Add design document: Support repeating transient-local (“latched”) messages in Rosbag2 recorder by MichaelOrlov · Pull Request #2327 · ros2/rosbag2

MichaelOrlov · 2026-02-07T09:01:22Z

Description

Add design document: Support repeating transient-local (“latched”) messages in Rosbag2 recorder.

Relates Support --repeat-latched in ROS 2 (transient local) #1159
Relates Snapshot mode throws away transient local topics when the buffer is full (in other words, tf_static is lost) #1886

Is this user-facing behavior change?

No.

Did you use Generative AI?

Ye. GitHub Copilot, GPT-5.0 and ClaudeCode 4.5

Additional Information

N/A

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

tonynajjar

In general looks good. My PR goes in that direction but of course doesn't completely align with all the points of this design documents - can be a good starting point.
@MichaelOrlov after this is merged do you plan on making the implementation?

ajsampathk · 2026-02-11T11:57:26Z

Hi, would it be possible to address this issue #2333 as well please? Related to latched topics and would be extremely useful.

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

- Mostly addressed style and some punctuations. Signed-off-by: Michael Orlov <morlovmr@gmail.com>

christophebedard

I have some minor questions/comments. Generally seems OK, but I didn't have that much time to properly digest it, and I'd really like to get input from users who originally requested this.

christophebedard · 2026-02-13T22:29:52Z

+**Example:**
+```
+Split at T=1000.5s, /tf_static originally at T=0.1s
+After prepend: /tf_static written with T=1000.5s
+Next message at T=1000.6s
+Playback: continuous timeline without hours-long gap
+```


What happens if you replay everything? Will that original message get published at T=0.1s and T=1000.5s? This is fine for /tf_static, but not for all topics.

Yes. By design, since a transient local message on a particular topic was explicitly chosen to be repeated during recording, the original message will appear in a playback stream on a T=0.1s and T=1000.5s.
That is a requested behavior. To be able to replay just one small split file independently.

I have mentioned above that this shouldn't be a default behavior, and the user shall explicitly select on what topics transient local messages will be repeated during recording.

christophebedard · 2026-02-13T22:35:48Z

+3. **Timestamp adjustment:** When prepending transient-local messages during split or snapshot, 
+   timestamps are overwritten to avoid playback gaps:
+   - **Split mode**: set to last message timestamp (T_last) from previous bag file.
+   - **Snapshot mode**: set to the earliest timestamp (T_earliest) from snapshot buffer range.


I'd like to get input on this behaviour from users who originally requested this feature.

tonynajjar · 2026-02-15T15:19:56Z

@MichaelOrlov I gave implementing a shot according to this design document: #2342

According to the review feedback. Signed-off-by: Michael Orlov <morlovmr@gmail.com>

MichaelOrlov · 2026-03-28T03:33:06Z

@christophebedard, @tonynajjar I've addressed review comments. Please reiterate on review.

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

Wire transient-local message support through the recorder and CLI layers: - Recorder: expand topic names in repeat_transient_local_messages map, route to create_transient_local_topic() during subscription setup, set transient_local() QoS for matching topics - config_options_from_node_params: parse record.repeat_transient_local ROS parameter (format: 'topic' or 'topic=depth') - ros2 bag record CLI: add --repeat-transient-local argument with parse_repeat_transient_local_topics() validator - pybind11: expose repeat_transient_local_messages on RecordOptions - Tests: recorder integration test verifying create_transient_local_topic() is called with correct depth, CLI parser tests for valid/invalid input Part 3 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327

Add the core data structures for repeating transient-local messages on bag split and snapshot: - TransientLocalMessagesCache: per-topic FIFO queues with configurable depth, thread-safe push/retrieval, timestamp-sorted output - RecordOptions: new repeat_transient_local_messages map field with YAML serialization/deserialization support - Unit tests for cache behavior (eviction, sorting, unregistered topics) - YAML roundtrip test for RecordOptions Part 1 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327 Signed-off-by: Tony Najjar <tony.najjar@dexory.com>

Extend the writer layer to support repeating transient-local messages on bag split and snapshot: - BaseWriterInterface: add create_transient_local_topic() virtual methods (with and without MessageDefinition) - SequentialWriter: integrate TransientLocalMessagesCache - create_transient_local_topic(): register topic in cache + storage - write(): dual-write messages to cache for transient-local topics - prepend_transient_local_messages(): prepend cached messages on split with timestamp adjustment to last message edge - write_messages(): merge transient-local cache with snapshot buffer, adjust timestamps, deduplicate, stable-sort - Writer: forwarding wrappers for new methods - Mock sequential writer: tracking for create_transient_local_topic() - Integration tests for split and snapshot modes Part 2 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327

Wire transient-local message support through the recorder and CLI layers: - Recorder: expand topic names in repeat_transient_local_messages map, route to create_transient_local_topic() during subscription setup, set transient_local() QoS for matching topics - config_options_from_node_params: parse record.repeat_transient_local ROS parameter (format: 'topic' or 'topic=depth') - ros2 bag record CLI: add --repeat-transient-local argument with parse_repeat_transient_local_topics() validator - pybind11: expose repeat_transient_local_messages on RecordOptions - Tests: recorder integration test verifying create_transient_local_topic() is called with correct depth, CLI parser tests for valid/invalid input Part 3 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327

) * feat: add TransientLocalMessagesCache and RecordOptions field Add the core data structures for repeating transient-local messages on bag split and snapshot: - TransientLocalMessagesCache: per-topic FIFO queues with configurable depth, thread-safe push/retrieval, timestamp-sorted output - RecordOptions: new repeat_transient_local_messages map field with YAML serialization/deserialization support - Unit tests for cache behavior (eviction, sorting, unregistered topics) - YAML roundtrip test for RecordOptions Part 1 of 3 for #1159, #1886 Design document: #2327 Signed-off-by: Tony Najjar <tony.najjar@dexory.com> * refactor: optimize message retrieval by reserving vector capacity Signed-off-by: Tony Najjar <tony.najjar@dexory.com> * feat: add YAML conversion support for unordered_map<string, size_t> Signed-off-by: Tony Najjar <tony.najjar@dexory.com> --------- Signed-off-by: Tony Najjar <tony.najjar@dexory.com>

Add the core data structures for repeating transient-local messages on bag split and snapshot: - TransientLocalMessagesCache: per-topic FIFO queues with configurable depth, thread-safe push/retrieval, timestamp-sorted output - RecordOptions: new repeat_transient_local_messages map field with YAML serialization/deserialization support - Unit tests for cache behavior (eviction, sorting, unregistered topics) - YAML roundtrip test for RecordOptions Part 1 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327 Signed-off-by: Tony Najjar <tony.najjar@dexory.com>

Extend the writer layer to support repeating transient-local messages on bag split and snapshot: - BaseWriterInterface: add create_transient_local_topic() virtual methods (with and without MessageDefinition) - SequentialWriter: integrate TransientLocalMessagesCache - create_transient_local_topic(): register topic in cache + storage - write(): dual-write messages to cache for transient-local topics - prepend_transient_local_messages(): prepend cached messages on split with timestamp adjustment to last message edge - write_messages(): merge transient-local cache with snapshot buffer, adjust timestamps, deduplicate, stable-sort - Writer: forwarding wrappers for new methods - Mock sequential writer: tracking for create_transient_local_topic() - Integration tests for split and snapshot modes Part 2 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327 Signed-off-by: Tony Najjar <tony.najjar@dexory.com>

…s2#2385) * feat: add TransientLocalMessagesCache and RecordOptions field Add the core data structures for repeating transient-local messages on bag split and snapshot: - TransientLocalMessagesCache: per-topic FIFO queues with configurable depth, thread-safe push/retrieval, timestamp-sorted output - RecordOptions: new repeat_transient_local_messages map field with YAML serialization/deserialization support - Unit tests for cache behavior (eviction, sorting, unregistered topics) - YAML roundtrip test for RecordOptions Part 1 of 3 for ros2#1159, ros2#1886 Design document: ros2#2327 Signed-off-by: Tony Najjar <tony.najjar@dexory.com> * refactor: optimize message retrieval by reserving vector capacity Signed-off-by: Tony Najjar <tony.najjar@dexory.com> * feat: add YAML conversion support for unordered_map<string, size_t> Signed-off-by: Tony Najjar <tony.najjar@dexory.com> --------- Signed-off-by: Tony Najjar <tony.najjar@dexory.com>

MichaelOrlov · 2026-04-02T16:01:16Z

@christophebedard @fujitatomoya, a friendly ping here to wrap-up review of this PR with design.
We have already almost done with the feature, but the design document is still in the review stage.

MichaelOrlov marked this pull request as ready for review February 7, 2026 09:01

This was referenced Feb 7, 2026

Snapshot mode throws away transient local topics when the buffer is full (in other words, tf_static is lost) #1886

Closed

Handle transient local messages in snapshot mode when the buffer is full #1887

Closed

Design: Support transient-local (“latched”) messages in rosbag2 recorder

5b3ec91

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

MichaelOrlov force-pushed the morlov/repeat-transient-local-msgs-design branch from 59155e3 to 5b3ec91 Compare February 7, 2026 09:16

MichaelOrlov requested review from Barry-Xu-2018, christophebedard, emersonknapp and fujitatomoya February 7, 2026 09:18

tonynajjar reviewed Feb 9, 2026

View reviewed changes

Comment thread docs/design/repeat_transient_local_messages_during_recording.md

tonynajjar reviewed Feb 9, 2026

View reviewed changes

Comment thread docs/design/repeat_transient_local_messages_during_recording.md Outdated

tonynajjar reviewed Feb 9, 2026

View reviewed changes

Renames in doc title and file

d9822d2

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

MichaelOrlov changed the title ~~Add design document: Support transient-local (“latched”) messages in Rosbag2 recorder~~ Add design document: Support repeating transient-local (“latched”) messages in Rosbag2 recorder Feb 13, 2026

Updates after a self-mock review

76ebe15

- Mostly addressed style and some punctuations. Signed-off-by: Michael Orlov <morlovmr@gmail.com>

christophebedard reviewed Feb 13, 2026

View reviewed changes

tonynajjar mentioned this pull request Feb 15, 2026

Support repeating transient-local (“latched”) messages in Rosbag2 recorder #2342

Closed

Replaced default --repeat-tl option with --repeat-transient-local

770a308

According to the review feedback. Signed-off-by: Michael Orlov <morlovmr@gmail.com>

Address review comments.

54e9da4

Signed-off-by: Michael Orlov <morlovmr@gmail.com>

MichaelOrlov force-pushed the morlov/repeat-transient-local-msgs-design branch from 9ff87aa to 54e9da4 Compare March 28, 2026 07:42

This was referenced Mar 28, 2026

[1/3] Repeat transient-local topics: Core cache and RecordOptions #2385

Merged

[2/3] Repeat transient-local topics: Writer API and split/snapshot integration #2386

Merged

[3/3] Repeat transient-local topics: Recorder, CLI, and Python bindings #2387

Merged

tonynajjar approved these changes Mar 29, 2026

View reviewed changes

christophebedard approved these changes Apr 3, 2026

View reviewed changes

MichaelOrlov merged commit 6ee13f1 into rolling Apr 3, 2026
12 of 13 checks passed

MichaelOrlov deleted the morlov/repeat-transient-local-msgs-design branch April 3, 2026 18:41

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add design document: Support repeating transient-local (“latched”) messages in Rosbag2 recorder#2327

Add design document: Support repeating transient-local (“latched”) messages in Rosbag2 recorder#2327
MichaelOrlov merged 5 commits intorollingfrom
morlov/repeat-transient-local-msgs-design

MichaelOrlov commented Feb 7, 2026 •

edited

Loading

Uh oh!

Uh oh!

Uh oh!

tonynajjar left a comment

Uh oh!

ajsampathk commented Feb 11, 2026

Uh oh!

christophebedard left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

christophebedard Feb 13, 2026

Uh oh!

MichaelOrlov Mar 28, 2026

Uh oh!

Uh oh!

christophebedard Feb 13, 2026

Uh oh!

tonynajjar commented Feb 15, 2026 •

edited

Loading

Uh oh!

MichaelOrlov commented Mar 28, 2026

Uh oh!

MichaelOrlov commented Apr 2, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

MichaelOrlov commented Feb 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Is this user-facing behavior change?

Did you use Generative AI?

Additional Information

Uh oh!

Uh oh!

Uh oh!

tonynajjar left a comment

Choose a reason for hiding this comment

Uh oh!

ajsampathk commented Feb 11, 2026

Uh oh!

christophebedard left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

christophebedard Feb 13, 2026

Choose a reason for hiding this comment

Uh oh!

MichaelOrlov Mar 28, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

christophebedard Feb 13, 2026

Choose a reason for hiding this comment

Uh oh!

tonynajjar commented Feb 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

MichaelOrlov commented Mar 28, 2026

Uh oh!

MichaelOrlov commented Apr 2, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

MichaelOrlov commented Feb 7, 2026 •

edited

Loading

tonynajjar commented Feb 15, 2026 •

edited

Loading