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2026-02-12 lttng-tools 2.15.0
* Fix: ust-consumerd: flush hangs on stalled channel without watchdog timer
* Fix: consumerd: link failure on 32-bit architectures due to missing libatomic
* tests/lttng.py: Honor timeout_s in _run_cmd
* Clean-up: tests: fix clang-tidy `const` warning
* Fix: tests: use portable format specifier in test_poller
* Fix: tests: use portable format specifier for int64_t in tap
* Fix: consumerd: silence -Wstringop-truncation warnings
* Fix: common: remove ambiguous operator[] from c_string_view
* tests: Exclude `.tmp_new_chunk` from rotation trace size calculation
* Fix: build failure of gen-many-event-classes with `--code-coverage`
* Tests: fix Automake warning about MANY_EVENTS_GENERATED_SOURCES
* Tests: regen-metadata: add regression test for regenerate and rotation race
* tests: Add test to ensure a new viewer doesn't see old events
* tests: Allow setting session live timer to a non-default value
* doc: generate man pages in section subdirectories
* Fix: sessiond: racy metadata update during re-generation
* Fix: consumerd: metadata regeneration and rotation race
* Refactor: consumerd: inline metadata version change handling
* Refactor: consumerd: track tracer metadata coherency indicator support
* Refactor: consumerd: rename ust_metadata_pushed to ust_metadata_cache_consumed
* Refactor: consumerd: add has_network_destination() helper method
* tests: Validate that trace formats handle fields with empty names
* sessiond: Relax CTF 1.8 TSDL identifier validation
* tests: Check if an exception is being handled for env preservation
2025-12-19 | lttng-tools 2.15.0-rc1 (National Ugly Christmas Sweater Day)
WHAT'S NEW?
━━━━━━━━━━━
New features and changes in LTTng 2.15:
General:
• CTF 2 (Common Trace Format) is now the default trace format for
all newly created recording sessions. Babeltrace 2 supports CTF 2
since version 2.1 (January 2025).
Choose the trace format for each recording session with the new
`--trace-format` option of the lttng-create(1) command:
$ lttng create my-session --trace-format=ctf-1.8
To keep the default set to CTF 1.8 for your setup, use the new
`--default-trace-format` option of lttng-sessiond(8), or set
the `LTTNG_SESSIOND_DEFAULT_TRACE_FORMAT` environment variable.
CTF 2 has many benefits over CTF 1.8: easier decoding (JSON-based
metadata), cleaner trace streaming (RS byte delimiters), and
future support for user-defined attributes and broader type
support.
• A new channel memory reclaim operation, exclusively available for
user space channels, can free memory used by eligible sub-buffers
by deallocating their backing memory when no longer needed.
Automatic reclaim:
Configure a per-channel, automatic reclaim policy which
periodically tries to reclaim memory for sub-buffers older
than a given age, or as soon as they're consumed, with the
new `--auto-reclaim-memory` option of lttng-enable-channel(1).
Immediate reclaim:
The new lttng-reclaim-memory(1) command reclaims memory
immediately for eligible sub-buffers of one or more channels.
• Choose the buffer preallocation policy of a user space channel
with the new `--buffer-preallocation` option of
lttng-enable-channel(1). LTTng can either preallocate all ring
buffer memory up front (pre-2.15 behavior; still the default) or
allocate as needed.
• A new watchdog timer mechanism monitors user space ring-buffers
and makes stalled sub-buffers (from terminated applications)
consumable again. Enabled by default; control with the new
`--watchdog-timer` option of lttng-enable-channel(1).
• The lttng-list(1) command output has been completely revamped with
a clean tree structure and terminal color support. New options:
`--style`, `--no-truncate`, and `--mem-usage` for memory usage
reporting per channel.
• The lttng-status(1) command now accepts the same options as
lttng-list(1).
• New trigger conditions for lttng-add-trigger(1):
`channel-buffer-usage-ge`, `channel-buffer-usage-le`,
`session-consumed-size-ge`, `session-rotation-starts`, and
`session-rotation-finishes`.
• The lttng(1) commands won't emit multi-byte UTF-8 sequences when
the `LTTNG_NO_UTF_8` environment variable is set to `1`.
• The lttng(1) Zsh completion function now fully completes the
`add-trigger` command.
• Both lttng-sessiond(8) and lttng-relayd(8) now support systemd's
sd_notify protocol for READY and STOPPING notifications. This
enables proper synchronization of service dependencies on
systemd-based systems.
liblttng-ctl:
• lttng_session_descriptor_set_trace_format(): set the trace format
of a recording session descriptor.
• lttng_reclaim_channel_memory(): immediately reclaim user space
channel memory for eligible sub-buffers.
• lttng_channel_set_automatic_memory_reclamation_policy() and
lttng_channel_get_automatic_memory_reclamation_policy(): set and
get the automatic memory reclamation policy of a channel.
• lttng_channel_set_preallocation_policy() and
lttng_channel_get_preallocation_policy(): set and get the buffer
preallocation policy of a channel.
• lttng_channel_set_watchdog_timer_interval() and
lttng_channel_get_watchdog_timer_interval(): set and get the
watchdog timer period of a channel.
• New data stream info API for querying CPU ID and memory usage:
lttng_channel_get_data_stream_info_sets() and related functions.
Compatibility:
• The internal v2.15 communication protocol between LTTng-tools and
LTTng-UST is incompatible with LTTng 2.14: you cannot use
LTTng-tools 2.15 with LTTng-UST 2.14 and vice versa.
• Minimum Linux kernel version is now 4.4.0 (was 2.6.30).
• Minimum Python version for tests is now 3.5 (was 3.4).
• MI schema version bumped to 4.2.
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