AppendService should retry on JOURNAL_NOT_FOUND

Partially roll back a prior commit which began erroring on
JOURNAL_NOT_FOUND. There are allowable data races where a created
journal is assigned to a primary broker, whose Etcd watch is currently
still unaware that the journal even exists.

broker/client/append_service.go

@@ -19,8 +19,7 @@ import (
 // pipelined and batched to amortize the cost of broker Append RPCs. It may
 // also simplify implementations for clients who would prefer to simply have
 // writes block until successfully committed, as opposed to handling errors
-// and retries themselves. AppendService will retry all errors except for
-// context cancellation and ErrJournalNotFound.
+// and retries themselves.
 //
 // For each journal, AppendService manages an ordered list of AsyncAppends,
 // each having buffered content to be appended. The list is dispatched in
@@ -279,8 +278,7 @@ func (p *AsyncAppend) Writer() *bufio.Writer { return p.fb.buf }
 // also roll back any writes queued by the caller, aborting the append
 // transaction. Require is valid for use only until Release is called.
 // Require returns itself, allowing uses like:
-//
-//	Require(maybeErrors()).Release()
+//      Require(maybeErrors()).Release()
 func (p *AsyncAppend) Require(err error) *AsyncAppend {
 	if err != nil && p.op.err == nil {
 		p.op.err = err
@@ -394,7 +392,7 @@ var serveAppends = func(s *AppendService, aa *AsyncAppend, err error) {
 						err2 = aa.app.Close()
 					}
 
-					if err2 == context.Canceled || err2 == context.DeadlineExceeded || err2 == ErrJournalNotFound {
+					if err2 == context.Canceled || err2 == context.DeadlineExceeded {
 						err = err2
 						return nil // Break retry loop.
 					} else if err2 != nil {

broker/client/append_service_test.go

@@ -66,17 +66,6 @@ func (s *AppendServiceSuite) TestBasicAppendWithRetry(c *gc.C) {
 	aaNext.mu.Unlock()
 
 	c.Check(as.PendingExcept(""), gc.HasLen, 0)
-
-	// Case: broker responds with a terminal JOURNAL_NOT_FOUND error.
-	aa = as.StartAppend(pb.AppendRequest{Journal: "a/journal"}, nil)
-	_, _ = aa.Writer().WriteString("hello, world")
-	c.Assert(aa.Release(), gc.IsNil)
-
-	readHelloWorldAppendRequest(c, broker) // RPC is dispatched to broker.
-	broker.AppendRespCh <- buildNotFoundFixture(broker)
-
-	c.Check(aa.Err(), gc.Equals, ErrJournalNotFound)
-	c.Check(aa.Response().Status, gc.DeepEquals, pb.Status_JOURNAL_NOT_FOUND)
 }
 
 func (s *AppendServiceSuite) TestAppendPipelineWithAborts(c *gc.C) {
@@ -622,11 +611,4 @@ func buildAppendResponseFixture(ep interface{ Endpoint() pb.Endpoint }) pb.Appen
 	}
 }
 
-func buildNotFoundFixture(ep interface{ Endpoint() pb.Endpoint }) pb.AppendResponse {
-	return pb.AppendResponse{
-		Status: pb.Status_JOURNAL_NOT_FOUND,
-		Header: *buildHeaderFixture(ep),
-	}
-}
-
 var _ = gc.Suite(&AppendServiceSuite{})