| // Copyright 2016 The Prometheus Authors |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package prometheus |
| |
| import ( |
| "errors" |
| "fmt" |
| "sort" |
| "strings" |
| |
| "github.com/golang/protobuf/proto" |
| "github.com/prometheus/common/model" |
| |
| dto "github.com/prometheus/client_model/go" |
| ) |
| |
| // Desc is the descriptor used by every Prometheus Metric. It is essentially |
| // the immutable meta-data of a Metric. The normal Metric implementations |
| // included in this package manage their Desc under the hood. Users only have to |
| // deal with Desc if they use advanced features like the ExpvarCollector or |
| // custom Collectors and Metrics. |
| // |
| // Descriptors registered with the same registry have to fulfill certain |
| // consistency and uniqueness criteria if they share the same fully-qualified |
| // name: They must have the same help string and the same label names (aka label |
| // dimensions) in each, constLabels and variableLabels, but they must differ in |
| // the values of the constLabels. |
| // |
| // Descriptors that share the same fully-qualified names and the same label |
| // values of their constLabels are considered equal. |
| // |
| // Use NewDesc to create new Desc instances. |
| type Desc struct { |
| // fqName has been built from Namespace, Subsystem, and Name. |
| fqName string |
| // help provides some helpful information about this metric. |
| help string |
| // constLabelPairs contains precalculated DTO label pairs based on |
| // the constant labels. |
| constLabelPairs []*dto.LabelPair |
| // VariableLabels contains names of labels for which the metric |
| // maintains variable values. |
| variableLabels []string |
| // id is a hash of the values of the ConstLabels and fqName. This |
| // must be unique among all registered descriptors and can therefore be |
| // used as an identifier of the descriptor. |
| id uint64 |
| // dimHash is a hash of the label names (preset and variable) and the |
| // Help string. Each Desc with the same fqName must have the same |
| // dimHash. |
| dimHash uint64 |
| // err is an error that occurred during construction. It is reported on |
| // registration time. |
| err error |
| } |
| |
| // NewDesc allocates and initializes a new Desc. Errors are recorded in the Desc |
| // and will be reported on registration time. variableLabels and constLabels can |
| // be nil if no such labels should be set. fqName must not be empty. |
| // |
| // variableLabels only contain the label names. Their label values are variable |
| // and therefore not part of the Desc. (They are managed within the Metric.) |
| // |
| // For constLabels, the label values are constant. Therefore, they are fully |
| // specified in the Desc. See the Collector example for a usage pattern. |
| func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc { |
| d := &Desc{ |
| fqName: fqName, |
| help: help, |
| variableLabels: variableLabels, |
| } |
| if !model.IsValidMetricName(model.LabelValue(fqName)) { |
| d.err = fmt.Errorf("%q is not a valid metric name", fqName) |
| return d |
| } |
| // labelValues contains the label values of const labels (in order of |
| // their sorted label names) plus the fqName (at position 0). |
| labelValues := make([]string, 1, len(constLabels)+1) |
| labelValues[0] = fqName |
| labelNames := make([]string, 0, len(constLabels)+len(variableLabels)) |
| labelNameSet := map[string]struct{}{} |
| // First add only the const label names and sort them... |
| for labelName := range constLabels { |
| if !checkLabelName(labelName) { |
| d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName) |
| return d |
| } |
| labelNames = append(labelNames, labelName) |
| labelNameSet[labelName] = struct{}{} |
| } |
| sort.Strings(labelNames) |
| // ... so that we can now add const label values in the order of their names. |
| for _, labelName := range labelNames { |
| labelValues = append(labelValues, constLabels[labelName]) |
| } |
| // Validate the const label values. They can't have a wrong cardinality, so |
| // use in len(labelValues) as expectedNumberOfValues. |
| if err := validateLabelValues(labelValues, len(labelValues)); err != nil { |
| d.err = err |
| return d |
| } |
| // Now add the variable label names, but prefix them with something that |
| // cannot be in a regular label name. That prevents matching the label |
| // dimension with a different mix between preset and variable labels. |
| for _, labelName := range variableLabels { |
| if !checkLabelName(labelName) { |
| d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName) |
| return d |
| } |
| labelNames = append(labelNames, "$"+labelName) |
| labelNameSet[labelName] = struct{}{} |
| } |
| if len(labelNames) != len(labelNameSet) { |
| d.err = errors.New("duplicate label names") |
| return d |
| } |
| |
| vh := hashNew() |
| for _, val := range labelValues { |
| vh = hashAdd(vh, val) |
| vh = hashAddByte(vh, separatorByte) |
| } |
| d.id = vh |
| // Sort labelNames so that order doesn't matter for the hash. |
| sort.Strings(labelNames) |
| // Now hash together (in this order) the help string and the sorted |
| // label names. |
| lh := hashNew() |
| lh = hashAdd(lh, help) |
| lh = hashAddByte(lh, separatorByte) |
| for _, labelName := range labelNames { |
| lh = hashAdd(lh, labelName) |
| lh = hashAddByte(lh, separatorByte) |
| } |
| d.dimHash = lh |
| |
| d.constLabelPairs = make([]*dto.LabelPair, 0, len(constLabels)) |
| for n, v := range constLabels { |
| d.constLabelPairs = append(d.constLabelPairs, &dto.LabelPair{ |
| Name: proto.String(n), |
| Value: proto.String(v), |
| }) |
| } |
| sort.Sort(labelPairSorter(d.constLabelPairs)) |
| return d |
| } |
| |
| // NewInvalidDesc returns an invalid descriptor, i.e. a descriptor with the |
| // provided error set. If a collector returning such a descriptor is registered, |
| // registration will fail with the provided error. NewInvalidDesc can be used by |
| // a Collector to signal inability to describe itself. |
| func NewInvalidDesc(err error) *Desc { |
| return &Desc{ |
| err: err, |
| } |
| } |
| |
| func (d *Desc) String() string { |
| lpStrings := make([]string, 0, len(d.constLabelPairs)) |
| for _, lp := range d.constLabelPairs { |
| lpStrings = append( |
| lpStrings, |
| fmt.Sprintf("%s=%q", lp.GetName(), lp.GetValue()), |
| ) |
| } |
| return fmt.Sprintf( |
| "Desc{fqName: %q, help: %q, constLabels: {%s}, variableLabels: %v}", |
| d.fqName, |
| d.help, |
| strings.Join(lpStrings, ","), |
| d.variableLabels, |
| ) |
| } |