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Asynchronous Reference Indexing for TYPO3

Delegates reference index updating to an asynchronous queue, processed by CLI / scheduler

What does it do?

Provides a couple of things:

  • An override class for DataHandler which replaces a single method, updateRefIndex, causing on-the-fly indexing to be skipped, instead delegating to a queue.
  • A similar override for the ReferenceIndex class which replaces methods called also outside of DataHandler, to catch those cases.
  • An SQL table storing queued reference index updates.
  • A CommandController which can be executed via CLI to process queued reference indexing without running into timeout or long wait issues.
  • Provides option to exclude tables from reference indexing (only on TYPO3 8.6+). See extension configuration.

Depending on how often your editors perform record imports, copies, deletions etc. this can over time save many, many hours of waiting for the TYPO3 backend to respond.

For further information about the performance aspects see the "Background" section below.

Installing

Only available through Packagist (or via GitHub). Installation via Composer is recommended:

composer require namelesscoder/asynchronous-reference-indexing

Then enable the extension in TYPO3. This can be done with a CLI command:

TYPO3_PATH_ROOT=$PWD/web vendor/bin/typo3 extensionmanager:extension:install asynchronous_reference_indexing

Word of warning

Failing to update the reference index can have negative effects on your site in some cases, both in frontend and backend. You are advised to add a scheduler task or cronjob for the included command controller and set the frequency to a very low value such as once every minute. The controller maintains a lock file and prevents parallel executions, so frequent runs are safe.

Note that this extension consistently captures all of the current reference indexing, including that which you can trigger using the existing (non-Extbase) CLI command or via the "DB check" backend module which is added when you install the lowlevel system extension. Using either of these methods to force reference index updating will instead fill the queue for the command controller included with this extension so that all existing records which have relations will be processed on the next run.

Possible side effects

Delaying update of the reference index has one main side effect: if the editor tries to delete a record whose relations have not been indexed, an appropriate warning may not be shown.

Secondary side effect is in listing of relationships between records. Such information will be updated only when the command controller runs.

Frontend rendering should not be affected negatively.

Usage

To re-index a site from scratch you would normally execute the following command, if you have a lot of garbage in the sys_refindex table you might wan't to truncate it before:

TYPO3_PATH_ROOT=$PWD/web vendor/bin/typo3cms asyncreferenceindex:update --force 1

Afterwards you can update the sys_refindex by executing the command:

TYPO3_PATH_ROOT=$PWD/web vendor/bin/typo3cms asyncreferenceindex:update

Alternatively you can setup a Scheduler Task to execute the command at a certain interval.

Background

This community extension exists for one reason alone: increasing responsiveness of the TYPO3 backend when performing record operations. Due to the internal structure of the ReferenceIndex class in TYPO3, any record operation which might potentially change references causes an extreme amount of SQL traffic.

At the time of writing this (2016-12-04) the problem can be illustrated as follows:

  • Assume you use sys_category relations for 10,000 different records (from any table to one sys_category)
  • Updating, importing, deleting or copying any record pointing to this sys_category triggers index update
  • Index update itself cascades to process all 10,000 sys_category records for every record you edited
  • Depending on the number of records you edited this may cause hundreds of thousands of SQL requests

A significant effort has already been made to improve the reference indexing performance, however, all improvements are inevitably minor without a complete rewrite of the entire reference indexing logic. Again, at the time of writing this, the ReferenceIndex and RelationHandler classes are mutually dependent and will recursively call each other, thus further compounding the performance problem described above. Since these technical challenges are very hard to overcome, this extension is presented as a temporary solution to increase responsiveness of record operations in TYPO3 by upwards of 90% reduction in wall time.

You read that right. 90% - nine-zero percent.

Credit

This work and all preceding investigation was sponsored by Systime. Systime is a Danish online publishing firm specialising in "i-books" for the educational market, and they faced severe problems with reference indexing in particular.

References

(performance profiles not linked as they are not permanently online)