Add JSON export plugin

NEWS

@@ -9,6 +9,7 @@ Enhancements and new features:
 
     * [WIP] Refactoring of the WebUI
     * New export plugin: standard and configurable Restfull exporter (issue #1129)
+    * Add a JSON export module
 
 Bugs corrected:
 

docs/gw/index.rst

@@ -10,6 +10,7 @@ to providing stats to multiple services (see list below).
    :maxdepth: 2
 
    csv
+   json
    cassandra
    couchdb
    elastic

docs/gw/json.rst

@@ -0,0 +1,16 @@
+.. _json:
+
+JSON
+====
+
+It's possible to export stats to a JSON file to be processed later by an
+external system.
+
+.. code-block:: console
+
+    $ glances --export-json /tmp/glances.json
+
+JSON file description:
+
+Each line would contain a JSON glance of the system. If this file needs to be
+processed it should be processed in a line by line basis.

glances/exports/glances_json.py

@@ -0,0 +1,64 @@
+"""JSON interface class."""
+
+import sys
+import json
+
+from glances.compat import PY3, listkeys
+from glances.logger import logger
+from glances.exports.glances_export import GlancesExport
+
+
+class Export(GlancesExport):
+
+    """This class manages the JSON export module."""
+
+    def __init__(self, config=None, args=None):
+        """Init the JSON export IF."""
+        super(Export, self).__init__(config=config, args=args)
+
+        # JSON file name
+        self.json_filename = args.export_json
+
+        # Set the JSON output file
+        try:
+            if PY3:
+                self.json_file = open(self.json_filename, 'w')
+            else:
+                self.json_file = open(self.json_filename, 'wb')
+        except IOError as e:
+            logger.critical("Cannot create the JSON file: {}".format(e))
+            sys.exit(2)
+
+        logger.info("Exporting stats to file: {}".format(self.json_filename))
+
+        self.export_enable = True
+
+        # Buffer for dict of stats
+        self.buffer = {}
+
+    def exit(self):
+        """Close the JSON file."""
+        logger.debug("Finalise export interface %s" % self.export_name)
+        self.json_file.close()
+
+    def export(self, name, columns, points):
+        """Export the stats to the JSON file."""
+
+        # Check for completion of loop for all exports
+        if name == self.plugins_to_export()[0] and self.buffer != {}:
+            # One whole loop has been completed
+            # Flush stats to file
+            logger.debug("Exporting stats ({}) to JSON file ({})".format(
+                listkeys(self.buffer),
+                self.json_filename)
+            )
+
+            # Export stats to JSON file
+            data_json = json.dumps(self.buffer)
+            self.json_file.write("{}\n".format(data_json))
+
+            # Reset buffer
+            self.buffer = {}
+
+        # Add current stat to the buffer
+        self.buffer[name] = dict(zip(columns, points))

glances/main.py

@@ -173,6 +173,8 @@ Examples of use:
                             dest='path_graph', help='set the export path for graphs (default is {})'.format(tempfile.gettempdir()))
         parser.add_argument('--export-csv', default=None,
                             dest='export_csv', help='export stats to a CSV file')
+        parser.add_argument('--export-json', default=None,
+                            dest='export_json', help='export stats to a JSON file')
         parser.add_argument('--export-cassandra', action='store_true', default=False,
                             dest='export_cassandra', help='export stats to a Cassandra or Scylla server (cassandra lib needed)')
         parser.add_argument('--export-couchdb', action='store_true', default=False,