Runtime Environment Variables

nros::init() reads these at startup when the locator argument is empty:

Variable	Description	Default
`ROS_DOMAIN_ID`	ROS 2 domain ID	`0`
`NROS_LOCATOR`	Router address (`tcp/…`, `udp/…`, `tls/…`). Legacy alias: `ZENOH_LOCATOR`.	`tcp/127.0.0.1:7447`
`NROS_SESSION_MODE`	Session mode: `client` or `peer`. Legacy alias: `ZENOH_MODE`.	`client`
`ZENOH_TLS_ROOT_CA_CERTIFICATE`	Path to CA certificate (PEM) for TLS	—
`ZENOH_TLS_ROOT_CA_CERTIFICATE_BASE64`	Base64-encoded CA cert (bare-metal)	—

C++ API Buffer Tuning (NROS_*)

Set these before cmake --build. After changing a value, delete CMakeCache.txt and rebuild so the new value takes effect. The C and C++ APIs share the same compile-time pool sizes.

Variable	Description	Default
`NROS_EXECUTOR_MAX_CBS`	Max executor callback slots	`4`
`NROS_SUBSCRIPTION_BUFFER_SIZE`	Per-subscription receive buffer	`1024`
`NROS_LET_BUFFER_SIZE`	Buffer size for LET semantics per handle	`512`
`NROS_MAX_CONCURRENT_GOALS`	Max concurrent goals per action server	`4`
`NROS_MAX_PARAMETERS`	Max parameters in parameter server	`32`
`NROS_MAX_PARAM_NAME_LEN`	Max parameter name length	`64`
`NROS_MAX_STRING_VALUE_LEN`	Max string parameter value length	`256`

C++ Storage Sizes

The compile-time storage occupied by nros::Publisher<M>, nros::Subscription<M>, etc. is derived from the matching Rust size_of::<RmwPublisher>() via the nros-sizes-build probe (Phase 87). You should not need to override these manually — they are populated in the generated nros_cpp_config_generated.h header at build time.

Transport Buffer Tuning

Zenoh Backend (ZPICO_*)

Variable	Description	Posix	Embedded
`ZPICO_FRAG_MAX_SIZE`	Max reassembled message size	65536	2048
`ZPICO_BATCH_UNICAST_SIZE`	Max unicast batch	65536	1024
`ZPICO_BATCH_MULTICAST_SIZE`	Max multicast batch	8192	1024
`ZPICO_SUBSCRIBER_BUFFER_SIZE`	Per-subscriber buffer in zenoh shim	1024	1024
`ZPICO_SERVICE_BUFFER_SIZE`	Per-service-server buffer in zenoh shim	1024	1024

XRCE-DDS Backend (XRCE_*)

Variable	Description	Posix	Embedded
`XRCE_TRANSPORT_MTU`	Transport MTU (also sizes stream buffers)	4096	512
`XRCE_BUFFER_SIZE`	Per-entity static buffer size	1024	1024
`XRCE_STREAM_HISTORY`	Reliable stream history depth (≥ 2)	4	4

Example

Increase zenoh defrag to 128 KB for large point clouds:

ZPICO_FRAG_MAX_SIZE=131072 cmake --build build

After changing any ZPICO_* or XRCE_* variable, clean the transport build cache:

cargo clean -p zpico-sys # or: cargo clean -p xrce-sys

rm CMakeCache.txt && cmake --build build