khenaidoo | ab1f7bd | 2019-11-14 14:00:27 -0500 | [diff] [blame] | 1 | // Copyright 2016 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 | "errors" |
| 18 | "fmt" |
| 19 | "sort" |
| 20 | "strings" |
| 21 | |
| 22 | "github.com/golang/protobuf/proto" |
| 23 | "github.com/prometheus/common/model" |
| 24 | |
| 25 | dto "github.com/prometheus/client_model/go" |
| 26 | ) |
| 27 | |
| 28 | // Desc is the descriptor used by every Prometheus Metric. It is essentially |
| 29 | // the immutable meta-data of a Metric. The normal Metric implementations |
| 30 | // included in this package manage their Desc under the hood. Users only have to |
| 31 | // deal with Desc if they use advanced features like the ExpvarCollector or |
| 32 | // custom Collectors and Metrics. |
| 33 | // |
| 34 | // Descriptors registered with the same registry have to fulfill certain |
| 35 | // consistency and uniqueness criteria if they share the same fully-qualified |
| 36 | // name: They must have the same help string and the same label names (aka label |
| 37 | // dimensions) in each, constLabels and variableLabels, but they must differ in |
| 38 | // the values of the constLabels. |
| 39 | // |
| 40 | // Descriptors that share the same fully-qualified names and the same label |
| 41 | // values of their constLabels are considered equal. |
| 42 | // |
| 43 | // Use NewDesc to create new Desc instances. |
| 44 | type Desc struct { |
| 45 | // fqName has been built from Namespace, Subsystem, and Name. |
| 46 | fqName string |
| 47 | // help provides some helpful information about this metric. |
| 48 | help string |
| 49 | // constLabelPairs contains precalculated DTO label pairs based on |
| 50 | // the constant labels. |
| 51 | constLabelPairs []*dto.LabelPair |
| 52 | // VariableLabels contains names of labels for which the metric |
| 53 | // maintains variable values. |
| 54 | variableLabels []string |
| 55 | // id is a hash of the values of the ConstLabels and fqName. This |
| 56 | // must be unique among all registered descriptors and can therefore be |
| 57 | // used as an identifier of the descriptor. |
| 58 | id uint64 |
| 59 | // dimHash is a hash of the label names (preset and variable) and the |
| 60 | // Help string. Each Desc with the same fqName must have the same |
| 61 | // dimHash. |
| 62 | dimHash uint64 |
| 63 | // err is an error that occurred during construction. It is reported on |
| 64 | // registration time. |
| 65 | err error |
| 66 | } |
| 67 | |
| 68 | // NewDesc allocates and initializes a new Desc. Errors are recorded in the Desc |
| 69 | // and will be reported on registration time. variableLabels and constLabels can |
| 70 | // be nil if no such labels should be set. fqName must not be empty. |
| 71 | // |
| 72 | // variableLabels only contain the label names. Their label values are variable |
| 73 | // and therefore not part of the Desc. (They are managed within the Metric.) |
| 74 | // |
| 75 | // For constLabels, the label values are constant. Therefore, they are fully |
| 76 | // specified in the Desc. See the Collector example for a usage pattern. |
| 77 | func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc { |
| 78 | d := &Desc{ |
| 79 | fqName: fqName, |
| 80 | help: help, |
| 81 | variableLabels: variableLabels, |
| 82 | } |
| 83 | if !model.IsValidMetricName(model.LabelValue(fqName)) { |
| 84 | d.err = fmt.Errorf("%q is not a valid metric name", fqName) |
| 85 | return d |
| 86 | } |
| 87 | // labelValues contains the label values of const labels (in order of |
| 88 | // their sorted label names) plus the fqName (at position 0). |
| 89 | labelValues := make([]string, 1, len(constLabels)+1) |
| 90 | labelValues[0] = fqName |
| 91 | labelNames := make([]string, 0, len(constLabels)+len(variableLabels)) |
| 92 | labelNameSet := map[string]struct{}{} |
| 93 | // First add only the const label names and sort them... |
| 94 | for labelName := range constLabels { |
| 95 | if !checkLabelName(labelName) { |
| 96 | d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName) |
| 97 | return d |
| 98 | } |
| 99 | labelNames = append(labelNames, labelName) |
| 100 | labelNameSet[labelName] = struct{}{} |
| 101 | } |
| 102 | sort.Strings(labelNames) |
| 103 | // ... so that we can now add const label values in the order of their names. |
| 104 | for _, labelName := range labelNames { |
| 105 | labelValues = append(labelValues, constLabels[labelName]) |
| 106 | } |
| 107 | // Validate the const label values. They can't have a wrong cardinality, so |
| 108 | // use in len(labelValues) as expectedNumberOfValues. |
| 109 | if err := validateLabelValues(labelValues, len(labelValues)); err != nil { |
| 110 | d.err = err |
| 111 | return d |
| 112 | } |
| 113 | // Now add the variable label names, but prefix them with something that |
| 114 | // cannot be in a regular label name. That prevents matching the label |
| 115 | // dimension with a different mix between preset and variable labels. |
| 116 | for _, labelName := range variableLabels { |
| 117 | if !checkLabelName(labelName) { |
| 118 | d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName) |
| 119 | return d |
| 120 | } |
| 121 | labelNames = append(labelNames, "$"+labelName) |
| 122 | labelNameSet[labelName] = struct{}{} |
| 123 | } |
| 124 | if len(labelNames) != len(labelNameSet) { |
| 125 | d.err = errors.New("duplicate label names") |
| 126 | return d |
| 127 | } |
| 128 | |
| 129 | vh := hashNew() |
| 130 | for _, val := range labelValues { |
| 131 | vh = hashAdd(vh, val) |
| 132 | vh = hashAddByte(vh, separatorByte) |
| 133 | } |
| 134 | d.id = vh |
| 135 | // Sort labelNames so that order doesn't matter for the hash. |
| 136 | sort.Strings(labelNames) |
| 137 | // Now hash together (in this order) the help string and the sorted |
| 138 | // label names. |
| 139 | lh := hashNew() |
| 140 | lh = hashAdd(lh, help) |
| 141 | lh = hashAddByte(lh, separatorByte) |
| 142 | for _, labelName := range labelNames { |
| 143 | lh = hashAdd(lh, labelName) |
| 144 | lh = hashAddByte(lh, separatorByte) |
| 145 | } |
| 146 | d.dimHash = lh |
| 147 | |
| 148 | d.constLabelPairs = make([]*dto.LabelPair, 0, len(constLabels)) |
| 149 | for n, v := range constLabels { |
| 150 | d.constLabelPairs = append(d.constLabelPairs, &dto.LabelPair{ |
| 151 | Name: proto.String(n), |
| 152 | Value: proto.String(v), |
| 153 | }) |
| 154 | } |
| 155 | sort.Sort(labelPairSorter(d.constLabelPairs)) |
| 156 | return d |
| 157 | } |
| 158 | |
| 159 | // NewInvalidDesc returns an invalid descriptor, i.e. a descriptor with the |
| 160 | // provided error set. If a collector returning such a descriptor is registered, |
| 161 | // registration will fail with the provided error. NewInvalidDesc can be used by |
| 162 | // a Collector to signal inability to describe itself. |
| 163 | func NewInvalidDesc(err error) *Desc { |
| 164 | return &Desc{ |
| 165 | err: err, |
| 166 | } |
| 167 | } |
| 168 | |
| 169 | func (d *Desc) String() string { |
| 170 | lpStrings := make([]string, 0, len(d.constLabelPairs)) |
| 171 | for _, lp := range d.constLabelPairs { |
| 172 | lpStrings = append( |
| 173 | lpStrings, |
| 174 | fmt.Sprintf("%s=%q", lp.GetName(), lp.GetValue()), |
| 175 | ) |
| 176 | } |
| 177 | return fmt.Sprintf( |
| 178 | "Desc{fqName: %q, help: %q, constLabels: {%s}, variableLabels: %v}", |
| 179 | d.fqName, |
| 180 | d.help, |
| 181 | strings.Join(lpStrings, ","), |
| 182 | d.variableLabels, |
| 183 | ) |
| 184 | } |