DEPRECATED

NAME

       lttng_health_check - Monitor health of the session daemon

SYNOPSIS

       #include <lttng/lttng.h>

       int lttng_health_check(enum lttng_health_component c);

       Link with -llttng-ctl.

DESCRIPTION

       The  lttng_health_check() is used to check the session daemon health for either a specific component c or
       for all of them. Each component represent a subsystem of the session daemon.  Those  components  are  set
       with  health  counters  that are atomically incremented once reached. An even value indicates progress in
       the execution of the component. An odd value means that the code has entered a blocking  state  which  is
       not a poll(7) wait period.

       A bad health is defined by a fatal error code path reached or any IPC used in the session daemon that was
       blocked for more than 20 seconds (default timeout).  The condition for this bad health to be detected  is
       that one or many of the counters are odd.

       The health check mechanism of the session daemon can only be reached through the health socket which is a
       different one from the command and the application socket. An isolated thread serves this socket and only
       computes  the  health counters across the code when asked by the lttng control library (using this call).
       This subsystem is highly unlikely to fail due to its simplicity.

       The c argument can be one of the following values:

       LTTNG_HEALTH_CMD
              Command subsystem which handles user commands coming from the liblttng-ctl or the lttng(1) command
              line interface.

       LTTNG_HEALTH_APP_MANAGE
              The  session  daemon manages application socket in order to route client command and check if they
              get closed which indicates the application shutdown.

       LTTNG_HEALTH_APP_REG
              The application registration mechanism is an important and vital part of for user  space  tracing.
              Upon  startup,  applications  instrumented with lttng-ust(3) try to register to the session daemon
              through this subsystem.

       LTTNG_HEALTH_KERNEL
              Monitor the Kernel tracer streams  and  main  channel  of  communication  (/proc/lttng).  If  this
              component malfunction, the Kernel tracer is not usable anymore by lttng-tools.

       LTTNG_HEALTH_CONSUMER
              The  session  daemon  can  spawn up to three consumer daemon for kernel, user space 32 and 64 bit.
              This subsystem monitors the consumer daemon(s). A bad health state means that the consumer(s)  are
              not usable anymore hence likely making tracing not usable.

       LTTNG_HEALTH_ALL
              Check all components. If only one of them is in a bad state, a health check error is returned.

RETURN VALUE

       Return 0 if the health is OK, or 1 is it's in a bad state. A return code of -1 indicates that the control
       library was not able to connect to the session daemon health socket.

LIMITATIONS

       For the LTTNG_HEALTH_CONSUMER, you can not know which consumer daemon has failed but only that either the
       consumer subsystem has failed or that a lttng-consumerd died.

AUTHORS

       lttng-health-check  was  originally  written  by  David  Goulet  and  is  currently maintained by Jérémie
       Galarneau <jeremie.galarneau@efficios.com>.