Use a common lock for the KMLgen and SQL threads to keep them from stepping on each other when reading the SQLite db

apps/modes_gui

@@ -252,11 +252,12 @@ class mainwindow(QtGui.QMainWindow):
 
             self.outputs = [self.datamodelout.output]
             self.updates = []
+            self.lock = threading.Lock() #grab a lock to ensure sql and kml don't step on each other
 
             #output options to populate outputs, updates
             if self.ui.check_kml.checkState():
                 #we spawn a thread to run every 30 seconds (or whatever) to generate KML
-                self.kmlgen = air_modes.output_kml(self.ui.line_kmlfilename.text(), self.dbname, my_position) #create a KML generating thread
+                self.kmlgen = air_modes.output_kml(self.ui.line_kmlfilename.text(), self.dbname, my_position, self.lock) #create a KML generating thread
 
             if self.ui.check_sbs1.checkState():
                 sbs1port = int(self.ui.line_sbs1port.text())
@@ -281,7 +282,7 @@ class mainwindow(QtGui.QMainWindow):
             self.outputs.append(self.output_live_data)
 
             #create SQL database for KML and dashboard displays
-            self.dbwriter = air_modes.output_sql(my_position, self.dbname)
+            self.dbwriter = air_modes.output_sql(my_position, self.dbname, self.lock)
             self.outputs.append(self.dbwriter.output) #now the db will update itself
 
             #output to update reports/sec widget

apps/modes_rx

@@ -194,8 +194,9 @@ if __name__ == '__main__':
   if options.kml is not None:
     #we spawn a thread to run every 30 seconds (or whatever) to generate KML
     dbname = 'adsb.db'
-    sqldb = air_modes.output_sql(my_position, dbname) #input into the db
+    lock = threading.Lock()
-    kmlgen = air_modes.output_kml(options.kml, dbname, my_position) #create a KML generating thread to read from the db
+    sqldb = air_modes.output_sql(my_position, dbname, lock) #input into the db
+    kmlgen = air_modes.output_kml(options.kml, dbname, my_position, lock) #create a KML generating thread to read from the db
     outputs.append(sqldb.output)
 
   if options.sbs1 is True:

python/kml.py

@@ -23,12 +23,13 @@ import sqlite3
 import string, math, threading, time
 
 class output_kml(threading.Thread):
-    def __init__(self, filename, dbname, localpos, timeout=5):
+    def __init__(self, filename, dbname, localpos, lock, timeout=5):
         threading.Thread.__init__(self)
         self._dbname = dbname
         self._filename = filename
         self.my_coords = localpos
         self._timeout = timeout
+        self._lock = lock
         
         self.done = False
         self.setDaemon(1)
@@ -51,6 +52,10 @@ class output_kml(threading.Thread):
             f.write(kmlstr)
             f.close()
 
+    def locked_execute(self, c, query):
+        with self._lock:
+            c.execute(query)
+    
     def draw_circle(self, center, rng):
         retstr = ""
         steps=30

python/sql.py

@@ -26,69 +26,65 @@ import sqlite3
 from air_modes.exceptions import *
 
 class output_sql(air_modes.parse):
-  def __init__(self, mypos, filename):
+  def __init__(self, mypos, filename, lock):
     air_modes.parse.__init__(self, mypos)
 
-    self._lock = threading.Lock()
+    self._lock = lock
-
+    with self._lock:
-    #create the database
+      #create the database
-    self.filename = filename
+      self.filename = filename
-    self.db = sqlite3.connect(filename)
+      self.db = sqlite3.connect(filename)
-    #now execute a schema to create the tables you need
+      #now execute a schema to create the tables you need
-    c = self.db.cursor()
+      c = self.db.cursor()
-    query = """CREATE TABLE IF NOT EXISTS "positions" (
+      query = """CREATE TABLE IF NOT EXISTS "positions" (
                 "icao" INTEGER KEY NOT NULL,
                 "seen" TEXT NOT NULL,
                 "alt"  INTEGER,
                 "lat"  REAL,
                 "lon"  REAL
             );"""
-    self.locked_execute(c, query)
+      self.execute(c, query)
-    query = """CREATE TABLE IF NOT EXISTS "vectors" (
+      query = """CREATE TABLE IF NOT EXISTS "vectors" (
                 "icao"     INTEGER KEY NOT NULL,
                 "seen"     TEXT NOT NULL,
                 "speed"    REAL,
                 "heading"  REAL,
                 "vertical" REAL
             );"""
-    self.locked_execute(c, query)
+      self.execute(c, query)
-    query = """CREATE TABLE IF NOT EXISTS "ident" (
+      query = """CREATE TABLE IF NOT EXISTS "ident" (
                 "icao"     INTEGER PRIMARY KEY NOT NULL,
                 "ident"    TEXT NOT NULL
             );"""
-    self.locked_execute(c, query)
+      self.execute(c, query)
-    c.close()
+      c.close()
-    self.db.commit()
+      self.db.commit()
-    #we close the db conn now to reopen it in the output() thread context.
+      #we close the db conn now to reopen it in the output() thread context.
-    self.db.close()
+      self.db.close()
-    self.db = None
+      self.db = None
 
   def __del__(self):
     self.db = None
 
-  def locked_execute(self, c, query):
-    with self._lock:
-      c.execute(query)
-
   def output(self, message):
-    try:
+    with self._lock:
-      #we're checking to see if the db is empty, and creating the db object
+      try:
-      #if it is. the reason for this is so that the db writing is done within
+        #we're checking to see if the db is empty, and creating the db object
-      #the thread context of output(), rather than the thread context of the
+        #if it is. the reason for this is so that the db writing is done within
-      #constructor. that way you can spawn a thread to do output().
+        #the thread context of output(), rather than the thread context of the
-      if self.db is None:
+        #constructor. that way you can spawn a thread to do output().
-        self.db = sqlite3.connect(self.filename)
+        if self.db is None:
+          self.db = sqlite3.connect(self.filename)
           
-      query = self.make_insert_query(message)
+        query = self.make_insert_query(message)
-      if query is not None:
+        if query is not None:
-        with self._lock:
+            c = self.db.cursor()
-          c = self.db.cursor()
+            c.execute(query)
-          c.execute(query)
+            c.close()
-          c.close()
+            self.db.commit()
-          self.db.commit()
 
-    except ADSBError:
+      except ADSBError:
-      pass
+        pass
 
   def make_insert_query(self, message):
     #assembles a SQL query tailored to our database