From 5610952da2f4190573bc10467fcf249a9e7eff4b Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Thu, 28 Nov 2013 18:28:26 +0100
Subject: [PATCH] frontend: Unified error reporting to the client.

Keep track of the latest error in a connection object and report that back to
the client in case a command handler failed.
---
 src/frontend/connection.c                 | 21 +++++++++++++++++----
 src/frontend/query.c                      |  5 ++---
 src/include/frontend/connection-private.h |  2 ++
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/frontend/connection.c b/src/frontend/connection.c
index 21bca4f..962cd9c 100644
--- a/src/frontend/connection.c
+++ b/src/frontend/connection.c
@@ -65,6 +65,12 @@ connection_init(sdb_object_t *obj, va_list ap)
 				"for a new connection");
 		return -1;
 	}
+	conn->errbuf = sdb_strbuf_create(0);
+	if (! conn->errbuf) {
+		sdb_log(SDB_LOG_ERR, "frontend: Failed to allocate an error buffer "
+				"for a new connection");
+		return -1;
+	}
 
 	conn->client_addr_len = sizeof(conn->client_addr);
 	conn->fd = accept(sock_fd, (struct sockaddr *)&conn->client_addr,
@@ -128,6 +134,8 @@ connection_destroy(sdb_object_t *obj)
 
 	sdb_strbuf_destroy(conn->buf);
 	conn->buf = NULL;
+	sdb_strbuf_destroy(conn->errbuf);
+	conn->errbuf = NULL;
 } /* connection_destroy */
 
 static sdb_type_t connection_type = {
@@ -164,6 +172,9 @@ command_handle(sdb_conn_t *conn)
 	sdb_log(SDB_LOG_DEBUG, "frontend: Handling command %u (len: %u)",
 			conn->cmd, conn->cmd_len);
 
+	/* reset */
+	sdb_strbuf_sprintf(conn->errbuf, "");
+
 	switch (conn->cmd) {
 		case CONNECTION_PING:
 			status = sdb_connection_ping(conn);
@@ -178,16 +189,18 @@ command_handle(sdb_conn_t *conn)
 
 		default:
 		{
-			char errbuf[1024];
 			sdb_log(SDB_LOG_WARNING, "frontend: Ignoring invalid command");
-			snprintf(errbuf, sizeof(errbuf), "Invalid command %#x", conn->cmd);
-			sdb_connection_send(conn, CONNECTION_ERROR,
-					(uint32_t)(strlen(errbuf) + 1), errbuf);
+			sdb_strbuf_sprintf(conn->errbuf, "Invalid command %#x", conn->cmd);
 			status = -1;
 			break;
 		}
 	}
 
+	if (status)
+		sdb_connection_send(conn, CONNECTION_ERROR,
+				(uint32_t)sdb_strbuf_len(conn->errbuf),
+				sdb_strbuf_string(conn->errbuf));
+
 	/* remove the command from the buffer */
 	if (conn->cmd_len)
 		sdb_strbuf_skip(conn->buf, conn->cmd_len);
diff --git a/src/frontend/query.c b/src/frontend/query.c
index 9e3b66a..fa493a6 100644
--- a/src/frontend/query.c
+++ b/src/frontend/query.c
@@ -50,8 +50,7 @@ sdb_fe_list(sdb_conn_t *conn)
 				"buffer to handle LIST command: %s",
 				sdb_strerror(errno, errbuf, sizeof(errbuf)));
 
-		/* XXX: send error message */
-		sdb_connection_send(conn, CONNECTION_ERROR, 0, NULL);
+		sdb_strbuf_sprintf(conn->errbuf, "Out of memory");
 		sdb_strbuf_destroy(buf);
 		return -1;
 	}
@@ -59,7 +58,7 @@ sdb_fe_list(sdb_conn_t *conn)
 	if (sdb_store_tojson(buf)) {
 		sdb_log(SDB_LOG_ERR, "frontend: Failed to serialize "
 				"store to JSON");
-		sdb_connection_send(conn, CONNECTION_ERROR, 0, NULL);
+		sdb_strbuf_sprintf(conn->errbuf, "Out of memory");
 		sdb_strbuf_destroy(buf);
 		return -1;
 	}
diff --git a/src/include/frontend/connection-private.h b/src/include/frontend/connection-private.h
index d484a08..6cf7395 100644
--- a/src/include/frontend/connection-private.h
+++ b/src/include/frontend/connection-private.h
@@ -60,6 +60,8 @@ struct sdb_conn {
 	uint32_t cmd;
 	uint32_t cmd_len;
 
+	sdb_strbuf_t *errbuf;
+
 	/* user information */
 	char *username; /* NULL if the user has not been authenticated */
 };
-- 
2.30.2