Struct mongodb::ClientSession

pub struct ClientSession { /* fields omitted */ }

A MongoDB client session. This struct represents a logical session used for ordering sequential operations. To create a ClientSession, call start_session on a Client.

ClientSession instances are not thread safe or fork safe. They can only be used by one thread or process at a time.

Transactions

Transactions are used to execute a series of operations across multiple documents and collections atomically. For more information about when and how to use transactions in MongoDB, see the manual.

Replica set transactions are supported on MongoDB 4.0+. Transactions are associated with a ClientSession. To begin a transaction, call ClientSession::start_transaction on a ClientSession. The ClientSession must be passed to operations to be executed within the transaction.

use mongodb::{
    bson::{doc, Document},
    error::{Result, TRANSIENT_TRANSACTION_ERROR, UNKNOWN_TRANSACTION_COMMIT_RESULT},
    options::{Acknowledgment, ReadConcern, TransactionOptions, WriteConcern},
    ClientSession,
    Collection,
};

let mut session = client.start_session(None).await?;
let options = TransactionOptions::builder()
    .read_concern(ReadConcern::majority())
    .write_concern(WriteConcern::builder().w(Acknowledgment::Majority).build())
    .build();
session.start_transaction(options).await?;
// A "TransientTransactionError" label indicates that the entire transaction can be retried
// with a reasonable expectation that it will succeed.
while let Err(error) = execute_transaction(&coll, &mut session).await {
    if !error.contains_label(TRANSIENT_TRANSACTION_ERROR) {
        break;
    }
}

async fn execute_transaction(coll: &Collection<Document>, session: &mut ClientSession) -> Result<()> {
    coll.insert_one_with_session(doc! { "x": 1 }, None, session).await?;
    coll.delete_one_with_session(doc! { "y": 2 }, None, session).await?;
    // An "UnknownTransactionCommitResult" label indicates that it is unknown whether the
    // commit has satisfied the write concern associated with the transaction. If an error
    // with this label is returned, it is safe to retry the commit until the write concern is
    // satisfied or an error without the label is returned.
    loop {
        let result = session.commit_transaction().await;
        if let Err(ref error) = result {
            if error.contains_label(UNKNOWN_TRANSACTION_COMMIT_RESULT) {
                continue;
            }
        }
        result?
    }
}

Note: the driver does not currently support transactions on sharded clusters.

Implementations

impl ClientSession

pub fn client(&self) -> Client

The client used to create this session.

pub fn id(&self) -> &Document

The id of this session.

pub fn cluster_time(&self) -> Option<&ClusterTime>

The highest seen cluster time this session has seen so far. This will be None if this session has not been used in an operation yet.

pub fn options(&self) -> Option<&SessionOptions>

The options used to create this session.

pub fn advance_cluster_time(&mut self, to: &ClusterTime)

Set the cluster time to the provided one if it is greater than this session’s highest seen cluster time or if this session’s cluster time is None.

pub async fn start_transaction(
    &mut self,
    options: impl Into<Option<TransactionOptions>>
) -> Result<()>

Starts a new transaction on this session with the given TransactionOptions. If no options are provided, the session’s defaultTransactionOptions will be used. This session must be passed into each operation within the transaction; otherwise, the operation will be executed outside of the transaction.

Errors returned from operations executed within a transaction may include a crate::error::TRANSIENT_TRANSACTION_ERROR label. This label indicates that the entire transaction can be retried with a reasonable expectation that it will succeed.

Transactions are supported on MongoDB 4.0+. The Rust driver currently only supports transactions on replica sets.

session.start_transaction(None).await?;
let result = coll.insert_one_with_session(doc! { "x": 1 }, None, &mut session).await?;
session.commit_transaction().await?;

pub async fn commit_transaction(&mut self) -> Result<()>

Commits the transaction that is currently active on this session.

This method may return an error with a crate::error::UNKNOWN_TRANSACTION_COMMIT_RESULT label. This label indicates that it is unknown whether the commit has satisfied the write concern associated with the transaction. If an error with this label is returned, it is safe to retry the commit until the write concern is satisfied or an error without the label is returned.

session.start_transaction(None).await?;
let result = coll.insert_one_with_session(doc! { "x": 1 }, None, &mut session).await?;
session.commit_transaction().await?;

This operation will retry once upon failure if the connection and encountered error support retryability. See the documentation here for more information on retryable writes.

pub async fn abort_transaction(&mut self) -> Result<()>

Aborts the transaction that is currently active on this session. Any open transaction will be aborted automatically in the Drop implementation of ClientSession.

session.start_transaction(None).await?;
match execute_transaction(&coll, &mut session).await {
    Ok(_) => session.commit_transaction().await?,
    Err(_) => session.abort_transaction().await?,
}

async fn execute_transaction(coll: &Collection<Document>, session: &mut ClientSession) -> Result<()> {
    coll.insert_one_with_session(doc! { "x": 1 }, None, session).await?;
    coll.delete_one_with_session(doc! { "y": 2 }, None, session).await?;
    Ok(())
}

This operation will retry once upon failure if the connection and encountered error support retryability. See the documentation here for more information on retryable writes.

Trait Implementations

impl Clone for ClientSession

fn clone(&self) -> ClientSession

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ClientSession

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for ClientSession

fn drop(&mut self)

Executes the destructor for this type.

impl From<ClientSession> for ClientSession

This is supported on crate feature sync only.

fn from(async_client_session: AsyncClientSession) -> Self

Performs the conversion.