Add methods to RunningJob to incrementally update cached stderr and t…

genie-client/src/main/python/pygenie/jobs/running.py

@@ -518,6 +518,62 @@ def status(self):
             self._info['status'] = self._status
 
         return self._status.upper() if self._status else None
+
+    @property
+    def stderr_url(self):
+        """
+        Returns a url for the stderr of the job.
+        """
+
+        return '{}/stderr'.format(self.output_uri.replace('/output/', '/file/', 1))
+
+    def update_stderr(self):
+        '''
+        Use the http Range header to incrementally update stderr output While
+        this version keeps all of stderr in memory, if it exceeds available
+        memory, we could instead use iterators to retrieve and print only new
+        lines, keeping only the number of bytes retrieved in memory.
+
+        Returns the updated fraction of stderr.
+        '''
+
+        headers = {
+            'user-agent': '/'.join([
+                socket.getfqdn(),
+                'nflx-genie-client',
+                pkg_resources.get_distribution('nflx-genie-client').version
+            ]),
+            'Range': 'bytes={}-'.format(len(self._cached_stderr) if self._cached_stderr else 0)
+        }
+
+        r = requests.request('get', url=self.stderr_url(), headers=headers, 
+                auth=self._adapter.auth_handler.auth, stream=False)
+
+        if r.status_code in (200, 206):
+        else:
+            print('\nError updating stderr: Status code {}'.format(r.status_code))
+
+        if self._cached_stderr:
+            self._cached_stderr += r.content
+        else
+            self._cached_stderr = r.content
+
+        return r.content
+
+    def watch_stderr(self, interval=1):
+        '''Tail output of a genie job's stderr to the terminal until the job is done.
+
+        Args:
+            interval (int or float, optional): Time between updates.
+        '''
+
+        while not self.is_done:
+            time.sleep(interval)
+            print(self.update_stderr())
+            sys.stdout.flush()
+
+        print(self.update_stderr())
+        print('\n\nGenie job {}. {}'.format(self.status, self.output_uri))
 
     def stderr(self, iterator=False, **kwargs):
         """
@@ -536,15 +592,10 @@ def stderr(self, iterator=False, **kwargs):
             str or iterator.
         """
 
-        if self.is_done:
-            if not self._cached_stderr:
-                self._cached_stderr = self._adapter.get_stderr(self._job_id,
-                                                               **kwargs)
-            return self._cached_stderr.split('\n') if iterator \
-                else self._cached_stderr
-        return self._adapter.get_stderr(self._job_id,
-                                        iterator=iterator,
-                                        **kwargs)
+        self.update_stderr()
+
+        return self._cached_stderr.split('\n') if iterator \
+            else self._cached_stderr
 
     @property
     def stdout_url(self):