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format_err!("could not open write handle to cache: {:?}", p)
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})?;
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db.put(&mut writer, &key, &rkv::Value::Blob(&got))
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.map_err(|p| format_err!("could not write to cache: {:?}", p))?;
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writer.commit()?;
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}
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}
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};
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Ok(())
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}
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}
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