Session daemon health check support

[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.c

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index 780b44dd7cdebba0ed70c69a4459abc42df38658..b6487b7c25f51c490ecb3f3bf28343244a6b680d 100644 (file)
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -20,6 +20,7 @@
  */
 
 #define _GNU_SOURCE
+#include <assert.h>
 #include <grp.h>
 #include <errno.h>
 #include <stdio.h>
@@ -55,6 +56,7 @@ do {                                                          \
 /* Socket to session daemon for communication */
 static int sessiond_socket;
 static char sessiond_sock_path[PATH_MAX];
+static char health_sock_path[PATH_MAX];
 
 /* Variables */
 static char *tracing_group;
@@ -1278,6 +1280,98 @@ int lttng_disable_consumer(struct lttng_handle *handle)
        return ask_sessiond(&lsm, NULL);
 }
 
+/*
+ * Set health socket path by putting it in the global health_sock_path
+ * variable.
+ *
+ * Returns 0 on success or assert(0) on ENOMEM.
+ */
+static int set_health_socket_path(void)
+{
+       int ret;
+       int in_tgroup = 0;      /* In tracing group */
+       uid_t uid;
+       const char *home;
+
+       uid = getuid();
+
+       if (uid != 0) {
+               /* Are we in the tracing group ? */
+               in_tgroup = check_tracing_group(tracing_group);
+       }
+
+       if ((uid == 0) || in_tgroup) {
+               copy_string(health_sock_path, DEFAULT_GLOBAL_HEALTH_UNIX_SOCK,
+                               sizeof(health_sock_path));
+       }
+
+       if (uid != 0) {
+               /*
+                * With GNU C <  2.1, snprintf returns -1 if the target buffer is too small;
+                * With GNU C >= 2.1, snprintf returns the required size (excluding closing null)
+                */
+               home = getenv("HOME");
+               if (home == NULL) {
+                       /* Fallback in /tmp .. */
+                       home = "/tmp";
+               }
+
+               ret = snprintf(health_sock_path, sizeof(health_sock_path),
+                               DEFAULT_HOME_HEALTH_UNIX_SOCK, home);
+               if ((ret < 0) || (ret >= sizeof(health_sock_path))) {
+                       /* ENOMEM at this point... just kill the control lib. */
+                       assert(0);
+               }
+       }
+
+       return 0;
+}
+
+/*
+ * Check session daemon health for a specific health component.
+ *
+ * Return 0 if health is OK or else 1 if BAD. A return value of -1 indicate
+ * that the control library was not able to connect to the session daemon
+ * health socket.
+ *
+ * Any other positive value is an lttcomm error which can be translate with
+ * lttng_strerror().
+ */
+int lttng_health_check(enum lttng_health_component c)
+{
+       int sock, ret;
+       struct lttcomm_health_msg msg;
+       struct lttcomm_health_data reply;
+
+       /* Connect to the sesssion daemon */
+       sock = lttcomm_connect_unix_sock(health_sock_path);
+       if (sock < 0) {
+               ret = -1;
+               goto error;
+       }
+
+       msg.cmd = LTTNG_HEALTH_CHECK;
+       msg.component = c;
+
+       ret = lttcomm_send_unix_sock(sock, (void *)&msg, sizeof(msg));
+       if (ret < 0) {
+               goto close_error;
+       }
+
+       ret = lttcomm_recv_unix_sock(sock, (void *)&reply, sizeof(reply));
+       if (ret < 0) {
+               goto close_error;
+       }
+
+       ret = reply.ret_code;
+
+close_error:
+       close(sock);
+
+error:
+       return ret;
+}
+
 /*
  * lib constructor
  */
@@ -1285,4 +1379,6 @@ static void __attribute__((constructor)) init()
 {
        /* Set default session group */
        lttng_set_tracing_group(DEFAULT_TRACING_GROUP);
+       /* Set socket for health check */
+       (void) set_health_socket_path();
 }