[stable20] Support LDAP dns longer than 255 characters

[come-nc]

Backport #29523

[skjnldsv]

Failure seems related. LDAP query is too big

+ bash tests/drone-run-php-tests.sh || exit 0
=========================
= List of changed files =
=========================
apps/user_ldap/appinfo/info.xml
apps/user_ldap/composer/composer/autoload_classmap.php
apps/user_ldap/composer/composer/autoload_static.php
apps/user_ldap/lib/Mapping/AbstractMapping.php
apps/user_ldap/lib/Migration/Version1010Date20200630192842.php
apps/user_ldap/lib/Migration/Version1120Date20210917155206.php
apps/user_ldap/lib/Migration/Version1130Date20211102154716.php
=========================
info.xml files are modified
+ NOCOVERAGE=true TEST_SELECTION=DB ./autotest.sh mysql
Using PHP executable /usr/bin/php
Using database oc_autotest
Setup environment for mysql testing on local storage ...
Waiting for MySQL initialisation ...
..
Installing ....
Nextcloud was successfully installed
Testing with mysql ...
No coverage
/usr/local/bin/phpunit --configuration phpunit-autotest.xml --group DB,SLOWDB --log-junit autotest-results-mysql.xml  
PHPUnit 8.5.2 by Sebastian Bergmann and contributors.

Runtime:       PHP 7.2.27-5+0~20200202.35+debian8~1.gbp2925f8
Configuration: /drone/src/tests/phpunit-autotest.xml

........

SQLSTATE[08S01]: Communication link failure: 1153 Got a packet bigger than 'max_allowed_packet' bytes

/drone/src/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:106
/drone/src/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php:169
/drone/src/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php:149
/drone/src/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php:914
/drone/src/lib/private/DB/Connection.php:202
/drone/src/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Query/QueryBuilder.php:206
/drone/src/lib/private/DB/QueryBuilder/QueryBuilder.php:248
/drone/src/apps/user_ldap/lib/Mapping/AbstractMapping.php:218
/drone/src/apps/user_ldap/lib/Mapping/AbstractMapping.php:259
/drone/src/apps/user_ldap/tests/Mapping/AbstractMappingTest.php:300

[come-nc]

Thank you for the information.

So after a bit more investigation:
The test failing maps 3332 users with short generated DNs (like uid=as_12,dc=example,dc=com).
Then it asks the mappers for their uids, passing the list of all the DNs.
Because the sha256 hash is longer than these DNs, we hit a request size limit.

I am not sure how to avoid this, whether this test makes sense, and especially why this is only failing on mysql5.6.

[juliusknorr]

MySQL 5.6 has a lower default value for the

https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_max_allowed_packet 4194304
https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_max_allowed_packet 67108864

Decreasing the chunking in

server/apps/user_ldap/lib/Mapping/AbstractMapping.php

Lines 232 to 241 in 5a2b7fb

	$sliceSize = 1000;
	$maxSlices = $totalDBParamLimit / $sliceSize;
	$results = [];
	$slice = 1;
	$fdns = array_map([$this, 'getDNHash'], $fdns);
	$fdnsSlice = count($fdns) > $sliceSize ? array_slice($fdns, 0, $sliceSize) : $fdns;
	$qb = $this->prepareListOfIdsQuery($fdnsSlice);
	while (isset($fdnsSlice[999])) {

to use a shorter sql query might be an option, but I'm wondering if maybe it would be better to just add a higher max_allowed_packet size to our db recommendations.