vlog.go: Fix wrongly maintain the offset of file in memory (#640)

When the write file but may successfully write some part of data
but we don's added the offset that we maintain, later successfully
write request will get a wrong offset.

Add a test when no disk space fail to write and should recover after disk space are free up
set file size resource limit to make it write fail like no disk space

pump/storage/vlog.go

@@ -329,6 +329,8 @@ func (vlog *valueLog) write(reqs []*request) error {
 
 	toDisk := func() error {
 		n, err := curFile.fd.Write(vlog.buf.Bytes())
+		atomic.AddInt64(&vlog.writableLogOffset, int64(n))
+
 		if err != nil {
 			return errors.Annotatef(err, "unable to write to log file: %s", curFile.path)
 		}
@@ -339,7 +341,6 @@ func (vlog *valueLog) write(reqs []*request) error {
 			}
 		}
 
-		atomic.AddInt64(&vlog.writableLogOffset, int64(n))
 		for _, req := range bufReqs {
 			curFile.updateMaxTS(req.ts())
 		}

pump/storage/vlog_test.go

@@ -18,6 +18,7 @@ import (
 	"os"
 	"path"
 	"strconv"
+	"syscall"
 	"time"
 
 	fuzz "github.com/google/gofuzz"
@@ -221,3 +222,59 @@ func (vps *ValuePointerSuite) TestValuePointerMarshalBinary(c *check.C) {
 
 	c.Assert(vp, check.Equals, expect)
 }
+
+// Test when no disk space write fail
+// and should recover after disk space are free up
+// set file size resource limit to make it write fail like no disk space
+func (vs *VlogSuit) TestNoSpace(c *check.C) {
+	dir := c.MkDir()
+	c.Log("use dir: ", dir)
+
+	var origRlimit syscall.Rlimit
+	err := syscall.Getrlimit(syscall.RLIMIT_FSIZE, &origRlimit)
+	c.Assert(err, check.IsNil)
+
+	// set file size limit to be 20k
+	err = syscall.Setrlimit(syscall.RLIMIT_FSIZE, &syscall.Rlimit{Cur: 20 * 1024, Max: origRlimit.Max})
+	c.Assert(err, check.IsNil)
+
+	defer func() {
+		err = syscall.Setrlimit(syscall.RLIMIT_FSIZE, &origRlimit)
+		c.Assert(err, check.IsNil)
+	}()
+
+	vlog := new(valueLog)
+	err = vlog.open(dir, DefaultOptions())
+	c.Assert(err, check.IsNil)
+
+	// 1k payload per record
+	payload := make([]byte, 1024)
+	req := &request{
+		payload: payload,
+	}
+
+	// should be enough space to write 19 records
+	for i := 0; i < 19; i++ {
+		err = vlog.write([]*request{req})
+		c.Assert(err, check.IsNil)
+	}
+
+	// failed because only 20k space available and may write a incomplete record
+	err = vlog.write([]*request{req})
+	c.Assert(err, check.NotNil)
+
+	// increase file size limit to be 40k
+	err = syscall.Setrlimit(syscall.RLIMIT_FSIZE, &syscall.Rlimit{Cur: 40 * 1024, Max: origRlimit.Max})
+	c.Assert(err, check.IsNil)
+
+	// should write success now
+	err = vlog.write([]*request{req})
+	c.Assert(err, check.IsNil)
+
+	// read back normally
+	_, err = vlog.readValue(req.valuePointer)
+	c.Assert(err, check.IsNil)
+
+	err = vlog.close()
+	c.Assert(err, check.IsNil)
+}