Added ability to handle non-json erroneous responses from API calls, modified readme, new screenshot

README.md

@@ -2,10 +2,12 @@
 
 [![Build Status](https://travis-ci.org/OpenDroneMap/WebODM.svg?branch=master)](https://travis-ci.org/OpenDroneMap/WebODM)
 
-A free, user-friendly application and API for drone image processing.
+A free, user-friendly, extendable application and API for drone image processing.
 
 ![Alt text](/screenshots/ui-mockup.png?raw=true "WebODM")
 
+![Alt text](/screenshots/dashboard.png?raw=true "Dashboard")
+
 If you know Python, web technologies (JS, HTML, CSS, etc.) or both, make a fork, contribute something that interests you, and make a pull request! All ideas are considered and people of all skill levels are welcome.
 
 ## Getting Started

app/scheduler.py

@@ -11,7 +11,10 @@ from nodeodm import status_codes
 import random
 
 logger = logging.getLogger('app.logger')
-scheduler = BackgroundScheduler()
+scheduler = BackgroundScheduler({
+    'apscheduler.job_defaults.coalesce': 'false',
+    'apscheduler.job_defaults.max_instances': '3',
+})
 
 def background(func):
     """

nodeodm/api_client.py

@@ -8,6 +8,7 @@ import json
 import os
 from urllib.parse import urlunparse
 
+
 class ApiClient:
     def __init__(self, host, port):
         self.host = host
@@ -55,10 +56,9 @@ class ApiClient:
         :param options: options to be used for processing ([{'name': optionName, 'value': optionValue}, ...])
         :return: UUID or error
         """
-
         files = [('images',
                   (os.path.basename(image), open(image, 'rb'), (mimetypes.guess_type(image)[0] or "image/jpg"))
                  ) for image in images]
         return requests.post(self.url("/task/new"),
                              files=files,
-                             data={'name': name, 'options': json.dumps(options)}).json()
+                             data={'name': name, 'options': json.dumps(options)}).json()

nodeodm/models.py

@@ -10,6 +10,19 @@ from django.db.models import signals
 from requests.exceptions import ConnectionError
 from .exceptions import ProcessingException
 
+def api(func):
+    """
+    Catches JSON decoding errors that might happen when the server
+    answers unexpectedly
+    """
+    def wrapper(*args,**kwargs):
+        try:
+            return func(*args, **kwargs)
+        except json.decoder.JSONDecodeError as e:
+            raise ProcessingException(str(e))
+
+    return wrapper
+
 class ProcessingNode(models.Model):
     hostname = models.CharField(max_length=255, help_text="Hostname where the node is located (can be an internal hostname as well)")
     port = models.PositiveIntegerField(help_text="Port that connects to the node's API")
@@ -21,6 +34,7 @@ class ProcessingNode(models.Model):
     def __str__(self):
         return '{}:{}'.format(self.hostname, self.port)
 
+    @api
     def update_node_info(self):
         """
         Retrieves information and options from the node API
@@ -52,6 +66,7 @@ class ProcessingNode(models.Model):
         kwargs = dict(indent=4, separators=(',', ": ")) if pretty else dict() 
         return json.dumps(self.available_options, **kwargs)
 
+    @api
     def process_new_task(self, images, name=None, options=[]):
         """
         Sends a set of images (and optional GCP file) via the API
@@ -72,6 +87,7 @@ class ProcessingNode(models.Model):
         elif result['error']:
             raise ProcessingException(result['error'])
 
+    @api
     def get_task_info(self, uuid):
         """
         Gets information about this task, such as name, creation date, 
@@ -87,6 +103,7 @@ class ProcessingNode(models.Model):
         else:
             raise ProcessingException("Unknown result from task info: {}".format(result))
 
+    @api
     def get_task_console_output(self, uuid, line):
         """
         Retrieves the console output of the OpenDroneMap's process.
@@ -101,6 +118,7 @@ class ProcessingNode(models.Model):
         else:
             raise ProcessingException("Unknown response for console output: {}".format(result))
 
+    @api
     def cancel_task(self, uuid):
         """
         Cancels a task (stops its execution, or prevents it from being executed)
@@ -108,6 +126,7 @@ class ProcessingNode(models.Model):
         api_client = self.api_client()
         return self.handle_generic_post_response(api_client.task_cancel(uuid))
 
+    @api
     def remove_task(self, uuid):
         """
         Removes a task and deletes all of its assets
@@ -115,6 +134,7 @@ class ProcessingNode(models.Model):
         api_client = self.api_client()
         return self.handle_generic_post_response(api_client.task_remove(uuid))
 
+    @api
     def download_task_asset(self, uuid, asset):
         """
         Downloads a task asset
@@ -126,6 +146,7 @@ class ProcessingNode(models.Model):
         else:
             return res
 
+    @api
     def restart_task(self, uuid):
         """
         Restarts a task that was previously canceled or that had failed to process