From: Christian Babeux <christian.babeux@efficios.com>
Date: Fri, 24 Aug 2012 02:05:12 +0000 (-0400)
Subject: Notify the user if a filter is already enabled
X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=commitdiff_plain;h=7671f53cf3b6029a3bf00e502a0a58ac7a82e378

Notify the user if a filter is already enabled

When using the enable-event command in conjunction with the --filter
option, a user can specify a filter expression to refine the trace
output.

As stated in the lttng(1) man page, only the first activation of a
filter on an event will work. Subsequent activation of any filter
expression on the same event will fail.

e.g:

> lttng enable-event app:tp -s session -u --filter 'somefield > 42'

Case: invalid filter expression
> lttng enable-event app:tp -s session -u --filter 'invalid expression'
  Error: Error setting filter
  Warning: Some command(s) went wrong

> ...

Case: filter already enabled for event app:tp
> lttng enable-event app:tp -s session -u --filter 'someotherfield < 42'
  Error: Error setting filter
  Warning: Some command(s) went wrong

This commit differentiate the case where a filter was already set for
the specified event from the generic 'Error setting filter' error
message.

e.g:

> lttng enable-event app:tp -s session -u --filter 'somefield > 42'

Case: invalid filter expression
> lttng enable-event app:tp -s session -u --filter 'invalid expression'
  Error: Error setting filter
  Warning: Some command(s) went wrong

> ...

Case: filter already enabled for event app:tp
> lttng enable-event app:tp -s session -u --filter 'someotherfield < 42'
  Error: Filter on event app:tp is already enabled (channel 0, session session)
  Warning: Some command(s) went wrong

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/src/bin/lttng/commands/enable_events.c b/src/bin/lttng/commands/enable_events.c
index 5a22c9513..90172e50a 100644
--- a/src/bin/lttng/commands/enable_events.c
+++ b/src/bin/lttng/commands/enable_events.c
@@ -384,7 +384,17 @@ static int enable_events(char *session_name)
 			ret = lttng_set_event_filter(handle, ev.name, channel_name,
 						opt_filter);
 			if (ret < 0) {
-				ERR("Error setting filter");
+				switch (-ret) {
+				case LTTNG_ERR_FILTER_EXIST:
+					ERR("Filter on events is already enabled"
+							" (channel %s, session %s)",
+						channel_name, session_name);
+					break;
+				default:
+					ERR("Error setting filter");
+					break;
+				}
+
 				ret = -1;
 				goto error;
 			}
@@ -554,7 +564,17 @@ static int enable_events(char *session_name)
 			ret = lttng_set_event_filter(handle, ev.name,
 				channel_name, opt_filter);
 			if (ret < 0) {
-				ERR("Error setting filter");
+				switch (-ret) {
+				case LTTNG_ERR_FILTER_EXIST:
+					ERR("Filter on event %s is already enabled"
+							" (channel %s, session %s)",
+						event_name, channel_name, session_name);
+					break;
+				default:
+					ERR("Error setting filter");
+					break;
+				}
+
 				ret = -1;
 				goto error;
 			}