Release Notes for MongoDB 4.0
On this page
- Patch Releases
- Multi-Document Transactions
- Aggregation
- MongoDB Drivers
- Security
- Deprecate MMAPv1
- Replica Set
- Change Streams
- Free Monitoring
- Sharded Clusters
.msi
Installer on Windows- Platform Support
- MongoDB Tools
- General Improvements
- Changes Affecting Compatibility
- Upgrade Procedures
- Download
- Known Issues in 4.0.3
- Known Issues in 4.0.2
- Known Issues in 4.0.1
- Known Issues in 4.0.0
- Report an Issue
Patch Releases
4.0.28 - January 31, 2022
Issues fixed:
SERVER-62065 Upgrade path from 3.6 to 4.0 can leave chunk entries without history on the shards
SERVER-55648 Mongos doesn't return top-level batch-write error in case of shutdown
SERVER-54064 Sessions on arbiters accumulate and cannot be cleared out
SERVER-53335 Queries, updates, and deletes with non-"simple" collations may miss documents when using hashed sharding
SERVER-45953 Exempt oplog readers from acquiring read tickets
4.0.27 - Sep 13, 2021
Issues fixed:
SERVER-59074 Do not acquire storage tickets just to set/wait on oplog visibility
SERVER-56516 Fix undefined behavior in parsing code for $slice projectional operator
SERVER-54729 MongoDB Enterprise Debian/Ubuntu packages should depend on libsasl2-modules and libsasl2-modules-gssapi-mit
SERVER-40712 Clarify the behavior of db.dropDatabase and the dropDatabase command
SERVER-34938 Secondary slowdown or hang due to content pinned in cache by single oplog batch
4.0.26 - Jul 23, 2021
Issues fixed:
SERVER-57064 Log create index and dropIndex(es) on mongos
SERVER-56779 Do not use the collection distributed lock for chunk merges
SERVER-56452 Self anchor in PooledLDAPConnection::setup's callback
SERVER-56240 Turn on checkpointing for the keystore Data Store
SERVER-56054 Change minThreads value for replication writer thread pool to 0
4.0.25 - Jun 10, 2021
Issues fixed:
SERVER-57102 Fixing invariants on ShardServerCatalogCacheLoader to consider different terms
SERVER-56854 Provide the ability for RSM requests to timeout and mark the server as failed
SERVER-56217 PoolForHost::_maxInUse is init to <int>::max and cannot be changed, and when connections are maxed DBConnectionPool::get() always throws
SERVER-47699 Change yield type used by range deleter from YIELD_MANUAL to YIELD_AUTO
4.0.24 - Apr 20, 2021
Issues fixed:
SERVER-54710 Large number of $or clauses can create profiling entry exceeding max BSON size, causing the query to fail when it should not
SERVER-54136 Make the authenticate command respect enforceUserClusterSeparation
SERVER-53566 Investigate and reproduce "opCtx != nullptr && _opCtx == nullptr" invariant
SERVER-45836 Provide more LDAP details (like server IP) at default log level
SERVER-35649 Nodes removed due to isSelf failure should re-attempt to find themselves
WT-7028 Sweep thread shouldn't lock during checkpoint gathering handles
4.0.23 - Feb 22, 2021
Issues fixed:
SERVER-40361 Reduce memory footprint of plan cache entries
SERVER-46740 establishCursors() must always drain the AsyncRequestsSender::_baton
SERVER-46876 During the eviction pressure, we should quit the compact operation instead of crashing the process
SERVER-50305 ARS::next() does not respect OperationContext deadline
SERVER-52879 Periodic operation latency spikes every 5 minutes due to closing idle cached WT sessions
4.0.22 - Jan 4, 2021
Issues fixed:
SERVER-48523 Unconditionally check the first entry in the oplog when attempting to resume a change stream
SERVER-50365 Stuck with long-running transactions that can't be timed out
SERVER-51303 Lookup stage followed by $match on type uses wrong field in matching condition
SERVER-52654 new signing keys not generated by the monitoring-keys-for-HMAC thread
SERVER-52955 KeysCollectionClientDirect should check if majority read concern is supported by storage engine
4.0.21 - Nov 10, 2020
Issues fixed:
SERVER-26726 Check number of arguments for createIndex() and throw error if more than two arguments
SERVER-40317 $facet execution has no limit on how much memory it can consume
SERVER-43233 Add ability to request only specific attribute(s) for the LDAP groups
SERVER-45803 mongodecrypt needs a ServiceContext
SERVER-45938 Allow matching O/OU/DC in client x509 cert if clusterMode:keyFile
SERVER-49990 Alias setSlaveOk() and getSlaveOk() shell helpers
SERVER-50291 Add query knob to enumerate $or children in a different order
SERVER-50463 Make PooledLDAPConnection::refresh take self-ownership
SERVER-50915 [v4.0] fsyncLock must not take a stable checkpoint when majority read concern is off
SERVER-51120 Find queries with SORT_MERGE incorrectly sort the results when the collation is specified
4.0.20 - Aug 21, 2020
Issues fixed:
SERVER-44051 getShardDistribution() does not report "Collection XYZ is not sharded" on dropped but previously sharded collections
SERVER-45610 Some reads work while system is RECOVERING
SERVER-46758 setFCV can be interrupted before an fCV change is majority committed and rollback the fCV without running the setFCV server logicbumping collection's major version during split
SERVER-47799 AsyncRequestsSender should update replica set monitor in between retries for InterruptedAtShutdown
SERVER-49233 Introduce a flag to toggle the logic for bumping collection's major version during split
4.0.19 - Jun 15, 2020
Issues fixed:
SERVER-42525 Single-node replica sets shouldn't wait for electable caught up secondaries during shutdown
SERVER-42862 Prevent shard refreshes in mergeChunks command from joining earlier refreshes
SERVER-46487 The mongos routing for scatter/gather ops can have unbounded latency
SERVER-46758 setFCV can be interrupted before an fCV change is majority committed and rollback the fCV without running the setFCV server logic
SERVER-47233 WriteOp can be left in pending state, leading to erroneous NoProgressMade write error from mongos
4.0.18 - Apr 15, 2020
Issues fixed:
SERVER-44892: getShardDistribution should use $collStats agg stage instead of collStats command
SERVER-45119: CollectionShardingState::getCurrentShardVersionIfKnown returns collection version instead of shard version
4.0.17 - Mar 25, 2020
Issues fixed:
SERVER-46466: Race with findAndModify retryable write and session migration
SERVER-46365: getMore command before rs.initiate() can trip invariant
SERVER-46238: Race between commitTransaction and transaction expiration leads to invariant
SERVER-44598: Shards do not treat the IGNORED version as "intended sharded"
SERVER-35050: Don't abort collection clone due to negative document count
WT-5395: Fix a bug in the read lock implementation when there is a lot of contention
4.0.16 - Feb 5, 2020
Issues fixed:
SERVER-38794: CollectionOptions can be lost in createCollection if a write conflict exception is thrown
SERVER-45831: [4.0] Performance regression processing large aggregation commands
4.0.15 - Jan 27, 2020
Issues fixed:
SERVER-42565: Aggregations and find commands sort missing fields differently
SERVER-44341: Do not choose only first shard of all shards associated with a zone when pre-splitting during shard collection
SERVER-40435: A clearJumboFlag command to clear the jumbo flag
SERVER-45309: Ensure bind credentials live longer than LDAP operations
SERVER-44733: Change stream should throw ChangeStreamFatalError if a single shard cannot be targeted for updateLookup
SERVER-45396: fix the "me" field in isMaster responses when using splithorizon
WT-5042: Reduce configuration parsing overhead from checkpoints
Note
Fixed issues include those that resolve the following Common Vulnerabilities and Exposure (CVE):
CVE-2020-7921 (See SERVER-45472)
4.0.14 - Dec 18, 2019
Issues fixed:
SERVER-31083: Allow passing primary shard to "enableSharding" command for a new
SERVER-44174: $push and $addToSet should restrict memory usage
SERVER-44050: Arrays along 'hashed' index key path are not correctly rejected
SERVER-43632: Possible memory leak in 4.0
4.0.13 - Oct 19, 2019
Issues fixed:
SERVER-37690: countDocuments throws an error when matching 0 document
SERVER-41939: Connect to fastest LDAP server first
WT-4869: Stop adding cache pressure when eviction is falling behind
WT-4882: Improve checkpoint performance when there are large metadata pages
WT-4898: Don't allow the eviction server to reconcile if it's busy
4.0.12 - Aug 12, 2019
Issues fixed:
SERVER-41829: findAndModify ignores filter expressions that are not objects.
SERVER-42603: Recent service file change may cause cyclic dependencies.
4.0.11 - Jul 26, 2019
Issues fixed:
SERVER-39756: Sharding a very large collection can result in a long stall of writes against this collection
SERVER-40134: Distinct command against a view can return incorrect results when the distinct path is multikey
SERVER-40535: Possibility to get a non-existent key if using ReadConcern level:local when reading signing keys in ReplicaSet
SERVER-41361: Do not read at lastApplied while already holding the PBWM lock on secondaries
SERVER-41869: Reverse mutex acquisition order in CatalogCache::_scheduleCollectionRefresh
SERVER-42055: Only acquire a collection IX lock to write the lastVote document
SERVER-42232: Adding a new shard renders all preceding resume tokens invalid
Note
Fixed issues include those that resolve the following Common Vulnerabilities and Exposures (CVEs):
CVE-2019-2389 (See SERVER-40563)
CVE-2019-2390 (See SERVER-42233)
4.0.10 - May 31, 2019
Issues fixed:
SERVER-37765: Remove Support for Ubuntu 14.04
SERVER-30356: Improve error report for validate command
SERVER-38867: Refine handling of system.* collections in listCollections/show collections
SERVER-39672: Default to
"local"
read concern if unspecified for multi-document transactionsWT-4769: Don't discard active history for empty pages
4.0.9 - Apr 16, 2019
Issues fixed:
SERVER-38949: Incorrect index bounds for {$ne: ["String"]} query
SERVER-38984: Attach IDs to users
SERVER-39178: Negotiate SCRAM mechanism in MongoURI::connect()
SERVER-40333: Only clone collection options once for each shard on shard collection
Note
Fixed issues include those that resolve the following Common Vulnerabilities and Exposures (CVEs):
CVE-2019-2386 (See SERVER-38984)
4.0.8 - Mar 29, 2019
Issues fixed:
SERVER-40355: rs.config that contains an
_id
greater than the number of nodes will crashSERVER-38994: Step down on SIGTERM. See
SIGTERM
and Replica Sets.SERVER-37722: Quiet mode does not suppress connection end events
SERVER-37389: Give different messages for different connection failure reasons
4.0.7 - Mar 25, 2019
Issues fixed:
SERVER-13779: Allow $not to be applied to $regex (currently only /regex/ syntax is allowed)
SERVER-35740: Report high-water-mark resume token with each (possibly empty) change stream batch
TOOLS-2158: mongodump failing on Windows with "error opening system CA store: Access is denied."
4.0.6 - Feb 7, 2019
Issues fixed:
SERVER-37778: Platform Support: Add Community & Enterprise Ubuntu 18.04 (zSeries)
SERVER-37777: Platform Support: Add Community SLES12 (zSeries)
SERVER-37775: Platform Support: Add Community RHEL7 (zSeries)
SERVER-39180: Wrong initial chunk owner shard can be selected when sharding non-empty collection with pre-created zones
SERVER-32146: Log slow oplog entry application
SERVER-38293: Make listDatabases understand collection privileges
SERVER-38887: Mongo.getDBs() does not correctly inspect privileges
4.0.5 - Dec 20, 2018
Issues fixed:
SERVER-36437: The dbstats command should lock the database in MODE_IS instead of MODE_S
SERVER-37182: Different values when referencing whole object vs. a field of that object after $arrayToObject
SERVER-37200: $match stage following $listSessions not working against mongos
SERVER-37557: Add startup warning about enableMajorityReadConcern and usage of arbiters
4.0.4 - Nov 8, 2018
Issues fixed:
SERVER-26854: LockStats for sub-operations should not include time for previous sub ops
SERVER-35323: sessionId matching ignores userId part of the lsid
SERVER-37058: Update with numeric field names inside an array can cause validation to fail
SERVER-37132: Negation of $in with regex can incorrectly plan from the cache, leading to missing query results
TOOLS-2069: mongoreplay does not support SCRAM-SHA-256
TOOLS-2131: mongorestore hang in replaying oplog with --archive and --oplogReplay option
4.0.3 - Oct 9, 2018
Issues fixed:
SERVER-19815: Make repair more robust with the WiredTiger storage engine
SERVER-35989:
db.collection.countDocuments()
anddb.collection.estimatedDocumentCount()
helpersSERVER-36982: Reintroduce
enableMajorityReadConcern:false
server parameter
4.0.2 - Aug 29, 2018
Issues fixed:
SERVER-35720: Allow zones to be created on non-existent collection
SERVER-35441: drop/dropDatabase does not cleanup config.tags
SERVER-36102: Create initial chunks on appropriate shards for zoned sharding
SERVER-36070: Aggregation with $out results in error when Auditing is enabled
SERVER-34846: Covered index with collated field returns incorrect result when collation not involved in match or sort
SERVER-34664: Commands that are unsupported in a transaction should error
4.0.1 - Aug 6, 2018
Issues fixed:
SERVER-33000: Platform Support: add Ubuntu 18.04.
SERVER-34933: PCRE verb support.
SERVER-35101: Handle bindIp argument that contains whitespaces.
SERVER-36027: Enterprise build does not recognize the
--redactClientLogData
flag.
Multi-Document Transactions
Starting in version 4.0, MongoDB provides the ability to perform multi-document transactions against replica sets. With multi-document transactions, until a transaction commits, no write operations in the transaction are visible outside the transaction. That is, the multi-document transactions are atomic.
Important
In most cases, a distributed transaction incurs a greater performance cost over single document writes, and the availability of distributed transactions should not be a replacement for effective schema design. For many scenarios, the denormalized data model (embedded documents and arrays) will continue to be optimal for your data and use cases. That is, for many scenarios, modeling your data appropriately will minimize the need for distributed transactions.
For additional transactions usage considerations (such as runtime limit and oplog size limit), see also Production Considerations.
Feature Compatibility
The featureCompatibilityVersion
of all members of the replica set
must be 4.0
or greater. To check the
featureCompatibilityVersion
for a member, connect to the member and
run the following command:
db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )
For more information on the featureCompatibilityVersion
flag, see
setFeatureCompatibilityVersion
.
mongo
Shell Methods
Method | Description |
---|---|
Starts a multi-statement transaction. | |
Commits the transaction. | |
Aborts the transaction. |
MongoDB Drivers
Clients require MongoDB drivers updated for MongoDB 4.0 to use transactions.
Read Concern snapshot
MongoDB 4.0 introduces a new read concern level
"snapshot"
for multi-document transaction.
For a multi-document transaction, MongoDB
may sometimes substitute a stronger read concern for
"local"
and "majority"
read concern.
For a list of all operations that accept read concerns, see Operations That Support Read Concern.
Read Preference
Distributed transactions that contain
read operations must use read preference primary
. All
operations in a given transaction must route to the same member.
Commands
abortTransaction
- Use the corresponding driver method or
mongo
shell helperSession.abortTransaction()
instead.
commitTransaction
- Use the corresponding driver method or
mongo
shell helperSession.commitTransaction()
instead.
Locks
By default, multi-document transactions
wait 5
milliseconds to acquire locks required by the operations in
the transaction. If the transaction cannot acquire its required locks
with the 5
milliseconds, the transaction aborts.
You can use the maxTransactionLockRequestTimeoutMillis
parameter to adjust how long transactions wait to acquire locks.
Transactions release all locks upon abort or commit.
$currentOp
The aggregation pipeline stage $currentOp
(and the
currentOp
command and mongo
shell helper
db.currentOp()
method) return information on inactive sessions
which are holding locks as part of a transaction.
Parameters
transactionLifetimeLimitSeconds
to specify the lifetime for a multi-document transaction after which the transaction is considered expired and will be aborted when the periodic cleanup process next runs.maxTransactionLockRequestTimeoutMillis
to specify how long multi-document transactions should wait to aquire locks required by the operations in the transaction.
Aggregation
New Type Conversion Operators
MongoDB 4.0 adds the following new aggregation operators for type conversion:
Operator | Description |
---|---|
Convert value to specified type. | |
Convert value to boolean. | |
Convert value to Date. | |
Convert value to Decimal128. | |
Convert value to Double. | |
Convert value to integer. | |
Convert value to long. | |
Convert value to ObjectId. | |
Convert value to string. |
New String Operators
MongoDB 4.0 adds the following new aggregation string operators:
Additional Improvements
$bucket
The $bucket
stage no longer requires boundaries
document arguments to be wrapped in $literal
.
$dateToString
The $dateToString
aggregation operator has the following
option changes:
Note
Requires featureCompatibilityVersion
(fcv) set to "4.0"
or greater.
A new option
onNull
specifies the value to return if thedate
is null or missing.The option
format
is now optional.
$dateFromParts
If the value specified for fields other than year
, isoYear
, and
timezone
is outside the valid range, $dateFromParts
carries or subtracts the difference from other date parts to calculate
the date. For more information, see Value Range.
$dateFromString
The $dateFromString
aggregation operator takes an
optional format
field.
$currentOp
The aggregation pipeline stage $currentOp
supports the
following new options:
idleSessions
option to return information on inactive sessions which are holding locks as part of a transaction.localOps
option to report operations that are running locally on the currentmongos
instance, rather than reporting operations that are running on the shards.
MongoDB Drivers
The following drivers are feature compatible with MongoDB 4.0:
|
|
|
Security
Add Support for SCRAM-SHA-256
Note
To use SCRAM-SHA-256, the
featureCompatibilityVersion
must be set to 4.0
. For more
information on featureCompatibilityVersion, see Get FeatureCompatibilityVersion and
setFeatureCompatibilityVersion
.
MongoDB adds support for SCRAM authentication
mechanism SCRAM-SHA-256, which uses the SHA-256
hash function. To modify the iteration count for SCRAM-SHA-256
,
MongoDB adds a new parameter scramSHA256IterationCount
.
New Option for Create and Update User Operations
When creating or updating a SCRAM user, you can indicate the specific
SCRAM mechanism or mechanisms to use for the user credentials.
Specifically, MongoDB 4.0 adds the mechanisms
option to the
following commands and mongo
shell helpers:
Command | Method |
---|---|
When using SCRAM-SHA-256
, MongoDB (i.e. the server) requires
undigested password. Starting in MongoDB 4.0, the default value of
digestPassword
is true
for createUser
, and the
default value of passwordDigestor
is "server"
. In earlier
MongoDB versions, digestPassword
is false
and client
respectively.
New Option for isMaster
Command
Starting in MongoDB 4.0, the isMaster
command accepts an
optional field saslSupportedMechs: <db.user>
to return an
additional field isMaster.saslSupportedMechs
in its result.
isMaster.saslSupportedMechs
is an array of SASL mechanisms used
to create the specified user's credentials.
Remove Support for MONGODB-CR
Starting in version 4.0, MongoDB removes support for the deprecated
MongoDB Challenge-Response (MONGODB-CR
) authentication mechanism.
Since version 3.0, MongoDB has not supported the creation of
MONGODB-CR
users unless the deployment had been upgraded from a 2.6
or earlier deployment that already had MONGODB-CR
users and had not
upgraded the authentication schema.
If your deployment has user credentials stored in MONGODB-CR
schema, you must upgrade to Salted Challenge Response
Authentication Mechanism (SCRAM) before you
upgrade to version 4.0. For information on upgrading to SCRAM
, see
Upgrade to SCRAM.
usersInfo
Enhancement
The usersInfo
command can return information across all databases
by specifying:
{ usersInfo: { forAllDBs: true } }
The usersInfo
and the mongo
shell helpers
db.getUser()
and db.getUsers()
method accept a new
optional filter
document. The filter document specifies
$match
stage conditions to return information only for
users that match the conditions.
The usersInfo
command and the mongo
shell helpers
db.getUser()
and db.getUsers()
method return the
mechanisms
field for the user.
TLS/SSL
MongoDB uses the native TLS/SSL OS libraries:
Platform | TLS/SSL Library |
---|---|
Windows | Secure Channel (Schannel) |
Linux/BSD | OpenSSL |
macOS | Secure Transport |
Associated with this change, the parameter
opensslCipherConfig
is supported for Linux/BSD and no
longer supported in Windows and macOS.
TLS 1.2 Support
MongoDB 4.0 binaries for macOS support TLS 1.2.
Disable TLS 1.0
MongoDB binaries (mongod
, mongos
, and
mongo
) disables support for TLS 1.0 encryption on
systems where TLS 1.1+ is available.
If you need to support TLS 1.0:
For
mongod
instances, you can specifynone
tonet.ssl.disabledProtocols
or--sslDisabledProtocols none
.For
mongos
instances, you can specifynone
tonet.ssl.disabledProtocols
or--sslDisabledProtocols none
.For the
mongo
shell, you can specify--sslDisabledProtocols none
.The
--sslDisabledProtocols
option is available for themongo
shell in:MongoDB version 4.0+
MongoDB version 3.6.5+
MongoDB version 3.4.15+
On macOS, to connect mongo
shell version 3.6.4 or
earlier to a MongoDB 4.0+ deployment requires explicit enabling of TLS
1.0.
AES-GCM
MongoDB Enterprise on Windows no longer supports AES256-GCM
as a
block cipher for encryption at rest. This usage is only supported on Linux.
New Privilege Actions
To support free Cloud monitoring, MongoDB
adds the following privilege actions available for the cluster
resource:
checkFreeMonitoringStatus
setFreeMonitoring
MongoDB modifies the clusterMonitor
role to include these
privileges.
x.509 Authentication Certificate Restrictions
Starting in MongoDB 4.0, if you specify any of the following x.509 authentication options, an invalid certificate is sufficient only to establish a TLS connection but it is insufficient for authentication:
--sslAllowInvalidCertificates
ornet.ssl.allowInvalidCertificates: true
for MongoDB 4.0 and later--tlsAllowInvalidCertificates
ornet.tls.allowInvalidCertificates: true
for MongoDB 4.2 and later
If you are using invalid certificates to perform x.509 authentication,
update your certificates to valid certificates. For example, you may
sign your existing certificates with a trusted CA, or if using a custom
CA, specify that CA using net.ssl.CAFile
.
Enable System Store for TLS/SSL on Windows and macOS
The --sslCertificateSelector
option (certificateSelector
setting) allows
mongod
, mongo
shell and
mongos
to use system SSL certificate stores for Windows
and macOS.
The --sslClusterCertificateSelector
option
(clusterCertificateSelector
setting) allows
mongod
and
mongos
to use system TLS/SSL certificate stores for Windows
and macOS for internal TLS/SSL communication within a cluster.
The option --kmipClientCertificateSelector
(security.kmip.clientCertificateSelector
) allows
mongod
to use system TLS/SSL certificate stores for
Windows and macOS when using TLS/SSL connection to the KMIP server.
Deprecate MMAPv1
Starting in version 4.0, MongoDB deprecates the MMAPv1 storage Engine and will remove MMAPv1 in a future release.
To change your MMAPv1 storage engine deployment to WiredTiger Storage Engine, see:
Replica Set
Remove pv0
for Replica Sets
MongoDB 4.0 removes the deprecated replica set protocol version 0
pv0
.
Before upgrading to MongoDB 4.0, you must upgrade to pv1
.
To upgrade to pv1
, connect a mongo
shell to the
replica set primary and perform the following sequence of operations:
cfg = rs.conf(); cfg.protocolVersion=1; rs.reconfig(cfg);
You can use catchUpTimeoutMillis
to prioritize
between faster failovers and preservation of w:1
writes.
For more information on pv1
, see
Replica Set Protocol Version.
Remove Master-Slave Replication
MongoDB 4.0 removes support for the deprecated master-slave replication. Before you can upgrade to MongoDB 4.0, if your deployment uses master-slave replication, you must upgrade to a replica set.
To convert from master-slave replication to a replica set, see Convert a Master-Slave Deployment to a Replica Set.
Journaling and Replica Sets
Starting in MongoDB 4.0, you cannot specify --nojournal
option or
storage.journal.enabled: false
for replica set members that use the
WiredTiger storage engine.
rollbackTimeLimitSecs
Parameter Available
Starting in MongoDB 4.0, a new rollbackTimeLimitSecs
parameter allows for the setting of the time limit in seconds between
the common point and the last oplog write entry for the member
indicated for rollback. The default rollback time limit is 1 day.
Wait for Background Index Builds
Starting in version 4.0, MongoDB waits for any in-progress background index builds to finish before starting a rollback.
Rollback Files
MongoDB adds the parameter createRollbackDataFiles
that
determines whether during a rollback, MongoDB creates rollback files
that contains documents affected during the rollback.
replSetGetStatus
Output Changes
The replSetGetStatus
returns the following new fields:
The following fields returned from replSetGetStatus
are
deprecated:
Oplog Size
The oplog can grow past its configured size
limit to avoid deleting the majority commit point
.
Change Streams
Database and Deployment Change Streams
MongoDB adds the ability to:
Open a change stream cursor for a single database (excluding
admin
,local
, andconfig
database) to watch for changes to all its non-system
collections.Open a change stream cursor for a deployment to watch for changes to all non-
system
collections across all databases except foradmin
,local
, andconfig
.
Note
Requires featureCompatibilityVersion
(fcv) set to "4.0"
or greater.
Start Time Option
MongoDB adds the ability to specify a start time
(startAtOperationTime
option) for a change stream.
Change Event Document Changes
The change event documents include the new fields:
the
clusterTime
which corresponds to timestamp from the oplog entry for the event.the
txnNumber
and thelsid
if the operation is part of a multi-document transaction.
Resume Token Data Type Change
MongoDB 4.0 introduces new hex-encoded string change streams resume tokens:
The resume token _data
type depends on the MongoDB versions and,
in some cases, the feature compatibility version (fcv) at the time
of the change stream's opening/resumption (i.e. a change in fcv
value does not affect the resume tokens for already opened change
streams):
MongoDB Version | Feature Compatibility Version | Resume Token _data Type |
---|---|---|
MongoDB 4.0.7 and later | "4.0" or "3.6" | Hex-encoded string ( v1 ) |
MongoDB 4.0.6 and earlier | "4.0" | Hex-encoded string ( v0 ) |
MongoDB 4.0.6 and earlier | "3.6" | BinData |
MongoDB 3.6 | "3.6" | BinData |
With hex-encoded string resume tokens, you can compare and sort the resume tokens.
Regardless of the fcv value, a 4.0 deployment can use either BinData resume tokens or hex string resume tokens to resume a change stream. As such, a 4.0 deployment can use a resume token from a change stream opened on a collection from a 3.6 deployment.
New resume token formats introduced in a MongoDB version cannot be consumed by earlier MongoDB versions.
A 3.6 deployment can, however, use the BinData resume token returned
from a change stream opened against a collection from a deployment
with fcv 3.6
. However, a 3.6 deployment cannot use the
hex-encoded string resume tokens.
mongo
Shell Methods
Method | Description |
---|---|
Opens a change stream cursor for a single database
(excluding For the corresponding MongoDB driver method, refer to your driver documentation. | |
Opens a change stream cursor for a
deployment to watch for changes to all non- For the corresponding MongoDB driver method, refer to your driver documentation. New in version 4.0. |
Free Monitoring
Warning
Free monitoring is decommissioned.
Free monitoring was decommissioned in August 2023.
Beginning in April 2023, you cannot enable free monitoring on MongoDB Community instances.
The following list shows monitoring options for your deployment:
Deploy a MongoDB Atlas dedicated cluster. Migrate your data to a MongoDB Atlas dedicated cluster sized M10 or greater, which includes several advanced monitoring and alerting features:
Deploy a MongoDB Atlas free cluster. A free Atlas cluster includes basic monitoring and alerting capabilities. After you create a free cluster, use
mongodump
andmongorestore
to manually create a backup of your database and import your data from your MongoDB Community instance.Use MongoDB Cloud Manager. The MongoDB Cloud Manager free tier includes basic monitoring capabilities.
MongoDB 4.0 (Community Edition) offers free Cloud monitoring for standalone or replica sets.
Enable/Disable
By default, you can enable/disable free monitoring during runtime using:
mongo Shell Methods | Command |
---|---|
db.enableFreeMonitoring() db.disableFreeMonitoring() | setFreeMonitoring |
You can also enable or disable free monitoring at startup using either:
the configuration file setting
cloud.monitoring.free.state
orthe command-line option
--enableFreeMonitoring
Note
Starting in MongoDB 7.0, free monitoring is decommissioned.
View Status
To view the state of your free monitoring, MongoDB provides the following command and shell helper:
mongo Shell Methods | Command |
---|---|
db.getFreeMonitoringStatus() | getFreeMonitoringStatus |
The serverStatus
and the helper
db.serverStatus()
also includes free monitoring statistics
in the freeMonitoring
field.
Access Control
To support free Cloud monitoring, MongoDB adds the following privilege
actions available for the cluster
resource:
checkFreeMonitoringStatus
setFreeMonitoring
The built-in role clusterMonitor
includes the new privilege
actions.
Sharded Clusters
mongos
uses "majority"
write concern
for the following operations that affect the sharded cluster
metadata:
Command | Method | Note |
---|---|---|
Changed in MongoDB 3.6 | ||
.msi
Installer on Windows
Starting in MongoDB 4.0, you can configure and start MongoDB as a service during the install.
Platform Support
MongoDB 4.0 (Community & Enterprise) adds support for:
MongoDB 4.0 (Community) adds support for:
s390x RHEL 6.x
MongoDB 4.0 does not support SLES 11.
Support for SLES 11 has also been removed in MongoDB 3.2.20+, 3.4.15+, and 3.6.4+.
MongoDB 4.0 does not support Ubuntu 12.04.
Support for Ubuntu 12.04 has also been removed in MongoDB 3.2.20+, 3.4.15+, and 3.6.4+.
Support for Ubuntu 12.04 has also been removed in MongoDB 3.2.20+, 3.4.15+, and 3.6.4+.
In future releases, MongoDB will end support for the following platforms:
Windows 7/2008R2
Windows 8/2012
Windows 8.1/2012R2
Ubuntu 14.04
Refer to Platform Support for the full platform support matrix.
MongoDB Tools
The mongoreplay play
command supports a new
MONGOREPLAY_HOST
environment variable that specifies the MongoDB
connection string when running mongoreplay play
. The new environment
variable can be usedinstead of the command-line --host
option.
For example, to play back a recording to a mongod
instance running with authentication at mongodb1.example.net:27017
,
you can specify the connection string in:
The
MONGOREPLAY_HOST
environment variable:export MONGOREPLAY_HOST="mongodb://myUserName:s0meD1fficultPassw0rd@mongodb1.example.net:27017/?authSource=admin" mongoreplay play -p /some/path/to/my/recording.bson The
--host
command-line option:mongoreplay play -p /some/path/to/my/recording.bson --host "mongodb://myUserName:s0meD1fficultPassw0rd@mongodb1.example.net:27017/?authSource=admin"
If --host
command-line option is specified, the --host
value
overrides the environment variable.
General Improvements
Commands
The command
listCollections
takes Intent Shared lock on the database. In previous versions, the command takes Shared lock on the database.The command
listCollections
and itsmongo
shell helperdb.getCollectionInfos()
accepts the following option:nameOnly
to return only the collection names and types (which does not require collection locks).authorizedCollections
to allow users without the required privilege to runlistCollections
can run the command, withnameOnly: true, authorizedCollections: true
, to return the the collection(s) to which the user has privileges.
The command
serverStatus
and itsmongo
shell helperdb.serverStatus()
includesshardingStatistics
in its output. TheshardingStatistics
includes data on metadata refresh on sharded clusters.The
mongo
shell helperdb.collection.drop()
accepts the write concern option.For cursors created inside a session, you cannot call
getMore
outside the session. Similarly, for cursors created outside of a session, you cannot callgetMore
inside a session.The command
dbHash
includes the following fields in its output:capped
field that lists the capped collectionsuuids
field that contains the collections and their corresponding UUIDs.
The command
killOp
now supports termination of queries that are running on amongos
. When run on themongos
,killOp
can kill queries that are running in more than one shard.
Geospatial Query Improvements
The geospatial query operators
$near
and$nearSphere
now supports querying on sharded collections.As of MongoDB 4.0, the
$geoNear
aggregation operator andgeoNear
command support using theminDistance
option with 2d indexes. Similarly,$near
and$nearSphere
support the$minDistance
option for 2d indexes. Previously,minDistance
and$minDistance
were only available for 2dsphere indexes.MongoDB 4.0 adds a
key
option for the$geoNear
aggregation operator andgeoNear
command that enables users to specify which geospatial index to use when querying a collection with multiple geospatial indexes. Previously, to use the$geoNear
aggregation operator orgeoNear
command, the collection could only have one geospatial index.
Network Layer Improvements
For the parameter
taskExecutorPoolSize
, change default value to1
.Add new parameter AsyncRequestsSenderUseBaton to enable performance optimization on Linux for scatter/gather operations on
mongos
when using a singleTask Executor connection pool
.Added the following parameters to manage connection pools:
Configuration Options
mongos
supports:Command line options:
slowms
and--slowOpSampleRate
Configuration file options:
operationProfiling.slowOpThresholdMs
andoperationProfiling.slowOpSampleRate
Miscellaneous
The JavaScript engine's JIT compiler is now disabled by default.
Upgrades MozJS to ESR 45.9.0.
Adds
RECOVERY
component to log messages.MongoDB 4.0 adds support for using the
appName
connection string option for setting a custom app name when connecting from themongo
shell. Previously, only MongoDB drivers supported using theappName
to set a custom value and themongo
shell used the defaultMongoDB Shell
value as the app name.Adds a
mongo
shell methodconvertShardKeyToHashed()
to return the hashed value for a document.Resolves
localhost
IP address as configured instead of assuming127.0.0.1
.When using the SRV Connection Format to connect to the
mongo
shell with authentication, themongo
shell will now prompt the user to provide their password when starting up.
Changes Affecting Compatibility
Some changes can affect compatibility and may require user actions. For a detailed list of compatibility changes, see Compatibility Changes in MongoDB 4.0.
Upgrade Procedures
Important
Feature Compatibility Version
To upgrade, the 3.6 instances must have
featureCompatibilityVersion
set to 3.6
. To check the version:
db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )
For specific details on verifying and setting the
featureCompatibilityVersion
as well as information on other
prerequisites/considerations for upgrades, refer to the individual
upgrade instructions:
If you need guidance on upgrading to 4.0, MongoDB offers major version upgrade services to help ensure a smooth transition without interruption to your MongoDB application.
Download
To download MongoDB 4.0, go to the MongoDB Download Center
Known Issues in 4.0.3
- WT-4018:
- MongoDB 4.0 may lose data during unclean shutdowns on macOS 10.12.x, 10.13.x, and 10.14.0. This issue was fixed by Apple in macOS 10.14.1.
- SERVER-35431:
- After a rollback, the 'dataSize' field reported in
collStats
anddbStats
output can be inaccurate.
Known Issues in 4.0.2
- WT-4018:
- MongoDB 4.0 may lose data during unclean shutdowns on macOS 10.12.x, 10.13.x, and 10.14.0. This issue was fixed by Apple in macOS 10.14.1.
- SERVER-35431:
- After a rollback, the 'dataSize' field reported in
collStats
anddbStats
output can be inaccurate.
- SERVER-35657:
- Using multi-document transactions with a single-member replica set
may have significant performance impact. Single-member replica sets
should only be for testing/development purposes and are not
recommended for production use.
Note
Multi-document transactions performance on a single-member replica set are not indicative of performance on a replica set with more than one member.
Known Issues in 4.0.1
- WT-4018:
- MongoDB 4.0 may lose data during unclean shutdowns on macOS 10.12.x, 10.13.x, and 10.14.0. This issue was fixed by Apple in macOS 10.14.1.
- SERVER-35431:
- After a rollback, the 'dataSize' field reported in
collStats
anddbStats
output can be inaccurate.
- SERVER-35657:
- Using multi-document transactions with a single-member replica set
may have significant performance impact. Single-member replica sets
should only be for testing/development purposes and are not
recommended for production use.
Note
Multi-document transactions performance on a single-member replica set are not indicative of performance on a replica set with more than one member.
Known Issues in 4.0.0
- TOOLS-1952:
- Users running MongoDB 4.0
mongodump
may experience slower performance compared to previous versions. Runningmongodump
with--forceTableScan
may resolve performance issues.
- TOOLS-2058:
mongoreplay
does not show insert/find commands for MongoDB 4.0.# Fixed in 4.0.1
- WT-4018:
- MongoDB 4.0 may lose data during unclean shutdowns on macOS 10.12.x, 10.13.x, and 10.14.0. This issue was fixed by Apple in macOS 10.14.1.
- SERVER-35431:
- After a rollback, the 'dataSize' field reported in
collStats
anddbStats
output can be inaccurate.
- SERVER-35657:
- Using multi-document transactions with a single-member replica set
may have significant performance impact. Single-member replica sets
should only be for testing/development purposes and are not
recommended for production use.
Note
Multi-document transactions performance on a single-member replica set are not indicative of performance on a replica set with more than one member.
- SERVER-35758:
- The shell prompt in the
mongo
shell will cause an error if you use the session associated with the globaldb
object to run transactions.# Fixed in 4.0.1
Report an Issue
To report an issue, see https://github.com/mongodb/mongo/wiki/Submit-Bug-Reports for instructions on how to file a JIRA ticket for the MongoDB server or one of the related projects.