[deliverable/lttng-ust.git] / README.md

LTTng-UST
=========

The LTTng User Space Tracing (LTTng-UST) library allows any C/C++
application to be instrumented for and traced by
[LTTng](http://lttng.org/). LTTng-UST also includes a logging
back-end for Java applications and various dynamically loadable
user space tracing helpers for any application.


Prerequisites
-------------

LTTng-UST depends on [liburcu](http://liburcu.org/) v0.7.2 at build and
run times. It also optionally depends on libnuma.


Building
--------

### Prerequisites

This source tree is based on the Autotools suite from GNU to simplify
portability. Here are some things you should have on your system in order to
compile the Git repository tree:

  - [GNU Autotools](http://www.gnu.org/software/autoconf/)
    (**Automake >= 1.10**, **Autoconf >= 2.50**,
    **Autoheader >= 2.50**;
    make sure your system-wide `automake` points to a recent version!)
  - **[GNU Libtool](https://www.gnu.org/software/libtool/) >= 2.2**


### Optional dependencies

Optional packages to build LTTng-ust man pages:

  - **[AsciiDoc](http://www.methods.co.nz/asciidoc/) >= 8.4.5**
    (previous versions may work, but were not tested)
  - **[xmlto](https://fedorahosted.org/xmlto/) >= 0.0.21** (previous
    versions may work, but were not tested)

Note that the man pages are already built in a distribution tarball.
In this case, you only need AsciiDoc and xmlto if you indend to modify
the AsciiDoc man page sources.

Needed for `make check` and tests:

  - **[Perl](https://www.perl.org/)**


### Building steps

If you get the tree from the Git repository, you will need to run

    ./bootstrap

in its root. It calls all the GNU tools needed to prepare the tree
configuration.

To build LTTng-UST, do:

    ./configure
    make
    sudo make install
    sudo ldconfig

**Note:** the `configure` script sets `/usr/local` as the default prefix for
files it installs. However, this path is not part of most distributions'
default library path, which will cause builds depending on `liblttng-ust`
to fail unless `-L/usr/local/lib` is added to `LDFLAGS`. You may provide a
custom prefix to `configure` by using the `--prefix` switch
(e.g., `--prefix=/usr`). LTTng-UST needs to be a shared library, _even if_
the tracepoint probe provider is statically linked into the application.


Using
-----

First of all, create an instrumentation header following the
[tracepoint examples](doc/examples).

There are two ways to compile the tracepoint provider and link it with
your application: statically or dynamically. Please follow carefully one
or the other method.


### Static linking

This method links the tracepoint provider with the application,
either directly or through a static library (`.a`):

  1. Into exactly one unit (C/C++ source file) of your _application_,
     define `TRACEPOINT_DEFINE` and include the tracepoint provider
     header.
  2. Include the tracepoint provider header into all C/C++ files using
     the provider and insert tracepoints using the `tracepoint()` macro.
  3. Use `-I.` when compiling the unit defining `TRACEPOINT_DEFINE`
     (e.g., `tp.c`).
  4. Link the application with `-ldl` on Linux, or with `-lc` on BSD,
     and with `-llttng-ust`.

Example:

    gcc -c -I. tp.c
    gcc -c some-source.c
    gcc -c other-source.c
    gcc -o my-app tp.o some-source.o other-source.o -ldl -llttng-ust

Run the application directly:

    ./my-app

Other relevant examples:

  - [`doc/examples/easy-ust`](doc/examples/easy-ust)
  - [`doc/examples/hello-static-lib`](doc/examples/hello-static-lib)


### Dynamic loading

This method decouples the tracepoint provider from the application,
making it dynamically loadable.

  1. Into exactly one unit of your _application_, define
     `TRACEPOINT_DEFINE` _and_ `TRACEPOINT_PROBE_DYNAMIC_LINKAGE`,
     then include the tracepoint provider header.
  2. Include the tracepoint provider header into all C/C++ files using
     the provider and insert tracepoints using the `tracepoint()` macro.
  3. Use `-I.` and `-fpic` when compiling the tracepoint provider
     (e.g., `tp.c`).
  4. Link the tracepoint provider with `-llttng-ust` and make it a
     shared object with `-shared`.
  5. Link the application with `-ldl` on Linux, or with `-lc` on BSD.

Example:

    gcc -c -I. -fpic tp.c
    gcc -o tp.so -shared tp.o -llttng-ust
    gcc -o my-app some-source.c other-source.c -ldl

To run _without_ LTTng-UST support:

    ./my-app

To run with LTTng-UST support (register your tracepoint provider,
`tp.so`):

    LD_PRELOAD=./tp.so ./my-app

You could also use `libdl` directly in your application and `dlopen()`
your tracepoint provider shared object (`tp.so`) to make LTTng-UST
tracing possible.

Other relevant examples:

  - [`doc/examples/demo`](doc/examples/demo)


### Controlling tracing and viewing traces

Use [LTTng-tools](https://lttng.org/download) to control the tracer.
Use [Babeltrace](https://lttng.org/babeltrace) to print traces as a
human-readable text log.


### Environment variables and compile flags

  - `liblttng-ust` debug can be activated by setting the environment
    variable `LTTNG_UST_DEBUG` when launching the user application. It
    can also be enabled at build time by compiling LTTng-UST with
    `-DLTTNG_UST_DEBUG`.
  - The environment variable `LTTNG_UST_REGISTER_TIMEOUT` can be used to
    specify how long the applications should wait for the session
    daemon  _registration done_ command before proceeding to execute the
    main program. The default is 3000 ms (3 seconds). The timeout value
    is specified in milliseconds. The value 0 means _don't wait_. The
    value -1 means _wait forever_. Setting this environment variable to 0
    is recommended for applications with time constraints on the process
    startup time.
  - The compilation flag `-DLTTNG_UST_DEBUG_VALGRIND` should be enabled
    at build time to allow `liblttng-ust` to be used with Valgrind
    (side-effect: disables per-CPU buffering).


### Notes

#### C++ support

Since LTTng-UST 2.3, both tracepoints and tracepoint providers can be
compiled in C++. To compile tracepoint probes in C++, you need
G++ >= 4.7 or Clang.


Contact
-------

Maintainer: [Mathieu Desnoyers](mailto:mathieu.desnoyers@efficios.com)

Mailing list: [`lttng-dev@lists.lttng.org`](https://lttng.org/cgi-bin/mailman/listinfo/lttng-dev)


Package contents
----------------

This package contains the following elements:

  - `doc`: LTTng-UST documentation and examples.
  - `include`: the public header files that will be installed on the
    system.
  - `liblttng-ust`: the actual userspace tracing library that must be
    linked to the instrumented programs.
  - `liblttng-ust-comm`: a static library shared between `liblttng-ust`
    and LTTng-tools, that provides functions that allow these components
    to communicate together.
  - `liblttng-ust-ctl`: a library to control tracing in other processes;
     used by LTTng-tools.
  - `liblttng-ust-cyg-profile`: a library that can be preloaded (using
    `LD_PRELOAD`) to instrument function entries and exits when the target
    application is built with the GCC flag `-finstrument-functions`.
  - `liblttng-ust-dl`: a library that can be preloaded to instrument
    calls to `dlopen()` and `dlclose()`.
  - `liblttng-ust-fork`: a library that is preloaded and that hijacks
    calls to several system calls in order to trace across these calls.
    It _has_ to be preloaded in order to hijack calls. In contrast,
    `liblttng-ust` may be linked at build time.
  - `liblttng-ust-java`: a simple library that uses JNI to allow tracing
    in Java programs. (Configure with `--enable-jni-interface`).
  - `liblttng-ust-java-agent`: a package that includes a JNI library and a
    JAR library to provide an LTTng-UST logging back-end for Java
    applications using Java Util Logging or Log4j. (Configure with
    `--enable-java-agent-jul` or `--enable-java-agent-log4j` or
    `--enable-java-agent-all`).
  - `liblttng-ust-libc-wrapper`: an example library that can be
    preloaded to instrument some calls to libc (currently `malloc()` and
    `free()`) and to POSIX threads (mutexes currently instrumented) in
    any program without need to recompile it.
  - `liblttng-ust-python-agent`: a library used by python-lttngust to allow
    tracing in Python applications. (Configure with `--enable-python-agent`)
  - `libringbuffer`: the ring buffer implementation used within LTTng-UST.
  - `python-lttngust`: a package to provide an LTTng-UST logging back-end
    for Python applications using the standard logging framework.
  - `snprintf`: an asynchronous signal-safe version of `snprintf()`.
  - `tests`: various test programs.
  - `tools`: home of `lttng-gen-tp`.
Commit	Line	Data
	1	LTTng-UST
	2	=========
	3
	4	The LTTng User Space Tracing (LTTng-UST) library allows any C/C++
	5	application to be instrumented for and traced by
	6	[LTTng](http://lttng.org/). LTTng-UST also includes a logging
	7	back-end for Java applications and various dynamically loadable
	8	user space tracing helpers for any application.
	9
	10
	11	Prerequisites
	12	-------------
	13
	14	LTTng-UST depends on [liburcu](http://liburcu.org/) v0.7.2 at build and
	15	run times. It also optionally depends on libnuma.
	16
	17
	18	Building
	19	--------
	20
	21	### Prerequisites
	22
	23	This source tree is based on the Autotools suite from GNU to simplify
	24	portability. Here are some things you should have on your system in order to
	25	compile the Git repository tree:
	26
	27	- [GNU Autotools](http://www.gnu.org/software/autoconf/)
	28	(Automake >= 1.10, Autoconf >= 2.50,
	29	Autoheader >= 2.50;
	30	make sure your system-wide `automake` points to a recent version!)
	31	- [GNU Libtool](https://www.gnu.org/software/libtool/) >= 2.2
	32
	33
	34	### Optional dependencies
	35
	36	Optional packages to build LTTng-ust man pages:
	37
	38	- [AsciiDoc](http://www.methods.co.nz/asciidoc/) >= 8.4.5
	39	(previous versions may work, but were not tested)
	40	- [xmlto](https://fedorahosted.org/xmlto/) >= 0.0.21 (previous
	41	versions may work, but were not tested)
	42
	43	Note that the man pages are already built in a distribution tarball.
	44	In this case, you only need AsciiDoc and xmlto if you indend to modify
	45	the AsciiDoc man page sources.
	46
	47	Needed for `make check` and tests:
	48
	49	- [Perl](https://www.perl.org/)
	50
	51
	52	### Building steps
	53
	54	If you get the tree from the Git repository, you will need to run
	55
	56	./bootstrap
	57
	58	in its root. It calls all the GNU tools needed to prepare the tree
	59	configuration.
	60
	61	To build LTTng-UST, do:
	62
	63	./configure
	64	make
	65	sudo make install
	66	sudo ldconfig
	67
	68	Note: the `configure` script sets `/usr/local` as the default prefix for
	69	files it installs. However, this path is not part of most distributions'
	70	default library path, which will cause builds depending on `liblttng-ust`
	71	to fail unless `-L/usr/local/lib` is added to `LDFLAGS`. You may provide a
	72	custom prefix to `configure` by using the `--prefix` switch
	73	(e.g., `--prefix=/usr`). LTTng-UST needs to be a shared library, _even if_
	74	the tracepoint probe provider is statically linked into the application.
	75
	76
	77	Using
	78	-----
	79
	80	First of all, create an instrumentation header following the
	81	[tracepoint examples](doc/examples).
	82
	83	There are two ways to compile the tracepoint provider and link it with
	84	your application: statically or dynamically. Please follow carefully one
	85	or the other method.
	86
	87
	88	### Static linking
	89
	90	This method links the tracepoint provider with the application,
	91	either directly or through a static library (`.a`):
	92
	93	1. Into exactly one unit (C/C++ source file) of your _application_,
	94	define `TRACEPOINT_DEFINE` and include the tracepoint provider
	95	header.
	96	2. Include the tracepoint provider header into all C/C++ files using
	97	the provider and insert tracepoints using the `tracepoint()` macro.
	98	3. Use `-I.` when compiling the unit defining `TRACEPOINT_DEFINE`
	99	(e.g., `tp.c`).
	100	4. Link the application with `-ldl` on Linux, or with `-lc` on BSD,
	101	and with `-llttng-ust`.
	102
	103	Example:
	104
	105	gcc -c -I. tp.c
	106	gcc -c some-source.c
	107	gcc -c other-source.c
	108	gcc -o my-app tp.o some-source.o other-source.o -ldl -llttng-ust
	109
	110	Run the application directly:
	111
	112	./my-app
	113
	114	Other relevant examples:
	115
	116	- [`doc/examples/easy-ust`](doc/examples/easy-ust)
	117	- [`doc/examples/hello-static-lib`](doc/examples/hello-static-lib)
	118
	119
	120	### Dynamic loading
	121
	122	This method decouples the tracepoint provider from the application,
	123	making it dynamically loadable.
	124
	125	1. Into exactly one unit of your _application_, define
	126	`TRACEPOINT_DEFINE` _and_ `TRACEPOINT_PROBE_DYNAMIC_LINKAGE`,
	127	then include the tracepoint provider header.
	128	2. Include the tracepoint provider header into all C/C++ files using
	129	the provider and insert tracepoints using the `tracepoint()` macro.
	130	3. Use `-I.` and `-fpic` when compiling the tracepoint provider
	131	(e.g., `tp.c`).
	132	4. Link the tracepoint provider with `-llttng-ust` and make it a
	133	shared object with `-shared`.
	134	5. Link the application with `-ldl` on Linux, or with `-lc` on BSD.
	135
	136	Example:
	137
	138	gcc -c -I. -fpic tp.c
	139	gcc -o tp.so -shared tp.o -llttng-ust
	140	gcc -o my-app some-source.c other-source.c -ldl
	141
	142	To run _without_ LTTng-UST support:
	143
	144	./my-app
	145
	146	To run with LTTng-UST support (register your tracepoint provider,
	147	`tp.so`):
	148
	149	LD_PRELOAD=./tp.so ./my-app
	150
	151	You could also use `libdl` directly in your application and `dlopen()`
	152	your tracepoint provider shared object (`tp.so`) to make LTTng-UST
	153	tracing possible.
	154
	155	Other relevant examples:
	156
	157	- [`doc/examples/demo`](doc/examples/demo)
	158
	159
	160	### Controlling tracing and viewing traces
	161
	162	Use [LTTng-tools](https://lttng.org/download) to control the tracer.
	163	Use [Babeltrace](https://lttng.org/babeltrace) to print traces as a
	164	human-readable text log.
	165
	166
	167	### Environment variables and compile flags
	168
	169	- `liblttng-ust` debug can be activated by setting the environment
	170	variable `LTTNG_UST_DEBUG` when launching the user application. It
	171	can also be enabled at build time by compiling LTTng-UST with
	172	`-DLTTNG_UST_DEBUG`.
	173	- The environment variable `LTTNG_UST_REGISTER_TIMEOUT` can be used to
	174	specify how long the applications should wait for the session
	175	daemon _registration done_ command before proceeding to execute the
	176	main program. The default is 3000 ms (3 seconds). The timeout value
	177	is specified in milliseconds. The value 0 means _don't wait_. The
	178	value -1 means _wait forever_. Setting this environment variable to 0
	179	is recommended for applications with time constraints on the process
	180	startup time.
	181	- The compilation flag `-DLTTNG_UST_DEBUG_VALGRIND` should be enabled
	182	at build time to allow `liblttng-ust` to be used with Valgrind
	183	(side-effect: disables per-CPU buffering).
	184
	185
	186	### Notes
	187
	188	#### C++ support
	189
	190	Since LTTng-UST 2.3, both tracepoints and tracepoint providers can be
	191	compiled in C++. To compile tracepoint probes in C++, you need
	192	G++ >= 4.7 or Clang.
	193
	194
	195	Contact
	196	-------
	197
	198	Maintainer: [Mathieu Desnoyers](mailto:mathieu.desnoyers@efficios.com)
	199
	200	Mailing list: [`lttng-dev@lists.lttng.org`](https://lttng.org/cgi-bin/mailman/listinfo/lttng-dev)
	201
	202
	203	Package contents
	204	----------------
	205
	206	This package contains the following elements:
	207
	208	- `doc`: LTTng-UST documentation and examples.
	209	- `include`: the public header files that will be installed on the
	210	system.
	211	- `liblttng-ust`: the actual userspace tracing library that must be
	212	linked to the instrumented programs.
	213	- `liblttng-ust-comm`: a static library shared between `liblttng-ust`
	214	and LTTng-tools, that provides functions that allow these components
	215	to communicate together.
	216	- `liblttng-ust-ctl`: a library to control tracing in other processes;
	217	used by LTTng-tools.
	218	- `liblttng-ust-cyg-profile`: a library that can be preloaded (using
	219	`LD_PRELOAD`) to instrument function entries and exits when the target
	220	application is built with the GCC flag `-finstrument-functions`.
	221	- `liblttng-ust-dl`: a library that can be preloaded to instrument
	222	calls to `dlopen()` and `dlclose()`.
	223	- `liblttng-ust-fork`: a library that is preloaded and that hijacks
	224	calls to several system calls in order to trace across these calls.
	225	It _has_ to be preloaded in order to hijack calls. In contrast,
	226	`liblttng-ust` may be linked at build time.
	227	- `liblttng-ust-java`: a simple library that uses JNI to allow tracing
	228	in Java programs. (Configure with `--enable-jni-interface`).
	229	- `liblttng-ust-java-agent`: a package that includes a JNI library and a
	230	JAR library to provide an LTTng-UST logging back-end for Java
	231	applications using Java Util Logging or Log4j. (Configure with
	232	`--enable-java-agent-jul` or `--enable-java-agent-log4j` or
	233	`--enable-java-agent-all`).
	234	- `liblttng-ust-libc-wrapper`: an example library that can be
	235	preloaded to instrument some calls to libc (currently `malloc()` and
	236	`free()`) and to POSIX threads (mutexes currently instrumented) in
	237	any program without need to recompile it.
	238	- `liblttng-ust-python-agent`: a library used by python-lttngust to allow
	239	tracing in Python applications. (Configure with `--enable-python-agent`)
	240	- `libringbuffer`: the ring buffer implementation used within LTTng-UST.
	241	- `python-lttngust`: a package to provide an LTTng-UST logging back-end
	242	for Python applications using the standard logging framework.
	243	- `snprintf`: an asynchronous signal-safe version of `snprintf()`.
	244	- `tests`: various test programs.
	245	- `tools`: home of `lttng-gen-tp`.