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use crate::directory::directory_lock::Lock;
use crate::directory::error::LockError;
use crate::directory::error::{DeleteError, OpenReadError, OpenWriteError};
use crate::directory::WatchHandle;
use crate::directory::{FileHandle, WatchCallback};
use crate::directory::{FileSlice, WritePtr};
use std::fmt;
use std::io;
use std::io::Write;
use std::marker::Send;
use std::marker::Sync;
use std::path::Path;
use std::path::PathBuf;
use std::thread;
use std::time::Duration;
/// Retry the logic of acquiring locks is pretty simple.
/// We just retry `n` times after a given `duratio`, both
/// depending on the type of lock.
struct RetryPolicy {
num_retries: usize,
wait_in_ms: u64,
}
impl RetryPolicy {
fn no_retry() -> RetryPolicy {
RetryPolicy {
num_retries: 0,
wait_in_ms: 0,
}
}
fn wait_and_retry(&mut self) -> bool {
if self.num_retries == 0 {
false
} else {
self.num_retries -= 1;
let wait_duration = Duration::from_millis(self.wait_in_ms);
thread::sleep(wait_duration);
true
}
}
}
/// The `DirectoryLock` is an object that represents a file lock.
/// See [`LockType`](struct.LockType.html)
///
/// It is transparently associated to a lock file, that gets deleted
/// on `Drop.` The lock is released automatically on `Drop`.
pub struct DirectoryLock(Box<dyn Send + Sync + 'static>);
struct DirectoryLockGuard {
directory: Box<dyn Directory>,
path: PathBuf,
}
impl<T: Send + Sync + 'static> From<Box<T>> for DirectoryLock {
fn from(underlying: Box<T>) -> Self {
DirectoryLock(underlying)
}
}
impl Drop for DirectoryLockGuard {
fn drop(&mut self) {
if let Err(e) = self.directory.delete(&*self.path) {
error!("Failed to remove the lock file. {:?}", e);
}
}
}
enum TryAcquireLockError {
FileExists,
IoError(io::Error),
}
fn try_acquire_lock(
filepath: &Path,
directory: &mut dyn Directory,
) -> Result<DirectoryLock, TryAcquireLockError> {
let mut write = directory.open_write(filepath).map_err(|e| match e {
OpenWriteError::FileAlreadyExists(_) => TryAcquireLockError::FileExists,
OpenWriteError::IoError { io_error, .. } => TryAcquireLockError::IoError(io_error),
})?;
write.flush().map_err(TryAcquireLockError::IoError)?;
Ok(DirectoryLock::from(Box::new(DirectoryLockGuard {
directory: directory.box_clone(),
path: filepath.to_owned(),
})))
}
fn retry_policy(is_blocking: bool) -> RetryPolicy {
if is_blocking {
RetryPolicy {
num_retries: 100,
wait_in_ms: 100,
}
} else {
RetryPolicy::no_retry()
}
}
/// Write-once read many (WORM) abstraction for where
/// tantivy's data should be stored.
///
/// There are currently two implementations of `Directory`
///
/// - The [`MMapDirectory`](struct.MmapDirectory.html), this
/// should be your default choice.
/// - The [`RamDirectory`](struct.RamDirectory.html), which
/// should be used mostly for tests.
pub trait Directory: DirectoryClone + fmt::Debug + Send + Sync + 'static {
/// Opens a file and returns a boxed `FileHandle`.
///
/// Users of `Directory` should typically call `Directory::open_read(...)`,
/// while `Directory` implementor should implement `get_file_handle()`.
fn get_file_handle(&self, path: &Path) -> Result<Box<dyn FileHandle>, OpenReadError>;
/// Once a virtual file is open, its data may not
/// change.
///
/// Specifically, subsequent writes or flushes should
/// have no effect on the returned `FileSlice` object.
///
/// You should only use this to read files create with [Directory::open_write].
fn open_read(&self, path: &Path) -> Result<FileSlice, OpenReadError> {
let file_handle = self.get_file_handle(path)?;
Ok(FileSlice::new(file_handle))
}
/// Removes a file
///
/// Removing a file will not affect an eventual
/// existing FileSlice pointing to it.
///
/// Removing a nonexistent file, yields a
/// `DeleteError::DoesNotExist`.
fn delete(&self, path: &Path) -> Result<(), DeleteError>;
/// Returns true iff the file exists
fn exists(&self, path: &Path) -> Result<bool, OpenReadError>;
/// Opens a writer for the *virtual file* associated with
/// a Path.
///
/// Right after this call, the file should be created
/// and any subsequent call to `open_read` for the
/// same path should return a `FileSlice`.
///
/// Write operations may be aggressively buffered.
/// The client of this trait is responsible for calling flush
/// to ensure that subsequent `read` operations
/// will take into account preceding `write` operations.
///
/// Flush operation should also be persistent.
///
/// The user shall not rely on `Drop` triggering `flush`.
/// Note that `RamDirectory` will panic! if `flush`
/// was not called.
///
/// The file may not previously exist.
fn open_write(&self, path: &Path) -> Result<WritePtr, OpenWriteError>;
/// Reads the full content file that has been written using
/// atomic_write.
///
/// This should only be used for small files.
///
/// You should only use this to read files create with [Directory::atomic_write].
fn atomic_read(&self, path: &Path) -> Result<Vec<u8>, OpenReadError>;
/// Atomically replace the content of a file with data.
///
/// This calls ensure that reads can never *observe*
/// a partially written file.
///
/// The file may or may not previously exist.
fn atomic_write(&self, path: &Path, data: &[u8]) -> io::Result<()>;
/// Acquire a lock in the given directory.
///
/// The method is blocking or not depending on the `Lock` object.
fn acquire_lock(&self, lock: &Lock) -> Result<DirectoryLock, LockError> {
let mut box_directory = self.box_clone();
let mut retry_policy = retry_policy(lock.is_blocking);
loop {
match try_acquire_lock(&lock.filepath, &mut *box_directory) {
Ok(result) => {
return Ok(result);
}
Err(TryAcquireLockError::FileExists) => {
if !retry_policy.wait_and_retry() {
return Err(LockError::LockBusy);
}
}
Err(TryAcquireLockError::IoError(io_error)) => {
return Err(LockError::IoError(io_error));
}
}
}
}
/// Registers a callback that will be called whenever a change on the `meta.json`
/// using the `atomic_write` API is detected.
///
/// The behavior when using `.watch()` on a file using [Directory::open_write] is, on the other
/// hand, undefined.
///
/// The file will be watched for the lifetime of the returned `WatchHandle`. The caller is
/// required to keep it.
/// It does not override previous callbacks. When the file is modified, all callback that are
/// registered (and whose `WatchHandle` is still alive) are triggered.
///
/// Internally, tantivy only uses this API to detect new commits to implement the
/// `OnCommit` `ReloadPolicy`. Not implementing watch in a `Directory` only prevents the
/// `OnCommit` `ReloadPolicy` to work properly.
fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle>;
}
/// DirectoryClone
pub trait DirectoryClone {
/// Clones the directory and boxes the clone
fn box_clone(&self) -> Box<dyn Directory>;
}
impl<T> DirectoryClone for T
where
T: 'static + Directory + Clone,
{
fn box_clone(&self) -> Box<dyn Directory> {
Box::new(self.clone())
}
}