Implemeted readAt

client/alloc_runner.go

@@ -3,6 +3,7 @@ package client
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -432,3 +433,7 @@ func (r *AllocRunner) FSList(path string) ([]*allocdir.AllocFile, error) {
 func (r *AllocRunner) FSStat(path string) (*allocdir.AllocFile, error) {
 	return r.ctx.AllocDir.FSStat(path)
 }
+
+func (r *AllocRunner) FSReadAt(allocID string, path string, offset int64, limit int64, w io.Writer) error {
+	return r.ctx.AllocDir.FSReadAt(allocID, path, offset, limit, w)
+}

client/allocdir/alloc_dir.go

@@ -254,15 +254,19 @@ func (d *AllocDir) FSStat(path string) (*AllocFile, error) {
 	}, nil
 }
 
-func (d *AllocDir) FSReadAt(allocID string, path string, offset int64, limit int64) ([]byte, error) {
+func (d *AllocDir) FSReadAt(allocID string, path string, offset int64, limit int64, w io.Writer) error {
+	buf := make([]byte, limit)
 	p := filepath.Join(d.AllocDir, path)
 	f, err := os.Open(p)
 	if err != nil {
-		return nil, err
+		return err
 	}
-	b := make([]byte, limit)
-	f.ReadAt(b, offset)
-	return b, nil
+	n, err := f.ReadAt(buf, offset)
+	if err != nil {
+		return err
+	}
+	w.Write(buf[:n])
+	return nil
 }
 
 func fileCopy(src, dst string, perm os.FileMode) error {

client/client.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log"
 	"net"
@@ -371,8 +372,12 @@ func (c *Client) FSStat(allocID string, path string) (*allocdir.AllocFile, error
 	return ar.FSStat(path)
 }
 
-func (c *Client) FSReadAt(allocID string, path string, offset int64, limit int64) ([]byte, error) {
-	return nil, nil
+func (c *Client) FSReadAt(allocID string, path string, offset int64, limit int64, w io.Writer) error {
+	ar, ok := c.allocs[allocID]
+	if !ok {
+		return fmt.Errorf("alloc not found")
+	}
+	return ar.FSReadAt(allocID, path, offset, limit, w)
 }
 
 // restoreState is used to restore our state from the data dir

command/agent/fs_endpoint.go

@@ -3,6 +3,7 @@ package agent
 import (
 	"fmt"
 	"net/http"
+	"strconv"
 	"strings"
 )
 
@@ -42,5 +43,34 @@ func (s *HTTPServer) FileStatRequest(resp http.ResponseWriter, req *http.Request
 }
 
 func (s *HTTPServer) FileReadAtRequest(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
+	allocID := strings.TrimPrefix(req.URL.Path, "/v1/client/fs/readat/")
+	path := req.URL.Query().Get("path")
+	ofs := req.URL.Query().Get("offset")
+	if ofs == "" {
+		ofs = "0"
+	}
+
+	offset, err := strconv.ParseInt(ofs, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing offset: %v", err)
+	}
+	lim := req.URL.Query().Get("limit")
+	limit, err := strconv.ParseInt(lim, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing limit: %v", err)
+	}
+
+	if path == "" {
+		resp.WriteHeader(http.StatusNotFound)
+		return nil, fmt.Errorf("must provide a file name")
+	}
+	if allocID == "" {
+		resp.WriteHeader(http.StatusNotFound)
+		return nil, fmt.Errorf("alloc id not found")
+	}
+	if err = s.agent.client.FSReadAt(allocID, path, offset, limit, resp); err != nil {
+		return nil, err
+	}
 	return nil, nil
+
 }