Release Notes

EventStoreDB 4.1.1 Release

Shaan Nobee  |  02 May 2018

We are excited to announce that Event Store 4.1.1 has just been released! It is available for the following operating systems:

  • Windows (via Chocolatey)
  • Ubuntu 18.04 (via packagecloud)
  • Ubuntu 16.04 (via packagecloud)
  • Ubuntu 14.04 (via packagecloud)

Major Bug Fixes

This release comes with two major bug fixes.

1. Overflow bug during PTable construction with –skip-index-verify

Affected OS: All OSes

Necessary Conditions:

  • Run EventStore with –skip-index-verify / SkipIndexVerify: True. This option is only available as from version 4.1.0.
  • An index merge happens resulting in a PTable with more than Int32.MaxValue (2147483647) index entries


The node will exit with an error similar to the following in the logs:

ReadIndex is corrupted...
EventStore.Core.Exceptions.CorruptIndexException: Error while loading IndexMap.
EventStore.Core.Exceptions.CorruptIndexException: Item index for midpoint 8856062 (2147483525) > Item index for midpoint 8856063 (-2147483526)
 at EventStore.Core.Index.PTable.CacheMidpointsAndVerifyHash(Int32 depth, Boolean skipIndexVerify)


  • The node will exit with the above exception just after the PTable merge when the new PTable is loaded
  • A full rebuild of indexes will occur on the next startup but the same error will be thrown again
  • There is no data corruption

There are two options to prevent this error from occuring:

  • The node must be upgraded to version 4.1.1
  • SkipIndexVerify option must not be enabled

2. Handle unauthorised access exceptions when replacing indexmap files

Affected OS: Windows only
The node will exit with an error similar to the following in the logs:

Error in TableIndex.ReadOffQueue
System.UnauthorizedAccessException: Access to the path '\path\to\index\indexmap' is denied.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.InternalDelete(String path, Boolean checkHost)
   at EventStore.Core.Index.IndexMap.SaveToFile(String filename)

This issue occurs when the Read-Only attribute is set on the indexmap file.


  • The node will exit with the above exception
  • There is no data corruption

Index Merge Improvements

PTable merges of index entries that map to scavenged chunks in the database are much slower than merging index entries mapping to non-scavenged chunks by a factor of approximately 10x. The main overhead is due to the time taken to verify if an index entry is still present in the scavenged chunk file. This check is not necessary for non-scavenged chunks because all the entries are still present.

We have made some performance improvements in this area where a user can choose to trade off some memory for speed gains and reduced disk pressure during merges. Our tests show speed gains of around 8x.

You can estimate the maximum amount of additional memory (in GB) you will need with the following formula:
Avg. number of events per chunk file / 40000

For example, with 200000 events per chunk file, the maximum amount of memory required will be 5GB.

This feature is not enabled by default. You can enable it by adding OptimizeIndexMerge: true to your config or adding –optimize-index-merge to your command line arguments.

Client Changes (Non-breaking)

#1583 - (All Platforms) Add ability to add custom node discovery

This allows custom implementation of node discovery by implementing the IEndPointDiscoverer interface (for example, to obtain IP endpoints from consul or text files). The method Create(ConnectionSettings connectionSettings, IEndPointDiscoverer endPointDiscoverer, string connectionName) has been added to EventStoreConnection.

#1582 - (All Platforms) Add queue timeout facility

SetQueueTimeoutTo(TimeSpan timeout) in ConnectionSettingsBuilder

This allows the client to apply backpressure during an overload when the operations queue is full and many operations are waiting to be processed. An OperationExpiredException exception will be thrown if an operation stays in the queue for longer than the timeout set.

By default, no exception will be thrown (as in previous versions) unless SetQueueTimeoutTo is called on the builder.

Thanks to bartelink for contributing this feature!

#1578 - (All Platforms) KeepDiscovering option added for infinite nodes discovery attempts

Add KeepDiscovering() to your ClusterSettingsBuilder

#1557 - (All Platforms) Add PreferSlaveNode to Connection Builder

Add PreferSlaveNode() to your ConnectionSettingsBuilder or ClusterSettingsBuilder to prefer doing operations on slave nodes. This also requires adding PerformOnAnyNode() on the ConnectionSettingsBuilder

Thanks to Salgat for contributing this feature!

Full Changelog


  • #1613 - (All Platforms) Handle unauthorised access exceptions when replacing indexmap files.
  • #1591 - (All Platforms) Overflow bug when caching midpoints to PTable with more than Int.MaxValue entries
  • #1580 - (All Platforms) Allow event data/metadata to be stored as JSON array through HTTP API
  • #1572 - (All Platforms) Add ResponseUrl to HttpEntity to allow prefixes to be used
  • #1561 - (All Platforms) Fix collection modified exceptions that can occur and fault a projection
  • #1555 - (All Platforms) Add timeout functionality to IODispatcher.
  • #1548 - (All Platforms) AsyncWrapper Log fix
  • #1547 - (All Platforms) Optimize existAt calls on scavenged chunks using bloom filters for faster index merges

Persistent Subscription

  • #1560 - (All Platforms) Persistent subscription bug fix: when reading end of stream and a live event is received


  • #1579 - (All Platforms) Add linkMetadata to event feed reader (Projection debugging)


  • #193 - (All Platforms) Reorder and keep next/prev button fixed
  • #191 - (All Platforms) UI fix: Long string in state/results box moves projection stats to far right
  • #190 - (All Platforms) Projection debugging: State was not being updated when processing last event
  • #189 - (All Platforms) linkMetadata parameter missing from runStep()
  • #187 - (All Platforms) Added EventId to the event details view

.NET Client

  • #1611 - (All Platforms) Add TRACE constant to ClientAPI to be able to use System.Diagnostics.WriteLine with Debug Logger
  • #1601 - (All Platforms) Make UseDebugLogger write to Debugger from NuGet version of client lib OOTB
  • #1583 - (All Platforms) Add ability to add custom node discovery
  • #1600 - (All Platforms) Handle IPv6 addresses from Dns.GetHostAddresses
  • #1582 - (All Platforms) Add queue timeout facility
  • #1578 - (All Platforms) KeepDiscovering option added for infinite nodes discovery
  • #1567 - (All Platforms) Remove Thread.Sleep from ClientAPI
  • #1557 - (All Platforms) Add PreferSlaveNode to Connection Builder

Photo of Shaan Nobee

Shaan Nobee Shaan joined Event Store in 2017 as a software engineer and works on the core database engine. He is from Mauritius, a beautiful and peaceful island in the Indian Ocean.