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// Copyright 2018-2019 Mozilla
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
// this file except in compliance with the License. You may obtain a copy of the
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
use std::{
collections::{btree_map::Entry, BTreeMap},
os::raw::c_uint,
path::{Path, PathBuf},
result,
sync::{Arc, RwLock},
};
use lazy_static::lazy_static;
#[cfg(feature = "lmdb")]
use crate::backend::LmdbEnvironment;
use crate::{
backend::{BackendEnvironment, BackendEnvironmentBuilder, SafeModeEnvironment},
error::{CloseError, StoreError},
helpers::canonicalize_path,
store::CloseOptions,
Rkv,
};
type Result<T> = result::Result<T, StoreError>;
type CloseResult<T> = result::Result<T, CloseError>;
type SharedRkv<E> = Arc<RwLock<Rkv<E>>>;
#[cfg(feature = "lmdb")]
lazy_static! {
static ref MANAGER_LMDB: RwLock<Manager<LmdbEnvironment>> = RwLock::new(Manager::new());
}
lazy_static! {
static ref MANAGER_SAFE_MODE: RwLock<Manager<SafeModeEnvironment>> =
RwLock::new(Manager::new());
}
/// A process is only permitted to have one open handle to each Rkv environment. This
/// manager exists to enforce that constraint: don't open environments directly.
///
/// By default, path canonicalization is enabled for identifying RKV instances. This
/// is true by default, because it helps enforce the constraints guaranteed by
/// this manager. However, path canonicalization might crash in some fringe
/// circumstances, so the `no-canonicalize-path` feature offers the possibility of
///
/// When path canonicalization is disabled, you *must* ensure an RKV environment is
/// always created or retrieved with the same path.
pub struct Manager<E> {
environments: BTreeMap<PathBuf, SharedRkv<E>>,
}
impl<'e, E> Manager<E>
where
E: BackendEnvironment<'e>,
{
fn new() -> Manager<E> {
Manager {
environments: Default::default(),
}
}
/// Return the open env at `path`, returning `None` if it has not already been opened.
pub fn get<'p, P>(&self, path: P) -> Result<Option<SharedRkv<E>>>
where
P: Into<&'p Path>,
{
let canonical = if cfg!(feature = "no-canonicalize-path") {
path.into().to_path_buf()
} else {
canonicalize_path(path)?
};
Ok(self.environments.get(&canonical).cloned())
}
/// Return the open env at `path`, or create it by calling `f`.
pub fn get_or_create<'p, F, P>(&mut self, path: P, f: F) -> Result<SharedRkv<E>>
where
F: FnOnce(&Path) -> Result<Rkv<E>>,
P: Into<&'p Path>,
{
let canonical = if cfg!(feature = "no-canonicalize-path") {
path.into().to_path_buf()
} else {
canonicalize_path(path)?
};
Ok(match self.environments.entry(canonical) {
Entry::Occupied(e) => e.get().clone(),
Entry::Vacant(e) => {
let k = Arc::new(RwLock::new(f(e.key().as_path())?));
e.insert(k).clone()
}
})
}
/// Return the open env at `path` with `capacity`, or create it by calling `f`.
pub fn get_or_create_with_capacity<'p, F, P>(
&mut self,
path: P,
capacity: c_uint,
f: F,
) -> Result<SharedRkv<E>>
where
F: FnOnce(&Path, c_uint) -> Result<Rkv<E>>,
P: Into<&'p Path>,
{
let canonical = if cfg!(feature = "no-canonicalize-path") {
path.into().to_path_buf()
} else {
canonicalize_path(path)?
};
Ok(match self.environments.entry(canonical) {
Entry::Occupied(e) => e.get().clone(),
Entry::Vacant(e) => {
let k = Arc::new(RwLock::new(f(e.key().as_path(), capacity)?));
e.insert(k).clone()
}
})
}
/// Return a new Rkv environment from the builder, or create it by calling `f`.
pub fn get_or_create_from_builder<'p, F, P, B>(
&mut self,
path: P,
builder: B,
f: F,
) -> Result<SharedRkv<E>>
where
F: FnOnce(&Path, B) -> Result<Rkv<E>>,
P: Into<&'p Path>,
B: BackendEnvironmentBuilder<'e, Environment = E>,
{
let canonical = if cfg!(feature = "no-canonicalize-path") {
path.into().to_path_buf()
} else {
canonicalize_path(path)?
};
Ok(match self.environments.entry(canonical) {
Entry::Occupied(e) => e.get().clone(),
Entry::Vacant(e) => {
let k = Arc::new(RwLock::new(f(e.key().as_path(), builder)?));
e.insert(k).clone()
}
})
}
/// Tries to close the specified environment.
/// Returns an error when other users of this environment still exist.
pub fn try_close<'p, P>(&mut self, path: P, options: CloseOptions) -> CloseResult<()>
where
P: Into<&'p Path>,
{
let canonical = if cfg!(feature = "no-canonicalize-path") {
path.into().to_path_buf()
} else {
canonicalize_path(path)?
};
match self.environments.entry(canonical) {
Entry::Vacant(_) => Ok(()),
Entry::Occupied(e) if Arc::strong_count(e.get()) > 1 => {
Err(CloseError::EnvironmentStillOpen)
}
Entry::Occupied(e) => {
let env = Arc::try_unwrap(e.remove())
.map_err(|_| CloseError::UnknownEnvironmentStillOpen)?;
env.into_inner()?.close(options)?;
Ok(())
}
}
}
}
#[cfg(feature = "lmdb")]
impl Manager<LmdbEnvironment> {
pub fn singleton() -> &'static RwLock<Manager<LmdbEnvironment>> {
&MANAGER_LMDB
}
}
impl Manager<SafeModeEnvironment> {
pub fn singleton() -> &'static RwLock<Manager<SafeModeEnvironment>> {
&MANAGER_SAFE_MODE
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::*;
use std::fs;
use tempfile::Builder;
#[cfg(feature = "lmdb")]
use backend::Lmdb;
/// Test that one can mutate managed Rkv instances in surprising ways.
#[cfg(feature = "lmdb")]
#[test]
fn test_mutate_managed_rkv() {
let mut manager = Manager::<LmdbEnvironment>::new();
let root1 = Builder::new()
.prefix("test_mutate_managed_rkv_1")
.tempdir()
.expect("tempdir");
fs::create_dir_all(root1.path()).expect("dir created");
let path1 = root1.path();
let arc = manager
.get_or_create(path1, Rkv::new::<Lmdb>)
.expect("created");
// Arc<RwLock<>> has interior mutability, so we can replace arc's Rkv instance with a new
// instance that has a different path.
let root2 = Builder::new()
.prefix("test_mutate_managed_rkv_2")
.tempdir()
.expect("tempdir");
fs::create_dir_all(root2.path()).expect("dir created");
let path2 = root2.path();
{
let mut rkv = arc.write().expect("guard");
let rkv2 = Rkv::new::<Lmdb>(path2).expect("Rkv");
*rkv = rkv2;
}
// Arc now has a different internal Rkv with path2, but it's still mapped to path1 in
// manager, so its pointer is equal to a new Arc for path1.
let path1_arc = manager.get(path1).expect("success").expect("existed");
assert!(Arc::ptr_eq(&path1_arc, &arc));
// Meanwhile, a new Arc for path2 has a different pointer, even though its Rkv's path is
// the same as arc's current path.
let path2_arc = manager
.get_or_create(path2, Rkv::new::<Lmdb>)
.expect("success");
assert!(!Arc::ptr_eq(&path2_arc, &arc));
}
}