issue #104: log.reopenFileStreams() convenience method to be used with external log rotation.

CHANGES.md

@@ -6,9 +6,10 @@ Known issues:
   bug](https://github.com/TooTallNate/node-gyp/issues/65).
 
 
-## bunyan 0.21.5 (not yet released)
+## bunyan 0.22.0 (not yet released)
 
-(nothing yet)
+- [issue #104] `log.reopenFileStreams()` convenience method to be used with
+  external log rotation.
 
 
 ## bunyan 0.21.4

README.md

@@ -720,6 +720,23 @@ used for anything else.</td>
 </table>
 
 
+**Note on log rotation**: Often you may be using external log rotation utilities
+like `logrotate` on Linux or `logadm` on SmartOS/Illumos. In those cases, unless
+your are ensuring "copy and truncate" sematics (via `copytruncate` with
+logrotate or `-c` with logadm) then the fd for your 'file' stream will change.
+You can tell bunyan to reopen the file stream with code like this in your
+app:
+
+    var log = bunyan.createLogger(...);
+    ...
+    process.on('SIGUSR2', function () {
+        log.reopenFileStreams();
+    });
+
+where you'd configure your log rotation to send SIGUSR2 (or some other signal)
+to your process. Any other mechanism to signal your app to run
+`log.reopenFileStreams()` would work as well.
+
 
 ## stream type: `raw`
 

bin/bunyan

@@ -6,7 +6,7 @@
 // See <https://github.com/trentm/node-bunyan>.
 //
 
-var VERSION = '0.21.5';
+var VERSION = '0.22.0';
 
 var p = console.log;
 var util = require('util');

lib/bunyan.js

@@ -4,7 +4,7 @@
  * The bunyan logging library for node.js.
  */
 
-var VERSION = '0.21.5';
+var VERSION = '0.22.0';
 
 // Bunyan log format version. This becomes the 'v' field on all log records.
 // `0` is until I release a version '1.0.0' of node-bunyan. Thereafter,
@@ -508,6 +508,44 @@ Logger.prototype.child = function (options, simple) {
 }
 
 
+/**
+ * A convenience method to reopen 'file' streams on a logger. This can be
+ * useful with external log rotation utilities that move and re-open log files
+ * (e.g. logrotate on Linux, logadm on SmartOS/Illumos). Those utilities
+ * typically have rotation options to copy-and-truncate the log file, but
+ * you may not want to use that. An alternative is to do this in your
+ * application:
+ *
+ *      var log = bunyan.createLogger(...);
+ *      ...
+ *      process.on('SIGUSR2', function () {
+ *          log.reopenFileStreams();
+ *      });
+ *      ...
+ *
+ * See <https://github.com/trentm/node-bunyan/issues/104>.
+ */
+Logger.prototype.reopenFileStreams = function () {
+    var self = this;
+    self.streams.forEach(function (s) {
+        if (s.type === 'file') {
+            if (s.stream) {
+                // Not sure if typically would want this, or more immediate
+                // `s.stream.destroy()`.
+                s.stream.end();
+                s.stream.destroySoon();
+                delete s.stream;
+            }
+            s.stream = fs.createWriteStream(s.path,
+                {flags: 'a', encoding: 'utf8'});
+            s.stream.on('error', function (err) {
+                self.emit('error', err, s);
+            });
+        }
+    });
+};
+
+
 /* BEGIN JSSTYLED */
 /**
  * Close this logger.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bunyan",
-  "version": "0.21.5",
+  "version": "0.22.0",
   "description": "a JSON Logger library for node.js services",
   "author": "Trent Mick <trentm@gmail.com> (http://trentm.com)",
   "main": "./lib/bunyan.js",