Statistics Module¶
The statistics module allows application, libraries, or drivers to record statistics that can be shown via the Newtmgr tool and console.
This allows easy integration of statistics for troubleshooting, maintenance, and usage monitoring.
By creating and registering your statistics, they are automatically included in the Newtmgr shell and console APIs.
Implementation Details¶
A statistic is an unsigned integer that can be set by the code. When building stats, the implementer chooses the size of the statistic depending on the frequency of the statistic and the resolution required before the counter wraps.
Typically the stats are incremented upon code events; however, they are not limted to that purpose.
Stats are organized into sections. Each section of stats has its own name and can be queried separately through the API. Each section of stats also has its own statistic size, allowing the user to separate large (64-bit) statistics from small (16 bit statistics). NOTE: It is not currently possible to group different size stats into the same section. Please ensure all stats in a section have the same size.
Stats sections are currently stored in a single global stats group.
Statistics are stored in a simple structure which contains a small stats header followed by a list of stats. The stats header contains:
struct stats_hdr {
char *s_name;
uint8_t s_size;
uint8_t s_cnt;
uint16_t s_pad1;
#if MYNEWT_VAL(STATS_NAMES)
const struct stats_name_map *s_map;
int s_map_cnt;
#endif
STAILQ_ENTRY(stats_hdr) s_next;
};
The fields define with in the #if MYNEWT_VAL(STATS_NAME)
directive
are only inincluded when the STATS_NAMES
syscfg setting is set to 1
and enables use statistic names.
Enabling Statistic Names¶
By default, statistics are queried by number. You can use the
STATS_NAMES
syscfg setting to enable statistic names and view the
results by name. Enabling statistic names provides better descriptions
in the reported statistics, but takes code space to store the strings
within the image.
To enable statistic names, set the STATS_NAMES
value to 1 in the
application syscfg.yml
file or use the newt target set
command
to set the syscfg setting value. Here are examples for each method:
Method 1 - Set the value in the application syscfg.yml
files:
# Package: apps/myapp
syscfg.vals:
STATS_NAMES: 1
Method 2 - Set the target syscfg
variable:
newt target set myapp syscfg=STATS_NAMES=1
Note: This newt target set
command only sets the syscfg variable
for the STATS_NAMES
setting as an example. For your target, you
should set the syscfg variable with the other settings that you want to
override.
Adding Stats to your code.¶
Creating new stats table requires the following steps.
Include the stats header file
Define a stats section
Declare an instance of the section
Define the stat sections names table
Implement stat in your code
Initialize the stats
Register the stats
Include the stats header file¶
Add the stats library to your pkg.yml file for your package or app by adding this line to your package dependencies.
pkg.deps:
- "@apache-mynewt-core/sys/stats"
Add this include directive to code files using the stats library.
#include <stats/stats.h>
Define a stats section¶
You must use the stats.h
macros to define your stats table. A stats
section definition looks like this.
STATS_SECT_START(my_stat_section)
STATS_SECT_ENTRY(attempt_stat)
STATS_SECT_ENTRY(error_stat)
STATS_SECT_END
In this case we chose to make the stats 32-bits each. stats.h
supports three different stats sizes through the following macros:
STATS_SIZE_16
– stats are 16 bits (wraps at 65536)STATS_SIZE_32
– stats are 32 bits (wraps at 4294967296)STATS_SIZE_64
– stats are 64-bits
When this compiles/pre-processes, it produces a structure definition like this
struct stats_my_stat_section {
struct stats_hdr s_hdr;
uint32_t sattempt_stat;
uint32_t serror_stat;
};
You can see that the defined structure has a small stats structure header and the two stats we have defined.
Depending on whether these stats are used in multiple modules, you may need to include this definition in a header file.
Declaring a variable to hold the stats¶
Declare the global variable to hold your statistics. Since it is possible to have multiple copies of the same section (for example a stat section for each of 5 identical peripherals), the variable name of the stats section must be unique.
STATS_SECT_DECL(my_stat_section) g_mystat;
Again, if your stats section is used in multiple C files you will need to include the above definition in one of the C files and ‘extern’ this declaration in your header file.
extern STATS_SECT_DECL(my_stat_section) g_mystat;
Define the stats section name table¶
Whether or not you have STATS_NAMES
enabled, you must define a stats
name table. If STATS_NAMES
is not enabled, this will not take any
code space or image size.
/* define a few stats for querying */
STATS_NAME_START(my_stat_section)
STATS_NAME(my_stat_section, attempt_stat)
STATS_NAME(my_stat_section, error_stat)
STATS_NAME_END(my_stat_section)
When compiled by the preprocessor, it creates a structure that looks like this.
struct stats_name_map g_stats_map_my_stat_section[] = {
{ __builtin_offsetof (struct stats_my_stat_section, sattempt_stat), "attempt_stat" },
{ __builtin_offsetof (struct stats_my_stat_section, serror_stat), "error_stat" },
};
This table will allow the UI components to find a nice string name for the stat.
Implement stats in your code.¶
You can use the STATS_INC
or STATS_INCN
macros to increment your
statistics within your C-code. For example, your code may do this:
STATS_INC(g_mystat, attempt_stat);
rc = do_task();
if(rc == ERR) {
STATS_INC(g_mystat, error_stat);
}
Initialize the statistics¶
You must initialize the stats so they can be operated on by the stats library. As per our example above, it would look like the following.
This tells the system how large each statistic is and the number of statistics in the section. It also initialize the name information for the statistics if enabled as shown above.
rc = stats_init(
STATS_HDR(g_mystat),
STATS_SIZE_INIT_PARMS(g_mystat, STATS_SIZE_32),
STATS_NAME_INIT_PARMS(my_stat_section));
assert(rc == 0);
Register the statistic section¶
If you want the system to know about your stats, you must register them.
rc = stats_register("my_stats", STATS_HDR(g_mystat));
assert(rc == 0);
There is also a method that does initialization and registration at the
same time, called stats_init_and_reg
.
Retrieving stats through console or Newtmgr¶
If you enable console in your project you can see stats through the serial port defined.
This is the stats as shown from the example above with names enabled.
stat my_stats
12274:attempt_stat: 3
12275:error_stat: 0
This is the stats as shown from the example without names enabled.
stat my_stats
29149:s0: 3
29150:s1: 0
A note on multiple stats sections¶
If you are implementing a device with multiple instances, you may want multiple stats sections with the exact same format.
For example, suppose I write a driver for an external distance sensor. My driver supports up to 5 sensors and I want to record the stats of each device separately.
This works identically to the example above, except you would need to register each one separately with a unique name. The stats system will not let two sections be entered with the same name.
API¶
Defines
-
STATS_HDR_F_PERSIST
¶ The stat group is periodically written to sys/config.
-
STATS_SECT_DECL
(__name)¶
-
STATS_SECT_START
(__name)¶
-
STATS_SECT_END
¶
-
STATS_SECT_VAR
(__var)¶
-
STATS_HDR
(__sectname)¶
-
STATS_SIZE_16
¶
-
STATS_SIZE_32
¶
-
STATS_SIZE_64
¶
-
STATS_SECT_ENTRY
(__var)¶
-
STATS_SECT_ENTRY16
(__var)¶
-
STATS_SECT_ENTRY32
(__var)¶
-
STATS_SECT_ENTRY64
(__var)¶
-
STATS_RESET
(__sectvarname)¶ Resets all stats in the provided group to 0.
NOTE: This must only be used with non-persistent stat groups.
-
STATS_SIZE_INIT_PARMS
(__sectvarname, __size)¶
-
STATS_GET
(__sectvarname, __var)¶
-
STATS_SET_RAW
(__sectvarname, __var, __val)¶
-
STATS_SET
(__sectvarname, __var, __val)¶
-
STATS_INCN_RAW
(__sectvarname, __var, __n)¶ Adjusts a stat’s in-RAM value by the specified delta.
For non-persistent stats, this is more efficient than
STATS_INCN()
. This must only be used with non-persistent stats; for persistent stats the behavior is undefined.- Parameters
__sectvarname
: The name of the stat group containing the stat to modify.__var
: The name of the individual stat to modify.__n
: The amount to add to the specified stat.
-
STATS_INC_RAW
(__sectvarname, __var)¶ Increments a stat’s in-RAM value.
For non-persistent stats, this is more efficient than
STATS_INCN()
. This must only be used with non-persistent stats; for persistent stats the behavior is undefined.- Parameters
__sectvarname
: The name of the stat group containing the stat to modify.__var
: The name of the individual stat to modify.
-
STATS_INCN
(__sectvarname, __var, __n)¶ Adjusts a stat’s value by the specified delta.
If the specified stat group is persistent, this also schedules the group to be flushed to disk.
- Parameters
__sectvarname
: The name of the stat group containing the stat to modify.__var
: The name of the individual stat to modify.__n
: The amount to add to the specified stat.
-
STATS_INC
(__sectvarname, __var)¶ Increments a stat’s value.
If the specified stat group is persistent, this also schedules the group to be flushed to disk.
- Parameters
__sectvarname
: The name of the stat group containing the stat to modify.__var
: The name of the individual stat to modify.
-
STATS_CLEAR
(__sectvarname, __var)¶
-
STATS_NAME_MAP_NAME
(__sectname)¶
-
STATS_NAME_START
(__sectname)¶
-
STATS_NAME
(__sectname, __entry)¶
-
STATS_NAME_END
(__sectname)¶
-
STATS_NAME_INIT_PARMS
(__name)¶
-
STATS_PERSISTED_SECT_START
(__name)¶ Starts the definition of a peristed stat group.
o Follow with invocations of the
STATS_SECT_ENTRY[...]
macros to define individual stats. o UseSTATS_SECT_END
to complete the group definition.
-
STATS_PERSISTED_HDR
(__sectname)¶
-
STATS_PERSIST_SCHED
(hdrp_)¶ (private) Starts the provided stat group’s persistence timer if it is a persistent group.
This should be used whenever a statistic’s value changes. This is a no-op for non-persistent stat groups.
Typedefs
Functions
-
int
stats_init
(struct stats_hdr *shdr, uint8_t size, uint8_t cnt, const struct stats_name_map *map, uint8_t map_cnt)¶
-
int
stats_init_and_reg
(struct stats_hdr *shdr, uint8_t size, uint8_t cnt, const struct stats_name_map *map, uint8_t map_cnt, const char *name)¶
-
int
stats_walk
(struct stats_hdr*, stats_walk_func_t, void*)¶
-
int
stats_group_walk
(stats_group_walk_func_t, void*)¶
-
int
stats_nmgr_register_group
(void)¶
-
int
stats_shell_register
(void)¶
-
void
stats_persist_sched
(struct stats_hdr *hdr)¶ (private) Starts the provided stat group’s persistence timer.
This should be used whenever a statistic’s value changes. This is a no-op for non-persistent stat groups.
-
int
stats_persist_flush
(void)¶ Flushes to disk all persisted stat groups with pending writes.
- Return
0 on success; nonzero on failure.
-
int
stats_persist_init
(struct stats_hdr *hdr, uint8_t size, uint8_t cnt, const struct stats_name_map *map, uint8_t map_cnt, os_time_t persist_delay)¶ Initializes a persistent stat group.
This function must be called before any other stats API functions are applied to the specified stat group. This is typically done during system startup.
Example usage: STATS_PERSISTED_SECT_START(my_stats) STATS_SECT_ENTRY(stat1) STATS_SECT_END(my_stats)
STATS_NAME_START(my_stats) STATS_SECT_ENTRY(my_stats, stat1) STATS_NAME_END(my_stats)
rc = stats_persist_init(STATS_PERSISTED_HDR(my_stats), STATS_SIZE_INIT_PARMS(my_stats, STATS_SIZE_32), STATS_NAME_INIT_PARMS(my_stats), 1 * OS_TICKS_PER_SEC); // One second.
- Return
0 on success; nonzero on failure.
- Parameters
hdr
: The header of the stat group to initialize. Use theSTATS_PERSISTED_HDR()
macro to generate this argument.size
: The size, in bytes, of each statistic. Use theSTATS_SIZE_INIT_PARMS()
macro to generate this and thecnt
arguments.cnt
: The number of statistics in the group. Use theSTATS_SIZE_INIT_PARMS()
macro to generate this and thesize
arguments.map
: Maps each stat to a human-readable name. Use theSTATS_NAME_INIT_PARMS()
macro to generate this and themap_cnt
arguments.map_cnt
: The number of names inmap. Use the the
STATS_NAME_INIT_PARMS()macro to generate this and the
map` arguments.persist_delay
: The delay, in OS ticks, before the stat group is flushed to disk after modification.
-
struct
stats_name_map
¶ - #include <stats.h>
-
struct
stats_hdr
¶ - #include <stats.h>
Public Functions
-
STAILQ_ENTRY (stats_hdr) s_next
-
-
struct
stats_persisted_hdr
¶ - #include <stats.h>
Header describing a persistent stat group.
A pointer to a regular
stats_hdr
can be safely cast to a pointer tostats_persisted_hdr
(and vice-versa) if theSTATS_HDR_F_PERSIST
flag is set.