foundationdb/

database.rs

// Copyright 2018 foundationdb-rs developers, https://github.com/Clikengo/foundationdb-rs/graphs/contributors
// Copyright 2013-2018 Apple, Inc and the FoundationDB project authors.
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

//! Implementations of the FDBDatabase C API
//!
//! <https://apple.github.io/foundationdb/api-c.html#database>

use std::convert::TryInto;
use std::marker::PhantomData;
use std::pin::Pin;
use std::ptr::NonNull;
use std::time::{Duration, Instant};

use fdb_sys::if_cfg_api_versions;
use foundationdb_macros::cfg_api_versions;
use foundationdb_sys as fdb_sys;

use crate::metrics::{MetricsReport, TransactionMetrics};
use crate::options;
use crate::transaction::*;
use crate::{error, FdbError, FdbResult};

use crate::error::FdbBindingError;
#[cfg_api_versions(min = 710)]
#[cfg(feature = "tenant-experimental")]
use crate::tenant::FdbTenant;
use futures::prelude::*;

/// Wrapper around the boolean representing whether the
/// previous transaction is still on fly
/// This wrapper prevents the boolean to be copy and force it
/// to be moved instead.
/// This pretty handy when you don't want to see the `Database::run` closure
/// capturing the environment.
pub struct MaybeCommitted(bool);

impl From<MaybeCommitted> for bool {
    fn from(value: MaybeCommitted) -> Self {
        value.0
    }
}

/// Represents a FoundationDB database
///
/// A mutable, lexicographically ordered mapping from binary keys to binary values.
///
/// Modifications to a database are performed via transactions.
pub struct Database {
    pub(crate) inner: NonNull<fdb_sys::FDBDatabase>,
}
unsafe impl Send for Database {}
unsafe impl Sync for Database {}
impl Drop for Database {
    fn drop(&mut self) {
        unsafe {
            fdb_sys::fdb_database_destroy(self.inner.as_ptr());
        }
    }
}

#[cfg_api_versions(min = 610)]
impl Database {
    /// Create a database for the given configuration path if any, or the default one.
    pub fn new(path: Option<&str>) -> FdbResult<Database> {
        let path_str =
            path.map(|path| std::ffi::CString::new(path).expect("path to be convertible to CStr"));
        let path_ptr = path_str
            .as_ref()
            .map(|path| path.as_ptr())
            .unwrap_or(std::ptr::null());
        let mut v: *mut fdb_sys::FDBDatabase = std::ptr::null_mut();
        let err = unsafe { fdb_sys::fdb_create_database(path_ptr, &mut v) };
        drop(path_str); // path_str own the CString that we are getting the ptr from
        error::eval(err)?;
        let ptr =
            NonNull::new(v).expect("fdb_create_database to not return null if there is no error");
        Ok(Self::new_from_pointer(ptr))
    }

    /// Create a new FDBDatabase from a raw pointer. Users are expected to use the `new` method.
    pub fn new_from_pointer(ptr: NonNull<fdb_sys::FDBDatabase>) -> Self {
        Self { inner: ptr }
    }

    /// Create a database for the given configuration path
    pub fn from_path(path: &str) -> FdbResult<Database> {
        Self::new(Some(path))
    }

    /// Create a database for the default configuration path
    #[allow(clippy::should_implement_trait)]
    pub fn default() -> FdbResult<Database> {
        Self::new(None)
    }
}

#[cfg_api_versions(min = 710)]
#[cfg(feature = "tenant-experimental")]
impl Database {
    pub fn open_tenant(&self, tenant_name: &[u8]) -> FdbResult<FdbTenant> {
        let mut ptr: *mut fdb_sys::FDB_tenant = std::ptr::null_mut();
        let err = unsafe {
            fdb_sys::fdb_database_open_tenant(
                self.inner.as_ptr(),
                tenant_name.as_ptr(),
                tenant_name.len().try_into().unwrap(),
                &mut ptr,
            )
        };
        error::eval(err)?;
        Ok(FdbTenant {
            inner: NonNull::new(ptr)
                .expect("fdb_database_open_tenant to not return null if there is no error"),
            name: tenant_name.to_owned(),
        })
    }
}

#[cfg_api_versions(min = 730)]
impl Database {
    /// Retrieve a client-side status information in a JSON format.
    pub fn get_client_status(
        &self,
    ) -> impl Future<Output = FdbResult<crate::future::FdbSlice>> + Send + Sync + Unpin {
        crate::future::FdbFuture::new(unsafe {
            fdb_sys::fdb_database_get_client_status(self.inner.as_ptr())
        })
    }
}

impl Database {
    /// Create a database for the given configuration path
    ///
    /// This is a compatibility api. If you only use API version ≥ 610 you should
    /// use `Database::new`, `Database::from_path` or  `Database::default`.
    pub async fn new_compat(path: Option<&str>) -> FdbResult<Database> {
        if_cfg_api_versions!(min = 510, max = 600 => {
            let cluster = crate::cluster::Cluster::new(path).await?;
            let database = cluster.create_database().await?;
            Ok(database)
        } else {
            Database::new(path)
        })
    }

    /// Called to set an option an on `Database`.
    pub fn set_option(&self, opt: options::DatabaseOption) -> FdbResult<()> {
        unsafe { opt.apply(self.inner.as_ptr()) }
    }

    /// Creates a new transaction on the given database.
    #[cfg_attr(feature = "trace", tracing::instrument(level = "debug", skip(self)))]
    pub fn create_trx(&self) -> FdbResult<Transaction> {
        let mut trx: *mut fdb_sys::FDBTransaction = std::ptr::null_mut();
        let err =
            unsafe { fdb_sys::fdb_database_create_transaction(self.inner.as_ptr(), &mut trx) };
        error::eval(err)?;
        Ok(Transaction::new(NonNull::new(trx).expect(
            "fdb_database_create_transaction to not return null if there is no error",
        )))
    }

    /// Creates a new transaction on the given database with metrics collection.
    ///
    /// This method is similar to `create_trx()` but additionally collects metrics about
    /// the transaction execution, including operation counts, bytes read/written, and retry counts.
    ///
    /// # Arguments
    /// * `metrics` - A TransactionMetrics instance to collect metrics
    ///
    /// # Returns
    /// * `Result<Transaction, (FdbBindingError, MetricsData)>` - A transaction with metrics collection enabled
    #[cfg_attr(feature = "trace", tracing::instrument(level = "debug", skip(self)))]
    pub fn create_instrumented_trx(
        &self,
        metrics: TransactionMetrics,
    ) -> Result<Transaction, FdbBindingError> {
        let mut trx: *mut fdb_sys::FDBTransaction = std::ptr::null_mut();
        let err =
            unsafe { fdb_sys::fdb_database_create_transaction(self.inner.as_ptr(), &mut trx) };
        error::eval(err)?;

        let inner = NonNull::new(trx)
            .expect("fdb_database_create_transaction to not return null if there is no error");
        Ok(Transaction::new_instrumented(inner, metrics))
    }

    #[cfg_attr(feature = "trace", tracing::instrument(level = "debug", skip(self)))]
    fn create_retryable_trx(&self) -> FdbResult<RetryableTransaction> {
        Ok(RetryableTransaction::new(self.create_trx()?))
    }

    /// Creates a new retryable transaction on the given database with metrics collection.
    ///
    /// This method is similar to `create_retryable_trx()` but additionally collects metrics about
    /// the transaction execution, including operation counts, bytes read/written, and retry counts.
    ///
    /// # Arguments
    /// * `metrics` - A TransactionMetrics instance to collect metrics
    ///
    /// # Returns
    /// * `Result<RetryableTransaction, (FdbBindingError, MetricsData)>` - A retryable transaction with metrics collection enabled
    #[cfg_attr(feature = "trace", tracing::instrument(level = "debug", skip(self)))]
    pub fn create_intrumented_retryable_trx(
        &self,
        metrics: TransactionMetrics,
    ) -> Result<RetryableTransaction, FdbBindingError> {
        Ok(RetryableTransaction::new(
            self.create_instrumented_trx(metrics.clone())?,
        ))
    }

    /// `transact` returns a future which retries on error. It tries to resolve a future created by
    /// caller-provided function `f` inside a retry loop, providing it with a newly created
    /// transaction. After caller-provided future resolves, the transaction will be committed
    /// automatically.
    ///
    /// # Warning
    ///
    /// It might retry indefinitely if the transaction is highly contentious. It is recommended to
    /// set `TransactionOption::RetryLimit` or `TransactionOption::SetTimeout` on the transaction
    /// if the task need to be guaranteed to finish.
    ///
    /// Once [Generic Associated Types](https://github.com/rust-lang/rfcs/blob/master/text/1598-generic_associated_types.md)
    /// lands in stable rust, the returned future of f won't need to be boxed anymore, also the
    /// lifetime limitations around f might be lowered.
    pub async fn transact<F>(&self, mut f: F, options: TransactOption) -> Result<F::Item, F::Error>
    where
        F: DatabaseTransact,
    {
        let is_idempotent = options.is_idempotent;
        let time_out = options.time_out.map(|d| Instant::now() + d);
        let retry_limit = options.retry_limit;
        let mut tries: u32 = 0;
        let mut trx = self.create_trx()?;
        let mut can_retry = move || {
            tries += 1;
            retry_limit.map(|limit| tries < limit).unwrap_or(true)
                && time_out.map(|t| Instant::now() < t).unwrap_or(true)
        };
        loop {
            let r = f.transact(trx).await;
            f = r.0;
            trx = r.1;
            trx = match r.2 {
                Ok(item) => match trx.commit().await {
                    Ok(_) => break Ok(item),
                    Err(e) => {
                        if (is_idempotent || !e.is_maybe_committed()) && can_retry() {
                            e.on_error().await?
                        } else {
                            break Err(F::Error::from(e.into()));
                        }
                    }
                },
                Err(user_err) => match user_err.try_into_fdb_error() {
                    Ok(e) => {
                        if (is_idempotent || !e.is_maybe_committed()) && can_retry() {
                            trx.on_error(e).await?
                        } else {
                            break Err(F::Error::from(e));
                        }
                    }
                    Err(user_err) => break Err(user_err),
                },
            };
        }
    }

    pub fn transact_boxed<'trx, F, D, T, E>(
        &'trx self,
        data: D,
        f: F,
        options: TransactOption,
    ) -> impl Future<Output = Result<T, E>> + Send + 'trx
    where
        for<'a> F: FnMut(
            &'a Transaction,
            &'a mut D,
        ) -> Pin<Box<dyn Future<Output = Result<T, E>> + Send + 'a>>,
        E: TransactError,
        F: Send + 'trx,
        T: Send + 'trx,
        E: Send + 'trx,
        D: Send + 'trx,
    {
        self.transact(
            boxed::FnMutBoxed {
                f,
                d: data,
                m: PhantomData,
            },
            options,
        )
    }

    pub fn transact_boxed_local<'trx, F, D, T, E>(
        &'trx self,
        data: D,
        f: F,
        options: TransactOption,
    ) -> impl Future<Output = Result<T, E>> + 'trx
    where
        for<'a> F:
            FnMut(&'a Transaction, &'a mut D) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>,
        E: TransactError,
        F: 'trx,
        T: 'trx,
        E: 'trx,
        D: 'trx,
    {
        self.transact(
            boxed_local::FnMutBoxedLocal {
                f,
                d: data,
                m: PhantomData,
            },
            options,
        )
    }

    /// Runs a transactional function against this Database with retry logic.
    /// The associated closure will be called until a non-retryable FDBError
    /// is thrown or commit(), returns success.
    ///
    /// Users are **not** expected to keep reference to the `RetryableTransaction`. If a weak or strong
    /// reference is kept by the user, the binding will throw an error.
    ///
    /// # Warning: retry
    ///
    /// It might retry indefinitely if the transaction is highly contentious. It is recommended to
    /// set [`options::TransactionOption::RetryLimit`] or [`options::TransactionOption::Timeout`] on the transaction
    /// if the task needs to be guaranteed to finish. These options can be safely set on every iteration of the closure.
    ///
    /// # Warning: Maybe committed transactions
    ///
    /// As with other client/server databases, in some failure scenarios a client may be unable to determine
    /// whether a transaction succeeded. You should make sure your closure is idempotent.
    ///
    /// The closure will notify the user in case of a maybe_committed transaction in a previous run
    ///  with the `MaybeCommitted` provided in the closure.
    ///
    /// This one can be used as boolean with
    /// ```ignore
    /// db.run(|trx, maybe_committed| async {
    ///     if maybe_committed.into() {
    ///         // Handle the problem if needed
    ///     }
    /// }).await;
    ///```
    #[cfg_attr(
        feature = "trace",
        tracing::instrument(level = "debug", skip(self, closure))
    )]
    pub async fn run<F, Fut, T>(&self, closure: F) -> Result<T, FdbBindingError>
    where
        F: Fn(RetryableTransaction, MaybeCommitted) -> Fut,
        Fut: Future<Output = Result<T, FdbBindingError>>,
    {
        let mut maybe_committed_transaction = false;
        // we just need to create the transaction once,
        // in case there is an error; it will be reset automatically
        let mut transaction = self.create_retryable_trx()?;
        #[cfg(feature = "trace")]
        let mut iteration = 0;

        loop {
            #[cfg(feature = "trace")]
            {
                iteration += 1;
            }
            // executing the closure
            let result_closure = closure(
                transaction.clone(),
                MaybeCommitted(maybe_committed_transaction),
            )
            .await;

            if let Err(e) = result_closure {
                // checks if it is an FdbError
                if let Some(e) = e.get_fdb_error() {
                    maybe_committed_transaction = e.is_maybe_committed();
                    // The closure returned an Error,
                    match transaction.on_error(e).await {
                        // we can retry the error
                        Ok(Ok(t)) => {
                            #[cfg(feature = "trace")]
                            {
                                let error_code = e.code();
                                tracing::warn!(iteration, error_code, "restarting transaction");
                            }

                            transaction = t;
                            continue;
                        }
                        Ok(Err(non_retryable_error)) => {
                            return Err(FdbBindingError::from(non_retryable_error))
                        }
                        // The only FdbBindingError that can be thrown here is `ReferenceToTransactionKept`
                        Err(non_retryable_error) => return Err(non_retryable_error),
                    }
                }
                // Otherwise, it cannot be retried
                return Err(e);
            }

            #[cfg(feature = "trace")]
            tracing::info!(iteration, "closure executed, checking result...");

            let commit_result = transaction.commit().await;

            match commit_result {
                // The only FdbBindingError that can be thrown here is `ReferenceToTransactionKept`
                Err(err) => {
                    #[cfg(feature = "trace")]
                    tracing::error!(
                        iteration,
                        "transaction reference kept, aborting transaction"
                    );
                    return Err(err);
                }
                Ok(Ok(_)) => {
                    #[cfg(feature = "trace")]
                    tracing::info!(iteration, "success, returning result");
                    return result_closure;
                }
                Ok(Err(transaction_commit_error)) => {
                    #[cfg(feature = "trace")]
                    let error_code = transaction_commit_error.code();

                    maybe_committed_transaction = transaction_commit_error.is_maybe_committed();
                    // we have an error during commit, checking if it is a retryable error
                    match transaction_commit_error.on_error().await {
                        Ok(t) => {
                            #[cfg(feature = "trace")]
                            tracing::warn!(iteration, error_code, "restarting transaction");

                            transaction = RetryableTransaction::new(t);
                            continue;
                        }
                        Err(non_retryable_error) => {
                            return Err(FdbBindingError::from(non_retryable_error))
                        }
                    }
                }
            }
        }
    }

    /// Runs a transactional function against this Database with retry logic and metrics collection.
    /// The associated closure will be called until a non-retryable FDBError
    /// is thrown or commit() returns success.
    ///
    /// This method is similar to `run()` but additionally collects and returns metrics about
    /// the transaction execution, including operation counts, bytes read/written, and retry counts.
    ///
    /// # Arguments
    /// * `closure` - A function that takes a RetryableTransaction and MaybeCommitted flag and returns a Future
    ///
    /// # Returns
    /// * `Result<(T, Metrics), (FdbBindingError, Metrics)>` - On success, returns the result of the transaction and collected metrics.
    ///   On failure, returns the error and the metrics collected up to the point of failure.
    ///
    /// # Warning: retry
    ///
    /// It might retry indefinitely if the transaction is highly contentious. It is recommended to
    /// set [`options::TransactionOption::RetryLimit`] or [`options::TransactionOption::Timeout`] on the transaction
    /// if the task needs to be guaranteed to finish.
    ///
    /// # Warning: Maybe committed transactions
    ///
    /// As with other client/server databases, in some failure scenarios a client may be unable to determine
    /// whether a transaction succeeded. The closure will be notified of a maybe_committed transaction
    /// in a previous run with the `MaybeCommitted` provided in the closure.
    #[cfg_attr(
        feature = "trace",
        tracing::instrument(level = "debug", skip(self, closure))
    )]
    pub async fn instrumented_run<F, Fut, T>(
        &self,
        closure: F,
    ) -> Result<(T, MetricsReport), (FdbBindingError, MetricsReport)>
    where
        F: Fn(RetryableTransaction, MaybeCommitted) -> Fut,
        Fut: Future<Output = Result<T, FdbBindingError>>,
    {
        let now_start = std::time::Instant::now();
        let metrics = TransactionMetrics::new();
        let mut maybe_committed_transaction = false;

        // we just need to create the transaction once,
        // in case there is a error, it will be reset automatically
        let mut transaction = match self.create_intrumented_retryable_trx(metrics.clone()) {
            Ok(trx) => trx,
            Err(err) => {
                // Update total execution time before returning
                let total_duration = now_start.elapsed().as_millis() as u64;
                metrics.set_execution_time(total_duration);
                return Err((err, metrics.get_metrics_data()));
            }
        };

        loop {
            // executing the closure
            let result_closure = closure(
                transaction.clone(),
                MaybeCommitted(maybe_committed_transaction),
            )
            .await;

            if let Err(error) = result_closure {
                if let Some(e) = error.get_fdb_error() {
                    // checks if it is an FdbError
                    maybe_committed_transaction = e.is_maybe_committed();
                    // The closure returned an Error,
                    let now_on_error = std::time::Instant::now();
                    let on_error_result = transaction.on_error(e).await;
                    let error_duration = now_on_error.elapsed().as_millis() as u64;
                    metrics.add_error_time(error_duration);

                    match on_error_result {
                        // we can retry the error
                        Ok(Ok(t)) => {
                            transaction = t;
                            // Use the original metrics instance to increment retry count
                            metrics.reset_current();
                            continue;
                        }
                        Ok(Err(non_retryable_error)) => {
                            let total_duration = now_start.elapsed().as_millis() as u64;
                            metrics.set_execution_time(total_duration);
                            return Err((
                                FdbBindingError::from(non_retryable_error),
                                metrics.get_metrics_data(),
                            ));
                        }
                        // The only FdbBindingError that can be thrown here is `ReferenceToTransactionKept`
                        Err(non_retryable_error) => {
                            let total_duration = now_start.elapsed().as_millis() as u64;
                            metrics.set_execution_time(total_duration);
                            return Err((non_retryable_error, metrics.get_metrics_data()));
                        }
                    }
                }
                // Otherwise, it cannot be retried
                let total_duration = now_start.elapsed().as_millis() as u64;
                metrics.set_execution_time(total_duration);
                return Err((error, metrics.get_metrics_data()));
            }

            let now_commit = std::time::Instant::now();
            let commit_result = transaction.commit().await;
            let commit_duration = now_commit.elapsed().as_millis() as u64;
            metrics.record_commit_time(commit_duration);

            match commit_result {
                // The only FdbBindingError that can be thrown here is `ReferenceToTransactionKept`
                Err(err) => {
                    let total_duration = now_start.elapsed().as_millis() as u64;
                    metrics.set_execution_time(total_duration);
                    return Err((err, metrics.get_metrics_data()));
                }
                Ok(Ok(committed)) => {
                    // Handle committed_version() result properly to match our tuple-based error handling
                    match committed.committed_version() {
                        Ok(version) => metrics.set_commit_version(version),
                        Err(_err) => {
                            // If we can't get the commit version, we still want to return the result
                            // but we'll log the error or handle it as needed
                            // For now, we just continue without setting the commit version
                        }
                    }

                    let total_duration = now_start.elapsed().as_millis() as u64;
                    metrics.set_execution_time(total_duration);
                    return Ok((result_closure.unwrap(), metrics.get_metrics_data()));
                }
                Ok(Err(transaction_commit_error)) => {
                    maybe_committed_transaction = transaction_commit_error.is_maybe_committed();
                    // we have an error during commit, checking if it is a retryable error
                    let now_on_error = std::time::Instant::now();
                    let on_error_result = transaction_commit_error.on_error().await;
                    let error_duration = now_on_error.elapsed().as_millis() as u64;
                    metrics.add_error_time(error_duration);

                    match on_error_result {
                        Ok(t) => {
                            transaction = RetryableTransaction::new(t);
                            // Use the original metrics instance for commit errors too
                            metrics.reset_current();
                            continue;
                        }
                        Err(non_retryable_error) => {
                            let total_duration = now_start.elapsed().as_millis() as u64;
                            metrics.set_execution_time(total_duration);
                            return Err((
                                FdbBindingError::from(non_retryable_error),
                                metrics.get_metrics_data(),
                            ));
                        }
                    }
                }
            }
        }
    }

    /// Perform a no-op against FDB to check network thread liveness. This operation will not change the underlying data
    /// in any way, nor will it perform any I/O against the FDB cluster. However, it will schedule some amount of work
    /// onto the FDB client and wait for it to complete. The FoundationDB client operates by scheduling onto an event
    /// queue that is then processed by a single thread (the "network thread"). This method can be used to determine if
    /// the network thread has entered a state where it is no longer processing requests or if its time to process
    /// requests has increased. If the network thread is busy, this operation may take some amount of time to complete,
    /// which is why this operation returns a future.
    pub async fn perform_no_op(&self) -> FdbResult<()> {
        let trx = self.create_trx()?;

        // Set the read version of the transaction, then read it back. This requires no I/O, but it does
        // require the network thread be running. The exact value used for the read version is unimportant.
        trx.set_read_version(42);
        trx.get_read_version().await?;
        Ok(())
    }

    /// Returns a value where 0 indicates that the client is idle and 1 (or larger) indicates that the client is saturated.
    /// By default, this value is updated every second.
    #[cfg_api_versions(min = 710)]
    pub async fn get_main_thread_busyness(&self) -> FdbResult<f64> {
        let busyness =
            unsafe { fdb_sys::fdb_database_get_main_thread_busyness(self.inner.as_ptr()) };
        Ok(busyness)
    }
}
pub trait DatabaseTransact: Sized {
    type Item;
    type Error: TransactError;
    type Future: Future<Output = (Self, Transaction, Result<Self::Item, Self::Error>)>;
    fn transact(self, trx: Transaction) -> Self::Future;
}

#[allow(clippy::needless_lifetimes)]
#[allow(clippy::type_complexity)]
mod boxed {
    use super::*;

    async fn boxed_data_fut<'t, F, T, E, D>(
        mut f: FnMutBoxed<'t, F, D>,
        trx: Transaction,
    ) -> (FnMutBoxed<'t, F, D>, Transaction, Result<T, E>)
    where
        F: for<'a> FnMut(
            &'a Transaction,
            &'a mut D,
        ) -> Pin<Box<dyn Future<Output = Result<T, E>> + Send + 'a>>,
        E: TransactError,
    {
        let r = (f.f)(&trx, &mut f.d).await;
        (f, trx, r)
    }

    pub struct FnMutBoxed<'t, F, D> {
        pub f: F,
        pub d: D,
        pub m: PhantomData<&'t ()>,
    }
    impl<'t, F, T, E, D> DatabaseTransact for FnMutBoxed<'t, F, D>
    where
        F: for<'a> FnMut(
            &'a Transaction,
            &'a mut D,
        ) -> Pin<Box<dyn Future<Output = Result<T, E>> + Send + 'a>>,
        F: 't + Send,
        T: 't,
        E: 't,
        D: 't + Send,
        E: TransactError,
    {
        type Item = T;
        type Error = E;
        type Future = Pin<
            Box<
                dyn Future<Output = (Self, Transaction, Result<Self::Item, Self::Error>)>
                    + Send
                    + 't,
            >,
        >;

        fn transact(self, trx: Transaction) -> Self::Future {
            boxed_data_fut(self, trx).boxed()
        }
    }
}

#[allow(clippy::needless_lifetimes)]
#[allow(clippy::type_complexity)]
mod boxed_local {
    use super::*;

    async fn boxed_local_data_fut<'t, F, T, E, D>(
        mut f: FnMutBoxedLocal<'t, F, D>,
        trx: Transaction,
    ) -> (FnMutBoxedLocal<'t, F, D>, Transaction, Result<T, E>)
    where
        F: for<'a> FnMut(
            &'a Transaction,
            &'a mut D,
        ) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>,
        E: TransactError,
    {
        let r = (f.f)(&trx, &mut f.d).await;
        (f, trx, r)
    }

    pub struct FnMutBoxedLocal<'t, F, D> {
        pub f: F,
        pub d: D,
        pub m: PhantomData<&'t ()>,
    }
    impl<'t, F, T, E, D> DatabaseTransact for FnMutBoxedLocal<'t, F, D>
    where
        F: for<'a> FnMut(
            &'a Transaction,
            &'a mut D,
        ) -> Pin<Box<dyn Future<Output = Result<T, E>> + 'a>>,
        F: 't,
        T: 't,
        E: 't,
        D: 't,
        E: TransactError,
    {
        type Item = T;
        type Error = E;
        type Future = Pin<
            Box<dyn Future<Output = (Self, Transaction, Result<Self::Item, Self::Error>)> + 't>,
        >;

        fn transact(self, trx: Transaction) -> Self::Future {
            boxed_local_data_fut(self, trx).boxed_local()
        }
    }
}

/// A trait that must be implemented to use `Database::transact` this application error types.
pub trait TransactError: From<FdbError> {
    fn try_into_fdb_error(self) -> Result<FdbError, Self>;
}
impl<T> TransactError for T
where
    T: From<FdbError> + TryInto<FdbError, Error = T>,
{
    fn try_into_fdb_error(self) -> Result<FdbError, Self> {
        self.try_into()
    }
}
impl TransactError for FdbError {
    fn try_into_fdb_error(self) -> Result<FdbError, Self> {
        Ok(self)
    }
}

/// A set of options that controls the behavior of `Database::transact`.
#[derive(Default, Clone)]
pub struct TransactOption {
    pub retry_limit: Option<u32>,
    pub time_out: Option<Duration>,
    pub is_idempotent: bool,
}

impl TransactOption {
    /// An idempotent TransactOption
    pub fn idempotent() -> Self {
        Self {
            is_idempotent: true,
            ..TransactOption::default()
        }
    }
}