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metrics: Enable gauges with fully-static labels

This commit is contained in:
Jack Grigg 2021-03-14 11:25:27 +13:00
parent 958ffeafd3
commit 78b83fd6e9
2 changed files with 81 additions and 18 deletions
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72
src/rust/include/rust/metrics.h
View File

@ -34,13 +34,20 @@ typedef struct MetricsKey MetricsKey;
/// Creates a metrics callsite.
///
/// This API supports labels that MUST have static values. For non-static label
/// values, use `metrics_key`.
///
/// You should usually call one of the helper macros such as `MetricsCounter`
/// instead of calling this directly.
///
/// This MUST ONLY be called to assign a `static MetricsCallsite*`, and all
/// string arguments MUST be static `const char*` constants, and MUST be valid
/// UTF-8.
MetricsCallsite* metrics_callsite(const char* name);
MetricsCallsite* metrics_callsite(
const char* name,
const char* const* label_names,
const char* const* label_values,
size_t labels_len);
/// Creates a metrics key.
///
@ -133,20 +140,26 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#ifdef __cplusplus
// Constructs a metrics callsite.
//
// The 'static constexpr' hack ensures that name is a compile-time constant
// with static storage duration. The output of this macro MUST be stored as a
// static MetricsCallsite*.
#define M_CALLSITE(name) ([&] { \
static constexpr const char* _m_name = name; \
return metrics_callsite(_m_name); \
// The 'static constexpr' hack ensures that all arguments are compile-time
// constants with static storage duration. The output of this macro MUST be
// stored as a static MetricsCallsite*.
#define M_CALLSITE(name, label_names, label_values) ([&] { \
static constexpr const char* _m_name = name; \
static constexpr const char* const* _m_label_names = \
label_names; \
static constexpr const char* const* _m_label_values = \
label_values; \
return metrics_callsite( \
_m_name, _m_label_names, _m_label_values, \
T_ARRLEN(label_names)); \
}())
#else
// Constructs a metrics callsite.
//
// name MUST be a static constant, and the output of this macro MUST be stored
// as a static MetricsCallsite*.
#define M_CALLSITE(name) \
metrics_callsite(name)
// All arguments MUST be static constants, and the output of this macro MUST be
// stored as a static MetricsCallsite*.
#define M_CALLSITE(name, label_names, label_values) \
metrics_callsite(name, label_names, label_values, T_ARRLEN(label_names))
#endif
// Constructs a metrics key.
@ -171,7 +184,9 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#define MetricsCounter(name, value, ...) \
do { \
IFE(__VA_ARGS__) \
(static MetricsCallsite* CALLSITE = M_CALLSITE(name); \
(static constexpr const char* const EMPTY[] = {}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, EMPTY, EMPTY); \
metrics_static_increment_counter(CALLSITE, value);) \
IFN(__VA_ARGS__)(const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \
@ -200,7 +215,9 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#define MetricsGauge(name, value, ...) \
do { \
IFE(__VA_ARGS__) \
(static MetricsCallsite* CALLSITE = M_CALLSITE(name); \
(static constexpr const char* const EMPTY[] = {}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, EMPTY, EMPTY); \
metrics_static_update_gauge(CALLSITE, value);) \
IFN(__VA_ARGS__)(const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \
@ -211,6 +228,23 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
metrics_update_gauge(KEY, value);) \
} while (0)
/// Updates a gauge with optional static labels.
///
/// Gauges represent a single value that can go up or down over time, and always
/// starts out with an initial value of zero.
///
/// name MUST be a static constant, and all strings MUST be valid UTF-8.
#define MetricsStaticGauge(name, value, ...) \
do { \
static constexpr const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \
static constexpr const char* M_VALUES[] = \
{T_FIELD_VALUES(__VA_ARGS__)}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, M_LABELS, M_VALUES); \
metrics_static_update_gauge(CALLSITE, value); \
} while (0)
/// Increments a gauge.
///
/// Gauges represent a single value that can go up or down over time, and always
@ -220,7 +254,9 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#define MetricsIncrementGauge(name, value, ...) \
do { \
IFE(__VA_ARGS__) \
(static MetricsCallsite* CALLSITE = M_CALLSITE(name); \
(static constexpr const char* const EMPTY[] = {}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, EMPTY, EMPTY); \
metrics_static_increment_gauge(CALLSITE, value);) \
IFN(__VA_ARGS__)(const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \
@ -240,7 +276,9 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#define MetricsDecrementGauge(name, value, ...) \
do { \
IFE(__VA_ARGS__) \
(static MetricsCallsite* CALLSITE = M_CALLSITE(name); \
(static constexpr const char* const EMPTY[] = {}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, EMPTY, EMPTY); \
metrics_static_decrement_gauge(CALLSITE, value);) \
IFN(__VA_ARGS__)(const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \
@ -260,7 +298,9 @@ void metrics_record_histogram(MetricsKey* callsite, double value);
#define MetricsHistogram(name, value, ...) \
do { \
IFE(__VA_ARGS__) \
(static MetricsCallsite* CALLSITE = M_CALLSITE(name); \
(static constexpr const char* const EMPTY[] = {}; \
static MetricsCallsite* CALLSITE = \
M_CALLSITE(name, EMPTY, EMPTY); \
metrics_static_record_histogram(CALLSITE, value);) \
IFN(__VA_ARGS__)(const char* M_LABELS[] = \
{T_FIELD_NAMES(__VA_ARGS__)}; \

27
src/rust/src/metrics_ffi.rs
View File

@ -72,10 +72,33 @@ pub struct FfiCallsite {
}
#[no_mangle]
pub extern "C" fn metrics_callsite(name: *const c_char) -> *mut FfiCallsite {
pub extern "C" fn metrics_callsite(
name: *const c_char,
label_names: *const *const c_char,
label_values: *const *const c_char,
labels_len: usize,
) -> *mut FfiCallsite {
let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();
let labels = unsafe { slice::from_raw_parts(label_names, labels_len) };
let values = unsafe { slice::from_raw_parts(label_values, labels_len) };
let stringify = |s: &[_]| {
s.iter()
.map(|&p| unsafe { CStr::from_ptr(p) })
.map(|cs| cs.to_string_lossy().into_owned())
.collect::<Vec<_>>()
};
let labels = stringify(labels);
let values = stringify(values);
let labels: Vec<_> = labels
.into_iter()
.zip(values.into_iter())
.map(|(name, value)| Label::new(name, value))
.collect();
Box::into_raw(Box::new(FfiCallsite {
key_data: KeyData::from_name(name),
key_data: KeyData::from_parts(name, labels),
}))
}