logs: explain client aborts better (#7783)

Users get confused by "Failed to acquire semaphore" error="context canceled"
messages in the logs, which are actually clients giving up.  While there could be
a legitimate hang bug in the system, sometimes this is just short client timeouts
with an overloaded system, so this should help users understand what's going on
better.

llama/runner/runner.go

@@ -651,7 +651,11 @@ func (s *Server) completion(w http.ResponseWriter, r *http.Request) {
 
 	// Ensure that a place to put the sequence is available
 	if err := s.seqsSem.Acquire(r.Context(), 1); err != nil {
-		slog.Error("Failed to acquire semaphore", "error", err)
+		if errors.Is(err, context.Canceled) {
+			slog.Info("aborting completion request due to client closing the connection")
+		} else {
+			slog.Error("Failed to acquire semaphore", "error", err)
+		}
 		return
 	}
 	defer s.seqsSem.Release(1)
@@ -740,7 +744,11 @@ func (s *Server) embeddings(w http.ResponseWriter, r *http.Request) {
 
 	// Ensure that a place to put the sequence is available
 	if err := s.seqsSem.Acquire(r.Context(), 1); err != nil {
-		slog.Error("Failed to acquire semaphore", "error", err)
+		if errors.Is(err, context.Canceled) {
+			slog.Info("aborting embeddings request due to client closing the connection")
+		} else {
+			slog.Error("Failed to acquire semaphore", "error", err)
+		}
 		return
 	}
 	defer s.seqsSem.Release(1)

llm/server.go

@@ -687,7 +687,11 @@ type CompletionResponse struct {
 
 func (s *llmServer) Completion(ctx context.Context, req CompletionRequest, fn func(CompletionResponse)) error {
 	if err := s.sem.Acquire(ctx, 1); err != nil {
-		slog.Error("Failed to acquire semaphore", "error", err)
+		if errors.Is(err, context.Canceled) {
+			slog.Info("aborting completion request due to client closing the connection")
+		} else {
+			slog.Error("Failed to acquire semaphore", "error", err)
+		}
 		return err
 	}
 	defer s.sem.Release(1)
@@ -865,7 +869,11 @@ type EmbeddingResponse struct {
 
 func (s *llmServer) Embedding(ctx context.Context, input string) ([]float32, error) {
 	if err := s.sem.Acquire(ctx, 1); err != nil {
-		slog.Error("Failed to acquire semaphore", "error", err)
+		if errors.Is(err, context.Canceled) {
+			slog.Info("aborting embedding request due to client closing the connection")
+		} else {
+			slog.Error("Failed to acquire semaphore", "error", err)
+		}
 		return nil, err
 	}
 	defer s.sem.Release(1)