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input.go
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input.go
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package main
import (
"context"
"fmt"
"io"
"os"
"path/filepath"
"runtime"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
"golang.org/x/sync/errgroup"
)
const stdinPlaceholder = "-"
var stdinReader io.ReadCloser = os.Stdin
type inputWrapper interface {
Name() string
Process(func(io.Reader) error) error
}
// processAndClose invokes the given function, passing the reader as an
// argument, and always closes the reader before returning.
func processAndClose(name string, r io.ReadCloser, fn func(io.Reader) error) error {
defer r.Close()
if err := fn(r); err != nil {
return fmt.Errorf("%s: %w", name, err)
}
return nil
}
type readerInputWrapper struct {
name string
r io.ReadCloser
}
var _ inputWrapper = (*readerInputWrapper)(nil)
func newReaderInputWrapper(r io.ReadCloser) *readerInputWrapper {
var name string
if rn, ok := r.(interface{ Name() string }); ok {
name = rn.Name()
} else {
name = fmt.Sprint(r)
}
return &readerInputWrapper{
name: name,
r: r,
}
}
func (w *readerInputWrapper) Name() string {
return w.name
}
func (w *readerInputWrapper) Process(fn func(io.Reader) error) error {
return processAndClose(w.name, w.r, fn)
}
type fileInputWrapper struct {
path string
}
var _ inputWrapper = (*fileInputWrapper)(nil)
func (w *fileInputWrapper) Name() string {
return w.path
}
func (w *fileInputWrapper) Process(fn func(io.Reader) error) error {
r, err := os.Open(w.path)
if err != nil {
return err
}
return processAndClose(r.Name(), r, fn)
}
func inputWrappersFromPaths(paths []string) []inputWrapper {
var result []inputWrapper
for _, i := range paths {
var r inputWrapper
if i == stdinPlaceholder {
r = newReaderInputWrapper(stdinReader)
} else {
r = &fileInputWrapper{path: i}
}
result = append(result, r)
}
return result
}
func inputWrappersFromDirs(paths []string, pattern string) ([]inputWrapper, error) {
var result []inputWrapper
for _, path := range paths {
entries, err := os.ReadDir(path)
if err != nil {
return nil, err
}
for _, i := range entries {
if !i.Type().IsRegular() {
continue
}
matched, err := filepath.Match(pattern, i.Name())
if err != nil {
return nil, err
}
if matched {
result = append(result, &fileInputWrapper{
path: filepath.Join(path, i.Name()),
})
}
}
}
return result, nil
}
func readMetricFamilies(w inputWrapper) (parsedInput, error) {
var families map[string]*dto.MetricFamily
if err := w.Process(func(r io.Reader) error {
var err error
var parser expfmt.TextParser
families, err = parser.TextToMetricFamilies(r)
return err
}); err != nil {
return parsedInput{}, err
}
return parsedInput{
name: w.Name(),
families: families,
}, nil
}
type parsedInput struct {
name string
families map[string]*dto.MetricFamily
}
// readInputs parses all inputs, up to GOMAXPROCS concurrently, before sending
// the resulting metric families to the given channel. Input order is preserved.
func readInputs(ctx context.Context, inputs []inputWrapper, parsedCh chan<- parsedInput) error {
g, ctx := errgroup.WithContext(ctx)
// Limit number of outstanding readers. The outer channel is used to
// preserve the input order.
readers := make(chan (<-chan parsedInput), runtime.GOMAXPROCS(0))
g.Go(func() error {
defer close(readers)
for _, w := range inputs {
w := w
r := make(chan parsedInput)
select {
case readers <- r:
case <-ctx.Done():
return ctx.Err()
}
g.Go(func() error {
defer close(r)
p, err := readMetricFamilies(w)
if err != nil {
return err
}
select {
case r <- p:
case <-ctx.Done():
return ctx.Err()
}
return nil
})
}
return nil
})
g.Go(func() error {
for r := range readers {
for p := range r {
parsedCh <- p
}
}
return nil
})
return g.Wait()
}