Docs: document the format of the lttng_session path member

Document that the path returned through a session listing operation
is not a path nor standard URL. While a UNIX path will be returned
when a session is configured to trace locally, a liblttng-ctl user
should not expect this field to contain a valid URL when a network
streaming (or live) output destination is configured. The "path"
field will hold a custom-formatted string describing the output.

This is arguably unexepected, but since this is currently the only
way to obtain the destination of an existing session, this format
will not be changed to preserve compatiblity with existing tools
which could rely on this format.

A description of the formating used by the session daemon is
added as part of this patch.

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

diff --git a/include/lttng/session.h b/include/lttng/session.h
index 91566e2845d452b6ad3bfab093a0c234db5ac575..e626b00814ea1fec171a7d508d8d3495c0ea950a 100644 (file)
--- a/include/lttng/session.h
+++ b/include/lttng/session.h
@@ -33,7 +33,15 @@ extern "C" {
 #define LTTNG_SESSION_PADDING1             12
 struct lttng_session {
        char name[LTTNG_NAME_MAX];
 #define LTTNG_SESSION_PADDING1             12
 struct lttng_session {
        char name[LTTNG_NAME_MAX];

-       /* The path where traces are written */
+       /*
+        * Human-readable representation of the trace's destination.
+        * In the case of a local tracing session, a path is provided:
+        *     /path/to/the/output
+        *
+        * In the case of a remote (network) tracing session, the string has
+        * the following format:
+        *     net://hostname/path:ctrl_port [data: data_port]
+        */

        char path[PATH_MAX];
        uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
        uint32_t snapshot_mode;
        char path[PATH_MAX];
        uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
        uint32_t snapshot_mode;