refactored for easier mainenance, add Alloc and Metrics classes

cmd/exporter.go

@@ -0,0 +1,115 @@
+package cmd
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"log/slog"
+	"os"
+	"time"
+
+	"github.com/ncw/directio"
+)
+
+func die(err error, fd *os.File) bool {
+	slog.Debug("failed to check io", "error", err)
+
+	if fd != nil {
+		if err := fd.Close(); err != nil {
+			slog.Debug("failed to close filehandle", "error", err)
+		}
+	}
+
+	return false
+}
+
+// Calls runcheck() with timeout
+func runExporter(file string, alloc *Alloc, timeout time.Duration) bool {
+	ctx := context.Background()
+	ctx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+
+	run := make(chan struct{}, 1)
+	var res bool
+
+	go func() {
+		res = runcheck(file, alloc)
+		run <- struct{}{}
+	}()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return die(ctx.Err(), nil)
+		case <-run:
+			return res
+		}
+	}
+}
+
+// Checks file io on the specified path:
+//
+// - open the file (create if it doesnt exist)
+// - truncate it if it already exists
+// - write some data to it
+// - closes the file
+// - re-opens it for reading
+// - reads the block
+// - compares if written block is equal to read block
+// - closes file again
+//
+// Returns false if anything failed during that sequence,
+// true otherwise.
+func runcheck(file string, alloc *Alloc) bool {
+	alloc.Clean()
+
+	// write
+	fd, err := directio.OpenFile(file, os.O_RDWR|os.O_TRUNC|os.O_CREATE, 0640)
+	if err != nil {
+		die(err, nil)
+	}
+
+	for i := 0; i < len(alloc.writeBlock); i++ {
+		alloc.writeBlock[i] = 'A'
+	}
+
+	n, err := fd.Write(alloc.writeBlock)
+	if err != nil {
+		return die(err, fd)
+	}
+
+	if n != len(alloc.writeBlock) {
+		return die(errors.New("failed to write block"), fd)
+	}
+
+	if err := fd.Close(); err != nil {
+		return die(err, nil)
+	}
+
+	// read
+	in, err := directio.OpenFile(file, os.O_RDONLY, 0640)
+	if err != nil {
+		die(err, nil)
+	}
+
+	n, err = io.ReadFull(in, alloc.readBlock)
+	if err != nil {
+		return die(err, in)
+	}
+
+	if n != len(alloc.writeBlock) {
+		return die(errors.New("failed to read block"), fd)
+	}
+
+	if err := in.Close(); err != nil {
+		return die(err, nil)
+	}
+
+	// compare
+	if !bytes.Equal(alloc.writeBlock, alloc.readBlock) {
+		return die(errors.New("Read not the same as written"), nil)
+	}
+
+	return true
+}