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From: sjcorbett <git@git.apache.org>
To: dev@brooklyn.incubator.apache.org
Reply-To: dev@brooklyn.incubator.apache.org
References: <git-pr-263-incubator-brooklyn@git.apache.org>
In-Reply-To: <git-pr-263-incubator-brooklyn@git.apache.org>
Subject: [GitHub] incubator-brooklyn pull request: DNS entity improvements
Content-Type: text/plain
Message-Id: <20141027202109.32D7298423D@tyr.zones.apache.org>
Date: Mon, 27 Oct 2014 20:21:09 +0000 (UTC)

Github user sjcorbett commented on a diff in the pull request:

    https://github.com/apache/incubator-brooklyn/pull/263#discussion_r19434229
  
    --- Diff: software/network/src/main/java/brooklyn/entity/network/bind/BindDnsServerImpl.java ---
    @@ -143,124 +167,133 @@ protected void preStart() {
             String reverseLookupDomain = Joiner.on('.').join(Iterables.skip(Lists.reverse(Lists.newArrayList(Splitter.on('.').split(reverse))), 1)) + ".in-addr.arpa";
             setAttribute(REVERSE_LOOKUP_DOMAIN, reverseLookupDomain);
     
    -        Map<?, ?> flags = MutableMap.builder()
    -                .build();
    -        policy = addPolicy(PolicySpec.create(MemberTrackingPolicy.class)
    +        addPolicy(PolicySpec.create(MemberTrackingPolicy.class)
                     .displayName("Address tracker")
                     .configure("sensorsToTrack", ImmutableSet.of(getConfig(HOSTNAME_SENSOR)))
    -                .configure("group", entities));
    +                .configure("group", getEntities()));
    +    }
     
    -        // For any entities that have already come up
    -        for (Entity member : entities.getMembers()) {
    -            if (Strings.isNonBlank(member.getAttribute(getConfig(HOSTNAME_SENSOR)))) added(member); // Ignore, unless hostname set
    -        }
    +    @Override
    +    public void postStart() {
    +        update();
         }
     
         public static class MemberTrackingPolicy extends AbstractMembershipTrackingPolicy {
             @Override
             protected void onEntityChange(Entity member) {
    -            // TODO Should we guard to only call if service_up and if hostname set?
    -            ((BindDnsServerImpl)entity).added(member);
    +            if (LOG.isTraceEnabled()) {
    +                LOG.trace("State of {} on change: {}", member, member.getAttribute(Attributes.SERVICE_STATE_ACTUAL).name());
    +            }
    +            ((BindDnsServerImpl) entity).update();
             }
             @Override
             protected void onEntityAdded(Entity member) {
    -            if (Strings.isNonBlank(member.getAttribute(getConfig(HOSTNAME_SENSOR)))) {
    -                ((BindDnsServerImpl)entity).added(member); // Ignore, unless hostname set
    +            if (LOG.isTraceEnabled()) {
    +                LOG.trace("State of {} on added: {}", member, member.getAttribute(Attributes.SERVICE_STATE_ACTUAL).name());
                 }
    -        }
    -        @Override
    -        protected void onEntityRemoved(Entity member) {
    -            ((BindDnsServerImpl)entity).removed(member);
    +            ((BindDnsServerImpl) entity).configureResolver(member);
             }
         }
     
    -    @Override
    -    public void postStart() {
    -        update();
    +    private class HasHostnameAndValidLifecycle implements Predicate<Entity> {
    +        @Override
    +        public boolean apply(Entity input) {
    +            switch (input.getAttribute(Attributes.SERVICE_STATE_ACTUAL)) {
    +            case STOPPED:
    +            case STOPPING:
    +            case DESTROYED:
    +                return false;
    +            }
    +            return input.getAttribute(getConfig(HOSTNAME_SENSOR)) != null;
    +        }
         }
     
    -    public void added(Entity member) {
    -        synchronized (mutex) {
    -            Optional<Location> location = Iterables.tryFind(member.getLocations(), Predicates.instanceOf(SshMachineLocation.class));
    -            String hostname = member.getAttribute(getConfig(HOSTNAME_SENSOR));
    -            if (location.isPresent() && Strings.isNonBlank(hostname)) {
    -                SshMachineLocation machine = (SshMachineLocation) location.get();
    -                String address = machine.getAddress().getHostAddress();
    -                if (!entityLocations.containsKey(machine)) {
    -                    entityLocations.put(machine, member);
    -                    addressMappings.putIfAbsent(address, hostname);
    +    public void update() {
    +        Lifecycle serverState = getAttribute(Attributes.SERVICE_STATE_ACTUAL);
    +        if (Lifecycle.STOPPED.equals(serverState) || Lifecycle.STOPPING.equals(serverState)
    +                || Lifecycle.DESTROYED.equals(serverState) || !getAttribute(Attributes.SERVICE_UP)) {
    +            LOG.debug("Skipped update of {} when service state is {} and running is {}",
    +                    new Object[]{this, getAttribute(Attributes.SERVICE_STATE_ACTUAL), getAttribute(SERVICE_UP)});
    +            return;
    +        }
    +        synchronized (this) {
    --- End diff --
    
    Why do you think it is better to synchronise on an explicit Object?
    
    I'm not really comfortable enough with Brooklyn's concurrency model to know for sure that `update` won't be called concurrently. If `MemberTrackingPolicy.onEntityChange` is guaranteed to be called synchronously then we should be able to drop the `synchronized` statement.


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