Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame] | 1 | // Copyright 2014 The Prometheus Authors |
| 2 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 3 | // you may not use this file except in compliance with the License. |
| 4 | // You may obtain a copy of the License at |
| 5 | // |
| 6 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 7 | // |
| 8 | // Unless required by applicable law or agreed to in writing, software |
| 9 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 10 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 11 | // See the License for the specific language governing permissions and |
| 12 | // limitations under the License. |
| 13 | |
| 14 | package prometheus |
| 15 | |
| 16 | import ( |
| 17 | "fmt" |
| 18 | "sync" |
| 19 | |
| 20 | "github.com/prometheus/common/model" |
| 21 | ) |
| 22 | |
| 23 | // MetricVec is a Collector to bundle metrics of the same name that |
| 24 | // differ in their label values. MetricVec is usually not used directly but as a |
| 25 | // building block for implementations of vectors of a given metric |
| 26 | // type. GaugeVec, CounterVec, SummaryVec, and UntypedVec are examples already |
| 27 | // provided in this package. |
| 28 | type MetricVec struct { |
| 29 | mtx sync.RWMutex // Protects the children. |
| 30 | children map[uint64][]metricWithLabelValues |
| 31 | desc *Desc |
| 32 | |
| 33 | newMetric func(labelValues ...string) Metric |
| 34 | hashAdd func(h uint64, s string) uint64 // replace hash function for testing collision handling |
| 35 | hashAddByte func(h uint64, b byte) uint64 |
| 36 | } |
| 37 | |
| 38 | // newMetricVec returns an initialized MetricVec. The concrete value is |
| 39 | // returned for embedding into another struct. |
| 40 | func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *MetricVec { |
| 41 | return &MetricVec{ |
| 42 | children: map[uint64][]metricWithLabelValues{}, |
| 43 | desc: desc, |
| 44 | newMetric: newMetric, |
| 45 | hashAdd: hashAdd, |
| 46 | hashAddByte: hashAddByte, |
| 47 | } |
| 48 | } |
| 49 | |
| 50 | // metricWithLabelValues provides the metric and its label values for |
| 51 | // disambiguation on hash collision. |
| 52 | type metricWithLabelValues struct { |
| 53 | values []string |
| 54 | metric Metric |
| 55 | } |
| 56 | |
| 57 | // Describe implements Collector. The length of the returned slice |
| 58 | // is always one. |
| 59 | func (m *MetricVec) Describe(ch chan<- *Desc) { |
| 60 | ch <- m.desc |
| 61 | } |
| 62 | |
| 63 | // Collect implements Collector. |
| 64 | func (m *MetricVec) Collect(ch chan<- Metric) { |
| 65 | m.mtx.RLock() |
| 66 | defer m.mtx.RUnlock() |
| 67 | |
| 68 | for _, metrics := range m.children { |
| 69 | for _, metric := range metrics { |
| 70 | ch <- metric.metric |
| 71 | } |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | // GetMetricWithLabelValues returns the Metric for the given slice of label |
| 76 | // values (same order as the VariableLabels in Desc). If that combination of |
| 77 | // label values is accessed for the first time, a new Metric is created. |
| 78 | // |
| 79 | // It is possible to call this method without using the returned Metric to only |
| 80 | // create the new Metric but leave it at its start value (e.g. a Summary or |
| 81 | // Histogram without any observations). See also the SummaryVec example. |
| 82 | // |
| 83 | // Keeping the Metric for later use is possible (and should be considered if |
| 84 | // performance is critical), but keep in mind that Reset, DeleteLabelValues and |
| 85 | // Delete can be used to delete the Metric from the MetricVec. In that case, the |
| 86 | // Metric will still exist, but it will not be exported anymore, even if a |
| 87 | // Metric with the same label values is created later. See also the CounterVec |
| 88 | // example. |
| 89 | // |
| 90 | // An error is returned if the number of label values is not the same as the |
| 91 | // number of VariableLabels in Desc. |
| 92 | // |
| 93 | // Note that for more than one label value, this method is prone to mistakes |
| 94 | // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as |
| 95 | // an alternative to avoid that type of mistake. For higher label numbers, the |
| 96 | // latter has a much more readable (albeit more verbose) syntax, but it comes |
| 97 | // with a performance overhead (for creating and processing the Labels map). |
| 98 | // See also the GaugeVec example. |
| 99 | func (m *MetricVec) GetMetricWithLabelValues(lvs ...string) (Metric, error) { |
| 100 | h, err := m.hashLabelValues(lvs) |
| 101 | if err != nil { |
| 102 | return nil, err |
| 103 | } |
| 104 | |
| 105 | return m.getOrCreateMetricWithLabelValues(h, lvs), nil |
| 106 | } |
| 107 | |
| 108 | // GetMetricWith returns the Metric for the given Labels map (the label names |
| 109 | // must match those of the VariableLabels in Desc). If that label map is |
| 110 | // accessed for the first time, a new Metric is created. Implications of |
| 111 | // creating a Metric without using it and keeping the Metric for later use are |
| 112 | // the same as for GetMetricWithLabelValues. |
| 113 | // |
| 114 | // An error is returned if the number and names of the Labels are inconsistent |
| 115 | // with those of the VariableLabels in Desc. |
| 116 | // |
| 117 | // This method is used for the same purpose as |
| 118 | // GetMetricWithLabelValues(...string). See there for pros and cons of the two |
| 119 | // methods. |
| 120 | func (m *MetricVec) GetMetricWith(labels Labels) (Metric, error) { |
| 121 | h, err := m.hashLabels(labels) |
| 122 | if err != nil { |
| 123 | return nil, err |
| 124 | } |
| 125 | |
| 126 | return m.getOrCreateMetricWithLabels(h, labels), nil |
| 127 | } |
| 128 | |
| 129 | // WithLabelValues works as GetMetricWithLabelValues, but panics if an error |
| 130 | // occurs. The method allows neat syntax like: |
| 131 | // httpReqs.WithLabelValues("404", "POST").Inc() |
| 132 | func (m *MetricVec) WithLabelValues(lvs ...string) Metric { |
| 133 | metric, err := m.GetMetricWithLabelValues(lvs...) |
| 134 | if err != nil { |
| 135 | panic(err) |
| 136 | } |
| 137 | return metric |
| 138 | } |
| 139 | |
| 140 | // With works as GetMetricWith, but panics if an error occurs. The method allows |
| 141 | // neat syntax like: |
| 142 | // httpReqs.With(Labels{"status":"404", "method":"POST"}).Inc() |
| 143 | func (m *MetricVec) With(labels Labels) Metric { |
| 144 | metric, err := m.GetMetricWith(labels) |
| 145 | if err != nil { |
| 146 | panic(err) |
| 147 | } |
| 148 | return metric |
| 149 | } |
| 150 | |
| 151 | // DeleteLabelValues removes the metric where the variable labels are the same |
| 152 | // as those passed in as labels (same order as the VariableLabels in Desc). It |
| 153 | // returns true if a metric was deleted. |
| 154 | // |
| 155 | // It is not an error if the number of label values is not the same as the |
| 156 | // number of VariableLabels in Desc. However, such inconsistent label count can |
| 157 | // never match an actual Metric, so the method will always return false in that |
| 158 | // case. |
| 159 | // |
| 160 | // Note that for more than one label value, this method is prone to mistakes |
| 161 | // caused by an incorrect order of arguments. Consider Delete(Labels) as an |
| 162 | // alternative to avoid that type of mistake. For higher label numbers, the |
| 163 | // latter has a much more readable (albeit more verbose) syntax, but it comes |
| 164 | // with a performance overhead (for creating and processing the Labels map). |
| 165 | // See also the CounterVec example. |
| 166 | func (m *MetricVec) DeleteLabelValues(lvs ...string) bool { |
| 167 | m.mtx.Lock() |
| 168 | defer m.mtx.Unlock() |
| 169 | |
| 170 | h, err := m.hashLabelValues(lvs) |
| 171 | if err != nil { |
| 172 | return false |
| 173 | } |
| 174 | return m.deleteByHashWithLabelValues(h, lvs) |
| 175 | } |
| 176 | |
| 177 | // Delete deletes the metric where the variable labels are the same as those |
| 178 | // passed in as labels. It returns true if a metric was deleted. |
| 179 | // |
| 180 | // It is not an error if the number and names of the Labels are inconsistent |
| 181 | // with those of the VariableLabels in the Desc of the MetricVec. However, such |
| 182 | // inconsistent Labels can never match an actual Metric, so the method will |
| 183 | // always return false in that case. |
| 184 | // |
| 185 | // This method is used for the same purpose as DeleteLabelValues(...string). See |
| 186 | // there for pros and cons of the two methods. |
| 187 | func (m *MetricVec) Delete(labels Labels) bool { |
| 188 | m.mtx.Lock() |
| 189 | defer m.mtx.Unlock() |
| 190 | |
| 191 | h, err := m.hashLabels(labels) |
| 192 | if err != nil { |
| 193 | return false |
| 194 | } |
| 195 | |
| 196 | return m.deleteByHashWithLabels(h, labels) |
| 197 | } |
| 198 | |
| 199 | // deleteByHashWithLabelValues removes the metric from the hash bucket h. If |
| 200 | // there are multiple matches in the bucket, use lvs to select a metric and |
| 201 | // remove only that metric. |
| 202 | func (m *MetricVec) deleteByHashWithLabelValues(h uint64, lvs []string) bool { |
| 203 | metrics, ok := m.children[h] |
| 204 | if !ok { |
| 205 | return false |
| 206 | } |
| 207 | |
| 208 | i := m.findMetricWithLabelValues(metrics, lvs) |
| 209 | if i >= len(metrics) { |
| 210 | return false |
| 211 | } |
| 212 | |
| 213 | if len(metrics) > 1 { |
| 214 | m.children[h] = append(metrics[:i], metrics[i+1:]...) |
| 215 | } else { |
| 216 | delete(m.children, h) |
| 217 | } |
| 218 | return true |
| 219 | } |
| 220 | |
| 221 | // deleteByHashWithLabels removes the metric from the hash bucket h. If there |
| 222 | // are multiple matches in the bucket, use lvs to select a metric and remove |
| 223 | // only that metric. |
| 224 | func (m *MetricVec) deleteByHashWithLabels(h uint64, labels Labels) bool { |
| 225 | metrics, ok := m.children[h] |
| 226 | if !ok { |
| 227 | return false |
| 228 | } |
| 229 | i := m.findMetricWithLabels(metrics, labels) |
| 230 | if i >= len(metrics) { |
| 231 | return false |
| 232 | } |
| 233 | |
| 234 | if len(metrics) > 1 { |
| 235 | m.children[h] = append(metrics[:i], metrics[i+1:]...) |
| 236 | } else { |
| 237 | delete(m.children, h) |
| 238 | } |
| 239 | return true |
| 240 | } |
| 241 | |
| 242 | // Reset deletes all metrics in this vector. |
| 243 | func (m *MetricVec) Reset() { |
| 244 | m.mtx.Lock() |
| 245 | defer m.mtx.Unlock() |
| 246 | |
| 247 | for h := range m.children { |
| 248 | delete(m.children, h) |
| 249 | } |
| 250 | } |
| 251 | |
| 252 | func (m *MetricVec) hashLabelValues(vals []string) (uint64, error) { |
| 253 | if len(vals) != len(m.desc.variableLabels) { |
| 254 | return 0, errInconsistentCardinality |
| 255 | } |
| 256 | h := hashNew() |
| 257 | for _, val := range vals { |
| 258 | h = m.hashAdd(h, val) |
| 259 | h = m.hashAddByte(h, model.SeparatorByte) |
| 260 | } |
| 261 | return h, nil |
| 262 | } |
| 263 | |
| 264 | func (m *MetricVec) hashLabels(labels Labels) (uint64, error) { |
| 265 | if len(labels) != len(m.desc.variableLabels) { |
| 266 | return 0, errInconsistentCardinality |
| 267 | } |
| 268 | h := hashNew() |
| 269 | for _, label := range m.desc.variableLabels { |
| 270 | val, ok := labels[label] |
| 271 | if !ok { |
| 272 | return 0, fmt.Errorf("label name %q missing in label map", label) |
| 273 | } |
| 274 | h = m.hashAdd(h, val) |
| 275 | h = m.hashAddByte(h, model.SeparatorByte) |
| 276 | } |
| 277 | return h, nil |
| 278 | } |
| 279 | |
| 280 | // getOrCreateMetricWithLabelValues retrieves the metric by hash and label value |
| 281 | // or creates it and returns the new one. |
| 282 | // |
| 283 | // This function holds the mutex. |
| 284 | func (m *MetricVec) getOrCreateMetricWithLabelValues(hash uint64, lvs []string) Metric { |
| 285 | m.mtx.RLock() |
| 286 | metric, ok := m.getMetricWithLabelValues(hash, lvs) |
| 287 | m.mtx.RUnlock() |
| 288 | if ok { |
| 289 | return metric |
| 290 | } |
| 291 | |
| 292 | m.mtx.Lock() |
| 293 | defer m.mtx.Unlock() |
| 294 | metric, ok = m.getMetricWithLabelValues(hash, lvs) |
| 295 | if !ok { |
| 296 | // Copy to avoid allocation in case wo don't go down this code path. |
| 297 | copiedLVs := make([]string, len(lvs)) |
| 298 | copy(copiedLVs, lvs) |
| 299 | metric = m.newMetric(copiedLVs...) |
| 300 | m.children[hash] = append(m.children[hash], metricWithLabelValues{values: copiedLVs, metric: metric}) |
| 301 | } |
| 302 | return metric |
| 303 | } |
| 304 | |
| 305 | // getOrCreateMetricWithLabelValues retrieves the metric by hash and label value |
| 306 | // or creates it and returns the new one. |
| 307 | // |
| 308 | // This function holds the mutex. |
| 309 | func (m *MetricVec) getOrCreateMetricWithLabels(hash uint64, labels Labels) Metric { |
| 310 | m.mtx.RLock() |
| 311 | metric, ok := m.getMetricWithLabels(hash, labels) |
| 312 | m.mtx.RUnlock() |
| 313 | if ok { |
| 314 | return metric |
| 315 | } |
| 316 | |
| 317 | m.mtx.Lock() |
| 318 | defer m.mtx.Unlock() |
| 319 | metric, ok = m.getMetricWithLabels(hash, labels) |
| 320 | if !ok { |
| 321 | lvs := m.extractLabelValues(labels) |
| 322 | metric = m.newMetric(lvs...) |
| 323 | m.children[hash] = append(m.children[hash], metricWithLabelValues{values: lvs, metric: metric}) |
| 324 | } |
| 325 | return metric |
| 326 | } |
| 327 | |
| 328 | // getMetricWithLabelValues gets a metric while handling possible collisions in |
| 329 | // the hash space. Must be called while holding read mutex. |
| 330 | func (m *MetricVec) getMetricWithLabelValues(h uint64, lvs []string) (Metric, bool) { |
| 331 | metrics, ok := m.children[h] |
| 332 | if ok { |
| 333 | if i := m.findMetricWithLabelValues(metrics, lvs); i < len(metrics) { |
| 334 | return metrics[i].metric, true |
| 335 | } |
| 336 | } |
| 337 | return nil, false |
| 338 | } |
| 339 | |
| 340 | // getMetricWithLabels gets a metric while handling possible collisions in |
| 341 | // the hash space. Must be called while holding read mutex. |
| 342 | func (m *MetricVec) getMetricWithLabels(h uint64, labels Labels) (Metric, bool) { |
| 343 | metrics, ok := m.children[h] |
| 344 | if ok { |
| 345 | if i := m.findMetricWithLabels(metrics, labels); i < len(metrics) { |
| 346 | return metrics[i].metric, true |
| 347 | } |
| 348 | } |
| 349 | return nil, false |
| 350 | } |
| 351 | |
| 352 | // findMetricWithLabelValues returns the index of the matching metric or |
| 353 | // len(metrics) if not found. |
| 354 | func (m *MetricVec) findMetricWithLabelValues(metrics []metricWithLabelValues, lvs []string) int { |
| 355 | for i, metric := range metrics { |
| 356 | if m.matchLabelValues(metric.values, lvs) { |
| 357 | return i |
| 358 | } |
| 359 | } |
| 360 | return len(metrics) |
| 361 | } |
| 362 | |
| 363 | // findMetricWithLabels returns the index of the matching metric or len(metrics) |
| 364 | // if not found. |
| 365 | func (m *MetricVec) findMetricWithLabels(metrics []metricWithLabelValues, labels Labels) int { |
| 366 | for i, metric := range metrics { |
| 367 | if m.matchLabels(metric.values, labels) { |
| 368 | return i |
| 369 | } |
| 370 | } |
| 371 | return len(metrics) |
| 372 | } |
| 373 | |
| 374 | func (m *MetricVec) matchLabelValues(values []string, lvs []string) bool { |
| 375 | if len(values) != len(lvs) { |
| 376 | return false |
| 377 | } |
| 378 | for i, v := range values { |
| 379 | if v != lvs[i] { |
| 380 | return false |
| 381 | } |
| 382 | } |
| 383 | return true |
| 384 | } |
| 385 | |
| 386 | func (m *MetricVec) matchLabels(values []string, labels Labels) bool { |
| 387 | if len(labels) != len(values) { |
| 388 | return false |
| 389 | } |
| 390 | for i, k := range m.desc.variableLabels { |
| 391 | if values[i] != labels[k] { |
| 392 | return false |
| 393 | } |
| 394 | } |
| 395 | return true |
| 396 | } |
| 397 | |
| 398 | func (m *MetricVec) extractLabelValues(labels Labels) []string { |
| 399 | labelValues := make([]string, len(labels)) |
| 400 | for i, k := range m.desc.variableLabels { |
| 401 | labelValues[i] = labels[k] |
| 402 | } |
| 403 | return labelValues |
| 404 | } |