4.14. Connext DDS Micro Hardcoded Resource Limits¶
4.14.1. Introduction¶
Connext DDS Micro contains a few resource limits that are not configurable in a QoS policy or property. Note that not every single constant used in Connext DDS Micro is addressed. The focus is on resource limits that may prevent an application using Connext DDS Micro from behaving correctly. For example, the maximum number of participants that can be discovered on a node may impact an application. On the other hand, a resource limit that has no functional impact, for example the maximum length of the discovery plugin name, is not described in this document.
When a resource limit is exceeded an error message is logged. An explanation can be found in the documentation. Note that some resource limits may be exceeded when calling an API and others may be exceeded as part of processing incoming data. Thus, it may be necessary to look at log output to see the failure reason.
Although Connext DDS Micro can be compiled from source it is recommended to consult with RTI before making any changes to the hard coded limits.
4.14.2. Summary¶
| Resource | Limit |
|---|---|
| Number of domain participants per OS process | 8 |
| Max topic name length | 255 |
| Max type name length | 255 |
| Max number of discovery plugins used by a domain participant | 1 |
| Max number of announced receive addresses for discovery data by a domain participant | 4 |
| Max number of announced receive addresses for user-data data by a domain participant | 4 |
| Max number of addresses that can be received (per meta-unicast, meta-multicast, user-unicast, user-multicast) | 4 |
4.14.3. Operating Services API (OSAPI)¶
- The maximum number of object ids are 2^32-1
- DDS objects require a unique object_id. The encoding dictated by the RTPS specification limits the number of DDS objects within a domain participant to 2^24.
- User impact - None.
- The Maximum number of timers that can be created is 8
- Each domain participant allocates 1 timer
- User impact - The maximum number of domain participants in a single OS process is limited to 8. This limit is based on empirical data; only specialized applications such as tools typically use more than 2 domain participants.
- Each domain participant allocates 1 timer
4.14.4. DDS C API¶
- Maximum Topic name length - 255 (including NUL termination)
- The limit is specified as 256 including NUL termination in the RTPS specification, refer to 9.6.2.2.2 in the RTPS specification (OMG formal/2009-01-05).
- Maximum Type name length - 255 (including NUL termination)
- The limit is specified as 256 including NUL termination in the RTPS specification, refer to 9.6.2.2.2 in the RTPS specification (OMG formal/2009-01-05).
- Maximum number of matched data-writers (per data-reader) - 100,000,000
- This limit determines how many data-writers each data-reader can match.
- Maximum number of matched data-readers (per data-writer) - 100,000,000
- This limit determines how many data-readers each data-writer can match.
- Maximum number of locators of each type which can be sent in the participant announcement - 4
- This limit determines the number of unique network address that can be advertised as part of discovery. The limit is per locator type. That is, the limit is applicable to discovery and user-data (total of 4 each)
- Maximum number of discovery plugins which can be used by the domain participant - 1
- User impact: Must choose either static or dynamic discovery.
4.14.5. Dynamic Discovery Plugin (DPDE)¶
- Maximum number of received locators - 4
- This limit determines the number of unique network address that can be advertised as part of discovery.
- The limit is per locator type. That is, the same limit is applicable to discovery unicast, discovery multicast, user-data unicast, and user-data multicast.
4.14.6. Static Discovery Plugin (DPSE)¶
- Maximum number of received locators - 4
- This limit determines the number of unique network address that can be advertised as part of discovery.
- The limit is per locator type. That is, the same limit is applicable to discovery unicast, discovery multicast, user-data unicast, and user-data multicast.
4.14.7. RTPS Protocol Implementation (RTPS)¶
- Unlimited max_samples is defined as 100000000
- Maximum number of external RTPS interfaces - 16
- This limits the number of participants to 16 per OS process.
- This limit is reduced to 8 due to the OS limit.