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Minimal “fix” for hash collisions 

This makes the collisions a bit less likely by XOR'ing descIDs rather
than adding them up for the collectorID.

Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7 2019-10-14 20:14:43 +02:00
parent bf9ff715fe
commit c2e3855f3b
1 changed files with 3 additions and 3 deletions
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6
prometheus/registry.go
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@ -266,7 +266,7 @@ func (r *Registry) Register(c Collector) error {
descChan = make(chan *Desc, capDescChan)
newDescIDs = map[uint64]struct{}{}
newDimHashesByName = map[string]uint64{}
collectorID uint64 // Just a sum of all desc IDs.
collectorID uint64 // All desc IDs XOR'd together.
duplicateDescErr error
)
go func() {
@ -293,12 +293,12 @@ func (r *Registry) Register(c Collector) error {
if _, exists := r.descIDs[desc.id]; exists {
duplicateDescErr = fmt.Errorf("descriptor %s already exists with the same fully-qualified name and const label values", desc)
}
// If it is not a duplicate desc in this collector, add it to
// If it is not a duplicate desc in this collector, XOR it to
// the collectorID. (We allow duplicate descs within the same
// collector, but their existence must be a no-op.)
if _, exists := newDescIDs[desc.id]; !exists {
newDescIDs[desc.id] = struct{}{}
collectorID += desc.id
collectorID ^= desc.id
}
// Are all the label names and the help string consistent with