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Add SRV resolver to loadbalancer exporter to use hostnames and track IPs
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| # Use this changelog template to create an entry for release notes. | ||
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| # One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix' | ||
| change_type: 'enhancement' | ||
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| # The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver) | ||
| component: loadbalancingexporter | ||
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| # A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`). | ||
| note: New SRV resolver for loadbalancing exporter for static hostnames with changing IPs | ||
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| # Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists. | ||
| issues: ["18412"] | ||
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| # (Optional) One or more lines of additional information to render under the primary note. | ||
| # These lines will be padded with 2 spaces and then inserted directly into the document. | ||
| # Use pipe (|) for multiline entries. | ||
| subtext: | ||
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| # If your change doesn't affect end users or the exported elements of any package, | ||
| # you should instead start your pull request title with [chore] or use the "Skip Changelog" label. | ||
| # Optional: The change log or logs in which this entry should be included. | ||
| # e.g. '[user]' or '[user, api]' | ||
| # Include 'user' if the change is relevant to end users. | ||
| # Include 'api' if there is a change to a library API. | ||
| # Default: '[user]' | ||
| change_logs: [] |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,252 @@ | ||
| // Copyright The OpenTelemetry Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
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| package loadbalancingexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/loadbalancingexporter" | ||
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| import ( | ||
| "context" | ||
| "errors" | ||
| "fmt" | ||
| "net" | ||
| "strings" | ||
| "sync" | ||
| "time" | ||
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| "go.opencensus.io/stats" | ||
| "go.opencensus.io/tag" | ||
| "go.uber.org/zap" | ||
| "golang.org/x/exp/slices" | ||
| ) | ||
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| // TODO: What is this? | ||
| var _ resolver = (*srvResolver)(nil) | ||
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| // TODO: Should these be moved to somethingl ike resolver_common.go? | ||
| // const ( | ||
| // defaultResInterval = 5 * time.Second | ||
| // defaultResTimeout = time.Second | ||
| // ) | ||
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| var ( | ||
| errNoSRV = errors.New("no SRV record found") | ||
| errBadSRV = errors.New("SRV hostname must be in the form of _service._proto.name") | ||
| errNotSingleIP = errors.New("underlying A record must return a single IP address") | ||
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| srvResolverMutator = tag.Upsert(tag.MustNewKey("resolver"), "srv") | ||
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| srvResolverSuccessTrueMutators = []tag.Mutator{srvResolverMutator, successTrueMutator} | ||
| srvResolverSuccessFalseMutators = []tag.Mutator{srvResolverMutator, successFalseMutator} | ||
| ) | ||
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| type srvResolver struct { | ||
| logger *zap.Logger | ||
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| srvService string | ||
| srvProto string | ||
| srvName string | ||
| port string | ||
| resolver multiResolver | ||
| resInterval time.Duration | ||
| resTimeout time.Duration | ||
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| endpoints []string | ||
| endpointsWithIPs map[string]string | ||
| onChangeCallbacks []func([]string) | ||
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| stopCh chan (struct{}) | ||
| updateLock sync.Mutex | ||
| shutdownWg sync.WaitGroup | ||
| changeCallbackLock sync.RWMutex | ||
| } | ||
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| type multiResolver interface { | ||
| LookupIPAddr(ctx context.Context, host string) ([]net.IPAddr, error) | ||
| LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error) | ||
| } | ||
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| func newSRVResolver(logger *zap.Logger, srvHostname string, port string, interval time.Duration, timeout time.Duration) (*srvResolver, error) { | ||
| if len(srvHostname) == 0 { | ||
| return nil, errNoSRV | ||
| } | ||
| if interval == 0 { | ||
| interval = defaultResInterval | ||
| } | ||
| if timeout == 0 { | ||
| timeout = defaultResTimeout | ||
| } | ||
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| service, proto, name, err := parseSRVHostname(srvHostname) | ||
| if err != nil { | ||
| logger.Warn("failed to parse SRV hostname", zap.Error(err)) | ||
| } | ||
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| return &srvResolver{ | ||
| logger: logger, | ||
| srvService: service, | ||
| srvProto: proto, | ||
| srvName: name, | ||
| port: port, | ||
| resolver: &net.Resolver{}, | ||
| resInterval: interval, | ||
| resTimeout: timeout, | ||
| stopCh: make(chan struct{}), | ||
| }, nil | ||
| } | ||
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| func (r *srvResolver) start(ctx context.Context) error { | ||
| if _, err := r.resolve(ctx); err != nil { | ||
| r.logger.Warn("failed to resolve", zap.Error(err)) | ||
| } | ||
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| go r.periodicallyResolve() | ||
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| r.logger.Debug("SRV resolver started", | ||
| zap.String("SRV name", r.srvName), zap.String("port", r.port), | ||
| zap.Duration("interval", r.resInterval), zap.Duration("timeout", r.resTimeout)) | ||
| return nil | ||
| } | ||
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| func (r *srvResolver) shutdown(_ context.Context) error { | ||
| r.changeCallbackLock.Lock() | ||
| r.onChangeCallbacks = nil | ||
| r.changeCallbackLock.Unlock() | ||
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| close(r.stopCh) | ||
| r.shutdownWg.Wait() | ||
| return nil | ||
| } | ||
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| func (r *srvResolver) periodicallyResolve() { | ||
| ticker := time.NewTicker(r.resInterval) | ||
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| for { | ||
| select { | ||
| case <-ticker.C: | ||
| ctx, cancel := context.WithTimeout(context.Background(), r.resTimeout) | ||
| if _, err := r.resolve(ctx); err != nil { | ||
| r.logger.Warn("failed to resolve", zap.Error(err)) | ||
| } else { | ||
| r.logger.Debug("resolved successfully") | ||
| } | ||
| cancel() | ||
| case <-r.stopCh: | ||
| return | ||
| } | ||
| } | ||
| } | ||
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| func (r *srvResolver) resolve(ctx context.Context) ([]string, error) { | ||
| r.shutdownWg.Add(1) | ||
| defer r.shutdownWg.Done() | ||
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| _, srvs, err := r.resolver.LookupSRV(ctx, r.srvService, r.srvProto, r.srvName) | ||
| if err != nil { | ||
| _ = stats.RecordWithTags(ctx, srvResolverSuccessFalseMutators, mNumResolutions.M(1)) | ||
| return nil, err | ||
| } | ||
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| _ = stats.RecordWithTags(ctx, srvResolverSuccessTrueMutators, mNumResolutions.M(1)) | ||
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| // backendsWithIPs tracks the IP addresses for changes | ||
| backendsWithIPs := make(map[string]string) | ||
| for _, srv := range srvs { | ||
| target := strings.TrimSuffix(srv.Target, ".") | ||
| backendsWithIPs[target] = "" | ||
| } | ||
| // backends is what we use to compare against the current endpoints | ||
| var backends []string | ||
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| // Lookup the IP addresses for the A records | ||
| for aRec := range backendsWithIPs { | ||
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| // handle backends first | ||
| backend := aRec | ||
| // if a port is specified in the configuration, add it | ||
| if r.port != "" { | ||
| backend = fmt.Sprintf("%s:%s", backend, r.port) | ||
| } | ||
| backends = append(backends, backend) | ||
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| ips, err := r.resolver.LookupIPAddr(ctx, aRec) | ||
| // Return the A record. If we can't resolve them, we'll try again next iteration | ||
| if err != nil { | ||
| _ = stats.RecordWithTags(ctx, srvResolverSuccessFalseMutators, mNumResolutions.M(1)) | ||
| continue | ||
| } | ||
| // A headless Service SRV target only returns 1 IP address for its A record | ||
| if len(ips) > 1 { | ||
| return nil, errNotSingleIP | ||
| } | ||
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| ip := ips[0] | ||
| if ip.IP.To4() != nil { | ||
| backendsWithIPs[aRec] = ip.String() | ||
| } else { | ||
| // it's an IPv6 address | ||
| backendsWithIPs[aRec] = fmt.Sprintf("[%s]", ip.String()) | ||
| } | ||
| } | ||
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| var freshBackends []string | ||
| for endpoint := range backendsWithIPs { | ||
| // If the old map doesn't have the endpoint, it's fresh | ||
| if _, ok := r.endpointsWithIPs[endpoint]; !ok { | ||
| freshBackends = append(freshBackends, endpoint) | ||
| // If the old map has the endpoint and IPs match it's still fresh | ||
| // Else freshBackends will be smaller and used later during callbacks | ||
| } else if backendsWithIPs[endpoint] == r.endpointsWithIPs[endpoint] { | ||
| freshBackends = append(freshBackends, endpoint) | ||
| } | ||
| } | ||
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| // keep both in the same order | ||
| slices.Sort(freshBackends) | ||
| slices.Sort(backends) | ||
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| if equalStringSlice(r.endpoints, freshBackends) { | ||
| r.logger.Debug("No change in endpoints") | ||
| return r.endpoints, nil | ||
| } | ||
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| // the list has changed! | ||
| r.updateLock.Lock() | ||
| r.logger.Debug("Updating endpoints", zap.Strings("new endpoints", backends)) | ||
| r.logger.Debug("Endpoints with IPs", zap.Any("old", r.endpointsWithIPs), zap.Any("new", backendsWithIPs)) | ||
| r.endpoints = backends | ||
| r.endpointsWithIPs = backendsWithIPs | ||
| r.updateLock.Unlock() | ||
| _ = stats.RecordWithTags(ctx, srvResolverSuccessTrueMutators, mNumBackends.M(int64(len(backends)))) | ||
|
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| // propagate the change | ||
| r.changeCallbackLock.RLock() | ||
| for _, callback := range r.onChangeCallbacks { | ||
| // If backends != freshBackends it means an endpoint needs refreshed | ||
| if !equalStringSlice(r.endpoints, freshBackends) { | ||
| r.logger.Debug("Stale endpoints present", zap.Strings("fresh endpoints", freshBackends)) | ||
| callback(freshBackends) | ||
| } | ||
| callback(r.endpoints) | ||
| } | ||
| r.changeCallbackLock.RUnlock() | ||
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| return r.endpoints, nil | ||
| } | ||
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| func (r *srvResolver) onChange(f func([]string)) { | ||
| r.changeCallbackLock.Lock() | ||
| defer r.changeCallbackLock.Unlock() | ||
| r.onChangeCallbacks = append(r.onChangeCallbacks, f) | ||
| } | ||
|
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| func parseSRVHostname(srvHostname string) (service string, proto string, name string, err error) { | ||
| parts := strings.Split(srvHostname, ".") | ||
| if len(parts) < 3 { | ||
| return "", "", "", errBadSRV | ||
| } | ||
|
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| service = strings.TrimPrefix(parts[0], "_") | ||
| proto = strings.TrimPrefix(parts[1], "_") | ||
| name = strings.Join(parts[2:], ".") | ||
|
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| return service, proto, name, nil | ||
| } |
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