Tests: add globbing pattern tests to test_java_log4j
[lttng-tools.git] / doc / man / lttng-enable-event.1.txt
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1lttng-enable-event(1)
2=====================
3
4
5NAME
6----
7lttng-enable-event - Create or enable LTTng event rules
8
9
10SYNOPSIS
11--------
12Create or enable Linux kernel event rules:
13
14[verse]
ce19b9ed 15*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event* option:--kernel
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16 [option:--probe='SOURCE' | option:--function='SOURCE' | option:--syscall]
17 [option:--filter='EXPR'] [option:--session='SESSION']
18 [option:--channel='CHANNEL'] 'EVENT'[,'EVENT']...
19
20Create or enable an "all" Linux kernel event rule:
21
22[verse]
ce19b9ed 23*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event* option:--kernel option:--all [option:--syscall]
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24 [option:--filter='EXPR'] [option:--session='SESSION'] [option:--channel='CHANNEL']
25
26Create or enable application event rules:
27
28[verse]
ce19b9ed 29*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event*
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30 (option:--userspace | option:--jul | option:--log4j | option:--python)
31 [option:--filter='EXPR'] [option:--exclude='EVENT'[,'EVENT']...]
32 [option:--loglevel='LOGLEVEL' | option:--loglevel-only='LOGLEVEL']
33 [option:--session='SESSION'] [option:--channel='CHANNEL'] (option:--all | 'EVENT'[,'EVENT']...)
34
35
36DESCRIPTION
37-----------
38The `lttng enable-event` command can create a new event rule, or enable
39one or more existing and disabled ones.
40
41An event rule created by `lttng enable-event` is a set of conditions
42that must be satisfied in order for an actual event to be emitted by
43an LTTng tracer when the execution of an application or the Linux kernel
44reaches an event source (tracepoint, system call, dynamic probe).
7c1a4458 45Event sources can be listed with the man:lttng-list(1) command.
e9b06e2b 46
7c1a4458 47The man:lttng-disable-event(1) command can be used to disable
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48existing event rules.
49
50Event rules are always assigned to a channel when they are created. If
51the option:--channel option is omitted, a default channel named
52`channel0` is used (and created automatically if it does not exist for
53the specified domain in the selected tracing session).
54
55If the option:--session option is omitted, the chosen channel is picked
56from the current tracing session.
57
58Events can be enabled while tracing is active
7c1a4458 59(use man:lttng-start(1) to make a tracing session active).
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60
61
62Event source types
63~~~~~~~~~~~~~~~~~~
64Four types of event sources are available in the Linux kernel tracing
65domain (option:--kernel option):
66
67Tracepoint (option:--tracepoint option; default)::
68 A Linux kernel tracepoint, that is, a static instrumentation point
69 placed in the kernel source code. Standard tracepoints are designed
70 and placed in the source code by developers and record useful
71 payload fields.
72
73Dynamic probe (option:--probe option)::
74 A Linux kernel kprobe, that is, an instrumentation point placed
75 dynamically in the compiled kernel code. Dynamic probe events do not
76 record any payload field.
77
78Function probe (option:--function option)::
79 A Linux kernel kretprobe, that is, two instrumentation points placed
80 dynamically where a function is entered and where it returns in the
81 compiled kernel code. Function probe events do not record any
82 payload field.
83
84System call (option:--syscall option)::
85 A Linux kernel system call. Two instrumentation points are
86 statically placed where a system call function is entered and where
87 it returns in the compiled kernel code. System call event sources
88 record useful payload fields.
89
90The application tracing domains (option:--userspace, option:--jul,
91option:--log4j, or option:--python options) only support tracepoints.
92In the cases of the JUL, Apache log4j, and Python domains, the event
93names correspond to _logger_ names.
94
95
96Understanding event rule conditions
97~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
98When creating an event rule with `lttng enable-event`, conditions are
99specified using options. The logical conjunction (logical AND) of all
100those conditions must be true when an event source is reached by an
101application or by the Linux kernel in order for an actual event
102to be emitted by an LTTng tracer.
103
104Any condition that is not explicitly specified on creation is considered
105a _don't care_.
106
107For example, consider the following commands:
108
d4f093aa 109[role="term"]
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110----
111$ lttng enable-event --userspace hello:world
112$ lttng enable-event --userspace hello:world --loglevel=TRACE_INFO
113----
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114
115Here, two event rules are created. The first one has a single condition:
116the tracepoint name must match `hello:world`. The second one has two
117conditions:
118
119* The tracepoint name must match `hello:world`, _and_
120* The tracepoint's defined log level must be at least as severe as
121 the `TRACE_INFO` level.
122
123In this case, the second event rule is pointless because the first one
124is more general: it does not care about the tracepoint's log level.
125If an event source matching both event rules is reached by the
126application's execution, only one event is emitted.
127
128The available conditions for the Linux kernel domain are:
129
130* Tracepoint/system call name ('EVENT' argument with
131 option:--tracepoint or option:--syscall options) or
132 dynamic probe/function name/address
133 (option:--probe or option:--function option's argument) which must
134 match event source's equivalent.
135+
136Wildcard using the `*` character are supported _at the end_ of
137tracepoint and system call names.
138
139* Filter expression (option:--filter option) executed against the
140 dynamic values of event fields at execution time that must evaluate
141 to true. See the <<filter-syntax,Filter expression syntax>> section
142 below for more information.
143
144The available conditions for the application domains are:
145
146* Tracepoint name ('EVENT' with option:--tracepoint option) which must
147 match event source's equivalent.
148+
149Wildcard using the `*` character are supported _at the end_ of
150tracepoint names. When creating an event rule with a tracepoint name
151containing a wildcard, specific tracepoint names can be excluded from
152the match using the option:--exclude option.
153
154* Filter expression (option:--filter option) executed against the
155 dynamic values of event fields at execution time that must evaluate
156 to true. See the <<filter-syntax,Filter expression syntax>> section
157 below for more information.
158* Event's log level that must be at least as severe as a given
159 log level (option:--loglevel option) or match exactly a given log
160 level (option:--loglevel-only option).
161
162When using `lttng enable-event` with a set of conditions that does not
163currently exist for the chosen tracing session, domain, and channel,
164a new event rule is created. Otherwise, the existing event rule is
165enabled if it is currently disabled
7c1a4458 166(see man:lttng-disable-event(1)).
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167
168The option:--all option can be used alongside the option:--tracepoint
169or option:--syscall options. When this option is used, no 'EVENT'
170argument must be specified. This option defines a single event rule
171matching _all_ the possible events of a given tracing domain for the
172chosen channel and tracing session. It is the equivalent of an 'EVENT'
173argument named `*` (wildcard).
174
175
176[[filter-syntax]]
177Filter expression syntax
178~~~~~~~~~~~~~~~~~~~~~~~~
179Filter expressions can be specified with the option:--filter option
180when creating a new event rule. If the filter expression evaluates
181to true when executed against the dynamic values of an event's fields
182when tracing, the filtering condition passes.
183
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184NOTE: Make sure to **single-quote** the filter expression when running
185the command from a shell, as filter expressions typically include
186characters having a special meaning for most shells.
187
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188The filter expression syntax is very similar to C language conditional
189expressions (expressions that can be evaluated by an `if` statement).
190
191The following logical operators are supported:
192
193[width="40%",options="header"]
194|=====================================
195| Name | Syntax
196| Logical negation (NOT) | `!a`
197| Logical conjunction (AND) | `a && b`
198| Logical disjunction (OR) | `a \|\| b`
199|=====================================
200
201The following comparison operators/relational operators are supported:
202
203[width="40%",options="header"]
204|====================================
205| Name | Syntax
206| Equal to | `a == b`
207| Not equal to | `a != b`
208| Greater than | `a > b`
209| Less than | `a < b`
210| Greater than or equal to | `a >= b`
211| Less than or equal to | `a <= b`
212|====================================
213
214The arithmetic and bitwise operators are :not: supported.
215
216The precedence table of the operators above is the same as the one of
217the C language. Parentheses are supported to bypass this.
218
219The dynamic value of an event field is read by using its name as
220a C identifier.
221
222The dynamic value of a statically-known context field is read by
223prefixing its name with `$ctx.`. Statically-known context fields are
224context fields added to channels without the `$app.` prefix using the
7c1a4458 225man:lttng-add-context(1) command.
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226
227The dynamic value of an application-specific context field is read by
228prefixing its name with `$app.` (follows the format used to add such a
7c1a4458 229context field with the man:lttng-add-context(1) command).
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230
231When a comparison includes a non existent event field, the whole filter
232expression evaluates to false (the event is discarded).
233
234C integer and floating point number constants are supported, as well as
235literal strings between double quotes (`"`). Literal strings can contain
236a wildcard character (`*`) at the end to match more than one string.
bca82bfe 237This wildcard can be escaped using :escwc:.
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238
239LTTng-UST enumeration fields can be compared to integer values (fields
240or constants).
241
242NOTE: Although it is possible to filter the process ID of an event when
243the `pid` context has been added to its channel using, for example,
244`$ctx.pid == 2832`, it is recommended to use the PID tracker instead,
7c1a4458 245which is much more efficient (see man:lttng-track(1)).
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246
247Examples:
248
249----------------------------
250msg_id == 23 && size >= 2048
251----------------------------
252
253-------------------------------------------------
254$ctx.procname == "lttng*" && (!flag || poel < 34)
255-------------------------------------------------
256
257---------------------------------------------------------
258$app.my_provider:my_context == 17.34e9 || some_enum >= 14
259---------------------------------------------------------
260
261
262[[log-levels]]
263Log levels
264~~~~~~~~~~
265Tracepoints and log statements in applications have an attached log
266level. Application event rules can contain a _log level_ condition.
267
268With the option:--loglevel option, the event source's log level must
269be at least as severe as the option's argument. With the
270option:--loglevel-only option, the event source's log level must match
271the option's argument.
272
273The available log levels are:
274
275User space domain (option:--userspace option)::
276 Shortcuts such as `system` are allowed.
277+
278* `TRACE_EMERG` (0)
279* `TRACE_ALERT` (1)
280* `TRACE_CRIT` (2)
281* `TRACE_ERR` (3)
282* `TRACE_WARNING` (4)
283* `TRACE_NOTICE` (5)
284* `TRACE_INFO` (6)
285* `TRACE_DEBUG_SYSTEM` (7)
286* `TRACE_DEBUG_PROGRAM` (8)
287* `TRACE_DEBUG_PROCESS` (9)
288* `TRACE_DEBUG_MODULE` (10)
289* `TRACE_DEBUG_UNIT` (11)
290* `TRACE_DEBUG_FUNCTION` (12)
291* `TRACE_DEBUG_LINE` (13)
292* `TRACE_DEBUG` (14)
293
294`java.util.logging` domain (option:--jul option)::
295 Shortcuts such as `severe` are allowed.
296+
297* `JUL_OFF` (`INT32_MAX`)
298* `JUL_SEVERE` (1000)
299* `JUL_WARNING` (900)
300* `JUL_INFO` (800)
301* `JUL_CONFIG` (700)
302* `JUL_FINE` (500)
303* `JUL_FINER` (400)
304* `JUL_FINEST` (300)
305* `JUL_ALL` (`INT32_MIN`)
306
307Apache log4j domain (option:--log4j option)::
308 Shortcuts such as `severe` are allowed.
309+
310* `LOG4J_OFF` (`INT32_MAX`)
311* `LOG4J_FATAL` (50000)
312* `LOG4J_ERROR` (40000)
313* `LOG4J_WARN` (30000)
314* `LOG4J_INFO` (20000)
315* `LOG4J_DEBUG` (10000)
316* `LOG4J_TRACE` (5000)
317* `LOG4J_ALL` (`INT32_MIN`)
318
319Python domain (option:--python option)::
320 Shortcuts such as `critical` are allowed.
321+
322* `PYTHON_CRITICAL` (50)
323* `PYTHON_ERROR` (40)
324* `PYTHON_WARNING` (30)
325* `PYTHON_INFO` (20)
326* `PYTHON_DEBUG` (10)
327* `PYTHON_NOTSET` (0)
328
329
330include::common-cmd-options-head.txt[]
331
332
333Domain
334~~~~~~
335One of:
336
337option:-j, option:--jul::
338 Create or enable event rules in the `java.util.logging`
339 (JUL) domain.
340
341option:-k, option:--kernel::
342 Create or enable event rules in the Linux kernel domain.
343
344option:-l, option:--log4j::
345 Create or enable event rules in the Apache log4j domain.
346
347option:-p, option:--python::
348 Create or enable event rules in the Python domain.
349
350option:-u, option:--userspace::
351 Create or enable event rules in the user space domain.
352
353
354Target
355~~~~~~
59b19c3c 356option:-c 'CHANNEL', option:--channel='CHANNEL'::
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357 Create or enable event rules in the channel named 'CHANNEL' instead
358 of the default channel name `channel0`.
359
59b19c3c 360option:-s 'SESSION', option:--session='SESSION'::
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361 Create or enable event rules in the tracing session named 'SESSION'
362 instead of the current tracing session.
363
364
365Event source type
366~~~~~~~~~~~~~~~~~
367One of:
368
369option:--function='SOURCE'::
370 Linux kernel kretprobe. Only available with the option:--kernel
371 domain option. 'SOURCE' is one of:
372+
373* Function address (`0x` prefix supported)
374* Function symbol
375* Function symbol and offset (`SYMBOL+OFFSET` format)
376
377option:--probe='SOURCE'::
378 Linux kernel kprobe. Only available with the option:--kernel
379 domain option. 'SOURCE' is one of:
380+
381* Address (`0x` prefix supported)
382* Symbol
383* Symbol and offset (`SYMBOL+OFFSET` format)
384
385option:--syscall::
386 Linux kernel system call. Only available with the option:--kernel
387 domain option.
388
389option:--tracepoint::
390 Linux kernel or application tracepoint (default).
391
392
393Log level
394~~~~~~~~~
395One of:
396
397option:--loglevel='LOGLEVEL'::
398 Add log level condition to the event rule: the event source's
399 defined log level must be at least as severe as 'LOGLEVEL'.
400 See the <<log-levels,Log levels>> section above for the available
401 log levels. Only available with application domains.
402
403option:--loglevel-only='LOGLEVEL'::
404 Add log level condition to the event rule: the event source's
405 defined log level must match 'LOGLEVEL'. See the
406 <<log-levels,Log levels>> section above for the available log
407 levels. Only available with application domains.
408
409
410Filtering and exclusion
411~~~~~~~~~~~~~~~~~~~~~~~
59b19c3c 412option:-x 'EVENT'[,'EVENT']..., option:--exclude='EVENT'[,'EVENT']...::
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413 Exclude events named 'EVENT' from the event rule. This option
414 can be used when the command's 'EVENT' argument contains a wildcard
415 (`*`) to exclude specific names. Only available with application
416 domains.
417
59b19c3c 418option:-f 'EXPR', option:--filter='EXPR'::
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419 Add filter expression condition to the event rule. Expression 'EXPR'
420 must evaluate to true when executed against the dynamic values of
421 event fields. See the <<filter-syntax,Filter expression syntax>>
422 section above for more information.
423
424
425Shortcuts
426~~~~~~~~~
427option:-a, option:--all::
428 Equivalent to an 'EVENT' argument named `*` (wildcard) when also
429 using the option:--tracepoint (default) or option:--syscall option.
430
431
432include::common-cmd-help-options.txt[]
433
434
435include::common-cmd-footer.txt[]
436
437
438SEE ALSO
439--------
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440man:lttng-disable-event(1),
441man:lttng(1)
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