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zaharidichevadleong
zaharidichev
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adleong
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Remove ZK candidate dep (linkerd#2361)
The artifact for com.twitter.common.zookeeper" % "candidate" % "0.0.84" on maven.twttr.com is not present anymore. Therefore we need to cpy the bits that we use from it and have it in our sourcecode. Fixes linkerd#2360 Signed-off-by: Zahari Dichev <[email protected]>
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‎namer/zk-leader/src/main/java/com/twitter/common/zookeeper/Candidate.java‎

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// =================================================================================================
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// Copyright 2011 Twitter, Inc.
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// -------------------------------------------------------------------------------------------------
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this work except in compliance with the License.
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// You may obtain a copy of the License in the LICENSE file, or at:
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// =================================================================================================
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package com.twitter.common.zookeeper;
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import com.google.common.base.Optional;
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import com.google.common.base.Supplier;
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import com.twitter.finagle.common.zookeeper.Group.JoinException;
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import com.twitter.finagle.common.zookeeper.Group.WatchException;
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import com.twitter.finagle.common.zookeeper.ZooKeeperClient.ZooKeeperConnectionException;
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import org.apache.zookeeper.KeeperException;
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/**
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* Interface definition for becoming or querying for a ZooKeeper-based group leader.
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*/
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public interface Candidate {
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/**
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* Returns the current group leader by querying ZooKeeper synchronously.
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*
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* @return the current group leader's identifying data or {@link Optional#absent()} if there is
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* no leader
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* @throws ZooKeeperConnectionException if there was a problem connecting to ZooKeeper
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* @throws KeeperException if there was a problem reading the leader information
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* @throws InterruptedException if this thread is interrupted getting the leader
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*/
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public Optional<byte[]> getLeaderData()
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throws ZooKeeperConnectionException, KeeperException, InterruptedException;
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/**
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* Encapsulates a leader that can be elected and subsequently defeated.
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*/
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interface Leader {
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/**
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* Called when this leader has been elected.
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*
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* @param abdicate a command that can be used to abdicate leadership and force a new election
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*/
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void onElected(ExceptionalCommand<JoinException> abdicate);
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/**
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* Called when the leader has been ousted. Can occur either if the leader abdicates or if an
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* external event causes the leader to lose its leadership role (session expiration).
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*/
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void onDefeated();
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}
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/**
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* Offers this candidate in leadership elections for as long as the current jvm process is alive.
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* Upon election, the {@code onElected} callback will be executed and a command that can be used
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* to abdicate leadership will be passed in. If the elected leader jvm process dies or the
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* elected leader successfully abdicates then a new leader will be elected. Leaders that
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* successfully abdicate are removed from the group and will not be eligible for leadership
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* election unless {@link #offerLeadership(Leader)} is called again.
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*
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* @param leader the leader to notify of election and defeat events
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* @throws JoinException if there was a problem joining the group
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* @throws WatchException if there is a problem generating the 1st group membership list
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* @throws InterruptedException if interrupted waiting to join the group and determine initial
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* election results
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* @return a supplier that can be queried to find out if this leader is currently elected
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*/
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public Supplier<Boolean> offerLeadership(Leader leader)
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throws JoinException, WatchException, InterruptedException;
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}

‎namer/zk-leader/src/main/java/com/twitter/common/zookeeper/CandidateImpl.java‎

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// =================================================================================================
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// Copyright 2011 Twitter, Inc.
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// -------------------------------------------------------------------------------------------------
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this work except in compliance with the License.
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// You may obtain a copy of the License in the LICENSE file, or at:
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// =================================================================================================
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package com.twitter.common.zookeeper;
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import java.net.InetAddress;
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import java.net.UnknownHostException;
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import java.util.concurrent.atomic.AtomicBoolean;
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import java.util.logging.Level;
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import java.util.logging.Logger;
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import javax.annotation.Nullable;
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import com.google.common.base.Charsets;
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import com.google.common.base.Function;
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import com.google.common.base.Optional;
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import com.google.common.base.Preconditions;
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import com.google.common.base.Supplier;
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import com.google.common.collect.Iterables;
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import com.google.common.collect.Ordering;
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import org.apache.zookeeper.KeeperException;
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import com.twitter.finagle.common.zookeeper.Group;
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import com.twitter.finagle.common.zookeeper.Group.JoinException;
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import com.twitter.finagle.common.zookeeper.Group.GroupChangeListener;
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import com.twitter.finagle.common.zookeeper.Group.Membership;
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import com.twitter.finagle.common.zookeeper.Group.WatchException;
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import com.twitter.finagle.common.zookeeper.ZooKeeperClient.ZooKeeperConnectionException;
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/**
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* Implements leader election for small groups of candidates. This implementation is subject to the
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* <a href="http://hadoop.apache.org/zookeeper/docs/r3.2.1/recipes.html#sc_leaderElection">
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* herd effect</a> for a given group and should only be used for small (~10 member) candidate pools.
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*/
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public class CandidateImpl implements Candidate {
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private static final Logger LOG = Logger.getLogger(CandidateImpl.class.getName());
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private static final byte[] UNKNOWN_CANDIDATE_DATA = "<unknown>".getBytes(Charsets.UTF_8);
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private static final Supplier<byte[]> IP_ADDRESS_DATA_SUPPLIER = new Supplier<byte[]>() {
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@Override public byte[] get() {
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try {
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return InetAddress.getLocalHost().getHostAddress().getBytes();
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} catch (UnknownHostException e) {
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LOG.log(Level.WARNING, "Failed to determine local address!", e);
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return UNKNOWN_CANDIDATE_DATA;
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}
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}
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};
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private static final Function<Iterable<String>, String> MOST_RECENT_JUDGE =
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new Function<Iterable<String>, String>() {
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@Override public String apply(Iterable<String> candidates) {
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return Ordering.natural().min(candidates);
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}
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};
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private final Group group;
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private final Function<Iterable<String>, String> judge;
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private final Supplier<byte[]> dataSupplier;
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/**
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* Equivalent to {@link #CandidateImpl(Group, com.google.common.base.Function, Supplier)} using a
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* judge that always picks the lowest numbered candidate ephemeral node - by proxy the oldest or
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* 1st candidate and a default supplier that provides the ip address of this host according to
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* {@link java.net.InetAddress#getLocalHost()} as the leader identifying data.
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*/
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public CandidateImpl(Group group) {
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this(group, MOST_RECENT_JUDGE, IP_ADDRESS_DATA_SUPPLIER);
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}
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/**
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* Creates a candidate that can be used to offer leadership for the given {@code group} using
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* a judge that always picks the lowest numbered candidate ephemeral node - by proxy the oldest
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* or 1st. The dataSupplier should produce bytes that identify this process as leader. These bytes
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* will become available to all participants via the {@link Candidate#getLeaderData()} method.
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*/
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public CandidateImpl(Group group, Supplier<byte[]> dataSupplier) {
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this(group, MOST_RECENT_JUDGE, dataSupplier);
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}
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/**
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* Creates a candidate that can be used to offer leadership for the given {@code group}. The
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* {@code judge} is used to pick the current leader from all group members whenever the group
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* membership changes. To form a well-behaved election group with one leader, all candidates
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* should use the same judge. The dataSupplier should produce bytes that identify this process
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* as leader. These bytes will become available to all participants via the
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* {@link Candidate#getLeaderData()} method.
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*/
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public CandidateImpl(
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Group group,
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Function<Iterable<String>, String> judge,
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Supplier<byte[]> dataSupplier) {
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this.group = Preconditions.checkNotNull(group);
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this.judge = Preconditions.checkNotNull(judge);
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this.dataSupplier = Preconditions.checkNotNull(dataSupplier);
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}
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@Override
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public Optional<byte[]> getLeaderData()
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throws ZooKeeperConnectionException, KeeperException, InterruptedException {
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String leaderId = getLeader(group.getMemberIds());
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return leaderId == null
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? Optional.<byte[]>absent()
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: Optional.of(group.getMemberData(leaderId));
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}
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@Override
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public Supplier<Boolean> offerLeadership(final Leader leader)
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throws JoinException, WatchException, InterruptedException {
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final Membership membership = group.join(dataSupplier, () -> leader.onDefeated());
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final AtomicBoolean elected = new AtomicBoolean(false);
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final AtomicBoolean abdicated = new AtomicBoolean(false);
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group.watch(new GroupChangeListener() {
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@Override public void onGroupChange(Iterable<String> memberIds) {
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boolean noCandidates = Iterables.isEmpty(memberIds);
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String memberId = membership.getMemberId();
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if (noCandidates) {
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LOG.warning("All candidates have temporarily left the group: " + group);
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} else if (!Iterables.contains(memberIds, memberId)) {
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LOG.severe(String.format(
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"Current member ID %s is not a candidate for leader, current voting: %s",
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memberId, memberIds));
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} else {
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boolean electedLeader = memberId.equals(getLeader(memberIds));
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boolean previouslyElected = elected.getAndSet(electedLeader);
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if (!previouslyElected && electedLeader) {
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LOG.info(String.format("Candidate %s is now leader of group: %s",
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membership.getMemberPath(), memberIds));
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leader.onElected(new ExceptionalCommand<JoinException>() {
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@Override public void execute() throws JoinException {
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membership.cancel();
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abdicated.set(true);
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}
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});
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} else if (!electedLeader) {
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if (previouslyElected) {
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leader.onDefeated();
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}
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LOG.info(String.format(
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"Candidate %s waiting for the next leader election, current voting: %s",
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membership.getMemberPath(), memberIds));
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}
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}
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}
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});
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return new Supplier<Boolean>() {
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@Override public Boolean get() {
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return !abdicated.get() && elected.get();
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}
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};
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}
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@Nullable
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private String getLeader(Iterable<String> memberIds) {
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return Iterables.isEmpty(memberIds) ? null : judge.apply(memberIds);
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}
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}

‎namer/zk-leader/src/main/java/com/twitter/common/zookeeper/ExceptionalCommand.java‎

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// =================================================================================================
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// Copyright 2011 Twitter, Inc.
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// -------------------------------------------------------------------------------------------------
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this work except in compliance with the License.
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// You may obtain a copy of the License in the LICENSE file, or at:
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// =================================================================================================
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package com.twitter.common.zookeeper;
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/**
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* An interface that captures a unit of work.
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*
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* @param <E> The type of exception that the command throws.
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*
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* @author John Sirois
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*/
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public interface ExceptionalCommand<E extends Exception> {
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/**
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* Performs a unit of work, possibly throwing {@code E} in the process.
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*
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* @throws E if there was a problem performing the work
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*/
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void execute() throws E;
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}

‎namer/zk-leader/src/main/scala/io/buoyant/namer/zk/ZkLeaderNamer.scala‎

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package io.buoyant.namer.zk
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import com.twitter.common.zookeeper.Group.GroupChangeListener
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import com.twitter.common.zookeeper._
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import com.twitter.finagle.util.InetSocketAddressUtil
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import com.twitter.finagle.{Group => _, _}
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import com.twitter.util._
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import io.buoyant.config.types.HostAndPort
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import java.net.InetSocketAddress
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import com.twitter.common.zookeeper.{Candidate, CandidateImpl}
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import com.twitter.finagle.common.zookeeper.Group.GroupChangeListener
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import com.twitter.finagle.common.zookeeper.{Group, ZooKeeperClient, ZooKeeperUtils}
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import org.apache.zookeeper.KeeperException.NoNodeException
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import org.apache.zookeeper.data.ACL
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import scala.collection.JavaConverters._
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/**
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)
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Closable.make { _ =>
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stop.execute()
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stop.run()
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Future.Unit
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}
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}

‎project/Deps.scala‎

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def twitterUtil(mod: String) =
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"com.twitter" %% s"util-$mod" % "19.5.1"
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// networking
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def finagle(mod: String) =
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"com.twitter" %% s"finagle-$mod" % "19.5.1"
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val boringssl = "io.netty" % "netty-tcnative-boringssl-static" % "2.0.19.Final"
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def zkCandidate =
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("com.twitter.common.zookeeper" % "candidate" % "0.0.84")
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.exclude("com.twitter.common", "util")
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// Jackson (parsing)
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val jacksonVersion = "2.9.6"
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val jacksonCore =

‎project/LinkerdBuild.scala‎

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val zkLeader = projectDir("namer/zk-leader")
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.dependsOn(core)
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.withLib(Deps.zkCandidate)
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.withTwitterLib(Deps.finagle("serversets").exclude("org.slf4j", "slf4j-jdk14"))
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.withTests()
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val rancher = projectDir("namer/rancher")

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