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configuration-guide.md

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Configuration guide

CMake switches for configuring iceoryx_hoofs and iceoryx_posh build

There are several configuration options set by default when iceoryx_hoofs and iceoryx_posh are build. These options adjust the minimal log level compiled into the binary and the global maximum amount of resources like Publisher and Subscriber Ports which can have a huge impact on the memory footprint of iceoryx since they define the size of the management structures in the shared memory segment called iceoryx_mgmt when RouDi is started.

switch description
IOX_MIN_LOG_LEVEL Minimal log level which will be compiled into the binary. Lower log levels will be optimized away during compilation
IOX_MAX_PUBLISHERS Maximum number of publishers in one iceoryx system
IOX_MAX_SUBSCRIBERS_PER_PUBLISHER Maximum number of connections one publisher port can handle
IOX_MAX_PUBLISHER_HISTORY Maximum size of a publishers history
IOX_MAX_CHUNKS_ALLOCATED_PER_PUBLISHER_SIMULTANEOUSLY Maximum number of chunks a publisher can allocate in parallel
IOX_MAX_SUBSCRIBERS Maximum number of subscribers in one iceoryx system
IOX_MAX_CHUNKS_HELD_PER_SUBSCRIBER_SIMULTANEOUSLY Maximum number of chunks a subscriber can take in parallel
IOX_MAX_INTERFACE_NUMBER Maximum number of interface ports which are used by gateways

Have a look at IceoryxHoofsDeployment.cmake and IceoryxPoshDeployment.cmake for the default values of the constants.

!!! hint With the default values set, the size of iceoryx_mgmt is ~64.5 MByte. You can reduce the size by decreasing the values from the table via the CMake options. The current values are printed in the CMake stage when building iceoryx.

Example:

cmake -Bbuild -Hiceoryx_meta -DIOX_MAX_CHUNKS_HELD_PER_SUBSCRIBER_SIMULTANEOUSLY=64

With that change, the footprint of the management segment is reduced to ~52.7 MBytes. For larger use cases you can increase the value to avoid that samples are dropped on the subscriber side (see also #615).

Configuring Mempools for RouDi

RouDi supports several shared memory segments with different access rights, to limit the read and write access between different applications. Memory pools manage those segments and organize the user payload data required for communication.

!!! note Actually only the chunk-payload size is configured and the size of the ChunkHeader will be added to the configured size. If a user-header or a user-payload alignment larger than 8 is used, the available size for the user-payload will be smaller than the configured chunk-payload since some space is needed for the other functionality. Please have a look at the chunk_header.md design document for a formula how to determine the necessary chunk-payload size with user-header and extended user-payload alignment.

For building RouDi, iceoryx ships a library named iceoryx_posh_roudi. This lib provides you an API for compiling your own RouDi application and is part of iceoryx_posh.

!!! note The chunk size for the memory pools needs to comply with the following restrictions:

1. Chunksize needs to be greater than the alignment
2. Chunksize needs to be a multiple of the alignment

The value for the alignment is set to 8.

Dynamic configuration

One way is to read a configuration dynamically during the startup of RouDi. Using the TOML Config in RouDi is not mandatory for configuring segments and mempools, but a comfortable alternative.

The CMake option -DTOML_CONFIG, which is ON by default, enables the TOML config for iceoryx. The iox-roudi application provided by iceoryx is compiled with TOML support and can be used out of the box.

If you create your own RouDi application you need to link against iceoryx_posh_config:

target_link_libraries(custom-roudi
    PRIVATE
    iceoryx_posh::iceoryx_posh_roudi
    iceoryx_posh::iceoryx_posh_config
)

The TOML config file can be passed to RouDi with the -c command-line option.

./iox-roudi -c /absolute/path/to/config/file.toml

This is an examplary config file with format version 1:

[general]
version = 1

[[segment]]

[[segment.mempool]]
size = 32
count = 10000

[[segment.mempool]]
size = 128
count = 10000

[[segment.mempool]]
size = 1024
count = 1000

With this configuration, one payload segment will be created. The access rights are set to the RouDi group id as default. There are three mempools within this segment. One with 10000 chunks of 32 byte payload size, one with 10000 chunks of 128 bytes, and one with 1000 chunks of 1024 bytes.

To restrict the access, a reader and writer group can be set:

[general]
version = 1

[[segment]]
reader = "foo"
writer = "bar"

[[segment.mempool]]
size = 32
count = 10000

[[segment.mempool]]
size = 128
count = 10000

[[segment.mempool]]
size = 1024
count = 1000

With this configuration, only applications from the bar group have write access and can allocate chunks. Applications from the foo group have only read access.

This is an example with multiple segments:

[general]
version = 1

[[segment]]
reader = "foo"
writer = "bar"

[[segment.mempool]]
size = 32
count = 10000

[[segment]]
reader = "alice"
writer = "eve"

[[segment.mempool]]
size = 1024
count = 100

When no configuration file is specified a hard-coded version similar to the default config will be used.

Static configuration

Another way is to have a static configuration that is compiled into the roudi application. As a consequence you have to recompile your RouDi application if you want to change your config (not the iceoryx_posh_roudi lib). You can create your custom configuration in the main() function where you then pass it as constructor argument to the RouDi instance. In the cmake file entry of the custom RouDi executable you need to ensure that it is not linking against iceoryx_posh_config to ensure using the static configuration.

An example of a static config can be found here.