14399: Don't insert error text in the middle of an index response.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tclegg@veritasgenetics.com>

diff --git a/services/keepstore/handlers.go b/services/keepstore/handlers.go
index 51dd73a513c1d4c729a6743aaabe0cefa1202c4b..9a4d02df850fab836cdafaa4e21abb070b492782 100644 (file)
--- a/services/keepstore/handlers.go
+++ b/services/keepstore/handlers.go
@@ -277,13 +277,19 @@ func (rtr *router) IndexHandler(resp http.ResponseWriter, req *http.Request) {
 
        for _, v := range vols {
                if err := v.IndexTo(prefix, resp); err != nil {
-                       // The only errors returned by IndexTo are
-                       // write errors returned by resp.Write(),
-                       // which probably means the client has
-                       // disconnected and this error will never be
-                       // reported to the client -- but it will
-                       // appear in our own error log.
-                       http.Error(resp, err.Error(), http.StatusInternalServerError)
+                       // We can't send an error message to the
+                       // client because we might have already sent
+                       // headers and index content. All we can do is
+                       // log the error in our own logs, and (in
+                       // cases where headers haven't been sent yet)
+                       // set a 500 status.
+                       //
+                       // If headers have already been sent, the
+                       // client must notice the lack of trailing
+                       // newline as an indication that the response
+                       // is incomplete.
+                       log.Printf("index error from volume %s: %s", v, err)
+                       http.Error(resp, "", http.StatusInternalServerError)
                        return
                }
        }