Two fixes regarding meter handling

First, while deleting an eapol flow, do not create a meter as a
side-effect of a lookup failure.
Second, do not remove bpInfo to Meter mapping when removing default eapol
flow, as other ONUs are still using it and new ones can reuse it instead
of creating duplicate meters.

Change-Id: I6d62b24b4d4f6e27eba28c35bab7c5a2f5144aa9
(cherry picked from commit 80b6b6c21c5e2f87da07d10df3d5a8faf99990fe)
diff --git a/app/src/main/java/org/opencord/olt/impl/Olt.java b/app/src/main/java/org/opencord/olt/impl/Olt.java
index 326767f..60d9feb 100644
--- a/app/src/main/java/org/opencord/olt/impl/Olt.java
+++ b/app/src/main/java/org/opencord/olt/impl/Olt.java
@@ -366,7 +366,12 @@
         CompletableFuture<ObjectiveError> filterFuture = new CompletableFuture();
         processEapolFilteringObjectives(deviceId, subscriberPortNo, defaultBpId, filterFuture,
                 VlanId.vlanId(EAPOL_DEFAULT_VLAN), false);
-        removeMeterIdFromBpMapping(deviceId, defaultBpId);
+        // do not remove meter from bpInfoToMeter mapping as flows for other ONUs
+        // could still be using it - this also prevents duplicate meters from being
+        // created for the same bandwidth profile
+        // we still need to remove from programmedMeters so the meter can be
+        // deleted if its reference count drops to zero
+        removeMeterIdFromPrgMeters(deviceId, defaultBpId);
 
         //install subscriber flows
         filterFuture.thenAcceptAsync(filterStatus -> {
@@ -473,7 +478,12 @@
             //wait until Eapol rule with defaultBpId is removed to install subscriber-based rules
             processEapolFilteringObjectives(subsPort.deviceId(), subsPort.port(), defaultBpId, filterFuture,
                     VlanId.vlanId(EAPOL_DEFAULT_VLAN), false);
-            removeMeterIdFromBpMapping(subsPort.deviceId(), defaultBpId);
+            // do not remove meter from bpInfoToMeter mapping as flows for other ONUs
+            // could still be using it - this also prevents duplicate meters from being
+            // created for the same bandwidth profile
+            // we still need to remove from programmedMeters so the meter can be
+            // deleted if its reference count drops to zero
+            removeMeterIdFromPrgMeters(subsPort.deviceId(), defaultBpId);
 
             //install subscriber flows
             filterFuture.thenAcceptAsync(filterStatus -> {
@@ -1205,7 +1215,6 @@
     private void processEapolFilteringObjectives(DeviceId devId, PortNumber portNumber, String bpId,
                                                  CompletableFuture<ObjectiveError> filterFuture,
                                                  VlanId vlanId, boolean install) {
-
         if (!enableEapol) {
             log.debug("Eapol filtering is disabled.");
             if (filterFuture != null) {
@@ -1220,21 +1229,43 @@
         DefaultFilteringObjective.Builder builder = DefaultFilteringObjective.builder();
         TrafficTreatment.Builder treatmentBuilder = DefaultTrafficTreatment.builder();
         CompletableFuture<Object> meterFuture = new CompletableFuture<>();
-        MeterId meterId;
 
         BandwidthProfileInformation bpInfo = getBandwidthProfileInformation(bpId);
-        if (bpInfo != null) {
-            meterId = createMeter(devId, bpInfo, meterFuture);
-            treatmentBuilder.meter(meterId);
-        } else {
-            log.warn("Bandwidth profile {} is not found. Authentication flow will not be installed", bpId);
+        if (bpInfo == null) {
+            log.warn("Bandwidth profile {} is not found. Authentication flow"
+                    + " will not be installed", bpId);
             return;
         }
 
+        // check if meter exists and create it only for an install
+        MeterId meterId = getMeterIdFromBpMapping(devId, bpInfo.id());
+        if (meterId == null) {
+            if (install) {
+                meterId = createMeter(devId, bpInfo, meterFuture);
+                treatmentBuilder.meter(meterId);
+            } else {
+                // this case should not happen as the request to remove an eapol
+                // flow should mean that the flow points to a meter that exists.
+                // Nevertheless we can still delete the flow as we only need the
+                // correct 'match' to do so.
+                log.warn("Unknown meter id for bp {}, still proceeding with "
+                        + "delete of eapol flow for {}/{}", bpInfo.id(), devId,
+                         portNumber);
+                meterFuture.complete(null);
+            }
+        } else {
+            log.debug("Meter {} was previously created for bp {}", meterId,
+                      bpInfo.id());
+            treatmentBuilder.meter(meterId);
+            meterFuture.complete(null);
+        }
+
+        final MeterId mId = meterId;
         meterFuture.thenAcceptAsync(result -> {
             if (result == null) {
-                log.info("Meter {} for the device {} is installed. " +
-                        "{} EAPOL trap flow", meterId, devId, install ? "Installing " : "Removing ");
+                log.info("Meter {} for {} on {}/{} exists. {} EAPOL trap flow",
+                         mId, bpId, devId, portNumber,
+                        (install) ? "Installing " : "Removing ");
                 int techProfileId = getDefaultTechProfileId(devId, portNumber);
 
                 //Authentication trap flow uses only tech profile id as write metadata value
@@ -1251,7 +1282,7 @@
                             @Override
                             public void onSuccess(Objective objective) {
                                 log.info("Eapol filter for {} on {} {} with meter {}.",
-                                        devId, portNumber, (install) ? INSTALLED : REMOVED, meterId);
+                                        devId, portNumber, (install) ? INSTALLED : REMOVED, mId);
                                 if (filterFuture != null) {
                                     filterFuture.complete(null);
                                 }
@@ -1260,7 +1291,7 @@
                             @Override
                             public void onError(Objective objective, ObjectiveError error) {
                                 log.info("Eapol filter for {} on {} with meter {} failed {} because {}",
-                                        devId, portNumber, meterId, (install) ? INSTALLATION : REMOVAL,
+                                        devId, portNumber, mId, (install) ? INSTALLATION : REMOVAL,
                                         error);
                                 if (filterFuture != null) {
                                     filterFuture.complete(error);
@@ -1271,7 +1302,7 @@
                 flowObjectiveService.filter(devId, eapol);
             } else {
                 log.warn("Meter installation error while sending eapol trap flow. " +
-                        "Result {} and MeterId {}", result, meterId);
+                        "Result {} and MeterId {}", result, mId);
             }
         });
     }
@@ -1614,13 +1645,21 @@
         }
     }
 
-    private void removeMeterIdFromBpMapping(DeviceId deviceId, String bandwidthProfileId) {
+    /**
+     * Removes meter key from programmed meters. If the meter has no reference
+     * count in the data plane and is not present in the programmed-meters store
+     * it will be removed.
+     *
+     * @param deviceId device identifier
+     * @param bandwidthProfileId name of bandwidth profile
+     */
+    private void removeMeterIdFromPrgMeters(DeviceId deviceId,
+                                             String bandwidthProfileId) {
         List<MeterKey> meterKeysForBp = bpInfoToMeter.get(bandwidthProfileId);
         if (meterKeysForBp != null) {
             meterKeysForBp.stream()
                     .filter(meterKey -> meterKey.deviceId().equals(deviceId))
                     .findFirst().ifPresent(mk -> {
-                meterKeysForBp.remove(mk);
                 programmedMeters.remove(mk);
             });
         }