From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Wed, 5 Aug 2015 18:57:36 +0000 (-0400)
Subject: Send data pending status as part of payload instead of an invalid error
X-Git-Tag: v2.8.0-rc1~521
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=f6151c55e2af06fe2204bcab62cc19e33964e5ce;p=lttng-tools.git

Send data pending status as part of payload instead of an invalid error

This ensures that the session daemon's logs don't contain false
positives every time a data pending command is replied-to.

The use of invalid error codes 0 and 1 causes the log to contain
misleading entries of the form:

Sending response (size: 16, retcode: Unknown error code (0)) [...]

This commit also proves that it is possible, contrary to what the
previous comment indicated, to send a boolean value over a socket
without using undocumented error codes.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index fa5cb901e..792f519ab 100644
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -3766,7 +3766,35 @@ skip_domain:
 	}
 	case LTTNG_DATA_PENDING:
 	{
-		ret = cmd_data_pending(cmd_ctx->session);
+		int pending_ret;
+
+		/* 1 byte to return whether or not data is pending */
+		ret = setup_lttng_msg(cmd_ctx, 1);
+		if (ret < 0) {
+			goto setup_error;
+		}
+
+		pending_ret = cmd_data_pending(cmd_ctx->session);
+		/*
+		 * FIXME
+		 *
+		 * This function may returns 0 or 1 to indicate whether or not
+		 * there is data pending. In case of error, it should return an
+		 * LTTNG_ERR code. However, some code paths may still return
+		 * a nondescript error code, which we handle by returning an
+		 * "unknown" error.
+		 */
+		if (pending_ret == 0 || pending_ret == 1) {
+			ret = LTTNG_OK;
+		} else if (pending_ret < 0) {
+			ret = LTTNG_ERR_UNK;
+			goto setup_error;
+		} else {
+			ret = pending_ret;
+			goto setup_error;
+		}
+
+		*cmd_ctx->llm->payload = (uint8_t) pending_ret;
 		break;
 	}
 	case LTTNG_SNAPSHOT_ADD_OUTPUT:
diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index 42c9d1390..5f078c94a 100644
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -1880,6 +1880,7 @@ int lttng_data_pending(const char *session_name)
 {
 	int ret;
 	struct lttcomm_session_msg lsm;
+	uint8_t *pending = NULL;
 
 	if (session_name == NULL) {
 		return -LTTNG_ERR_INVALID;
@@ -1891,18 +1892,18 @@ int lttng_data_pending(const char *session_name)
 	lttng_ctl_copy_string(lsm.session.name, session_name,
 			sizeof(lsm.session.name));
 
-	ret = lttng_ctl_ask_sessiond(&lsm, NULL);
-
-	/*
-	 * The lttng_ctl_ask_sessiond function negate the return code if it's not
-	 * LTTNG_OK so getting -1 means that the reply ret_code was 1 thus meaning
-	 * that the data is available. Yes it is hackish but for now this is the
-	 * only way.
-	 */
-	if (ret == -1) {
-		ret = 1;
+	ret = lttng_ctl_ask_sessiond(&lsm, (void **) &pending);
+	if (ret < 0) {
+		goto end;
+	} else if (ret != 1) {
+		/* Unexpected payload size */
+		ret = -LTTNG_ERR_INVALID;
+		goto end;
 	}
 
+	ret = (int) *pending;
+end:
+	free(pending);
 	return ret;
 }