Flex time for periodic jobs in JobScheduler

A periodic job will start only within time
satisfying period - flex < time % period < period.

Bug: 26254850
Change-Id: I97a840446e5592e5151d784800855d909f1790b8
diff --git a/api/current.txt b/api/current.txt
index 42e72e3..693d9f4 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -6166,6 +6166,7 @@
     method public int describeContents();
     method public int getBackoffPolicy();
     method public android.os.PersistableBundle getExtras();
+    method public long getFlexMillis();
     method public int getId();
     method public long getInitialBackoffMillis();
     method public long getIntervalMillis();
@@ -6183,6 +6184,8 @@
     field public static final android.os.Parcelable.Creator<android.app.job.JobInfo> CREATOR;
     field public static final long DEFAULT_INITIAL_BACKOFF_MILLIS = 30000L; // 0x7530L
     field public static final long MAX_BACKOFF_DELAY_MILLIS = 18000000L; // 0x112a880L
+    field public static final long MIN_FLEX_MILLIS = 300000L; // 0x493e0L
+    field public static final long MIN_PERIOD_MILLIS = 3600000L; // 0x36ee80L
     field public static final int NETWORK_TYPE_ANY = 1; // 0x1
     field public static final int NETWORK_TYPE_NONE = 0; // 0x0
     field public static final int NETWORK_TYPE_UNMETERED = 2; // 0x2
@@ -6196,6 +6199,7 @@
     method public android.app.job.JobInfo.Builder setMinimumLatency(long);
     method public android.app.job.JobInfo.Builder setOverrideDeadline(long);
     method public android.app.job.JobInfo.Builder setPeriodic(long);
+    method public android.app.job.JobInfo.Builder setPeriodic(long, long);
     method public android.app.job.JobInfo.Builder setPersisted(boolean);
     method public android.app.job.JobInfo.Builder setRequiredNetworkType(int);
     method public android.app.job.JobInfo.Builder setRequiresCharging(boolean);
diff --git a/api/system-current.txt b/api/system-current.txt
index b34a7f4..d4a97b6 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -6381,6 +6381,7 @@
     method public int describeContents();
     method public int getBackoffPolicy();
     method public android.os.PersistableBundle getExtras();
+    method public long getFlexMillis();
     method public int getId();
     method public long getInitialBackoffMillis();
     method public long getIntervalMillis();
@@ -6398,6 +6399,8 @@
     field public static final android.os.Parcelable.Creator<android.app.job.JobInfo> CREATOR;
     field public static final long DEFAULT_INITIAL_BACKOFF_MILLIS = 30000L; // 0x7530L
     field public static final long MAX_BACKOFF_DELAY_MILLIS = 18000000L; // 0x112a880L
+    field public static final long MIN_FLEX_MILLIS = 300000L; // 0x493e0L
+    field public static final long MIN_PERIOD_MILLIS = 3600000L; // 0x36ee80L
     field public static final int NETWORK_TYPE_ANY = 1; // 0x1
     field public static final int NETWORK_TYPE_NONE = 0; // 0x0
     field public static final int NETWORK_TYPE_UNMETERED = 2; // 0x2
@@ -6411,6 +6414,7 @@
     method public android.app.job.JobInfo.Builder setMinimumLatency(long);
     method public android.app.job.JobInfo.Builder setOverrideDeadline(long);
     method public android.app.job.JobInfo.Builder setPeriodic(long);
+    method public android.app.job.JobInfo.Builder setPeriodic(long, long);
     method public android.app.job.JobInfo.Builder setPersisted(boolean);
     method public android.app.job.JobInfo.Builder setRequiredNetworkType(int);
     method public android.app.job.JobInfo.Builder setRequiresCharging(boolean);
diff --git a/api/test-current.txt b/api/test-current.txt
index bcab75b..2f24953 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -6168,6 +6168,7 @@
     method public int describeContents();
     method public int getBackoffPolicy();
     method public android.os.PersistableBundle getExtras();
+    method public long getFlexMillis();
     method public int getId();
     method public long getInitialBackoffMillis();
     method public long getIntervalMillis();
@@ -6185,6 +6186,8 @@
     field public static final android.os.Parcelable.Creator<android.app.job.JobInfo> CREATOR;
     field public static final long DEFAULT_INITIAL_BACKOFF_MILLIS = 30000L; // 0x7530L
     field public static final long MAX_BACKOFF_DELAY_MILLIS = 18000000L; // 0x112a880L
+    field public static final long MIN_FLEX_MILLIS = 300000L; // 0x493e0L
+    field public static final long MIN_PERIOD_MILLIS = 3600000L; // 0x36ee80L
     field public static final int NETWORK_TYPE_ANY = 1; // 0x1
     field public static final int NETWORK_TYPE_NONE = 0; // 0x0
     field public static final int NETWORK_TYPE_UNMETERED = 2; // 0x2
@@ -6198,6 +6201,7 @@
     method public android.app.job.JobInfo.Builder setMinimumLatency(long);
     method public android.app.job.JobInfo.Builder setOverrideDeadline(long);
     method public android.app.job.JobInfo.Builder setPeriodic(long);
+    method public android.app.job.JobInfo.Builder setPeriodic(long, long);
     method public android.app.job.JobInfo.Builder setPersisted(boolean);
     method public android.app.job.JobInfo.Builder setRequiredNetworkType(int);
     method public android.app.job.JobInfo.Builder setRequiresCharging(boolean);
diff --git a/core/java/android/app/job/JobInfo.java b/core/java/android/app/job/JobInfo.java
index 0d9e778..b899710 100644
--- a/core/java/android/app/job/JobInfo.java
+++ b/core/java/android/app/job/JobInfo.java
@@ -64,6 +64,11 @@
      */
     public static final int BACKOFF_POLICY_EXPONENTIAL = 1;
 
+    /* Minimum interval for a periodic job, in milliseconds. */
+    public static final long MIN_PERIOD_MILLIS = 60 * 60 * 1000L;   // 60 minutes
+    /* Minimum flex for a periodic job, in milliseconds. */
+    public static final long MIN_FLEX_MILLIS = 5 * 60 * 1000L; // 5 minutes
+
     /**
      * Default type of backoff.
      * @hide
@@ -83,6 +88,7 @@
     private final boolean isPeriodic;
     private final boolean isPersisted;
     private final long intervalMillis;
+    private final long flexMillis;
     private final long initialBackoffMillis;
     private final int backoffPolicy;
 
@@ -165,7 +171,17 @@
      * job does not recur periodically.
      */
     public long getIntervalMillis() {
-        return intervalMillis;
+        return intervalMillis >= MIN_PERIOD_MILLIS ? intervalMillis : MIN_PERIOD_MILLIS;
+    }
+
+    /**
+     * Flex time for this job. Only valid if this is a periodic job.
+     */
+    public long getFlexMillis() {
+        long interval = getIntervalMillis();
+        long percentClamp = 5 * interval / 100;
+        long clampedFlex = Math.max(flexMillis, Math.max(percentClamp, MIN_FLEX_MILLIS));
+        return clampedFlex <= interval ? clampedFlex : interval;
     }
 
     /**
@@ -216,6 +232,7 @@
         isPeriodic = in.readInt() == 1;
         isPersisted = in.readInt() == 1;
         intervalMillis = in.readLong();
+        flexMillis = in.readLong();
         initialBackoffMillis = in.readLong();
         backoffPolicy = in.readInt();
         hasEarlyConstraint = in.readInt() == 1;
@@ -234,6 +251,7 @@
         isPeriodic = b.mIsPeriodic;
         isPersisted = b.mIsPersisted;
         intervalMillis = b.mIntervalMillis;
+        flexMillis = b.mFlexMillis;
         initialBackoffMillis = b.mInitialBackoffMillis;
         backoffPolicy = b.mBackoffPolicy;
         hasEarlyConstraint = b.mHasEarlyConstraint;
@@ -258,6 +276,7 @@
         out.writeInt(isPeriodic ? 1 : 0);
         out.writeInt(isPersisted ? 1 : 0);
         out.writeLong(intervalMillis);
+        out.writeLong(flexMillis);
         out.writeLong(initialBackoffMillis);
         out.writeInt(backoffPolicy);
         out.writeInt(hasEarlyConstraint ? 1 : 0);
@@ -299,6 +318,7 @@
         private boolean mHasEarlyConstraint;
         private boolean mHasLateConstraint;
         private long mIntervalMillis;
+        private long mFlexMillis;
         // Back-off parameters.
         private long mInitialBackoffMillis = DEFAULT_INITIAL_BACKOFF_MILLIS;
         private int mBackoffPolicy = DEFAULT_BACKOFF_POLICY;
@@ -373,8 +393,21 @@
          * @param intervalMillis Millisecond interval for which this job will repeat.
          */
         public Builder setPeriodic(long intervalMillis) {
+            return setPeriodic(intervalMillis, intervalMillis);
+        }
+
+        /**
+         * Specify that this job should recur with the provided interval and flex. The job can
+         * execute at any time in a window of flex length at the end of the period.
+         * @param intervalMillis Millisecond interval for which this job will repeat.
+         * @param flexMillis Millisecond flex for this job. Flex is clamped to be at least
+         *                   {@link #MIN_FLEX_MILLIS} or 5 percent of the period, whichever is
+         *                   higher.
+         */
+        public Builder setPeriodic(long intervalMillis, long flexMillis) {
             mIsPeriodic = true;
             mIntervalMillis = intervalMillis;
+            mFlexMillis = flexMillis;
             mHasEarlyConstraint = mHasLateConstraint = true;
             return this;
         }
diff --git a/services/core/java/com/android/server/job/JobSchedulerService.java b/services/core/java/com/android/server/job/JobSchedulerService.java
index 4eabe36..3530d80 100644
--- a/services/core/java/com/android/server/job/JobSchedulerService.java
+++ b/services/core/java/com/android/server/job/JobSchedulerService.java
@@ -613,9 +613,10 @@
         if (periodicToReschedule.hasDeadlineConstraint()) {
             runEarly = Math.max(periodicToReschedule.getLatestRunTimeElapsed() - elapsedNow, 0L);
         }
-        long newEarliestRunTimeElapsed = elapsedNow + runEarly;
+        long flex = periodicToReschedule.getJob().getFlexMillis();
         long period = periodicToReschedule.getJob().getIntervalMillis();
-        long newLatestRuntimeElapsed = newEarliestRunTimeElapsed + period;
+        long newLatestRuntimeElapsed = elapsedNow + runEarly + period;
+        long newEarliestRunTimeElapsed = newLatestRuntimeElapsed - flex;
 
         if (DEBUG) {
             Slog.v(TAG, "Rescheduling executed periodic. New execution window [" +
diff --git a/services/core/java/com/android/server/job/JobStore.java b/services/core/java/com/android/server/job/JobStore.java
index 472e8f6..b8aa9dd 100644
--- a/services/core/java/com/android/server/job/JobStore.java
+++ b/services/core/java/com/android/server/job/JobStore.java
@@ -397,6 +397,7 @@
             if (jobStatus.getJob().isPeriodic()) {
                 out.startTag(null, XML_TAG_PERIODIC);
                 out.attribute(null, "period", Long.toString(job.getIntervalMillis()));
+                out.attribute(null, "flex", Long.toString(job.getFlexMillis()));
             } else {
                 out.startTag(null, XML_TAG_ONEOFF);
             }
@@ -594,13 +595,17 @@
                     String val = parser.getAttributeValue(null, "period");
                     final long periodMillis = Long.valueOf(val);
                     jobBuilder.setPeriodic(periodMillis);
-                    // As a sanity check, cap the recreated run time to be no later than 2 periods
+                    val = parser.getAttributeValue(null, "flex");
+                    final long flexMillis = (val != null) ? Long.valueOf(val) : periodMillis;
+                    // As a sanity check, cap the recreated run time to be no later than flex+period
                     // from now. This is the latest the periodic could be pushed out. This could
-                    // happen if the periodic ran early (at the start of its period), and then the
+                    // happen if the periodic ran early (at flex time before period), and then the
                     // device rebooted.
-                    if (elapsedRuntimes.second > elapsedNow + 2 * periodMillis) {
-                        final long clampedEarlyRuntimeElapsed = elapsedNow + periodMillis;
-                        final long clampedLateRuntimeElapsed = elapsedNow + 2 * periodMillis;
+                    if (elapsedRuntimes.second > elapsedNow + periodMillis + flexMillis) {
+                        final long clampedLateRuntimeElapsed = elapsedNow + flexMillis
+                                + periodMillis;
+                        final long clampedEarlyRuntimeElapsed = clampedLateRuntimeElapsed
+                                - flexMillis;
                         Slog.w(TAG,
                                 String.format("Periodic job for uid='%d' persisted run-time is" +
                                                 " too big [%s, %s]. Clamping to [%s,%s]",
diff --git a/services/core/java/com/android/server/job/controllers/JobStatus.java b/services/core/java/com/android/server/job/controllers/JobStatus.java
index c02611f..060a93e 100644
--- a/services/core/java/com/android/server/job/controllers/JobStatus.java
+++ b/services/core/java/com/android/server/job/controllers/JobStatus.java
@@ -96,8 +96,8 @@
         final long elapsedNow = SystemClock.elapsedRealtime();
 
         if (job.isPeriodic()) {
-            earliestRunTimeElapsedMillis = elapsedNow;
             latestRunTimeElapsedMillis = elapsedNow + job.getIntervalMillis();
+            earliestRunTimeElapsedMillis = latestRunTimeElapsedMillis - job.getFlexMillis();
         } else {
             earliestRunTimeElapsedMillis = job.hasEarlyConstraint() ?
                     elapsedNow + job.getMinLatencyMillis() : NO_EARLIEST_RUNTIME;