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# 8 Known issues

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#### Proxy startup with MySQL 8.0.0-8.0.17

zabbix\_proxy on MySQL versions 8.0.0-8.0.17 fails with the following
"access denied" error:

    [Z3001] connection to database 'zabbix' failed: [1227] Access denied; you need (at least one of) the SUPER, SYSTEM_VARIABLES_ADMIN or SESSION_VARIABLES_ADMIN privilege(s) for this operation

That is due to MySQL 8.0.0 starting to enforce special permissions for
setting session variables. However, in 8.0.18 this behavior was removed:
[As of MySQL 8.0.18, setting the session value of this system variable
is no longer a restricted
operation.](https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html)

The workaround is based on granting additional privileges to the
`zabbix` user:

For MySQL versions 8.0.14 - 8.0.17:

    grant SESSION_VARIABLES_ADMIN on *.* to 'zabbix'@'localhost';

For MySQL versions 8.0.0 - 8.0.13:

    grant SYSTEM_VARIABLES_ADMIN on *.* to 'zabbix'@'localhost';

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. 
#### Installation from packages

It has been observed that it is impossible to install a specific frontend version 
by running, e.g.:

    yum install -v zabbix-web-mysql-scl-5.0.0

As a workaround to this issue, if you wish to install a specific frontend version, 
specify version for all components, e.g.:

    yum install zabbix-web-mysql-scl-5.0.0 zabbix-apache-conf-scl-5.0.0 zabbix-web-5.0.0 zabbix-web-deps-scl-5.0.0

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#### Database connection encryption

Database connection encryption is not supported on RHEL/CentOS 7,
because these systems ship with packages that are too old:

    Name        : mariadb-libs
    Version     : 5.5.65

    Name        : postgresql-libs
    Version     : 9.2.24

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#### Timescale DB

PostgreSQL versions 9.6-12 use too much memory when updating tables with
a large number of partitions ([see problem
report](https://www.postgresql-archive.org/memory-problems-and-crash-of-db-when-deleting-data-from-table-with-thousands-of-partitions-td6108612.html)).
This issue manifests itself when Zabbix updates trends on systems with
TimescaleDB if trends are split into relatively small (e.g. 1 day)
chunks. This leads to hundreds of chunks present in the trends tables
with default housekeeping settings - the condition where PostgreSQL is
likely to run out of memory.

The issue has been resolved since Zabbix 5.0.1 for new installations
with TimescaleDB, but if TimescaleDB was set up with Zabbix before that,
please see
[ZBX-16347](https://support.zabbix.com/browse/ZBX-16347?focusedCommentId=430816&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-430816)
for the migration notes.

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#### Upgrade with MySQL below 5.7.0 or MariaDB below 10.2.2

Upgrading Zabbix may fail if database tables were created with older DB
versions (MySQL versions prior to 5.7 or MariaDB versions prior to
10.2.2), because in those versions the default row format is compact.

This can be fixed by changing the row format to dynamic. See also
[ZBX-17690](https://support.zabbix.com/browse/ZBX-17690) (MariaDB) and
[ZBX-20165](https://support.zabbix.com/browse/ZBX-20165) (MySQL).

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#### Database TLS connection with MariaDB

Database TLS connection is not supported with the 'verify\_ca' option
for the DBTLSConnect [parameter](/manual/appendix/config/zabbix_server)
if MariaDB is used.

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#### Possible deadlocks with MySQL/MariaDB

When running under high load, and with more than one LLD worker involved, it is possible to run into a deadlock caused by an 
InnoDB error related to the row-locking strategy (see [upstream bug](https://github.com/mysql/mysql-server/commit/7037a0bdc83196755a3bf3e935cfb3c0127715d5)). 
The error has been fixed in MySQL since 8.0.29, but not in MariaDB. For more details, see [ZBX-21506](https://support.zabbix.com/browse/ZBX-21506).

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#### Global event correlation

Events may not get correlated correctly if the time interval between the
first and second event is very small, i.e. half a second and less.

[comment]: # ({/70c19e71-70c19e71})

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#### Numeric (float) data type range with PostgreSQL 11 and earlier

PostgreSQL 11 and earlier versions only support floating point value
range of approximately -1.34E-154 to 1.34E+154.

[comment]: # ({/215c95a7-215c95a7})

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#### NetBSD 8.0 and newer

Various Zabbix processes may randomly crash on startup on the NetBSD
versions 8.X and 9.X. That is due to the too small default stack size
(4MB), which must be increased by running:

    ulimit -s 10240

For more information, please see the related problem report:
[ZBX-18275](https://support.zabbix.com/browse/ZBX-18275).

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#### IPMI checks

IPMI checks will not work with the standard OpenIPMI library package on
Debian prior to 9 (stretch) and Ubuntu prior to 16.04 (xenial). To fix
that, recompile OpenIPMI library with OpenSSL enabled as discussed in
[ZBX-6139](https://support.zabbix.com/browse/ZBX-6139).

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#### SSH checks

Some Linux distributions like Debian, Ubuntu do not support encrypted
private keys (with passphrase) if the libssh2 library is installed from
packages. Please see
[ZBX-4850](https://support.zabbix.com/browse/ZBX-4850) for more details.

When using libssh 0.9.x on CentOS 8 with OpenSSH 8 SSH checks may
occasionally report "Cannot read data from SSH server". This is caused
by a libssh
[issue](https://gitlab.com/libssh/libssh-mirror/-/merge_requests/101)
([more detailed report](https://bugs.libssh.org/T231)). The error is
expected to have been fixed by a stable libssh 0.9.5 release. See also
[ZBX-17756](https://support.zabbix.com/browse/ZBX-17756) for details.

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#### ODBC checks

-   MySQL unixODBC driver should not be used with Zabbix server or
    Zabbix proxy compiled against MariaDB connector library and vice
    versa, if possible it is also better to avoid using the same
    connector as the driver due to an [upstream
    bug](https://bugs.mysql.com/bug.php?id=73709). Suggested setup:

```{=html}
<!-- -->
```
    PostgreSQL, SQLite or Oracle connector → MariaDB or MySQL unixODBC driver
    MariaDB connector → MariaDB unixODBC driver
    MySQL connector → MySQL unixODBC driver

Please see [ZBX-7665](https://support.zabbix.com/browse/ZBX-7665) for
more information and available workarounds.

-   XML data queried from Microsoft SQL Server may get truncated in
    various ways on Linux and UNIX systems.

```{=html}
<!-- -->
```
-   It has been observed that using ODBC checks on CentOS 8 for
    monitoring Oracle databases using Oracle Instant Client for Linux
    11.2.0.4.0 causes the Zabbix server to crash. The issue can be
    solved by upgrading Oracle Instant Client to 12.1.0.2.0, 12.2.0.1.0,
    18.5.0.0.0 or 19. See also
    [ZBX-18402](https://support.zabbix.com/browse/ZBX-18402).

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#### Incorrect request method parameter in items

The request method parameter, used only in HTTP checks, may be
incorrectly set to '1', a non-default value for all items as a result of
upgrade from a pre-4.0 Zabbix version. For details on how to fix this
situation, see [ZBX-19308](https://support.zabbix.com/browse/ZBX-19308).

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#### Web monitoring and HTTP agent

Zabbix server leaks memory on CentOS 6, CentOS 7 and possibly other
related Linux distributions due to an [upstream
bug](https://bugzilla.redhat.com/show_bug.cgi?id=1057388) when "SSL
verify peer" is enabled in web scenarios or HTTP agent. Please see
[ZBX-10486](https://support.zabbix.com/browse/ZBX-10486) for more
information and available workarounds.

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#### Simple checks

There is a bug in **fping** versions earlier than v3.10 that mishandles
duplicate echo replay packets. This may cause unexpected results for
`icmpping`, `icmppingloss`, `icmppingsec` items. It is recommended to
use the latest version of **fping**. Please see
[ZBX-11726](https://support.zabbix.com/browse/ZBX-11726) for more
details.

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#### Errors with fping execution in rootless containers

When containers are running in rootless mode or in a specific-restrictions environment, you may face errors related to fping execution when performing ICMP checks, such as `fping: Operation not permitted` or all packets to all resources lost. 

To fix this problem add `--cap-add=net_raw` to "docker run" or "podman run" commands. 

Additionally fping execution in non-root environments may require sysctl modification, i.e.: 

    sudo sysctl -w "net.ipv4.ping_group_range=0 1995"

where "1995" is the zabbix GID. For more details, see [ZBX-22833](https://support.zabbix.com/browse/ZBX-22833).

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#### SNMP checks

If the OpenBSD operating system is used, a use-after-free bug in the
Net-SNMP library up to the 5.7.3 version can cause a crash of Zabbix
server if the SourceIP parameter is set in the Zabbix server
configuration file. As a workaround, please do not set the SourceIP
parameter. The same problem applies also for Linux, but it does not
cause Zabbix server to stop working. A local patch for the net-snmp
package on OpenBSD was applied and will be released with OpenBSD 6.3.

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#### SNMP data spikes

Spikes in SNMP data have been observed that may be related to certain
physical factors like voltage spikes in the mains. See
[ZBX-14318](https://support.zabbix.com/browse/ZBX-14318) more details.

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#### SNMP traps

The "net-snmp-perl" package, needed for SNMP traps, has been removed in
RHEL/CentOS 8.0-8.2; re-added in RHEL 8.3.

So if you are using RHEL 8.0-8.2, the best solution is to upgrade to
RHEL 8.3; if you are using CentOS 8.0-8.2, you may wait for CentOS 8.3
or use a package from EPEL.

Please also see [ZBX-17192](https://support.zabbix.com/browse/ZBX-17192)
for more information.

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#### Alerter process crash in Centos/RHEL 7

Instances of a Zabbix server alerter process crash have been encountered
in Centos/RHEL 7. Please see
[ZBX-10461](https://support.zabbix.com/browse/ZBX-10461) for details.

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#### Flipping frontend locales

It has been observed that frontend locales may flip without apparent
logic, i. e. some pages (or parts of pages) are displayed in one
language while other pages (or parts of pages) in a different language.
Typically the problem may appear when there are several users, some of
whom use one locale, while others use another.

A known workaround to this is to disable multithreading in PHP and
Apache.

The problem is related to how setting the locale works [in
PHP](https://www.php.net/manual/en/function.setlocale): locale
information is maintained per process, not per thread. So in a
multi-thread environment, when there are several projects run by same
Apache process, it is possible that the locale gets changed in another
thread and that changes how data can be processed in the Zabbix thread.

For more information, please see related problem reports:

-   [ZBX-10911](https://support.zabbix.com/browse/ZBX-10911) (Problem
    with flipping frontend locales)
-   [ZBX-16297](https://support.zabbix.com/browse/ZBX-16297) (Problem
    with number processing in graphs using the `bcdiv` function of BC
    Math functions)

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#### PHP 7.3 opcache configuration

If "opcache" is enabled in the PHP 7.3 configuration, Zabbix frontend
may show a blank screen when loaded for the first time. This is a
registered [PHP bug](https://bugs.php.net/bug.php?id=78015). To work
around this, please set the "opcache.optimization\_level" parameter to
`0x7FFFBFDF` in the PHP configuration (php.ini file).

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#### Graphs

Changes to Daylight Saving Time (DST) result in irregularities when
displaying X axis labels (date duplication, date missing, etc).

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#### Log file monitoring

`log[]` and `logrt[]` items repeatedly reread log file from the
beginning if file system is 100% full and the log file is being appended
(see [ZBX-10884](https://support.zabbix.com/browse/ZBX-10884) for more
information).

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#### Slow MySQL queries

Zabbix server generates slow select queries in case of non-existing
values for items. This is caused by a known
[issue](https://bugs.mysql.com/bug.php?id=74602) in MySQL 5.6/5.7
versions. A workaround to this is disabling the
index\_condition\_pushdown optimizer in MySQL. For an extended
discussion, see
[ZBX-10652](https://support.zabbix.com/browse/ZBX-10652).

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##### Permission checks for dashboards with graphs
If SVG graphs are used in Zabbix dashboards, Zabbix frontend may generate non-optimized API queries when checking user permissions to hosts and items. 
This is happening because such searches support wildcards and case-insensitive name matching. 

To improve performance of SQL statements, manually apply the patch *index_host_and_item_name_upper_field.sql* provided in Zabbix 5.0.31 and newer. 

For MySQL, run:

    shell> mysql -uzabbix -p<password> zabbix < index_host_and_item_name_upper_field.sql

For PostgreSQL, run:

    shell> cat index_host_and_item_name_upper_field.sql | sudo -u zabbix psql zabbix

For Oracle, run:
    
    sqlplus> @index_host_and_item_name_upper_field.sql

Creation of deterministic triggers should be enabled for the time of patch application. 
On MySQL and MariaDB, this requires `GLOBAL log_bin_trust_function_creators = 1` to be set 
if binary logging is enabled and there is no superuser privileges and `log_bin_trust_function_creators = 1` is not set in MySQL configuration file. 
To set the variable using MySQL console, run:

    mysql> SET GLOBAL log_bin_trust_function_creators = 1;

Once the patch has been successfully applied, `log_bin_trust_function_creators` can be disabled:

    mysql> SET GLOBAL log_bin_trust_function_creators = 0;

Triggers are also created for PostgreSQL and Oracle database.

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##### Non-existing item value retrieval with MySQL 5.6/5.7
Zabbix server generates slow select queries in case of non-existing
values for items. This is caused by a known
[issue](https://bugs.mysql.com/bug.php?id=74602) in MySQL 5.6/5.7
versions. A workaround to this is disabling the
index\_condition\_pushdown optimizer in MySQL. For an extended
discussion, see
[ZBX-10652](https://support.zabbix.com/browse/ZBX-10652).

[comment]: # ({/new-1fb1a6a2})

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##### Slow event info retrieval with older MySQL databases

Zabbix 5.0 installations with MySQL 5.X and 8.0.19 might run a slow query when retrieving problem/event information from
the database. In particular, this affects the *Problems by severity* widget, `event.get` and `problem.get` API methods.
To improve performance of SQL statements, apply the patch provided in [ZBX-18080](https://support.zabbix.com/browse/ZBX-18080?focusedCommentId=477904&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-477904)
(available for Zabbix 5.0.4 and newer).

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#### API login

A large number of open user sessions can be created when using custom
scripts with the `user.login` [method](/manual/api/reference/user/login)
without a following `user.logout`.

[comment]: # ({/b393528e-b393528e})

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#### IPv6 address issue in SNMPv3 traps

Due to a net-snmp bug, IPv6 address may not be correctly displayed when
using SNMPv3 in SNMP traps. For more details and a possible workaround,
see [ZBX-14541](https://support.zabbix.com/browse/ZBX-14541).

[comment]: # ({/17c4463f-17c4463f})

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#### Trimmed long IPv6 IP address in failed login information

Failed login attempt message will display only the first 39 characters
of a stored IP address as that's the character limit in the database
field. That means that IPv6 IP addresses longer than 39 characters will
be shown incompletely.

[comment]: # ({/430b9c2e-430b9c2e})

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#### Zabbix agent checks on Windows

Non-existing DNS entries in a `Server` parameter of Zabbix agent
configuration file (zabbix\_agentd.conf) may increase Zabbix agent
response time on Windows. This happens because Windows DNS caching
daemon doesn't cache negative responses for IPv4 addresses. However, for
IPv6 addresses negative responses are cached, so a possible workaround
to this is disabling IPv4 on the host.

[comment]: # ({/57420738-57420738})

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#### Setup wizard on SUSE with NGINX and php-fpm

Frontend setup wizard cannot save configuration file on SUSE with NGINX
+ php-fpm. This is caused by a setting in
/usr/lib/systemd/system/php-fpm.service unit, which prevents Zabbix from
writing to /etc. (introduced in [PHP
7.4](https://bugs.php.net/bug.php?id=72510)).

There are two workaround options available:

-   Set the
    [ProtectSystem](https://www.freedesktop.org/software/systemd/man/systemd.exec.html#ProtectSystem=)
    option to 'true' instead of 'full' in the php-fpm systemd unit.
-   Manually save /etc/zabbix/web/zabbix.conf.php file.

[comment]: # ({/fcbf4bce-fcbf4bce})

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#### MySQL custom error codes

If Zabbix is used with MySQL installation on Azure, an unclear error
message *\[9002\] Some errors occurred* may appear in Zabbix logs. This
generic error text is sent to Zabbix server or proxy by the database. To
get more information about the cause of the error, check Azure logs.

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