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@jgalar jgalar released this 27 Jun 14:36
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v2.14.0
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jgalar Jérémie Galarneau
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Hi everyone,

We're excited to announce the first release candidate of LTTng 2.15, codenamed "Orbitales"!

This release brings a host of new features, improvements, and experimental capabilities for you to explore.

What's new?

New features and changes in LTTng 2.14:

General

  • User space channels now have a buffer allocation policy which specifies whether LTTng tracers allocate ring buffers per CPU (what you've always known) or per channel.

    The buffering scheme term now refers to the ownership model (system, user, or process) and the allocation policy together.

  • The new per-channel allocation policy means each user/process (depending on the buffer ownership model), instead of each CPU of each user/process, gets its own ring buffer.

  • User space tracing now supports the Apache Log4j 2 tracing domain in addition to the existing support for Apache log4j 1.2.

  • LTTng 2.14 brings experimental support of CTF 2 for both the user space and kernel tracers.

    CTF 2 output isn't enabled by default and is intended solely for preview and feedback purposes: having an experimental support will allow users to test and evaluate CTF 2 until we make it the default output format.

Tracing control

  • The new --buffer-allocation option of the lttng-enable-channel(1) command can set the buffer allocation policy of the channel to create.

    The default per-cpu value is what you've always known while the new per-channel value is available for user space channels.

  • The new --buffer-ownership option of the enable-channel command of the lttng CLI tool replaces the --buffers-global, --buffers-uid, and --buffers-pid options (now deprecated).

  • The enable-channel command of the lttng CLI tool, when creating a user space channel with the usual per-CPU buffer allocation policy, automatically adds a cpu_id context field which, as of LTTng 2.14, you cannot remove. This has always been the case and remains true, but cpu_id is now an offically supported context field.

    Knowing this, with the new per-channel buffer allocation policy, the enable-channel command doesn't add the cpu_id context field: add it afterwards with the lttng-add-context(1) command if needed, for example:

    $ lttng add-context -u --channel=my-channel --type=cpu_id

  • Everywhere the Apache log4j 1.2 --log4j option or log4j:logging option value is available with the lttng CLI tool, you may now use resp. --log4j2 and log4j2:logging to target the new Apache Log4j 2 tracing domain.

  • The liblttng-ctl C API is updated to support the new features:

    • Set and get the buffer allocation policy of a channel with lttng_channel_set_allocation_policy() and lttng_channel_get_allocation_policy().

    • Add the cpu_id context field to a channel with the LTTNG_EVENT_CONTEXT_CPU_ID enumerator when calling lttng_add_context().

    • Apache Log4j 2 functions and enumerators are available everywhere there are Apache Log4j 2 equivalents:

      • LTTNG_DOMAIN_LOG4J2
      • LTTNG_EVENT_RULE_TYPE_LOG4J2_LOGGING
      • enum lttng_loglevel_log4j2
      • lttng_event_rule_log4j2_logging_create()
      • lttng_event_rule_log4j2_logging_get_filter()
      • lttng_event_rule_log4j2_logging_get_log_level_rule()
      • lttng_event_rule_log4j2_logging_get_name_pattern()
      • lttng_event_rule_log4j2_logging_set_filter()
      • lttng_event_rule_log4j2_logging_set_log_level_rule()
      • lttng_event_rule_log4j2_logging_set_name_pattern()

    • Get the status of the Linux kernel tracer with lttng_get_kernel_tracer_status().

    • Get the shared memory directory path of a recording session with lttng_get_session_shm_path_override().

  • Set the LTTNG_EXPERIMENTAL_FORCE_CTF_2 environment variable to 1 when starting lttng-sessiond to enable the experimental CTF 2 output format.

    With this setting, all the recording sessions which the session daemon manages produce CTF 2 traces. As of LTTng 2.14, this is not a per-session configuration.

    The produced CTF 2 traces are expected to be semantically equivalent to what the tracers would have procuced without LTTNG_EXPERIMENTAL_FORCE_CTF_2 set to 1 (CTF 1.8).

    NOTE: A client of a session daemon started with the LTTNG_EXPERIMENTAL_FORCE_CTF_2 environment variable set to 1 cannot create:

    • A network streaming mode recording session.
    • A snapshot mode recording session where you send the trace data over the network.
    • A live mode recording session.

  • The --all option of the lttng-start(1) and lttng-stop(1) commands is now available to start/stop all the recording sessions.

  • The --glob option of the start, and stop, and lttng-destroy(1) commands is now available to start/stop/destroy recording sessions of which some globbing pattern matches the name.

  • New lttng-relayd(8) options are available to help control its process:

    • --dynamic-port-allocation: Let the operating system assign the control, data, and live ports if their respective option is missing (--control-port, --data-port, and --live-port) or if their port number part is 0.

      With this option, lttng-relayd writes the control.port, data.port, and live.port files, as needed, to its runtime and configuration directory ($LTTNG_HOME/.lttng).

    • --pid-file: Write the process ID (PID) of the lttng-relayd process to some file (like the --pidfile option of lttng-sessiond(8)).

    • --sig-parent: Send the USR1 signal to the parent process to notify readiness (like the --sig-parent option of lttng-sessiond).

  • You can now override the path of the directory where lttng-sessiond places special files for user space tracing applications with the LTTNG_UST_CTL_PATH environment variable.

    See lttng-sessiond(8).

  • You can now override the path of the directory where lttng-sessiond places its control files with the LTTNG_RUNDIR environment variable.

    See lttng-sessiond(8).

User space tracing specifics

  • You can now override the path of the directory where a user application instrumented with liblttng-ust looks for special registration and control files of lttng-sessiond with the LTTNG_UST_APP_PATH environment variable.

    See lttng-ust(3).

  • You can now override the policy used to populate shared memory pages within the instrumented application with the LTTNG_UST_MAP_POPULATE_POLICY environment variable.

    See lttng-ust(3).

  • We improved the memory usage of lttng_ust_tracef() and lttng_ust_tracelog().

Kernel tracing specifics

  • The minimum supported Linux kernel version is now 4.4 instead of 3.0.

Version name

This release is named after "Orbitales", a bold creation from Noctem Artisans Brasseurs in Québec City.

Pitch black and dense—one team member compared the color to used motor oil—this beer offers an intriguing sensory experience. Aged in wood casks, it delivers rich aromas and flavors of blackberry as well as a hint of acidity. There’s no head to speak of, but a whisper of blue cheese funk lingers just enough to keep you curious.

Important links

LTTng Tarballs

LTTng Website

Mailing List for Support and Development

IRC Channel

  • #lttng on irc.oftc.net

Bug Tracker

GitHub Organization

Continuous Integration

Code Review

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