Github user aledsage commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/879#discussion_r149341592
--- Diff:
policy/src/main/java/org/apache/brooklyn/policy/ha/ElectPrimaryEffector.java ---
@@ -0,0 +1,440 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.brooklyn.policy.ha;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Callable;
+
+import org.apache.brooklyn.api.effector.Effector;
+import org.apache.brooklyn.api.entity.Entity;
+import org.apache.brooklyn.api.entity.EntityInitializer;
+import org.apache.brooklyn.api.entity.Group;
+import org.apache.brooklyn.api.mgmt.Task;
+import org.apache.brooklyn.core.config.ConfigKeys;
+import org.apache.brooklyn.core.effector.EffectorBody;
+import
org.apache.brooklyn.core.effector.EffectorTasks.EffectorBodyTaskFactory;
+import org.apache.brooklyn.core.effector.Effectors;
+import org.apache.brooklyn.core.entity.Attributes;
+import org.apache.brooklyn.core.entity.Entities;
+import org.apache.brooklyn.core.entity.EntityInternal;
+import org.apache.brooklyn.core.entity.lifecycle.Lifecycle;
+import org.apache.brooklyn.core.entity.lifecycle.ServiceStateLogic;
+import
org.apache.brooklyn.core.entity.lifecycle.ServiceStateLogic.ServiceProblemsLogic;
+import org.apache.brooklyn.core.sensor.Sensors;
+import org.apache.brooklyn.util.collections.MutableList;
+import org.apache.brooklyn.util.collections.MutableMap;
+import org.apache.brooklyn.util.core.config.ConfigBag;
+import org.apache.brooklyn.util.core.task.DynamicTasks;
+import org.apache.brooklyn.util.core.task.Tasks;
+import org.apache.brooklyn.util.exceptions.Exceptions;
+import org.apache.brooklyn.util.exceptions.UserFacingException;
+import org.apache.brooklyn.util.time.Duration;
+import org.apache.brooklyn.util.time.Time;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.Stopwatch;
+import com.google.common.collect.Iterables;
+
+/**
+This effector will scan candidates among children or members to determine
which should be noted as "primary".
+The primary is selected from service-up candidates based on a numeric
weight as a sensor or config on the candidates
+(`ha.primary.weight`, unless overridden), with higher weights being
preferred.
+In the case of ties, or a new candidate emerging with a weight higher than
a current healthy primary,
+behaviour can be configured with `primary.selection.mode`.
+
+Returns a map containing a message, newPrimary, oldPrimary, and a {@link
ResultCode} code.
+*/
+public class ElectPrimaryEffector implements EntityInitializer,
ElectPrimaryConfig {
+
+ private static final Logger log =
LoggerFactory.getLogger(ElectPrimaryEffector.class);
+
+ public static enum ResultCode { PRIMARY_UNCHANGED,
NEW_PRIMARY_ELECTED, NO_PRIMARY_AVAILABLE }
+
+ public static final Effector<Object> EFFECTOR =
Effectors.effector(Object.class, "electPrimary").
+ description("Scan to detect whether there is or should be a new
primary").buildAbstract();
+
+ private final ConfigBag paramsCreationTime;
+
+ public ElectPrimaryEffector(ConfigBag params) {
+ this.paramsCreationTime = params;
+ }
+
+ public ElectPrimaryEffector(Map<String,String> params) {
+ this(ConfigBag.newInstance(params));
+ }
+
+
+ // wire up the entity to call the task factory to create the task on
invocation
+
+ @Override
+ public void apply(@SuppressWarnings("deprecation")
org.apache.brooklyn.api.entity.EntityLocal entity) {
+
((EntityInternal)entity).getMutableEntityType().addEffector(makeEffector(paramsCreationTime));
+ }
+
+ public static Effector<Object> makeEffector(ConfigBag params) {
+ return Effectors.effector(EFFECTOR).impl(new
EffectorBodyTaskFactory<Object>(new ElectPrimaryEffectorBody(params))).build();
+ }
+
+ protected static class ElectPrimaryEffectorBody extends
EffectorBody<Object> {
+ private final ConfigBag paramsCreationTime;
+
+ public ElectPrimaryEffectorBody(ConfigBag paramsCreationTime) {
+ this.paramsCreationTime = paramsCreationTime;
+ }
+
+ // these are the actual tasks we do
+
+ @Override
+ public Object call(ConfigBag paramsInvocationTime) {
+ ConfigBag params =
ConfigBag.newInstanceCopying(paramsCreationTime).copy(paramsInvocationTime);
+
+ try {
+ Entity newPrimary = DynamicTasks.queue("check primaries",
new CheckPrimaries(params)).getUnchecked();
+
+ Entity currentActive = getCurrentActive(params);
+ if (newPrimary==null) {
+// If no primary can be found, the effector will:
+// * add a "primary-election" problem so that
service state logic, if applicable, will know that the entity is unhealthy
+// * set service up false
+// * if the local entity is expected to be RUNNING,
it will set actual state to ON_FIRE
+// * if the local entity has no expectation, it
will set actual state to STOPPED
+// * demote any old primary
+ ServiceProblemsLogic.updateProblemsIndicator(entity(),
"primary", "No primary could be found");
+ entity().sensors().set(Sensors.newSensor(Entity.class,
params.get(PRIMARY_SENSOR_NAME)), null);
+ entity().sensors().set(Attributes.SERVICE_UP, false);
+ if (Lifecycle.RUNNING.equals(
entity().getAttribute(Attributes.SERVICE_STATE_EXPECTED) )) {
+
entity().sensors().set(Attributes.SERVICE_STATE_ACTUAL, Lifecycle.ON_FIRE);
+ } else {
+
entity().sensors().set(Attributes.SERVICE_STATE_ACTUAL, Lifecycle.STOPPED);
+ }
+ DynamicTasks.queue(Tasks.create("demote
"+currentActive, new Demote(params)) ).getUnchecked();
+ return MutableMap.of("code",
ResultCode.NO_PRIMARY_AVAILABLE, "message", "No primary available", "primary",
null);
+ }
+
+ if (newPrimary.equals(currentActive)) {
+ // If there is a primary and it is unchanged, the
effector will end.
+ return MutableMap.of("code",
ResultCode.PRIMARY_UNCHANGED, "message", "No change required", "primary",
newPrimary);
+ }
+
+ log.info("Detected new primary "+newPrimary+" at
"+entity()+" (previously had "+currentActive+")");
+// If a new primary is detected, the effector will:
+// * set the local entity to the STARTING state
+// * clear any "primary-election" problem
+// * publish the new primary in a sensor called
`primary` (or the sensor set in `primary.sensor.name`)
+// * cancel any other ongoing promote calls, and if
there is an ongoing demote call on the entity being promoted, cancel that also
+// * in parallel
+// * invoke `promote` (or the effector called
`primary.promote.effector.name`) on the local entity or the entity being
promoted
+// * invoke `demote` (or the effector called
`primary.promote.effector.name`) on the local entity or the entity being
demoted, if an entity is being demoted
+// * set service up true
+// * set the local entity to the RUNNING state
+
+ boolean wasRunning =
entity().sensors().get(Attributes.SERVICE_STATE_ACTUAL) == Lifecycle.RUNNING;
+ if (wasRunning) {
+ log.debug("Transititioning "+entity()+" to starting
while promoting/demoting");
+ ServiceStateLogic.setExpectedState(entity(),
Lifecycle.STARTING);
+ }
+ ServiceProblemsLogic.clearProblemsIndicator(entity(),
"primary");
+ entity().sensors().set(Sensors.newSensor(Entity.class,
params.get(PRIMARY_SENSOR_NAME)), newPrimary);
--- End diff --
I lean towards not just re-setting the "primary" sensor like this, when we
don't know if `promoteAndDemote` is going to work. e.g. the catch block will
not change the sensor's value if that has failed.
Perhaps we should have another sensor that shows the active transition
(saying oldPrimary -> newPrimary). Then if it goes wrong, someone can look at
the sensors to get an idea of what state the system is in.
---
If Brooklyn server is shutdown while executing this, the thread executing
`promoteAndDemote` will be interrupted. The catch block will do the
`propagateIfFatal` so we'll leave the sensors in a state that looks quite like
promotion has completed successfully, except the expectedState is still
starting.
I think that's another good argument for giving more indication of what
it's doing in a "transition" sensor.
---
