rotating-file: auto rotate file on startup if needed

Fixes #239

lib/bunyan.js

@@ -1168,8 +1168,7 @@ if (mv) {
 
 RotatingFileStream = function RotatingFileStream(options) {
     this.path = options.path;
-    this.stream = fs.createWriteStream(this.path,
+
-        {flags: 'a', encoding: 'utf8'});
     this.count = (options.count == null ? 10 : options.count);
     assert.equal(typeof (this.count), 'number',
         format('rotating-file stream "count" is not a number: %j (%s) in %j',
@@ -1206,6 +1205,22 @@ RotatingFileStream = function RotatingFileStream(options) {
         this.periodScope = 'd';
     }
 
+    var lastModified = null;
+    try {
+        var fileInfo = fs.statSync(this.path);
+        lastModified = fileInfo.mtime.getTime();
+    }
+    catch (err) {
+        // file doesn't exist
+    }
+    var rotateAfterOpen = false;
+    if (lastModified) {
+        var lastRotTime = this._calcRotTime(0);
+        if (lastModified < lastRotTime) {
+            rotateAfterOpen = true;
+        }
+    }
+
     // TODO: template support for backup files
     // template: <path to which to rotate>
     //      default is %P.%n
@@ -1222,15 +1237,21 @@ RotatingFileStream = function RotatingFileStream(options) {
     //                          prior art? Want to avoid ':' in
     //                          filenames (illegal on Windows for one).
 
+    this.stream = fs.createWriteStream(this.path,
+        {flags: 'a', encoding: 'utf8'});
+
     this.rotQueue = [];
     this.rotating = false;
+    if (rotateAfterOpen) {
+        this.rotate();
+    }
     this._setupNextRot();
 }
 
 util.inherits(RotatingFileStream, EventEmitter);
 
 RotatingFileStream.prototype._setupNextRot = function () {
-    this.rotAt = this._nextRotTime();
+    this.rotAt = this._calcRotTime(1);
     this._setRotationTimer();
 }
 
@@ -1251,10 +1272,11 @@ RotatingFileStream.prototype._setRotationTimer = function () {
     }
 }
 
-RotatingFileStream.prototype._nextRotTime = function _nextRotTime(first) {
+RotatingFileStream.prototype._calcRotTime =
+function _calcRotTime(periodOffset) {
     var _DEBUG = false;
     if (_DEBUG)
-        console.log('-- _nextRotTime: %s%s', this.periodNum, this.periodScope);
+        console.log('-- _calcRotTime: %s%s', this.periodNum, this.periodScope);
     var d = new Date();
 
     if (_DEBUG) console.log('  now local: %s', d);
@@ -1264,54 +1286,65 @@ RotatingFileStream.prototype._nextRotTime = function _nextRotTime(first) {
     case 'ms':
         // Hidden millisecond period for debugging.
         if (this.rotAt) {
-            rotAt = this.rotAt + this.periodNum;
+            rotAt = this.rotAt + this.periodNum * periodOffset;
         } else {
-            rotAt = Date.now() + this.periodNum;
+            rotAt = Date.now() + this.periodNum * periodOffset;
         }
         break;
     case 'h':
         if (this.rotAt) {
-            rotAt = this.rotAt + this.periodNum * 60 * 60 * 1000;
+            rotAt = this.rotAt + this.periodNum * 60 * 60 * 1000 * periodOffset;
         } else {
             // First time: top of the next hour.
             rotAt = Date.UTC(d.getUTCFullYear(), d.getUTCMonth(),
-                d.getUTCDate(), d.getUTCHours() + 1);
+                d.getUTCDate(), d.getUTCHours() + periodOffset);
         }
         break;
     case 'd':
         if (this.rotAt) {
-            rotAt = this.rotAt + this.periodNum * 24 * 60 * 60 * 1000;
+            rotAt = this.rotAt + this.periodNum * 24 * 60 * 60 * 1000
+                * periodOffset;
         } else {
             // First time: start of tomorrow (i.e. at the coming midnight) UTC.
             rotAt = Date.UTC(d.getUTCFullYear(), d.getUTCMonth(),
-                d.getUTCDate() + 1);
+                d.getUTCDate() + periodOffset);
         }
         break;
     case 'w':
         // Currently, always on Sunday morning at 00:00:00 (UTC).
         if (this.rotAt) {
-            rotAt = this.rotAt + this.periodNum * 7 * 24 * 60 * 60 * 1000;
+            rotAt = this.rotAt + this.periodNum * 7 * 24 * 60 * 60 * 1000
+                * periodOffset;
         } else {
             // First time: this coming Sunday.
+            var dayOffset = (7 - d.getUTCDay());
+            if (periodOffset < 1) {
+                dayOffset = -d.getUTCDay();
+            }
+            if (periodOffset > 1 || periodOffset < -1) {
+                dayOffset += 7 * periodOffset;
+            }
             rotAt = Date.UTC(d.getUTCFullYear(), d.getUTCMonth(),
-                d.getUTCDate() + (7 - d.getUTCDay()));
+                d.getUTCDate() + dayOffset);
         }
         break;
     case 'm':
         if (this.rotAt) {
             rotAt = Date.UTC(d.getUTCFullYear(),
-                d.getUTCMonth() + this.periodNum, 1);
+                d.getUTCMonth() + this.periodNum * periodOffset, 1);
         } else {
             // First time: the start of the next month.
-            rotAt = Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 1);
+            rotAt = Date.UTC(d.getUTCFullYear(),
+                d.getUTCMonth() + periodOffset, 1);
         }
         break;
     case 'y':
         if (this.rotAt) {
-            rotAt = Date.UTC(d.getUTCFullYear() + this.periodNum, 0, 1);
+            rotAt = Date.UTC(d.getUTCFullYear() + this.periodNum * periodOffset,
+                0, 1);
         } else {
             // First time: the start of the next year.
-            rotAt = Date.UTC(d.getUTCFullYear() + 1, 0, 1);
+            rotAt = Date.UTC(d.getUTCFullYear() + periodOffset, 0, 1);
         }
         break;
     default: