1LTTNG_HEALTH_CHECK(3) LTTng Developer Manual LTTNG_HEALTH_CHECK(3)
2
6 DEPRECATED
7 lttng_health_check - Monitor health of the session daemon
9
11 #include <lttng/lttng.h>
12 int lttng_health_check(enum lttng_health_component c);
14 Link with -llttng-ctl.
16
18 The lttng_health_check() is used to check the session daemon health for
19 either a specific component c or for all of them. Each component repre‐
20 sent a subsystem of the session daemon. Those components are set with
21 health counters that are atomically incremented once reached. An even
22 value indicates progress in the execution of the component. An odd
23 value means that the code has entered a blocking state which is not a
24 poll(7) wait period.
25 A bad health is defined by a fatal error code path reached or any IPC
27 used in the session daemon that was blocked for more than 20 seconds
28 (default timeout). The condition for this bad health to be detected is
29 that one or many of the counters are odd.
30 The health check mechanism of the session daemon can only be reached
32 through the health socket which is a different one from the command and
33 the application socket. An isolated thread serves this socket and only
34 computes the health counters across the code when asked by the lttng
35 control library (using this call). This subsystem is highly unlikely to
36 fail due to its simplicity.
37 The c argument can be one of the following values:
39 LTTNG_HEALTH_CMD
41 Command subsystem which handles user commands coming from the
42 liblttng-ctl or the lttng(1) command line interface.
43 LTTNG_HEALTH_APP_MANAGE
45 The session daemon manages application socket in order to route
46 client command and check if they get closed which indicates the
47 application shutdown.
48 LTTNG_HEALTH_APP_REG
50 The application registration mechanism is an important and vital
51 part of for user space tracing. Upon startup, applications
52 instrumented with lttng-ust(3) try to register to the session
53 daemon through this subsystem.
54 LTTNG_HEALTH_KERNEL
56 Monitor the Kernel tracer streams and main channel of communica‐
57 tion (/proc/lttng). If this component malfunction, the Kernel
58 tracer is not usable anymore by lttng-tools.
59 LTTNG_HEALTH_CONSUMER
61 The session daemon can spawn up to three consumer daemon for
62 kernel, user space 32 and 64 bit. This subsystem monitors the
63 consumer daemon(s). A bad health state means that the con‐
64 sumer(s) are not usable anymore hence likely making tracing not
65 usable.
66 LTTNG_HEALTH_ALL
68 Check all components. If only one of them is in a bad state, a
69 health check error is returned.
70
73 Return 0 if the health is OK, or 1 is it's in a bad state. A return
74 code of -1 indicates that the control library was not able to connect
75 to the session daemon health socket.
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79 For the LTTNG_HEALTH_CONSUMER, you can not know which consumer daemon
80 has failed but only that either the consumer subsystem has failed or
81 that a lttng-consumerd died.
82
85 lttng-health-check was originally written by David Goulet and is cur‐
86 rently maintained by Jérémie Galarneau <jeremie.galarneau@effi‐
87 cios.com>.
88LTTng 2012-09-19 LTTNG_HEALTH_CHECK(3)