Open only recently changed files to conserve file descriptors

kitsune

@@ -12,14 +12,19 @@ class WatchedFile:
     def __init__(self, path, seek_to_end):
         self.path = path
         self.seek_to_end = seek_to_end
-        self.reopen()
+        stf = os.stat(self.path)
+        self.st_ctime_ns = stf.st_ctime_ns
+        self.st_size = stf.st_size
+        self.fileno = None
+        if stf.st_ctime_ns >= time.time_ns() - 1E9:
+            self.reopen()
 
     def reopen(self):
         self.fd = open(self.path, errors='replace')
         self.fileno = self.fd.fileno()
         self.last_ts = 0
         if self.seek_to_end:
-            self.fd.seek(0, 2)
+            self.fd.seek(self.st_size, 0)
             self.seek_to_end = False
 
 def format_ts(ts_ns):
@@ -59,30 +64,35 @@ def watch(args):
         # has any of the files changed
         for f in watched_files.values():
             # XXX - we should also detect replaced files. 
-            st = os.stat(f.fileno)
+            if f.fileno:
-            try:
+                st = os.stat(f.fileno)
+                try:
+                    stf = os.stat(f.path)
+                    if stf.st_ino != st.st_ino:
+                        f.reopen()
+                        st = os.stat(f.fileno)
+                except FileNotFoundError:
+                    # ignore,
+                    # or maybe remove from watched_files?
+                    # or just mark as deleted?
+                    pass
+                if st.st_mtime_ns > f.last_ts:
+                    if st.st_size < f.fd.tell():
+                        # We are beyond the end of the file, so it has probably
+                        # been truncated and rewritten - read from beginning
+                        f.fd.seek(0, 0)
+                    dead = "✝" if st.st_nlink == 0 else " "
+                    f.last_ts = st.st_mtime_ns
+                    new_content = f.fd.read()
+                    lines = new_content.split("\n")
+                    if lines[-1] == "":
+                        lines.pop()
+                    for ln in lines:
+                        print(f"{f.path:{filename_length}}", format_ts(f.last_ts), dead, ln)
+            else:
                 stf = os.stat(f.path)
-                if stf.st_ino != st.st_ino:
+                if stf.st_ctime_ns != f.st_ctime_ns:
                     f.reopen()
-                    st = os.stat(f.fileno)
-            except FileNotFoundError:
-                # ignore,
-                # or maybe remove from watched_files?
-                # or just mark as deleted?
-                pass
-            if st.st_mtime_ns > f.last_ts:
-                if st.st_size < f.fd.tell():
-                    # We are beyond the end of the file, so it has probably
-                    # been truncated and rewritten - read from beginning
-                    f.fd.seek(0, 0)
-                dead = "✝" if st.st_nlink == 0 else " "
-                f.last_ts = st.st_mtime_ns
-                new_content = f.fd.read()
-                lines = new_content.split("\n")
-                if lines[-1] == "":
-                    lines.pop()
-                for ln in lines:
-                    print(f"{f.path:{filename_length}}", format_ts(f.last_ts), dead, ln)
         time.sleep(0.1)
         seek_to_end = False