Thanks for your response, Nicholas. No, site is unavailable for everybody. Users cant open the site in this time. Reindex may take 5 or 15 minutes. Sometimes it takes longer time.

That's not normal and sounds like this bug: http://issues.umbraco.org/issue/U4-6338

Basically, publish operations can cause an application pool restart, which can cause your website to be slow for a few minutes.

That issue has info on how to check if you are affected. The fix is to do Windows Update. Alternatively, you could just install this hotfix in particular: https://support.microsoft.com/en-us/kb/3052480

Thanks for suggestion, Nicholas. But we dont have installed KB3000850 or KB3007507, that can cause this problem. Furthermore, our umbraco version is 7.2.4, not 7.2.1, 6.2.5, 7.2.2. And also we have problems with loading images throw code. I use this code:

byte []mediaBytes=GetImageBytes();
    var newImage = mediaService.CreateMedia(fileName, parentId, "Image");
            MemoryStream strm = new MemoryStream(mediaBytes);
            newImage.SetValue("umbracoFile", fileName, strm);
            mediaService.Save(newImage);

After execution of this code we have following lines in log on main server: 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 71] ReIndexNode with type: media, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 71] AddSingleNodeToIndex with type: media, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 71] ReIndexNode with type: media, Provider=ExternalIndexer, NodeId=429675 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 71] AddSingleNodeToIndex with type: media, Provider=ExternalIndexer, NodeId=429675 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 84] Index created for node 429675, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:29,367 [45] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 81] Index created for node 429675, Provider=ExternalIndexer, NodeId=429675 2015-10-26 11:02:30,539 [45] DEBUG Umbraco.Web.UmbracoModule - [Thread 84] Begin request: http://srv-01.tdec.local/umbraco/backoffice/UmbracoApi/Authentication/GetRemainingTimeoutSeconds. 2015-10-26 11:02:31,023 [45] DEBUG Umbraco.Core.Sync.DefaultServerMessenger - [Thread 71] Performing distributed call for refresher Umbraco.Web.Cache.MediaCacheRefresher, message type: RefreshByJson, servers: http://srv-01.tdec.local/umbraco/webservices/cacheRefresher.asmx;http://serv-2.tdec.local/umbraco/webservices/cacheRefresher.asmx;http://serv-3.tdec.local/umbraco/webservices/cacheRefresher.asmx, ids: , json: [{"Path":"-1,1063,429676","Id":429676,"Operation":0}] 2015-10-26 11:02:31,023 [45] DEBUG Umbraco.Core.Sync.DefaultServerMessenger - [Thread 71] Invoking refresher Umbraco.Web.Cache.MediaCacheRefresher on single server instance, message type RefreshByJson

And lines in log on child (frontend servers): [Thread 57] ReIndexNode with type: media, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:44,293 [16] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 57] AddSingleNodeToIndex with type: media, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:44,293 [16] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 57] ReIndexNode with type: media, Provider=ExternalIndexer, NodeId=429675 2015-10-26 11:02:44,293 [16] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 57] AddSingleNodeToIndex with type: media, Provider=ExternalIndexer, NodeId=429675 2015-10-26 11:02:44,434 [16] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 61] Index created for node 429675, Provider=InternalIndexer, NodeId=429675 2015-10-26 11:02:44,512 [16] DEBUG UmbracoExamine.DataServices.UmbracoLogService - [Thread 37] Index created for node 429675, Provider=ExternalIndexer, NodeId=429675

When MediaCacheRefresher is running, we have database timeout errors on pages of our site. We use dedicated server with MS SQL 2012.

Timeout errors in log on frontend servers: [16] WARN NHibernate.Util.ADOExceptionReporter - System.ComponentModel.Win32Exception (0x80004005): The wait operation timed out [16] ERROR NHibernate.Util.ADOExceptionReporter - The wait operation timed out [16] WARN NHibernate.Util.ADOExceptionReporter - System.Data.SqlClient.SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. ---> System.ComponentModel.Win32Exception (0x80004005): The wait operation timed out at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at System.Data.SqlClient.SqlDataReader.TryReadInternal(Boolean setTimeout, Boolean& more) at System.Data.SqlClient.SqlDataReader.Read() at NHibernate.Driver.NHybridDataReader.Read() at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies, IResultTransformer forcedResultTransformer) at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies, IResultTransformer forcedResultTransformer) at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters, IResultTransformer forcedResultTransformer) ClientConnectionId:d6d9e7a2-cef2-4109-88a1-f9505da108b4 [16] ERROR NHibernate.Util.ADOExceptionReporter - Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Can you suggest something how to solve this problems with MediaCacheRefresher?