From: Kienan Stewart <kstewart@efficios.com>
Date: Mon, 15 Apr 2024 19:15:28 +0000 (-0400)
Subject: lttng: Indicate file path and error reason when open_config fails
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=dcffe9462d11f9de5b441b801da5b2b7ae42c79a;p=lttng-tools.git

lttng: Indicate file path and error reason when open_config fails

Observed issue
==============

In a test environment where the configuration file had been chowned to
no longer be writeable by the current user, `lttng` commands would work
but return a non-zero exit code and print `Error: Unable to create
config file`.

This doesn't give the user much information to work with to address the
issue.

Solution
========

The `PWARN` macro is used to print the file_path and reason when the
call to `fopen` fails.

This is done since the `file_path` percolated up to where the existing
error message is may be null for multiple reasons (eg. allocation
failure).

Known drawbacks
===============

The output of `PWARN` is inconsistent with the output used for most of
the `lttng` client.

Eg.

```
$ lttng create
Spawning a session daemon
Session auto-20240415-151450 created.
Traces will be output to /home/lttng-traces/auto-20240415-151450
PWARN - 15:14:50.420628389 [1184515/1184515]: fopen '/home/.lttngrc': Permission denied (in open_config() at conf.cpp:57)
Error: Unable to create config file
```

Change-Id: I5a9253fb02f3a712e7c5c2567311920dc33d36c7
Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng/commands/create.cpp b/src/bin/lttng/commands/create.cpp
index dce13866f..e1756c3d3 100644
--- a/src/bin/lttng/commands/create.cpp
+++ b/src/bin/lttng/commands/create.cpp
@@ -479,7 +479,8 @@ static int create_session(const char *session_name)
 	/* Init lttng session config */
 	ret = config_init(created_session_name);
 	if (ret < 0) {
-		ret = CMD_ERROR;
+		MSG("Unable to initialize configuration for created session: future commands will require the target session name explicitly");
+		ret = CMD_WARNING;
 		goto error;
 	}
 
diff --git a/src/bin/lttng/conf.cpp b/src/bin/lttng/conf.cpp
index 65be35a15..81aa65438 100644
--- a/src/bin/lttng/conf.cpp
+++ b/src/bin/lttng/conf.cpp
@@ -54,6 +54,7 @@ static FILE *open_config(const char *path, const char *mode)
 
 	fp = fopen(file_path, mode);
 	if (fp == nullptr) {
+		PWARN("Failed to open configuration file '%s'", file_path);
 		goto error;
 	}
 
@@ -74,7 +75,6 @@ static int create_config_file(const char *path)
 
 	fp = open_config(path, "w+");
 	if (fp == nullptr) {
-		ERR("Unable to create config file");
 		ret = -1;
 		goto error;
 	}