Release Notes for MongoDB 3.4¶

3.4.24 - Jan 27, 2020¶

Issues fixed:

• SERVER-37772: Platform Support: Add Community & Enterprise RHEL 8 x64
• SERVER-37135: TLSVersionCounts needs to track and report TLS 1.3
• SERVER-36315: After stepdown the CSRS dist lock manager keeps trying to unlock locks
• SERVER-37846: writeConcern can be satisfied with an arbiter if the write was committed
• SERVER-38945: SSL performance regression
• SERVER-40355: rs.config that contains an _id greater than the number of nodes will crash
• SERVER-43151: Error in aggregation assertion at value.cpp:1368
• SERVER-44050: Arrays along ‘hashed’ index key path are not correctly rejected
• WT-4956: Handle the case where 4 billion updates are made to a page without eviction
• 3.4.24 Changelog
• All JIRA issues closed in 3.4.24

3.4.23 - Sep 16, 2019¶

Issues fixed:

• SERVER-36394: mongos should reset chunk size tracking information when autosplit = false or splitvector returns too few split points
• SERVER-41829: findAndModify ignores filter expressions that are not objects
• SERVER-42055: Only acquire a collection IX lock to write the lastVote document
• 3.4.23 Changelog
• All JIRA issues closed in 3.4.23

3.4.22 - Aug 6, 2019¶

Issues fixed:

• SERVER-17010: Reduce file handle usage in File based Sorter.
• SERVER-38984: Attach IDs to users (CVE-2019-2386).
• SERVER-42089: Platform Support: Remove Enterprise RHEL 6.7 zSeries
• 3.4.22 Changelog
• All JIRA issues closed in 3.4.22

3.4.21 - Jun 14, 2019¶

Issues fixed:

• SERVER-39820: Add the client IP address to the successful authentication log message
• SERVER-41213: Unique background index builds may produce inconsistent keys
• SERVER-37765: Platform Support: Remove Ubuntu 14.04
• SERVER-37774: Platform Support: Remove Enterprise Ubuntu 16.04 PPCLE
• WT-4615: Sync backup file before returning backup cursor
• 3.4.21 Changelog
• All JIRA issues closed in 3.4.21

3.4.20 - Mar 13, 2019¶

Issues fixed:

• SERVER-39166: $graphLookup should force a pipeline to split in sharded cluster
• SERVER-39723: Change listIndexes command behavior to show in-progress index builds
• TOOLS-2158: mongodump failing on Windows with “error opening system CA store: Access is denied.”
• 3.4.20 Changelog
• All JIRA issues closed in 3.4.20

3.4.19 - Jan 28, 2019¶

Issues fixed:

• SERVER-18985: setParameter should log at level 0
• SERVER-22766: Dynamic oplog sizing for WiredTiger nodes
• SERVER-33469: Make syslog log lines consistent with mongod log lines
• SERVER-37132: Negation of $in with regex can incorrectly plan from the cache, leading to missing query results
• SERVER-37182: Different values when referencing whole object vs. a field of that object after $arrayToObject
• SERVER-37616: Implement tuneable batch size for the rangedeleter
• 3.4.19 Changelog
• All JIRA issues closed in 3.4.19

3.4.18 - Nov 7, 2018¶

Issues fixed:

• SERVER-25175: listIndexes shouldn’t include in-progress background indexes
• SERVER-35418: Allow specifying CAs for incoming and outgoing connections separately.
• SERVER-36944: applyOps does not permit unknown field names when creating a v:1 index.
• SERVER-37058: Update with numeric field names inside an array can cause validation to fail.
• 3.4.18 Changelog
• All JIRA issues closed in 3.4.18

3.4.17 - Sep 7, 2018¶

Issues fixed:

• SERVER-33857 Missing log redaction due to confusion with Command::redactForLogging().
• SERVER-34846 Covered index with collated field returns incorrect result when collation not involved in match or sort.
• SERVER-36010 Change log messages for Windows stacktraces to use error() or severe() rather than log().
• SERVER-34558: Add SSL_version to client metadata logging.
• 3.4.17 Changelog
• All JIRA issues closed in 3.4.17

3.4.16 - Jul 10, 2018¶

Issues fixed:

• SERVER-32999: Platform Support: Remove Debian 7 builds.
• SERVER-29301: Upgrade MozJS to ESR 45.9.0
• SERVER-5461: Add syncSourceHost field to replSetGetStatus output.
• 3.4.16 Changelog
• All JIRA issues closed in 3.4.16

3.4.15 - May 16, 2018¶

Issues fixed:

• SERVER-31535: Platform Support: remove Ubuntu 12.04 builds.
• SERVER-32923: Platform Support: remove SLES11 builds.
• SERVER-20056: Log a startup warning if wiredTigerCacheSizeGB is > 80% of RAM.
• SERVER-28981: Sharding balancer prefers shards in a specific order when moving chunks.
• 3.4.15 Changelog
• All JIRA issues closed in 3.4.15

3.4.14 - March 20, 2018¶

Issues fixed:

• SERVER-28151: Authentication database should be synced first during an initial sync.
• SERVER-32886: Unnecessary sleeps during chunk migration.
• SERVER-32933: Allow mongod to start when unable to reach LDAP server.
• 3.4.14 Changelog
• All JIRA issues closed in 3.4.14

3.4.13 - Feb 10, 2018¶

Issues fixed:

• SERVER-33238: Prevent WiredTiger read ticket count from going negative.
• 3.4.13 Changelog
• All JIRA issues closed in 3.4.13

3.4.12 - Feb 8, 2018¶

Issues fixed:

• SERVER-31437: Fix parsing of mongo host/db connect string.
• SERVER-32875: Don’t stall ftdc due to running out of tickets.
• SERVER-33089: Unable to start queryable mongod because it failed to regenerate index for admin.system.users.
• 3.4.12 Changelog
• All JIRA issues closed in 3.4.12

3.4.11 - Jan 31, 2018¶

Issues fixed:

• SERVER-19605: Oplog timeout should be configurable.
• SERVER-19919: Chunks that exceed 250000 docs but are under half chunk size get marked as jumbo.
• SERVER-29293: Recipient shard fails to abort migration on stepdown.
• SERVER-32001: unindexing a key in a partial unique index may cause server crash
• 3.4.11 Changelog
• All JIRA issues closed in 3.4.11

3.4.10 - Oct 31, 2017¶

Issues fixed:

• SERVER-15723: Avoid G_X lock for rename_collection within database
• SERVER-31049: View with collation doesn’t work as expected in sharded cluster
• SERVER-29287: Upgrade pcre to 8.41
• SERVER-31204: Calling shardCollection after enableSharding may fail if executed against different mongos
• 3.4.10 Changelog
• All JIRA issues closed in 3.4.10

3.4.9 - Sept 11, 2017¶

Issues fixed:

• SERVER-20392: Sharding an existing small collection results in large number of chunks
• SERVER-30189: Reduce calls to allocator for large $in expressions
• SERVER-30487: RangeDeleter holds WT transaction open while waiting for majority
• SERVER-30636: Range deleter assert failed because of replication lag
• 3.4.9 Changelog
• All JIRA issues closed in 3.4.9

3.4.7 – Aug 8, 2017¶

Issues fixed:

• SERVER-29282: BSON Document Size can be exceeded when grouping inserts on SECONDARY nodes
• SERVER-29568: Enable configuration of OpenSSL cipher suite via setParameter
• SERVER-29817: Optimize incremental update performance of ChunkManager and CollectionMetadata
• 3.4.7 Changelog
• All JIRA issues closed in 3.4.7

3.4.6 – Jul 5, 2017¶

Issues fixed:

• SERVER-27347: Only close idle cached cursors on the WiredTiger ident that is busy.
• SERVER-29618: $geoWithin in aggregation pipeline after $lookup and $unwind returns incorrect results.
• WT-3362: Cursor opens should never block for the duration of a checkpoint.
• 3.4.6 Changelog
• All JIRA issues closed in 3.4.6

3.4.5 – Jun 14, 2017¶

Issues fixed:

• SERVER-28952: Multikey indexes should not be eligible for DISTINCT_SCAN if distinct key is an array component.
• SERVER-28427: GlobalLock with timeout can still block indefinitely.
• SERVER-29018 mongos can segfault in getMore on views with find batchSize of 0.
• 3.4.5 Changelog
• All JIRA issues closed in 3.4.5

3.4.4 – Apr 21, 2017¶

Issues fixed:

• SERVER-18794: Add an aggregation operator $objectToArray to convert an object to an array of key, value pairs.
• SERVER-23310: Add an aggregation operator $arrayToObject to convert an array of pairs to an object.
• SERVER-22611: ChunkManager refresh can occasionally cause a full reload.
• 3.4.4 Changelog
• All JIRA issues closed in 3.4.4

3.4.3 – Mar 28, 2017¶

Issues fixed:

• SERVER-27863: Reschedule firing of early alarms in NetworkInterfaceASIO to avoid mongos crash.
• SERVER-28017: $ne should respect collection’s default collation.
• SERVER-27700: Improve WiredTiger performance on secondary when cache is full.
• 3.4.3 Changelog
• All JIRA issues closed in 3.4.3

3.4.2 – Feb 1, 2017¶

Issues fixed:

• SERVER-27125: Arbiters in pv1 should vote no in elections if they can see a healthy primary of equal or greater priority to the candidate.
• SERVER-27584 Add support for filter to listDatabases
• WT-2670 Inefficient I/O when read full DB (poor readahead)
• 3.4.2 Changelog
• All JIRA issues closed in 3.4.2

3.4.1 – Dec 20, 2016¶

Issues fixed:

• SERVER-27124: Disallow readConcern: majority reads on replica set protocolVersion 0 (pv0).
• SERVER-27201: $graphLookup triggers null pointer dereference.
• SERVER-27207: Find operation with a sort on a view via mongos may incorrectly return empty result set.
• SERVER-27213: Two $match pipeline stages can combine incorrectly to produce incorrect results.
• 3.4.1 Changelog
• All JIRA issues closed in 3.4.1

Membership Awareness¶

Starting in 3.4, sharded cluster components (shards, config servers, mongos instances) recognize their membership in a sharded cluster, including the name of the sharded cluster, the location of the config servers.

To support this awareness:

• shardsvr Requirement

  For a 3.4 sharded cluster, mongod instances for the shards must explicitly specify its role as a shardsvr, either via the configuration file setting sharding.clusterRole or via the command line option --shardsvr.

  Note

  Default port for mongod instances with the shardsvr role is 27018. To use a different port, specify net.port setting or --port option.

• 3.4 mongos Incompatibility with Earlier Versions of mongod

  Version 3.4 mongos instances cannot connect to earlier versions of mongod instances.

Balancer on Config Server Primary¶

The balancer process has moved from the mongos to the primary member of the config server replica set. Associated with this change:

• The primary of the CSRS config server holds the "balancer" lock, using a process id named "ConfigServer", which is never released.
• MongoDB 3.4 adds:
  • balancerStart command and updates the 3.4 mongo shell method sh.startBalancer() to wrap the new command. A 3.2 or earlier mongo shell method sh.startBalancer() is incompatible with a 3.4 sharded cluster.
  • balancerStop command and updates the 3.4 mongo shell method sh.stopBalancer() to wrap the new command. A 3.2 or earlier mongo shell method sh.stopBalancer() is incompatible with a 3.4 sharded cluster.
  • balancerStatus command.
• MongoDB 3.4 deprecates mongo shell method sh.getBalancerHost(). A 3.2 or earlier mongo shell method sh.getBalancerHost() is incompatible with a 3.4 sharded cluster.
• MongoDB 3.4 removes the following configuration options from the mongos:
  • sharding.chunkSize configuration file setting and --chunkSize command-line option
  • sharding.autoSplit configuration file setting and --noAutoSplit command-line option

Faster Balancing¶

Starting in MongoDB 3.4:

• For WiredTiger, the default value secondaryThrottle is false for all chunk migrations. The balancer does not wait for replication to a secondary and instead continues with the next document.
• MongoDB can perform parallel chunk migrations. Similar to earlier versions, a shard can participate in at most one migration at a time. Observing this restriction, for a sharded cluster with n shards, MongoDB can perform at most n/2 (rounded down) simultaneous chunk migrations.

Removal of Support for SCCC Config Servers¶

3.4 sharded clusters no longer support the use of mirrored (SCCC) mongod instances as config servers. The use of SCCC config servers, deprecated in the 3.2 release, is no longer valid. Instead, deploy your config servers as a replica set (CSRS).

To upgrade your sharded cluster to version 3.4, the config servers must be running as a replica set.

To convert your existing config servers from SCCC to CSRS, see the Upgrade Config Servers to Replica Set.

Sharding Zones¶

MongoDB 3.4 introduces Zones, which supersedes tag-aware sharding available in earlier versions.

To support zones, MongoDB introduces the following commands and mongo shell helpers:

Default Journaling Behavior of majority Write Concern¶

A new replica set configuration setting writeConcernMajorityJournalDefault determines whether an acknowledgement for a write concern of majority returns after the majority of the voting members apply the write in memory or to the on-disk journal if the j option is unspecified in the write concern.

Adjustable Catchup Period for Newly Elected Primary¶

A new replica set configuration setting settings.catchUpTimeoutMillis defines the time limit for a newly elected primary to catch up with the other replica set members that may have more recent writes.

Linearizable Read Concern¶

MongoDB 3.4 introduces a read concern level of "linearizable" to read data that reflects all successful writes issued with a "majority" and acknowledged prior to the start of the read operation. Linearizable read concern guarantees only apply if read operations specify a query filter that uniquely identifies a single document.

Linearizable read concern is available for all MongoDB supported storage engines.

Combined with "majority" write concern, "linearizable" read concern enables multiple threads to perform reads and writes on a single document as if a single thread performed these operations in real time; that is, the corresponding schedule for these reads and writes is considered linearizable.

Reads with linearizable read concern may be significantly slower than reads with "majority" or "local" read concerns. Always use maxTimeMS with linearizable read concern, in case a majority of data bearing members are unavailable. For example:例如：

db.restaurants.find( { _id: 5 } ).readConcern("linearizable").maxTimeMS(10000)

db.runCommand( {
     find: "restaurants",
     filter: { _id: 5 },
     readConcern: { level: "linearizable" },
     maxTimeMS: 10000
} )

For more information on read concern, including operations that support read concerns, see Read Concern.

Improved Initial Sync¶

• MongoDB 3.4 improves the performance of initial sync by having initial sync build the indexes as the documents are copied.
• MongoDB 3.4 improves the initial sync retry logic to be more resilient to intermittent failures on the network.
• To avoid potential data corruption, MongoDB 3.4 fails and restarts initial sync if a collection is renamed on the sync source during the initial sync. With MongoDB 3.2.11 or earlier, initial syncs did not fail and restart but instead continued the process, which could lead to potential data corruption.

  For details, see Initial Sync and renameCollection.

• Modified replSetGetStatus command to accept the optional initialSync: 1 in the command to report on initial sync status and progress if run on the secondary:

  db.adminCommand( { replSetGetStatus: 1, initialSync: 1 } )

New Aggregation Stage for Recursive Search¶

3.4 introduces a stage to the aggregation pipeline that allows for recursive search.

New Aggregation Stages for Faceted Search¶

Faceted search allows for the categorization of documents into classifications. For example, given a collection of inventory documents, you may want to classify items by a single category, such as by the price range, or by multiple categories, such as by price range as well as separately by the departments.

3.4 introduces stages to the aggregation pipeline that allow for faceted search.

New Aggregation Stages to Facilitate Reshaping Documents¶

3.4 introduces stages to the aggregation pipeline that faciliate replacing documents as well as adding new fields.

New Aggregation Stage to Count¶

3.4 introduces a new stage to the aggregation pipeline that faciliate counting document.

New Aggregation Array Operators¶

New Aggregation String Operators¶

New Aggregation Control Flow Expression¶

New Date Aggregation Operators¶

New Monitoring Aggregation Sources¶

New Type Operator¶

Additional Changes¶

$project stage adds support for field exclusion in the output document. Previously, you could only exclude the _id field in the stage. If you specify the exclusion of a field or fields,

• All other fields are returned in the output documents.
• You cannot specify new fields or the inclusion of other fields.

Transition to Auth¶

MongoDB 3.4 adds support for rolling transition to internal authentication for replica sets and sharded clusters. For details, see security.transitionToAuth setting and --transitionToAuth command line option for mongod and mongos.

User Roles Changes¶

The privileges of the following built-in roles no longer apply to the local and config databases:

Correspondingly, the following built-in roles include additional read and write privileges on local and config databases:

• clusterManager
• clusterMonitor
• backup
• restore.

mongoreplay¶

MongoDB introduces mongoreplay, a workload capture and analysis tool that replaces mongosniff. You can use mongoreplay to inspect and record commands sent to a MongoDB instance, and then replay the commands back onto another host at a later time.

mongoreplay is available for Linux and macOS.

Log Redaction¶

MongoDB Enterprise adds support for log redaction for use in conjunction with MongoDB’s encrypted storage engine. Log redaction prevents potentially sensitive information from being written to the diagnostic log; however, diagnostics on redacted logs may be more difficult due to the lack of data related to a log event.

To enable log redaction, see the security.redactClientLogData setting and the --redactClientLogData option for mongod.

LDAP Enhancements¶