Backport: relayd: rename fd-cap parameter to fd-pool-size

Rename the fd-cap parameter and change its default behaviour.
The minimum number of file descriptor is raised to 100 and a
"reserve" amount of 10 fds is allowed to accomodate transient
fd uses that can't be tracked by the relay daemon.

The --fd-pool-size will accept parameters in the
[100, fileno soft limit] interval.

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

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index d1ee84eae836739c3addd70cb7ec63a337af682c..107ea14e113fe4ba500ab21c2229fe2ef375fd5e 100644 (file)
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -152,7 +152,7 @@ static uint64_t last_relay_stream_id;
 static struct relay_conn_queue relay_conn_queue;
 
 /* Cap of file desriptors to be in simultaneous use by the relay daemon. */
-static unsigned int lttng_opt_fd_cap;
+static unsigned int lttng_opt_fd_pool_size = -1;
 
 /* Global relay stream hash table. */
 struct lttng_ht *relay_streams_ht;
@@ -176,7 +176,7 @@ static struct option long_options[] = {
        { "daemonize", 0, 0, 'd', },
        { "background", 0, 0, 'b', },
        { "group", 1, 0, 'g', },
-       { "fd-cap", 1, 0, '\0', },
+       { "fd-pool-size", 1, 0, '\0', },
        { "help", 0, 0, 'h', },
        { "output", 1, 0, 'o', },
        { "verbose", 0, 0, 'v', },
@@ -219,28 +219,22 @@ static int set_option(int opt, const char *arg, const char *optname)
 
        switch (opt) {
        case 0:
-               if (!strcmp(optname, "fd-cap")) {
+               if (!strcmp(optname, "fd-pool-size")) {
                        unsigned long v;
 
                        errno = 0;
                        v = strtoul(arg, NULL, 0);
                        if (errno != 0 || !isdigit(arg[0])) {
-                               ERR("Wrong value in --fd-cap parameter: %s", arg);
+                               ERR("Wrong value in --fd-pool-size parameter: %s", arg);
                                ret = -1;
                                goto end;
                        }
-                       if (v < DEFAULT_RELAYD_MINIMAL_FD_CAP) {
-                               ERR("File descriptor cap must be set to at least %d",
-                                               DEFAULT_RELAYD_MINIMAL_FD_CAP);
-                       }
                        if (v >= UINT_MAX) {
-                               ERR("File descriptor cap overflow in --fd-cap parameter: %s", arg);
+                               ERR("File descriptor cap overflow in --fd-pool-size parameter: %s", arg);
                                ret = -1;
                                goto end;
                        }
-                       lttng_opt_fd_cap = (unsigned int) v;
-                       DBG3("File descriptor cap set to %u", lttng_opt_fd_cap);
-
+                       lttng_opt_fd_pool_size = (unsigned int) v;
                } else {
                        fprintf(stderr, "unknown option %s", optname);
                        if (arg) {
@@ -454,6 +448,56 @@ static void parse_env_options(void)
        }
 }
 
+static int set_fd_pool_size(void)
+{
+       int ret = 0;
+       struct rlimit rlimit;
+
+       ret = getrlimit(RLIMIT_NOFILE, &rlimit);
+       if (ret) {
+               PERROR("Failed to get file descriptor limit");
+               ret = -1;
+               goto end;
+       }
+
+       DBG("File descriptor count limits are %lu (soft) and %lu (hard)",
+                       rlimit.rlim_cur, rlimit.rlim_max);
+       if (lttng_opt_fd_pool_size == -1) {
+               /* Use default value (soft limit - reserve). */
+               if (rlimit.rlim_cur < DEFAULT_RELAYD_MIN_FD_POOL_SIZE) {
+                       ERR("The process' file number limit is too low (%lu). The process' file number limit must be set to at least %i.",
+                                       rlimit.rlim_cur, DEFAULT_RELAYD_MIN_FD_POOL_SIZE);
+                       ret = -1;
+                       goto end;
+               }
+               lttng_opt_fd_pool_size = rlimit.rlim_cur -
+                               DEFAULT_RELAYD_FD_POOL_SIZE_RESERVE;
+               goto end;
+       }
+
+       if (lttng_opt_fd_pool_size < DEFAULT_RELAYD_MIN_FD_POOL_SIZE) {
+               ERR("File descriptor pool size must be set to at least %d",
+                               DEFAULT_RELAYD_MIN_FD_POOL_SIZE);
+               ret = -1;
+               goto end;
+       }
+
+       if (lttng_opt_fd_pool_size > rlimit.rlim_cur) {
+               ERR("File descriptor pool size argument (%u) exceeds the process' soft limit (%lu).",
+                               lttng_opt_fd_pool_size, rlimit.rlim_cur);
+               ret = -1;
+               goto end;
+       }
+
+
+       DBG("File descriptor pool size argument (%u) adjusted to %u to accomodate transient fd uses",
+                       lttng_opt_fd_pool_size,
+                       lttng_opt_fd_pool_size - DEFAULT_RELAYD_FD_POOL_SIZE_RESERVE);
+       lttng_opt_fd_pool_size -= DEFAULT_RELAYD_FD_POOL_SIZE_RESERVE;
+end:
+       return ret;
+}
+
 static int set_options(int argc, char **argv)
 {
        int c, ret = 0, option_index = 0, retval = 0;
@@ -571,17 +615,10 @@ static int set_options(int argc, char **argv)
                        goto exit;
                }
        }
-       if (lttng_opt_fd_cap == 0) {
-               int ret;
-               struct rlimit rlimit;
-
-               ret = getrlimit(RLIMIT_NOFILE, &rlimit);
-               if (ret) {
-                       PERROR("Failed to get file descriptor limit");
-                       retval = -1;
-               }
-
-               lttng_opt_fd_cap = rlimit.rlim_cur;
+       ret = set_fd_pool_size();
+       if (ret) {
+               retval = -1;
+               goto exit;
        }
 
        if (!opt_group_output_by_session && !opt_group_output_by_host) {
@@ -3458,7 +3495,7 @@ int main(int argc, char **argv)
         */
        rcu_register_thread();
 
-       the_fd_tracker = fd_tracker_create(lttng_opt_fd_cap);
+       the_fd_tracker = fd_tracker_create(lttng_opt_fd_pool_size);
        if (!the_fd_tracker) {
                retval = -1;
                goto exit_options;
@@ -3467,7 +3504,7 @@ int main(int argc, char **argv)
        ret = track_stdio();
        if (ret) {
                retval = -1;
-               goto exit_options;
+               goto exit_tracker;
        }
 
        /* Initialize thread health monitoring */
@@ -3620,7 +3657,7 @@ exit_health_quit_pipe:
 exit_init_data:
        health_app_destroy(health_relayd);
 exit_health_app_create:
-exit_options:
+
        /*
         * Wait for all pending call_rcu work to complete before tearing
         * down data structures. call_rcu worker may be trying to
@@ -3631,7 +3668,7 @@ exit_options:
 
        /* Ensure all prior call_rcu are done. */
        rcu_barrier();
-
+exit_tracker:
        untrack_stdio();
        /*
         * fd_tracker_destroy() will log the contents of the fd-tracker
@@ -3639,7 +3676,7 @@ exit_options:
         */
        fd_tracker_destroy(the_fd_tracker);
        rcu_unregister_thread();
-
+exit_options:
        if (!retval) {
                exit(EXIT_SUCCESS);
        } else {

diff --git a/src/common/defaults.h b/src/common/defaults.h
index 71a1194217ffa0f0795f49e94614d4fcb7370fa1..2dff3908768ab24157dfd94cad012696520bcaa5 100644 (file)
--- a/src/common/defaults.h
+++ b/src/common/defaults.h
@@ -90,7 +90,20 @@
 #define DEFAULT_RELAYD_RUNDIR                  "%s"
 #define DEFAULT_RELAYD_PATH                    DEFAULT_RELAYD_RUNDIR "/relayd"
 
-#define DEFAULT_RELAYD_MINIMAL_FD_CAP          30
+#define DEFAULT_RELAYD_MIN_FD_POOL_SIZE                100
+/*
+ * The file descriptor pool size needs a reserve buffer to accomodate the
+ * indirect use of short-lived file descriptors. For instance, glibc will
+ * create a socket (and thus, use an fd) during calls to gethostname() or
+ * when querying the user's group. Other calls also probably make use of
+ * short-lived FDs.
+ *
+ * The theoritical maximal reserve corresponds to the number of threads as,
+ * in the worst case, they could all be making such calls.
+ *
+ * This value must be less than DEFAULT_RELAYD_MIN_FD_POOL_SIZE.
+ */
+#define DEFAULT_RELAYD_FD_POOL_SIZE_RESERVE    10
 
 /* Default lttng run directory */
 #define DEFAULT_LTTNG_HOME_ENV_VAR              "LTTNG_HOME"