better log

internal/engine.cm

@@ -900,7 +900,11 @@ function build_sink_routing() {
     if (!is_array(sink.exclude)) sink.exclude = []
     if (is_text(sink.stack)) sink.stack = [sink.stack]
     if (!is_array(sink.stack)) sink.stack = []
-    if (sink.type == "file" && sink.path) ensure_log_dir(sink.path)
+    if (sink.type == "file" && sink.path) {
+      ensure_log_dir(sink.path)
+      if (sink.mode == "overwrite")
+        fd.slurpwrite(sink.path, stone(_make_blob("")))
+    }
     arrfor(sink.stack, function(ch) {
       stack_channels[ch] = true
     })
@@ -936,6 +940,12 @@ function load_log_config() {
     }
   }
   build_sink_routing()
+  var names = array(log_config.sink)
+  arrfor(names, function(name) {
+    var sink = log_config.sink[name]
+    if (sink.type == "file")
+      os.print("[log] " + name + " -> " + sink.path + "\n")
+  })
 }
 
 function pretty_format(rec) {
@@ -1001,6 +1011,7 @@ function sink_excluded(sink, channel) {
 
 function dispatch_to_sink(sink, rec) {
   var line = null
+  var st = null
   if (sink_excluded(sink, rec.channel)) return
   if (sink.type == "console") {
     if (sink.format == "json")
@@ -1013,7 +1024,12 @@ function dispatch_to_sink(sink, rec) {
       os.print(pretty_format(rec))
   } else if (sink.type == "file") {
     line = json.encode(rec, false) + "\n"
-    fd.slurpappend(sink.path, stone(blob(line)))
+    if (sink.max_size) {
+      st = fd.stat(sink.path)
+      if (st && st.size > sink.max_size)
+        fd.slurpwrite(sink.path, stone(_make_blob("")))
+    }
+    fd.slurpappend(sink.path, stone(_make_blob(line)))
   }
 }