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[#1892] Fixed sphinx error, rewording

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Tomek Mrugalski
2021-06-25 09:41:51 +02:00
parent ef8a5b1698
commit db758a6606
1 changed files with 33 additions and 27 deletions
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doc/sphinx/arm/install.rst
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@@ -426,7 +426,7 @@ external dependencies, MySQL, PostgreSQL, and Cassandra support are
disabled by default and only memfile is available. Support for the
optional external database backend must be explicitly included when Kea
is built. This section covers the building of Kea with one of the
optional backends and the creation of the lease database. (*Note that
optional backends and the creation of the lease database. (* Note that
as of Kea 1.9.9 support for Cassandra is deprecated and will be removed
in a future version.)
@@ -677,17 +677,23 @@ now limited to Debian only. The quick introduction seems to favor Docker contain
replacement. The Debian packages available require Python 2 (which reached end of life at
1 Jan 2020) and will uninstall some python 3 packages. This is very risky step in a production
environment, because it removes the current 3.8 or 3.9 python and installs an old, unsupported
version. The Cassandra software is written in Java, so it is unclear why it even does anything
with Python.
version. Support for python 3 is only available in alpha release of upcoming Cassandra 4.0,
which is not released yet as of June 2021. The user has a tough choice between running antiquated
version past its end of life or running unreleased alpha software. Neither option is reasonable
in production environment.
Cassandra is also very picky about the Java version. For example, on modern systems such as
Ubuntu 21.04, it simply doesn't start and produces no logs. After running the Cassandra manually,
it produces a cryptic `Improperly specified VM option 'ThreadPriorityPolicy=42'` error message.
This is an obscure information that the Java version is too new (11.x) and needs to be downgraded
(to 8.x).
To use C++ bindings (Kea is written in C++), a data driver is required. For a while, around
2020 there was a message about it being in maintenance mode, but as of now (June 2021) this
message disappeared. The data driver does not use the standard `pkg-config` approach and requires
custom hacking. Cassandra itself requires a Java JVM to run. In the past, we experienced serious
problems with the Java VM machine versioning, which impedes Cassandra operation and produces
cryptic error messages. Compared to MySQL and PostgreSQL, which are widely available in all popular
Linux and BSD distributions, setting up Cassandra is complex and the complexity is not decreasing
over time.
message disappeared. For a long time the data driver didn't not use the standard `pkg-config`
approach and required custom hacking with regards to the software detection. Compared to
MySQL and PostgreSQL, which are widely available in all popular Linux and BSD distributions,
setting up Cassandra is complex and the complexity is not decreasing over time.
Cassandra is also an ongoing maintenance burden. As we introduce new features to Kea, such
as the ability to get database statistics that are synced between multiple Kea instances sharing