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Version: Tenzir v4.6

Command Line

The command line tools are at the core of a deployment. Every installation ships with the following executables:

  1. tenzir: runs a pipeline
  2. tenzir-node: spawns a node

There is also the tenzir-ctl "master" executable to invoke various commands. This is a temporary solution that we will sunset in the future after having migrated its functionality into tenzir and tenzir-node.

The executables support several configuration options:

  1. Command-line arguments
  2. Environment variables
  3. Configuration files
  4. Compile-time defaults

These options are sorted by precedence, i.e., command-line arguments override environment variables, which override configuration file settings. Compile-time defaults can only be changed by rebuilding Tenzir from source.

Let's discuss the first three options in more detail.

Command Line Arguments

The command line arguments of the executables have the following synopis:

tenzir [opts] <pipeline>
tenzir-node [opts]
tenzir-ctl [opts] cmd1 [opts1] cmd2 [opts2] ...

We have both long --long=X and short -s X options. Boolean options do not require explicit specification of a value, and it suffices to write --long and -s to set an option to true. For tenzir-ctl, = is mandatory for long options. This differs from pipeline operator options where = is optional.

Get help

You get short usage instructions for every command by adding the help sub-command or providing the option --help (which has the shorthand -h):

tenzir-ctl help
tenzir-ctl --help
tenzir-ctl -h

The same help pattern applies to (sub-)commands:

tenzir-ctl export help
tenzir-ctl export --help
tenzir-ctl export -h

Environment Variables

In addition to the command line, Tenzir offers environment variables as an equivalent mechanism to provide options. This comes in handy when working with non-interactive deployments where the command line is hard-coded, such as in Docker containers.

An environment variable has the form KEY=VALUE, and we discuss the format of KEY and VALUE below. Tenzir processes only environment variables having the form TENZIR_{KEY}=VALUE. For example, TENZIR_ENDPOINT=1.2.3.4 translates to the the command line option --endpoint=1.2.3.4 and YAML configuration tenzir.endpoint: 1.2.3.4.

Regarding precedence, environment variables override configuration file settings, and command line arguments override environment variables.

Keys

There exists a one-to-one mapping from configuration file keys to environment variable names. Here are two examples:

  • tenzir.import.batch-size 👈 configuration file key
  • TENZIR_IMPORT__BATCH_SIZE 👈 environment variable

A hierarchical key of the form tenzir.x.y.z maps to the environment variable TENZIR_X__Y__Z. More generally, the KEY in TENZIR_{KEY}=VALUE adheres to the following rules:

  1. Double underscores map to the . separator of YAML dictionaries.

  2. Single underscores _ map to a - in the corresponding configuration file key. This is unambiguous because Tenzir does not have any options that include a literal underscore.

From the perspective of the command line, the environment variable key TENZIR_X__Y__Z maps to tenzir-ctl x y --z. Here are two examples with identical semantics:

TENZIR_IMPORT__BATCH_SIZE=42 tenzir-ctl import json < data
tenzir-ctl import --batch-size=42 json < data
CAF and plugin Settings

To provide CAF and plugin settings, which have the form caf.x.y.z and plugins.name.x.y.z in the configuration file, the environment variable must have the form TENZIR_CAF__X__Y__Z and TENZIR_PLUGINS__NAME__X__Y__Z respectively.

The configuration file is an exception in this regard: tenzir.caf. and tenzir.plugins. are invalid key prefixes. Instead, CAF and plugin configuration file keys have the prefixes caf. and plugins., i.e., they are hoisted into the global scope.

Values

While all environment variables are strings on the shell, Tenzir parses them into a typed value internally. In general, parsing values from the environment follows the same syntactical rules as command line parsing.

In particular, this applies to lists. For example, TENZIR_PLUGINS="foo,bar" is equivalent to --plugins=foo,bar.

Tenzir ignores environment variables with an empty value because the type cannot be inferred. For example, TENZIR_PLUGINS= will not be considered.

Configuration files

Tenzir's configuration file is in YAML format. On startup, Tenzir attempts to read configuration files from the following places, in order:

  1. <sysconfdir>/tenzir/tenzir.yaml for system-wide configuration, where sysconfdir is the platform-specific directory for configuration files, e.g., <install-prefix>/etc.

  2. ~/.config/tenzir/tenzir.yaml for user-specific configuration. Tenzir respects the XDG base directory specification and its environment variables.

  3. A path to a configuration file passed via --config=/path/to/tenzir.yaml.

If there exist configuration files in multiple locations, options from all configuration files are merged in order, with the latter files receiving a higher precedence than former ones. For lists, merging means concatenating the list elements.

Plugin Configuration Files

In addition to tenzir/tenzir.yaml, Tenzir loads tenzir/plugin/<plugin>.yaml for plugin-specific configuration for a given plugin named <plugin>. The same rules apply as for the regular configuration file directory lookup.

Bare Mode

Sometimes, users may wish to run Tenzir without side effects, e.g., when wrapping Tenzir in their own scripts. Run with --bare-mode to disable looking at all system- and user-specified configuration paths.

Plugins

Tenzir's plugin architecture allows for flexible replacement and enhancement of functionality at various pre-defined customization points. There exist dynamic plugins that ship as shared libraries and static plugins that are compiled into libtenzir.

Install plugins

Dynamic plugins are just shared libraries and can be placed at a location of your choice. We recommend putting them into a single directory and add the path to the tenzir.plugin-dirs configuration option..

Static plugins do not require installation since they are compiled into Tenzir.

Load plugins

The onfiguration key tenzir.plugins specifies the list of plugins that should load at startup. The all plugin name is reserved. When all is specified Tenzir loads all available plugins in the configured plugin directories. If no tenzir.plugins key is specified, Tenzir will load all plugins by default. To load no plugins at all, specify a tenzir.plugins configuration key with no plugin values, e.g. the configuration file entry plugins: [] or launch parameter --plugins=.

Since dynamic plugins are shared libraries, they must be loaded first into the running Tenzir process. At startup, Tenzir looks for the tenzir.plugins inside the tenzir.plugin-dirs directories configured in tenzir.yaml. For example:

tenzir:
plugin-dirs:
- .
- /opt/foo/lib
plugins:
- example
- /opt/bar/lib/libtenzir-plugin-example.so

Before executing plugin code, Tenzir loads the specified plugins via dlopen(3) and attempts to initialize them as plugins. Part of the initilization is passing configuration options to the plugin. To this end, Tenzir looks for a YAML dictionary under plugins.<name> in the tenzir.yaml file. For example:

# <configdir>/tenzir/tenzir.yaml
plugins:
example:
option: 42

Alternatively, you can specify a plugin/<plugin>.yaml file. The example configurations above and below are equivalent. This makes plugin deployments easier, as plugins can be installed and uninstalled alongside their respective configuration.

# <configdir>/tenzir/plugin/example.yaml
option: 42

After initialization with the configuration options, the plugin is fully operational and Tenzir will call its functions at the plugin-specific customization points.

List plugins

You can get the list of available plugins using the show operator:

tenzir 'show plugins'

Block plugins

As part of your Tenzir deployment, you can selectively disable plugins by name. For example, if you do not want the shell operator and the kafka connector to be available, set this in your configuration:

# <configdir>/tenzir/tenzir.yaml
tenzir:
disable-plugins
- shell
- kafka