(fix):attempt to fix potential problem with job service items piling up (#243)

* attempt to fix potential problem with job service items piling up

* added javadoc for allowPendingJobs.

Author: thomaszurkan-optimizely

datafile-handler/src/main/java/com/optimizely/ab/android/datafile_handler/DatafileRescheduler.java

@@ -97,7 +97,7 @@ void dispatch(Intent intent) {
                 // so, we don't need to do anything.
                // if (android.os.Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
                     intent.putExtra(DatafileService.EXTRA_DATAFILE_CONFIG, datafileConfig.toJSONString());
-                    ServiceScheduler.startService(context, DatafileService.JOB_ID, intent);
+                    ServiceScheduler.startService(context, DatafileService.JOB_ID, intent, false);
                     logger.info("Rescheduled data file watching for project {}", datafileConfig);
                 //}
             }

event-handler/src/main/java/com/optimizely/ab/android/event_handler/DefaultEventHandler.java

@@ -97,7 +97,7 @@ public void dispatchEvent(@NonNull LogEvent logEvent) {
         intent.putExtra(EventIntentService.EXTRA_REQUEST_BODY, logEvent.getBody());
         intent.putExtra(EventIntentService.EXTRA_INTERVAL, dispatchInterval);
 
-        ServiceScheduler.startService(context, EventIntentService.JOB_ID, intent);
+        ServiceScheduler.startService(context, EventIntentService.JOB_ID, intent, true);
 
         logger.info("Sent url {} to the event handler service", logEvent.getEndpointUrl());
     }

event-handler/src/main/java/com/optimizely/ab/android/event_handler/EventRescheduler.java

@@ -90,7 +90,7 @@ public void onReceive(Context context, Intent intent) {
     void reschedule(@NonNull Context context, @NonNull Intent broadcastIntent, @NonNull Intent eventServiceIntent, @NonNull ServiceScheduler serviceScheduler) {
         if (broadcastIntent.getAction().equals(Intent.ACTION_BOOT_COMPLETED) ||
                 broadcastIntent.getAction().equals(Intent.ACTION_MY_PACKAGE_REPLACED)) {
-            ServiceScheduler.startService(context,  EventIntentService.JOB_ID, eventServiceIntent);
+            ServiceScheduler.startService(context,  EventIntentService.JOB_ID, eventServiceIntent, false);
             logger.info("Rescheduling event flushing if necessary");
         } else if (broadcastIntent.getAction().equals(WifiManager.SUPPLICANT_CONNECTION_CHANGE_ACTION)
                 && broadcastIntent.getBooleanExtra(WifiManager.EXTRA_SUPPLICANT_CONNECTED, false)) {
@@ -101,7 +101,7 @@ void reschedule(@NonNull Context context, @NonNull Intent broadcastIntent, @NonN
                     // with wifi the service will be rescheduled on the interval.
                     // Wifi connection state changes all the time and starting services is expensive
                     // so it's important to only do this if we have stored events.
-                    ServiceScheduler.startService(context, EventIntentService.JOB_ID, eventServiceIntent);
+                    ServiceScheduler.startService(context, EventIntentService.JOB_ID, eventServiceIntent, false);
                     logger.info("Preemptively flushing events since wifi became available");
                 }
         } else {

shared/src/main/java/com/optimizely/ab/android/shared/ServiceScheduler.java

@@ -259,10 +259,13 @@ private PendingIntent getPendingIntent(Intent intent, int flag) {
      * For example, the BroadcastReceivers use this to handle all versions of the API.
      *
      * @param context - Application context
-     * @param jobId - job id for the job to start if it is a job
+     * @param jobId - job id for the job to start if it is a job. Jobs are used in Android O and later.
      * @param intent - Intent you want to run.
+     * @param allowPendingJobs - If true in versions greater than O, the jobs will be scheduled even if there are pending
+     *                         jobs with the same job id.  If false, then, the intent will not be started if there are already
+     *                         pending jobs with the same id.
      */
-    public static void startService(Context context, Integer jobId, Intent intent) {
+    public static void startService(Context context, Integer jobId, Intent intent, Boolean allowPendingJobs) {
         if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
 
             JobInfo jobInfo = new JobInfo.Builder(jobId,
@@ -273,6 +276,11 @@ public static void startService(Context context, Integer jobId, Intent intent) {
                     .build();
             JobScheduler jobScheduler = (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE);
 
+            if (!allowPendingJobs && jobScheduler.getPendingJob(jobId) != null) {
+                LoggerFactory.getLogger("ServiceScheduler").debug("Jobs already pending.");
+                return;
+            }
+
             JobWorkItem jobWorkItem = new JobWorkItem(intent);
             try {
                 jobScheduler.enqueue(jobInfo, jobWorkItem);