Release Notes for Couchbase Server 6.0

Couchbase Server 6.0 is an important release that adds the Analytics service to the Couchbase Data Platform. It also includes enhancements to the Eventing and Search services.

Take a look at What’s New? for a list of new features and improvements that are available in this release.

Release 6.0.1

Couchbase Server 6.0.1, released in February 2019, is the first maintenance release in the 6.0.x series for Couchbase Server.

New Supported Platforms

This release adds support for the following platforms:

  • Amazon Linux 2

  • Ubuntu 18.04

See Supported Platforms for the complete list of supported platforms.

Deprecated Platforms

Support for the following platforms will be removed in a future release:

  • macOS 10.12 (Sierra)

Fixed Issues

The notable fixes in this release are listed below.

Analytics Service

Issue Description


Summary: Index creation on meta fields is not allowed and trying to do so will result in an error.


Summary: Fixed an issue where rebalance failed to complete with a badmatch error.


Summary: Fixed an issue where a rebalance operation could fail due to the reuse of dataset IDs internally.


Summary: When a dataverse was dropped, bucket listeners were not unregistered. Consequently, when the dataverse was re-created, the CONNECT LINK statement failed as it picked up the old bucket listeners. This has been fixed.


Summary: Fixed an issue where the AnalyticsReader role, a read-only role, was incorrectly able to change the metadata and drop dataverses.


Summary: Starting this release, the OpenJDK version 11 is bundled with the service. See install:install-environment.adoc for details.

Cross Datacenter Replication (XDCR)

Issue Description


Summary: XDCR failed to replicate files larger than the network usage limit. This has been fixed so the bandwidth throttler can handle large documents with sizes greater than the usage limit.


Summary: Uncompressed replication from 6.0 nodes to 5.0 nodes failed due to partial information being returned from the parts. This has been fixed to enable accurate detection of compression error code.


Summary: Fixed an issue where replication stops and throws an exception due to a nil error.


Summary: Fixed an issue where the XDCR log level setting was not retained when upgrading Couchbase Server from version 4.x to newer version.


Summary: Fixed an issue where encrypted XDCR was incorrectly using port 8091.


Summary: An error was thrown when DNS alternate addresses were used. This has been fixed so utilities return the hostname even if they can’t find the port numbers.


Summary: The unit of interval for XmemSelfMonitorInterval was incorrectly set to millisecond instead of second, causing an increase in the frequency of Xmem self monitor and the spurious Xmem is stuck error. This has been fixed.

Data Service

Issue Description


Summary: Fixed an issue where a chain of events, active compression of an extended attribute value followed by eviction and then expiry, triggered an exception.


Summary: Sub-document API single-path mutation ignored expiry if doc_flags included extras.


Summary: If one or more Ephemeral buckets were present, then nonIO background tasks could be incorrectly scheduled, potentially resulting in DCP connection instability (premature disconnection). This has been fixed.


Summary: When data corruption is detected on a data service node, relevant information that can help troubleshoot is now being logged.


Summary: In some cases, the memory allocation failures were not handled causing "Write Commit Failure" errors or corruption in vBucket files.


Summary: If an append/prepend request contended with another request at the Server, instead of automatically retrying on the Server (as expected), it returned EEXISTs back to the application.


Summary: Audit logging has been updated to capture the user name when documents are created, updated, or deleted from the web console.


Summary: Fixed an issue where the datatype field when using the DCP_OPEN flags incorrectly reflected the contents of the body payload and not the original datatype.


Summary: If bucket memory usage exceeded the high watermark and reached 99% of the bucket quota, a race condition in KV-Engine DCP consumer was exposed. This could result in DCP messages being processed out-of-order.

Eventing Service

Issue Description


Summary: Reduced excessive logging by Eventing service when the debugger is turned on.


Summary: Following the failover of a vBucket, the Eventing service restarted streams with seqno from the latest failover log entry instead of using the entry where seqnoInFailoverLog ⇐ lastProcessedSeqno. This resulted in missed events.


Summary: Fixed an issue where some events were missing after a source bucket flush operation.

Index Service

Issue Description


Summary: Fixed an issue where the index service exceeded the memory quota even though only the number of items that were indexed was low.


Summary: In a cluster with duplicate index names across buckets, replica repair failed after a node was added back to the cluster. This has been fixed.


Summary: Plasma memory tuner will now increment indexer memory quota only if the indexer process' RSS is below the memory quota.


Summary: The DCP noop interval has been lowered to 20sec to improve the chances of the projector receiving the noop message early and thus avoiding frequent roll backs.


Summary: During warmup, one of the indexes with low number of items triggered an issue and caused the internal garbage collector to run forever. Thus causing the entire index service to stall during warmup. This issue was observed when using Plasma storage engine.


Summary: Improved the DCP rollback handling mechanism. Instead of ignoring the disk snapshots before rolling back, the index service will now exhaust trying DCP stream requests with all the disk snapshots before rolling back to 0.


Summary: An error is seen during a SUM aggregate pushdown when the entry value is greater than MaxInt64.


Summary: Fixed an issue to enable creating secondary indexes on binary documents on, meta.cas(), and meta.expiration().


Summary: The index service would crash under some conditions if the data bucket was flushed while the index was being built.

Query Service

Issue Description


Summary: Starting this release, you can use the UNNEST scan to generate index spans on non-leading keys (non-array-index keys) if appropriate predicates exist on those keys.


Summary: Index creation using the IN clause did not work as expected. This has been fixed.

However, when using the IN clause, ensure that your queries use the same IN terms in the same order as in the index.


Summary: Fixed an issue so that when an on connection error is encountered, certain operations are retried before returning an error.


Summary: Fixed an issue so that connections are properly discarded when an Out of Bound data error is encountered.

Tools, Web Console (UI), and REST API

Issue Description


Summary: Fixed an issue where the Views UI was unable to process the "undefined" value in a binary JSON document.


Summary: The cbbackupmgr utility would hang and not return an error when trying to backup a cluster in which at least one node was down and had not failed over.


Summary: All requests originating from the UI were authenticated using token based authentication, even when client certificate authentication is enabled on the Server and a client certificate is configured in the browser. This has been fixed to use client certificates for authentication in such scenarios.

Release 6.0

Couchbase Server 6.0 was released in October 2018.

Major Behavior Changes

There are a few significant changes to the production-ready version of the Analytics service. You’ll find this information handy if you’ve used the Analytics service in any of the Developer Preview versions of Couchbase Server.

  • Bucket association is now automatic

    The Developer Preview versions required you to explicitly associate the Couchbase Server buckets and Analytics buckets. For example:

    CREATE BUCKET ha WITH {"name":"health"}

    The Analytics service buckets now automatically mirror Couchbase Server buckets and no special configuration is required to be able to create a dataset on a bucket.

  • Dataset definitions no longer require the SHADOW keyword

    The early Developer Preview releases (earlier than Couchbase Server 5.5) required the SHADOW keyword.

    The Analytics service (Developer Preview version) was integrated with Couchbase Server during release 5.5 and the SHADOW keyword was made optional.

    Starting with this release, using the SHADOW keyword is no longer allowed, and using it will return an error.

    CREATE DATASET ((dataverse_name.)? dataset_name)? ON bucket_name (WHERE where_exp)?.

    The CONNECT and DISCONNECT commands would activate or deactivate the dataset processing of data from Couchbase Server buckets.

    You can now use the following syntax to connect all datasets in a dataverse:

    CONNECT LINK (dataverse_name.)? Local (, (dataverse_name.)? Local)*

Deprecated Platforms

Support for the following platforms will be removed in a future release:

  • CentOS 6

  • macOS 10.11 (El Capitan)

  • Oracle Linux 6

  • Red Hat Enterprise Linux 6

  • SUSE Linux Enterprise Server (SLES) 11

  • Ubuntu 14.04

  • Windows Server 2012

New Supported Platforms

There are no new supported platforms in this release.

See Supported Platforms for the complete list of supported platforms.

Known Issues

Administration/Cluster Management

Issue Description


Summary: Performance issues may be observed when running Couchbase Server on CentOS 7.3 with kernel 3.10.0-514.6.

Analytics Service

Issue Description


Summary: Backup and restore for the Analytics service artifacts using the cbbackupmgr utility is currently not supported.


Summary: It is possible for a CONNECT BUCKET statement to fail temporarily with the error message "The vbucket belongs to another server(0x7)" when rebalancing Data nodes.

Workaround: Retry the operation.


Summary: Currently, the Analytics service supports index creation only when a dataset is disconnected.


Summary: The UNION ALL operation does not work for all query types. For example, a query of the form shown below is not parsed correctly.

---- (SELECT …​ FROM …​ WHERE …​) UNION ALL (SELECT …​ FROM …​ WHERE …​) ----

Workaround: Remove the parentheses around the first subquery block.


Data Service

Issue Description


Summary: If bucket memory usage exceeds the high watermark and reaches 99% of the bucket quota, a race condition in KV-Engine DCP consumer is exposed. This may result in DCP messages being processed out-of-order.


Summary: If the memcached process crashes while indexes are being rebalanced, the memcached process can fail to be brought online and the rebalance can get stuck. Manually stopping rebalance will bring the memcached process online.


Summary: The last_modified attribute can be incorrect if a bucket was upgraded and contains old documents.

Eventing Service

Issue Description


Summary: Killing an Eventing process externally may result in a loss of timers that have been dequeued but not run to completion.


Summary: When Sync Gateway is deployed against a bucket, a single document update can be seen over DCP as multiple mutations, some modifying body and others modifying XATTRs. The Eventing service invokes OnUpdate for each such mutation as it does not distinguish at the DCP level if an update modified the body of a document, the XATTRs, or both.

Workaround: When both Eventing service and Sync Gateway are deployed against the same bucket, you must ensure that the Eventing code written is idempotent.

Full-Text Search Service

Issue Description


Summary: The Search index file deletions take longer time than expected especially when the index is very large and is in a building-up phase while deleting. This delays the expected freeing up of the actual disk space right after an index deletion. No file leaks have been observed yet.

Workaround: If you wait long enough, all the index files will get cleaned up eventually. Hence in a tight disk space situation, you should be careful of this fact while performing subsequent index deletions and creations. With enough disk space configured, everything ought to work without much perceivable problems.


Summary: This problem becomes a concern when the system is under heavy DGM (Disk Greater than Memory) condition. In such cases, the Search service ends up having too many files in the system and due to concurrent file compactions, the overall indexing and querying becomes very slow.

Workaround: While there is no proper workaround for this issue, lowering the FTS memory quota (< 10GB) seems to help maintain a reasonably high average indexing throughput.


Summary: Scorch indexes were found to contain duplicate pindexes.

Index Service

Issue Description


Summary: A disk usage spike is observed during the initial index build. The disk usage comes down once the log cleaner catches up.


Summary: The rebalance progress (in percentage) during a GSI swap rebalance does not always increase linearly. Note that this issue does not persist and the percentage displayed returns to normal quickly.


Summary: Rebalance fails when taking out failed over nodes running views, in certain circumstances.

Install and Upgrade

Issue Description


Summary: In some instances, the Windows Uninstaller can leave behind registry entries and subsequently block upgrades on these machines.

Workaround: Remove the registry entries manually before installing newer versions of Couchbase Server.


Summary: On an undersized node, the default memory quota assigned to all the selected services by the server might result in a failure.

Workaround: Manually adjust the memory allocations appropriately.

Query Service

Issue Description

MB-29391, MB-29393

Summary: Large numeric values are reported incorrectly. For example, the modulo operation or a scan for min int64 value returns an incorrect result in case of int64.


Issue Description


Summary: All requests originating from the UI are currently authenticated using token based authentication, even when client certificate authentication is enabled on the Server and a client certificate is configured in the browser.


Summary: The Security > Users tab in the UI does not list the default "administrator" user.

Tools, Web Console (UI), and REST API

Issue Description


Summary: Unable to log in to the Couchbase Server Web Console (UI) using Internet Explorer 11 or Edge browsers.

Fixed Issues

The notable fixes in this release are listed below. See the Couchbase issue tracker for the complete list of enhancements and fixes in this release.

Data Service

Issue Description


Summary: The Memcached logs always use Z (UTC) for timezone when logging instead of the current system timezone offset.


Summary: Fetching a random key from the Data service may hang if the bucket contains zero documents.


Summary: The data service engine may not send STREAM_END message to consumers if non-infinity end sequence number and cursor dropping occurs. This could cause clients such as cbbackupmgr to hang indefinitely.


Summary: Ephemeral buckets can have tombstones purged before the configured metadata purge interval.

Ephemeral buckets can prematurely purge (discard) tombstones when under high memory and op/s load. As a consequence, DCP consumers fed by KV-Engine (such as replication, secondary indexing, views) may have tombstones not sent to them, meaning their dataset diverges from the Data Service - documents are not deleted from the DCP consumer.


Authenticated users with full administrative privileges were able to access the diagnostic endpoint, /diag/eval remotely, allowing these users to run arbitrary code on the server host. This issue is addressed by only allowing full administrators to access this endpoint from localhost. This mitigates the issue as users that have access to the server host are already in a position to run arbitrary code.

Note that the diag/eval endpoint is authenticated and requires the highest privileges in the system (Full Admin). It is the case that a user with access to this endpoint can already delete, corrupt or coy all the data in the system. Customers can mitigate this issue by tightly controlling access to full administrative privileges.

Full-Text Search Service

Issue Description


Summary: Fixed an issue where documents were missing from the Scorch index but were intact in an upside_down index.


Summary: Fixed an issue where the memory usage during search index build was found to overshoot the RAM quota.


Summary: Scorch indexes were found to contain duplicate pindexes.


Summary: On Windows platform, a very high memory/CPU usage was observed when search service was indexing using the fts index. This issue is not seen with the new default 'Scorch' index.

Index Service

Issue Description


Summary: Fixed an issue where the index service threw an error if an index was dropped when index mutation was ongoing.