Value list
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(Redirected from Value list t)
The value_list_t data structure is the main data structure because it is used to pass measured values around inside the daemon. It is often accompanied by data_set_t which is used to describe the stored values in more detail.
The following information is included in the data structure:
- One or more values of data sources of undefined type. Only the number of values is included in the structure. What type a specific data source has (for example
GAUGEorCOUNTER) is described by thedata_set_tstructure. - Fields to uniquely identify the value.
- The timestamp at which the value was collected.
- The interval in which new values are to be expected.
- A pointer to a meta data structure.
The structure is defined in src/plugin.h. It should be initialized using VALUE_LIST_INIT or VALUE_LIST_STATIC.
[edit] Definition of the struct
The structure is defined in src/plugin.h as follows:
struct value_list_s { value_t *values; int values_len; time_t time; int interval; char host[DATA_MAX_NAME_LEN]; char plugin[DATA_MAX_NAME_LEN]; char plugin_instance[DATA_MAX_NAME_LEN]; char type[DATA_MAX_NAME_LEN]; char type_instance[DATA_MAX_NAME_LEN]; meta_data_t *meta; }; typedef struct value_list_s value_list_t;
[edit] Example
static void submit (int cpu_num, const char *type_instance, counter_t value) { value_t values[1]; value_list_t vl = VALUE_LIST_INIT; values[0].counter = value; vl.values = values; vl.values_len = 1; sstrncpy (vl.host, hostname_g, sizeof (vl.host)); sstrncpy (vl.plugin, "cpu", sizeof (vl.plugin)); ssnprintf (vl.plugin_instance, sizeof (vl.plugin_instance), "%i", cpu_num); sstrncpy (vl.type, "cpu", sizeof (vl.type)); sstrncpy (vl.type_instance, type_instance, sizeof (vl.type_instance)); plugin_dispatch_values (&vl); }
This example initializes, fills and dispatches a value_list_t data structure as seen in nearly every collectd plugin.
