seastar::metrics Namespace Reference

Detailed Description

metrics creation and registration

the metrics namespace holds the relevant method and classes to generate metrics.

The metrics layer support registering metrics, that later will be exported via different API protocols.

To be able to support multiple protocols the following simplifications where made:

1. The id of the metrics is based on the collectd id
2. A metric could be a single value either a reference or a function

To add metrics definition to class A do the following:

• Add a metrics_group memeber to A
• Add a a set_metrics() method that would be called in the constructor.

In A header file

#include "core/metrics_registration.hh"
class A {
  metric_groups _metrics
 
  void setup_metrics();
 
};

In A source file:

include "core/metrics.hh"
 
void A::setup_metrics() {
  namespace sm = seastar::metrics;
  _metrics = sm::create_metric_group();
  _metrics->add_group("cache", {sm::make_gauge("bytes", "used", [this] { return _region.occupancy().used_space(); })});
}

Classes
class	double_registration
class	description
	Human-readable description of a metric/group. More...
class	label_instance
	Label a metrics. More...
class	label
	Class that creates label instances. More...
struct	metric_relabeling_result
	result of metric relabeling More...
struct	options
	Metrics configuration options. More...
class	metric_definition
class	metric_group_definition
class	metric_groups
	holds the metric definition. More...
class	metric_group
	hold a single metric group Initialization is done in the constructor or with a call to add_group More...
struct	histogram_bucket
	Histogram bucket type. More...
struct	histogram
	Histogram data type. More...
class	relabel_config_regex
	a wrapper class around regex with the original expr More...
struct	relabel_config
	a relabel_config allows changing metrics labels dynamically More...

Typedefs
using	metric_type_def = sstring
using	metric_name_type = sstring
using	instance_id_type = sstring
using	skip_when_empty = bool_class< class skip_when_empty_tag >
using	group_name_type = sstring

Functions
template<typename T >
impl::metric_definition_impl	make_gauge (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={})
	Gauge are a general purpose metric. More...
template<typename T >
impl::metric_definition_impl	make_gauge (metric_name_type name, description d, T &&val)
	Gauge are a general purpose metric. More...
template<typename T >
impl::metric_definition_impl	make_gauge (metric_name_type name, description d, std::vector< label_instance > labels, T &&val)
	Gauge are a general purpose metric. More...
template<typename T >
impl::metric_definition_impl	make_derive (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={})
	Derive are used when a rate is more interesting than the value. More...
template<typename T >
impl::metric_definition_impl	make_derive (metric_name_type name, description d, T &&val)
	Derive are used when a rate is more interesting than the value. More...
template<typename T >
impl::metric_definition_impl	make_derive (metric_name_type name, description d, std::vector< label_instance > labels, T &&val)
	Derive are used when a rate is more interesting than the value. More...
template<typename T >
impl::metric_definition_impl	make_counter (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={})
	create a counter metric More...
template<typename T >
impl::metric_definition_impl	make_counter (metric_name_type name, description d, T &&val)
	create a counter metric More...
template<typename T >
impl::metric_definition_impl	make_counter (metric_name_type name, description d, std::vector< label_instance > labels, T &&val)
	create a counter metric More...
template<typename T >
impl::metric_definition_impl	make_absolute (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={})
	create an absolute metric. More...
template<typename T >
impl::metric_definition_impl	make_histogram (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={})
	create a histogram metric. More...
template<typename T >
impl::metric_definition_impl	make_histogram (metric_name_type name, description d, std::vector< label_instance > labels, T &&val)
	create a histogram metric. More...
template<typename T >
impl::metric_definition_impl	make_histogram (metric_name_type name, description d, T &&val)
	create a histogram metric. More...
template<typename T >
impl::metric_definition_impl	make_summary (metric_name_type name, description d, T &&val)
	create a summary metric. More...
template<typename T >
impl::metric_definition_impl	make_total_bytes (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={}, instance_id_type=impl::shard())
	create a total_bytes metric. More...
template<typename T >
impl::metric_definition_impl	make_current_bytes (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={}, instance_id_type=impl::shard())
	create a current_bytes metric. More...
template<typename T >
impl::metric_definition_impl	make_queue_length (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={}, instance_id_type=impl::shard())
	create a queue_length metric. More...
template<typename T >
impl::metric_definition_impl	make_total_operations (metric_name_type name, T &&val, description d=description(), std::vector< label_instance > labels={}, instance_id_type=impl::shard())
	create a total operation metric. More...
future	configure (const options &opts)
	set the metrics configuration
future< metric_relabeling_result >	set_relabel_configs (const std::vector< relabel_config > &relabel_configs)
	Perform relabeling and operation on metrics dynamically. More...
const std::vector< relabel_config > &	get_relabel_configs ()
relabel_config::relabel_action	relabel_config_action (const std::string &action)
	a helper function to translate a string to relabel_config::relabel_action enum values

Variables
const bool	metric_disabled
label	shard_label

---

Class Documentation

seastar::metrics::metric_relabeling_result

struct seastar::metrics::metric_relabeling_result

Class Members
size_t	metrics_relabeled_due_to_collision

seastar::metrics::histogram_bucket

struct seastar::metrics::histogram_bucket

Class Members
uint64_t	count
double	upper_bound

Typedef Documentation

group_name_type

using seastar::metrics::group_name_type = typedef sstring

A group of logically related metrics

Function Documentation

set_relabel_configs()

future<metric_relabeling_result> seastar::metrics::set_relabel_configs

(

const std::vector< relabel_config > &

relabel_configs

)

Perform relabeling and operation on metrics dynamically.

The function would return true if the changes were applied with no conflict or false, if there was a conflict in the registration.

The general logic follows Prometheus metrics_relabel_config configuration. The relabel rules are applied one after the other. You can add or change a label. you can enable or disable a metric, in that case the metrics will not be reported at all. You can turn on and off the skip_when_empty flag.

Using the Prometheus convention, the metric name is name. Names cannot be changed.

Import notes:

• The relabeling always starts from the original set of labels the metric was created with.
• calling with an empty set will remove the relabel config and will return all metrics to their original labels
• To prevent a situation that calling this function would crash the system. in a situation where a conflicting metrics name are entered, an additional label will be added to the labels with a unique ID.

A few examples: To add a level label with a value 1, to the reactor_utilization metric: std::vector<sm::relabel_config> rl(1); rl[0].source_labels = {"__name__"}; rl[0].target_label = "level"; rl[0].replacement = "1"; rl[0].expr = "reactor_utilization"; set_relabel_configs(rl);

To report only the metrics with the level label equals 1

std::vector<sm::relabel_config> rl(2); rl[0].source_labels = {"__name__"}; rl[0].action = sm::relabel_config::relabel_action::drop;

rl[1].source_labels = {"level"}; rl[1].expr = "1"; rl[1].action = sm::relabel_config::relabel_action::keep; set_relabel_configs(rl);