Add 'ignore_unavailable' config option to in_tail plugin

plugins/in_tail/tail.c

@@ -576,6 +576,11 @@ static struct flb_config_map config_map[] = {
      "Set one or multiple shell patterns separated by commas to exclude "
      "files matching a certain criteria, e.g: 'exclude_path *.gz,*.zip'"
     },
+    {
+     FLB_CONFIG_MAP_BOOL, "ignore_unavailable", "false",
+     0, FLB_TRUE, offsetof(struct flb_tail_config, ignore_unavailable),
+     "Do not search directories that do not exist for files."
+    },
     {
      FLB_CONFIG_MAP_STR, "key", "log",
      0, FLB_TRUE, offsetof(struct flb_tail_config, key),

plugins/in_tail/tail_config.h

@@ -88,6 +88,7 @@ struct flb_tail_config {
     long refresh_interval_nsec;/* nanoseconds to re-scan       */
     int read_newly_discovered_files_from_head; /* read new files from head after startup */
     int read_from_head;        /* read new files from head     */
+    int ignore_unavailable;    /* ignore unavailable paths during scanning */
     int rotate_wait;           /* sec to wait on rotated files */
     int watcher_interval;      /* watcher interval             */
     int ignore_older;          /* ignore fields older than X seconds */

plugins/in_tail/tail_scan.c

@@ -110,13 +110,13 @@ int flb_tail_scan(struct mk_list *path_list, struct flb_tail_config *ctx)
     mk_list_foreach(head, path_list) {
         pattern = mk_list_entry(head, struct flb_slist_entry, _head);
         ret = tail_scan_path(pattern->str, ctx);
-        if (ret == -1) {
-            flb_plg_warn(ctx->ins, "error scanning path: %s", pattern->str);
-        }
-        else {
+        if (ret != -1) {
             flb_plg_debug(ctx->ins, "%i new files found on path '%s'",
                           ret, pattern->str);
         }
+        else if (!ctx->ignore_unavailable) {
+            flb_plg_warn(ctx->ins, "error scanning path: %s", pattern->str);
+        }
     }
 
     return 0;

plugins/in_tail/tail_scan_glob.c

@@ -183,7 +183,6 @@ static inline int do_glob(const char *pattern, int flags,
     return ret;
 }
 
-
 /* Scan a path, register the entries and return how many */
 static int tail_scan_path(const char *path, struct flb_tail_config *ctx)
 {
@@ -212,12 +211,27 @@ static int tail_scan_path(const char *path, struct flb_tail_config *ctx)
             flb_plg_error(ctx->ins, "no memory space available");
             return -1;
         case GLOB_ABORTED:
-            flb_plg_error(ctx->ins, "read error, check permissions: %s", path);
+            if (errno == EACCES) {
+                flb_plg_error(ctx->ins, "No read access for path: %s", path);
+            } else if (errno == ENOENT || errno == ENOTDIR) {
+                if (!ctx->ignore_unavailable) {
+                    flb_plg_error(ctx->ins, "%s at path: %s", 
+                                    (errno == ENOENT) ? "No such file" : "Not a directory",
+                                    path);
+                }
+            } else {
+                flb_plg_error(ctx->ins, "Unable to scan path (system error: %s): %s",
+                            strerror(errno), path);
+            }
             return -1;
         case GLOB_NOMATCH:
             ret = stat(path, &st);
             if (ret == -1) {
-                flb_plg_debug(ctx->ins, "cannot read info from: %s", path);
+                if (errno == ENOTDIR && !ctx->ignore_unavailable) {
+                    flb_plg_error(ctx->ins, "Not a directory at path: %s", path);
+                } else {
+                    flb_plg_debug(ctx->ins, "cannot read info from: %s", path);
+                }
             }
             else {
                 ret = access(path, R_OK);