bookmark_borderDAVx5 CalDAV may break with Unicode symbols in Horde/Kronolith syncs.

If you get user complaints about broken CalDAV syncs with Horde, there’s many places to look at. In one particular instance, an event was created from travelling app Transportr into the stock android Calendar app. Through the DAVx5 sync app, the user wanted to push these events to Horde’s SabreDAV interface – and from there, also sync it to his desktop email solution, Mozilla Thunderbird.

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However, his sync application told him about an error. The server administrator saw a 500 status code in the server log. - user [24/Jan/2021:18:48:26 +0000] "PUT /horde/rpc/calendars/user/calendar~KL14jYhCMpbet4ecYzAg1bn/2bace303-f0d8-4df6-9652-baa5fb9e86c4.ics HTTP/1.1" 500 892 "-" "DAVx5/3.3.8-ose (2021/01/13; dav4jvm; okhttp/4.9.0) Android/11

The root cause was actually not in the software code but in the MariaDB database configuration. The calendar entry from Transportr included some Unicode icon characters like a fast train and some arrows. These characters are part of the standard unicode encoding, utf-8.

Now you might wonder: New installations of mysql and MariaDB default to a character set they call utf-8 since 2010 or so. This shouldn’t be an issue. However, what they call utf-8 is not what you would expect.

Some years ago, TV sets which did not support the full HD resolution were marketed as “HD ready”. In some sense, the default character set is “unicode ready” at best. The default data type saves on disk space by encoding a subset of utf-8 into up to three bytes. While this supports most natural language characters, it is only a fraction of what Unicode can offer. Database manufacturers are well aware that this is not something you should run nowadays that unicode icons like the hamburger are all over the place is user generated content. The mysql manual even says:

“Please use utf8mb4 instead. Although utf8 is currently an alias for utf8mb3, at some point utf8 is expected to become a reference to utf8mb4. To avoid ambiguity about the meaning of utf8, consider specifying utf8mb4 explicitly for character set references instead of utf8.”

Now that’s what I did. First I changed horde’s database encoding to utf8mb4 in conf.php:

$conf['sql']['protocol'] = 'tcp';
$conf['sql']['charset'] = 'utf8mb4';

Then I changed the mysql server’s and client’s default charset:

cat /etc/mysql/my.cnf
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
default-character-set = utf8mb4
default-character-set = utf8mb4
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

I have obviously stripped a lot of file content not relevant to our story. After reloading the database, all new connections should use the real utf8 encoding and new tables should be created with the new standard. But what about existing content? We need to convert all tables and all their text-like columns, varchars, mediumtexts etc.

First, it’s backup time – better safe than sorry.

Then, let’s find all tables in our db server and feed them conversion commands.

mysql --database=horde -B -N -e "SHOW TABLES" | awk '{print "ALTER TABLE", $1, "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"}' | mysql --database=horde

Do this in a downtime or ensure HA some way or other. It will take some time. Some sources suggest it might be sensible to also rebuild the tables with the optimize command. I am not very convinced, but it won’t harm.

mysqlcheck --auto-repair --optimize --user="hidden" -p --databases mysql horde

After this, repeat the sync test. It should work this time.

bookmark_borderSLES 11: Upgrading mysql from SP2 to SP3

Under some condition, mysql is not able to restart after an upgrade from SLES11 SP2 to SLES11 SP3. The output messages are a bit misleading

131122 14:41:28 InnoDB: The InnoDB memory heap is disabled
131122 14:41:28 InnoDB: Mutexes and rw_locks use GCC atomic builtins
131122 14:41:28 InnoDB: Compressed tables use zlib 1.2.7
131122 14:41:28 InnoDB: Using Linux native AIO
131122 14:41:28 InnoDB: Initializing buffer pool, size = 128.0M
131122 14:41:28 InnoDB: Completed initialization of buffer pool
131122 14:41:28 InnoDB: highest supported file format is Barracuda.
131122 14:41:28 InnoDB: Waiting for the background threads to start
131122 14:41:29 InnoDB: 5.5.33 started; log sequence number 4796605421
/usr/sbin/mysqld: Out of memory (Needed 64 bytes)
131122 14:41:29 [ERROR] Plugin 'INNODB_CMP' registration as a INFORMATION SCHEMA failed.
131122 14:41:29 InnoDB: Unable to allocate memory of size 8120.
131122 14:41:29 InnoDB: Assertion failure in thread 140387876259584 in file mem0mem.c line 361
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: about forcing recovery.
13:41:29 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.


In the end it turned out to be a permission problem with /var/run/mysql
To fix this:

chown -R mysql /var/run/mysql
rcmysql restart

This did it for me. I had this problem on several but not all instances of mysql on SLES11SP2 upgrading to SLES11SP3. My wild guess is that it is based upon if this was a fresh SP2 install or upgraded from an earlier service pack.

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bookmark_borderHeads Up: PHP deprecates mysql extension in 5.5.

In a recent developer vote, the php project decided to deprecate the mysql extension in PHP 5.5 and finally remove it from the main PHP project. It may or may not be available for a longer period as a PECL extension.

The mysql extension has long been superseded by two more powerful extensions, PDO/Mysql and mysqli (improved). For years, the older extension has not received any new features and the developers kept it around just to keep compatibility with old code. Framework and application developers are now urged to update their code to use one of the alternative mysql APIs. There are a lot of old code snippets and tutorials around which describe the old API. Eventually, this code will begin to throw warnings and finally stop to work.

Developers discussed the impact of this move on end users. While it might be shocking to see hordes of old installations break just because the hoster updates his PHP version, there is no need to panic. Most hosters have not clenbuterol hydroklorid clen kjope even upgraded to the recent PHP 5.4 release and it might be years to go until PHP 5.6 finally hits enterprise distributions like SLES or RHEL. Additionally, distributors and hosters might opt to provide the PECL version of the mysql extension for backward compatibility. There is enough time left for developers and end users to react on the coming change.

More on the deprecation vote