SegmentNotFoundException in AEM

Fixing SegmentNotFoundException issue:

In this blog I am going to explain how we can fix the repository inconsistencies. When the repository corrupts due to inconsistencies in the repository, the server itself start properly.

Whenever we see an exception like below in the error log, we need to revert back the oak repository to good revision of a segment store.

Exception in thread "main" org.apache.jackrabbit.oak.plugins.segment.SegmentNotFoundException: Segment a7aecb54-aec0-4bec-a3cc-0721b81a60b0 not found

To fix the above problem we need to run the oak utility to find the last latest good revision change into Oak's working directory (the one containing the crx-quickstart folder). Please follow the below steps to fix the issue.

• Run the consistency check,

java -jar oak-run.jar check -d1 --bin=-1 -p /<aem-install-dir>/crx-quickstart/repository/segmentstore/

• It will search backwards through the revisions until it finds a consistent one:

14:00:30.783 [main] INFO  o.a.j.o.p.s.f.t.ConsistencyChecker - Found latest good revision afdb922d-ba53-4a1b-aa1b-1cb044b535cf:234880

16:52:16.937 [main] DEBUG o.a.j.o.p.s.f.t.ConsistencyChecker - Checking /apps/psw/www-perceptivesoftware-com/install/psw.com-services-1.0.0.0.1-SNAPSHOT.jar/jcr:content/jcr:uuid = bd9c3908-4f27-4d64-becf-b12b15792da7

16:52:17.050 [main] INFO  o.a.j.o.p.s.f.t.ConsistencyChecker - Traversed 35427133 nodes and 40187798 properties

16:52:17.050 [main] INFO  o.a.j.o.p.s.f.t.ConsistencyChecker - Found latest good revision dc9944de-71bd-4804-a494-9b277bcac833:261784

16:52:17.050 [main] INFO  o.a.j.o.p.s.f.t.ConsistencyChecker - Searched through 462 revisions

• Revert the repository to this revision by editing

./crx-quickstart/repository/segmentstore/journal.log

• Delete all lines after the line containing the latest good revision from journal.log
• Remove all ./crx-quickstart/repository/segmentstore/*.bak files.
• Run checkpoint clean-up to remove orphaned checkpoints:

java -jar oak-run-*.jar checkpoints ./crx-quickstart/repository/segmentstore rm-unreferenced

• Finally compact the repository:

java -jar oak-run-*.jar compact ./crx-quickstart/repository/segmentstore/

MORE INFORMATION ABOUT OAK TOOL CAN BE FOUND HERE:

https://github.com/apache/jackrabbit-oak/blob/trunk/oak-run/README.md#check

Warning: When we run this consistency check, due to the nature of this function the latest changes will lost and reverts to the last good revision available in journey.log.

Major Differences from AEM 6.1 & 6.2

Changes from AEM 6.1 to 6.2

Adobe Experience Manager 6.2 is generally available since April 21, 2016.

User Interface

• The user interface is in transition from Coral UI 2 to the Web Component based Coral 3 UI library.
• The product navigation has moved from the side rail to an overlay and provides access to the product areas - and the tools.

Template Editor

The Template Editor introduces a few new concepts that makes it easier to create a template in the 1st place, and allow components to be reused more often.

• First, instead of using Sling includes in the components to nested them to a template, the nesting is stored in a new way - and while rendering the page merged with the content structure.
• Second, with the introduction of the Policies it's possible to have component design configuration being reused.
• Third, while technically not new, an easy way to manage the initial content that should appear when a new page is created with the template.

The Template Editor UI works very much like the Page Editor, with the difference that it starts with a blank canvas.

The template editor allows authors to:

• Add (available) components to the template and position them on a responsive grid.
• Pre-configure the components.
• Define which components can be edited on the resultant pages (created from the template).

Note: The Templates console and editor are only available with the touch-optimized UI.

Click here for the Editable Templates workbook: Templates Work book

Content Distribution

The next generation content replication capability - was 1st introduced in AEM 6.1(only UGC replication). With AEM 6.2, additional supported use cases were added:

• Package replication to support extra large activation volumes
• Priority-Queuing configuration to allow split between urgent activations and backlog
• Auto-unlocking stuck replication queues incl advanced notifications

Content Distribution comes with an UI in the Tools/Deployment section.

Technical requirement

Software	Version
Java	1.8
Apache httpd	2.2/2.4.x
Dispatcher	4.1.12
Cloud	AWS/Rackspace/VMware VCloud
OS	Linux Kernel 2.6 and 3.x includes derivatives from Red Hat distribution, including Red Hat Enterprise Linux, CentOS, Oracle Linux and Amazon Linux

Hardware	Type
Linux/Windows	Intel Xeon or AMD Opteron CPU with at least 4 cores
RAM	16GB Minimum
Linux	64-bit

Offline revision cleanup(tar compaction) is the recommended way of performing revision cleanup. Support for Online revision cleanup in AEM 6.2 is restricted. For more guidelines please see Choosing the Type of Revision Cleanup.

Thread dumps

With AEM6.2, the thread dumps are enabled by default and collects the data every minute. They will be available on the physical location of <aem-install-dir>/crx-quickstart folder. We can also download them from UI from below path.

Tools → Operations → Diagnosis → Download Thread Dump.

This will contain the gzip files of last two days. We can download them. But in my personal opinion, we don’t need them on daily basis. We can collect them manually whenever we need so. We can turn off this from the Felix console. Below is the config name:

Granite Thread Dumps Collector

CRXDE

With the 6.2 version for security reasons when we bring the servers in production ready mode(nosamplecontent as runmode) then the crxde will not show anything. To get the nodes back in crxde execute the below curl command.

curl -u admin:<password> -F "jcr:primaryType=sling:OsgiConfig" -F "alias=/crx/server" -F "dav.create-absolute-uri=true" -F "dav.create-absolute-uri@TypeHint=Boolean" http://<host>:<port>/apps/system/config/org.apache.sling.jcr.davex.impl.servlets.SlingDavExServlet

For More Information:

https://docs.adobe.com/docs/en/aem/6-2/administer/security/security-checklist/enabling-crxde-lite.html

Content Fragment in Detail: Details can be found at here: https://docs.adobe.com/docs/en/aem/6-2/author/page-authoring/content-fragments.html

• The functionality of Content Fragment Management is only available with the touch-optimized UI.
• The Content Fragment component can be seen in the classic UI sidekick, but further functions are not available.