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fetcher.go
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fetcher.go
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package main
import (
"bytes"
"context"
"fmt"
"io"
"net/http"
"net/url"
"path"
"strings"
"sync"
rulesspec "github.com/observatorium/api/rules"
"github.com/prometheus/prometheus/model/rulefmt"
"gopkg.in/yaml.v3"
)
// RulesObjstoreFetcher fetches rules for all configured tenants from the rules-objstore.
type RulesObjstoreFetcher struct {
client rulesspec.ClientInterface
tenants []string
tenantsMtx sync.Mutex
}
// NewRulesObjstoreFetcher creates a new RulesObjtoreFetcher.
// The tenants list must be deduplicated otherwise, rules groups will not be unique.
func NewRulesObjstoreFetcher(baseURL string, tenants []string, client *http.Client) (*RulesObjstoreFetcher, error) {
if client == nil {
client = http.DefaultClient
}
baseURLParsed, err := url.Parse(baseURL)
if err != nil {
return nil, fmt.Errorf("failed to parse RulesObjtoreFetcher URL: %w", err)
}
rulesClient, err := rulesspec.NewClient(baseURLParsed.String(), rulesspec.WithHTTPClient(client))
if err != nil {
return nil, fmt.Errorf("failed to create rules-objstore client: %w", err)
}
return &RulesObjstoreFetcher{
client: rulesClient,
tenants: tenants,
}, nil
}
type tenantFetchResult struct {
tenant string
res *http.Response
err error
}
// GetTenantsRules fetches rules for all configured tenants from the rules-objstore.
func (f *RulesObjstoreFetcher) GetTenantsRules(ctx context.Context) (io.ReadCloser, error) {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
concurrency := 10
var sem = make(chan struct{}, concurrency)
results := make(chan tenantFetchResult)
// Launch goroutines that fetch rules for each tenant concurrently.
go func() {
var wg sync.WaitGroup
defer func() {
wg.Wait() // Wait for all goroutines to finish before closing results channel.
close(results)
}()
// tenants can be changed concurrently, we copy the list to avoid locking for too long.
f.tenantsMtx.Lock()
tenants := make([]string, len(f.tenants))
copy(tenants, f.tenants)
f.tenantsMtx.Unlock()
for _, tenantID := range f.tenants {
// Use semaphore to limit concurrency, and return early if context is cancelled.
select {
case <-ctx.Done():
results <- tenantFetchResult{tenantID, nil, ctx.Err()}
return
case sem <- struct{}{}:
}
// Launch goroutine to fetch rules for a tenant.
wg.Add(1)
go func(tenantID string) {
defer func() {
wg.Done()
<-sem
}()
res, err := f.client.ListRules(ctx, tenantID)
results <- tenantFetchResult{tenantID, res, err}
}(tenantID)
}
}()
// Consume results and return on first error.
// Returning cancels the context, which in turn cancels all goroutines.
var rules []rulefmt.RuleGroup
for result := range results {
if result.err != nil {
return nil, fmt.Errorf("failed to do http request: %w", result.err)
}
if result.res.StatusCode/100 != 2 {
return nil, fmt.Errorf("got unexpected status from Observatorium API: %d", result.res.StatusCode)
}
// Read and parse response body
body, err := io.ReadAll(result.res.Body)
result.res.Body.Close()
if err != nil {
return nil, fmt.Errorf("failed to read response body: %w", err)
}
rulesParsed, errors := rulefmt.Parse(body)
if len(errors) > 0 {
return nil, fmt.Errorf(aggregateErrorMessages(errors))
}
// Prepend tenant name to all rules group names to avoid conflicts
// This reflects the behavior of the rules-objstore api for ListAllRules.
for i, group := range rulesParsed.Groups {
rulesParsed.Groups[i].Name = result.tenant + "." + group.Name
}
rules = append(rules, rulesParsed.Groups...)
}
returnData, err := yaml.Marshal(rulefmt.RuleGroups{Groups: rules})
if err != nil {
return nil, fmt.Errorf("failed to marshal rules: %w", err)
}
ret := io.NopCloser(bytes.NewReader(returnData))
return ret, nil
}
// GetAllRules fetches all rules from the rules-objstore.
func (f *RulesObjstoreFetcher) GetAllRules(ctx context.Context) (io.ReadCloser, error) {
res, err := f.client.ListAllRules(ctx)
if err != nil {
return nil, fmt.Errorf("failed to do http request: %w", err)
}
if res.StatusCode/100 != 2 {
return nil, fmt.Errorf("got unexpected status from rules backend: %d", res.StatusCode)
}
return res.Body, nil
}
// SetTenants sets the tenants to fetch rules for.
// This method is thread-safe.
func (f *RulesObjstoreFetcher) SetTenants(tenants []string) {
f.tenantsMtx.Lock()
f.tenants = tenants
f.tenantsMtx.Unlock()
}
// observatoriumAPIFetcher fetches rules for a tenant from Observatorium API.
type observatoriumAPIFetcher struct {
endpoint *url.URL
client *http.Client
}
func newObservatoriumAPIFetcher(baseURL string, tenant string, client *http.Client) (*observatoriumAPIFetcher, error) {
u, err := url.Parse(baseURL)
if err != nil {
return nil, fmt.Errorf("failed to parse Observatorium API URL: %w", err)
}
u.Path = path.Join("/api/metrics/v1", tenant, "/api/v1/rules/raw")
return &observatoriumAPIFetcher{
endpoint: u,
client: client,
}, nil
}
func (f *observatoriumAPIFetcher) getRules(ctx context.Context) (io.ReadCloser, error) {
req, err := http.NewRequest(http.MethodGet, f.endpoint.String(), nil)
if err != nil {
return nil, fmt.Errorf("failed to create request: %w", err)
}
req = req.WithContext(ctx)
res, err := f.client.Do(req)
if err != nil {
return nil, fmt.Errorf("failed to do http request: %w", err)
}
if res.StatusCode/100 != 2 {
return nil, fmt.Errorf("got unexpected status from Observatorium API: %d", res.StatusCode)
}
return res.Body, nil
}
func aggregateErrorMessages(errs []error) string {
var builder strings.Builder
for i, err := range errs {
if i > 0 {
builder.WriteString(", ")
}
builder.WriteString(err.Error())
}
return builder.String()
}