Runtime Environment Variables

nros_support_init() reads these at startup when locator is NULL:

Variable	Description	Default
`ROS_DOMAIN_ID`	ROS 2 domain ID	`0`
`NROS_LOCATOR`	Router address (`tcp/…`, `udp/…`, or `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 environment variables before cmake --build. After changing a value, delete CMakeCache.txt and rebuild to force the new values to take effect.

Variable	Description	Default
`NROS_EXECUTOR_MAX_CBS`	Max executor callback slots (shared with Rust API)	`4`
`NROS_SUBSCRIPTION_BUFFER_SIZE`	Per-entity receive buffer size (shared with Rust API)	`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`
`NROS_MAX_ARRAY_LEN`	Max parameter array length	`32`
`NROS_MAX_BYTE_ARRAY_LEN`	Max byte array parameter length	`256`

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 before fragmentation	65536	1024
`ZPICO_BATCH_MULTICAST_SIZE`	Max multicast batch size	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-based build
cargo clean -p zpico-sys    # or: cargo clean -p xrce-sys
 
# CMake-based build
rm CMakeCache.txt && cmake --build build