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MongoDB::ClientSession(3pm) User Contributed Perl Documentation MongoDB::ClientSession(3pm)
NAME
MongoDB::ClientSession - MongoDB session and transaction management
VERSION
version v2.2.2
SYNOPSIS
my $session = $client->start_session( $options );
# use session in operations
my $result = $collection->find( { id => 1 }, { session => $session } );
# use sessions for transactions
$session->start_transaction;
...
if ( $ok ) {
$session->commit_transaction;
}
else {
$session->abort_transaction;
}
DESCRIPTION
This class encapsulates an active session for use with the current client. Sessions
support is new with MongoDB 3.6, and can be used in replica set and sharded MongoDB
clusters.
Explicit and Implicit Sessions
If you specifically apply a session to an operation, then the operation will be performed
with that session id. If you do not provide a session for an operation, and the server
supports sessions, then an implicit session will be created and used for this operation.
The only exception to this is for unacknowledged writes - the driver will not provide an
implicit session for this, and if you provide a session then the driver will raise an
error.
Cursors
During cursors, if a session is not provided then an implicit session will be created
which is then used for the lifetime of the cursor. If you provide a session, then note
that ending the session and then continuing to use the cursor will raise an error.
Thread Safety
NOTE: Per threads documentation, use of Perl threads is discouraged by the maintainers of
Perl and the MongoDB Perl driver does not test or provide support for use with threads.
Sessions are NOT thread safe, and should only be used by one thread at a time. Using a
session across multiple threads is unsupported and unexpected issues and errors may occur.
Note that the driver does not check for multi-threaded use.
Transactions
A session may be associated with at most one open transaction (on MongoDB 4.0+). For
detailed instructions on how to use transactions with drivers, see the MongoDB manual
page: Transactions <https://docs.mongodb.com/master/core/transactions>.
ATTRIBUTES
client
The client this session was created using. Sessions may only be used with the client that
created them.
cluster_time
Stores the last received $clusterTime for the client session. This is an opaque value, to
set it use the advance_cluster_time function.
options
Options provided for this particular session. Available options include:
o "causalConsistency" - If true, will enable causalConsistency for this session. For
more information, see MongoDB documentation on Causal Consistency
<https://docs.mongodb.com/manual/core/read-isolation-consistency-recency/#causal-
consistency>. Note that causalConsistency does not apply for unacknowledged writes.
Defaults to true.
o "defaultTransactionOptions" - Options to use by default for transactions created with
this session. If when creating a transaction, none or only some of the transaction
options are defined, these options will be used as a fallback. Defaults to inheriting
from the parent client. See "start_transaction" for available options.
operation_time
The last operation time. This is updated when an operation is performed during this
session, or when "advance_operation_time" is called. Used for causal consistency.
METHODS
session_id
The session id for this particular session. This should be considered an opaque value.
If "end_session" has been called, this returns "undef".
get_latest_cluster_time
my $cluster_time = $session->get_latest_cluster_time;
Returns the latest cluster time, when compared with this session's recorded cluster time
and the main client cluster time. If neither is defined, returns undef.
advance_cluster_time
$session->advance_cluster_time( $cluster_time );
Update the $clusterTime for this session. Stores the value in "cluster_time". If the
cluster time provided is more recent than the sessions current cluster time, then the
session will be updated to this provided value.
Setting the $clusterTime with a manually crafted value may cause a server error. It is
recommended to only use $clusterTime values retrieved from database calls.
advance_operation_time
$session->advance_operation_time( $operation_time );
Update the "operation_time" for this session. If the value provided is more recent than
the sessions current operation time, then the session will be updated to this provided
value.
Setting "operation_time" with a manually crafted value may cause a server error. It is
recommended to only use an "operation_time" retrieved from another session or directly
from a database call.
start_transaction
$session->start_transaction;
$session->start_transaction( $options );
Start a transaction in this session. If a transaction is already in progress or if the
driver can detect that the client is connected to a topology that does not support
transactions, this method will throw an error.
A hash reference of options may be provided. Valid keys include:
o "readConcern" - The read concern to use for the first command in this transaction. If
not defined here or in the "defaultTransactionOptions" in "options", will inherit from
the parent client.
o "writeConcern" - The write concern to use for committing or aborting this transaction.
As per "readConcern", if not defined here then the value defined in
"defaultTransactionOptions" will be used, or the parent client if not defined.
o "readPreference" - The read preference to use for all read operations in this
transaction. If not defined, then will inherit from "defaultTransactionOptions" or
from the parent client. This value will override all other read preferences set in any
subsequent commands inside this transaction.
o "maxCommitTimeMS" - The "maxCommitTimeMS" specifies a cumulative time limit in
milliseconds for processing operations on the cursor. MongoDB interrupts the operation
at the earliest following interrupt point.
commit_transaction
$session->commit_transaction;
Commit the current transaction. This will use the writeConcern set on this transaction.
If called when no transaction is in progress, then this method will throw an error.
If the commit operation encounters an error, an error is thrown. If the error is a
transient commit error, the error object will have a label containing
"UnknownTransactionCommitResult" as an element and the commit operation can be retried.
This can be checked via the "has_error_label":
LOOP: {
eval {
$session->commit_transaction;
};
if ( my $error = $@ ) {
if ( $error->has_error_label("UnknownTransactionCommitResult") ) {
redo LOOP;
}
else {
die $error;
}
}
}
abort_transaction
$session->abort_transaction;
Aborts the current transaction. If no transaction is in progress, then this method will
throw an error. Otherwise, this method will suppress all other errors (including network
and database errors).
end_session
$session->end_session;
Close this particular session and release the session ID for reuse or recycling. If a
transaction is in progress, it will be aborted. Has no effect after calling for the first
time.
This will be called automatically by the object destructor.
with_transaction
$session->with_transaction($callback, $options);
Execute a callback in a transaction.
This method starts a transaction on this session, executes $callback, and then commits the
transaction, returning the return value of the $callback. The $callback will be executed
at least once.
If the $callback throws an error, the transaction will be aborted. If less than 120
seconds have passed since calling "with_transaction", and the error has a
"TransientTransactionError" label, the transaction will be restarted and the callback will
be executed again. Otherwise, the error will be thrown.
If the $callback succeeds, then the transaction will be committed. If an error is thrown
from committing the transaction, and it is less than 120 seconds since calling
"with_transaction", then:
o If the error has a "TransientTransactionError" label, the transaction will be
restarted.
o If the error has an "UnknownTransactionCommitResult" label, and is not a
"MaxTimeMSExpired" error, then the commit will be retried.
If the $callback aborts or commits the transaction, no other actions are taken and the
return value of the $callback is returned.
The callback is called with the first (and only) argument being the session, after
starting the transaction:
$session->with_transaction( sub {
# this is the same session as used for with_transaction
my $cb_session = shift;
...
}, $options);
To pass arbitrary arguments to the $callback, wrap your callback in a coderef:
$session->with_transaction(sub { $callback->($session, $foo, ...) }, $options);
Warning: you must either use the provided session within the callback, or otherwise pass
the session in use to the callback. You must pass the $session as an option to all
database operations that need to be included in the transaction.
Warning: The $callback can be called multiple times, so it is recommended to make it
idempotent.
A hash reference of options may be provided. these are the same as for
"start_transaction".
AUTHORS
o David Golden <david AT mongodb.com>
o Rassi <rassi AT mongodb.com>
o Mike Friedman <friedo AT friedo.com>
o Kristina Chodorow <k.chodorow AT gmail.com>
o Florian Ragwitz <rafl AT debian.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2020 by MongoDB, Inc.
This is free software, licensed under:
The Apache License, Version 2.0, January 2004
perl v5.30.3 2020-08-15 MongoDB::ClientSession(3pm)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2025-12-22 05:34 @216.73.216.1 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)