Add support for consul shared configuration

exhibitor-core/pom.xml

@@ -94,6 +94,11 @@
             <artifactId>jersey-json</artifactId>
         </dependency>
 
+        <dependency>
+            <groupId>com.orbitz.consul</groupId>
+            <artifactId>consul-client</artifactId>
+        </dependency>
+
         <dependency>
             <groupId>org.apache.curator</groupId>
             <artifactId>curator-test</artifactId>
@@ -111,5 +116,11 @@
             <artifactId>testng</artifactId>
             <scope>test</scope>
         </dependency>
+
+        <dependency>
+            <groupId>com.pszymczyk.consul</groupId>
+            <artifactId>embedded-consul</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

exhibitor-core/src/main/java/com/netflix/exhibitor/core/config/consul/ConsulConfigProvider.java

@@ -0,0 +1,128 @@
+package com.netflix.exhibitor.core.config.consul;
+
+import com.netflix.exhibitor.core.config.*;
+import com.orbitz.consul.Consul;
+import com.orbitz.consul.KeyValueClient;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.util.Properties;
+import java.util.concurrent.TimeUnit;
+
+public class ConsulConfigProvider implements ConfigProvider {
+    private static final Long DEFAULT_LOCK_TIMEOUT_MS = 5L * 60L * 1000L;  // 5 minutes;
+    private final Consul consul;
+    private final Properties defaults;
+    private final String basePath;
+    private final String versionPath;
+    private final String propertiesPath;
+    private final ConsulKvLock lock;
+    private final String pseudoLockPath;
+    private final Long lockTimeoutMs;
+
+    /**
+     * @param consul consul client instance for connecting to consul cluster
+     * @param prefix consul key-value path under which configs are stored
+     * @param defaults default properties
+     */
+    public ConsulConfigProvider(Consul consul, String prefix, Properties defaults) {
+        this(consul, prefix, defaults, DEFAULT_LOCK_TIMEOUT_MS);
+    }
+
+    /**
+     * @param consul consul client instance for connecting to consul cluster
+     * @param prefix consul key-value path under which configs are stored
+     * @param defaults default properties
+     * @param lockTimeoutMs timeout, in milliseconds, for lock acquisition
+     */
+    public ConsulConfigProvider(Consul consul, String prefix, Properties defaults, Long lockTimeoutMs) {
+        this.consul = consul;
+        this.defaults = defaults;
+        this.lockTimeoutMs = lockTimeoutMs;
+
+        this.basePath = prefix.endsWith("/") ? prefix : prefix + "/";
+        this.versionPath = basePath + "version";
+        this.propertiesPath = basePath + "properties";
+        this.pseudoLockPath = basePath + "pseudo-locks";
+
+        this.lock = new ConsulKvLock(consul, basePath + "lock", "exhibitor");
+    }
+
+    @Override
+    public void start() throws Exception {
+        // NOP
+    }
+
+    @Override
+    public void close() throws IOException {
+        // NOP
+    }
+
+    @Override
+    public LoadedInstanceConfig loadConfig() throws Exception {
+        ConsulVersionedProperties properties;
+
+        lock.acquireLock(lockTimeoutMs, TimeUnit.MILLISECONDS);
+        try {
+            properties = loadProperties();
+        }
+        finally {
+            lock.releaseLock();
+        }
+
+        PropertyBasedInstanceConfig config = new PropertyBasedInstanceConfig(
+                properties.getProperties(), defaults);
+        return new LoadedInstanceConfig(config, properties.getVersion());
+    }
+
+    @Override
+    public LoadedInstanceConfig storeConfig(ConfigCollection config, long compareVersion) throws Exception {
+        Long currentVersion = loadProperties().getVersion();
+        if (currentVersion != compareVersion) {
+            return null;
+        }
+
+        KeyValueClient kv = consul.keyValueClient();
+        PropertyBasedInstanceConfig instanceConfig = new PropertyBasedInstanceConfig(config);
+        StringWriter writer = new StringWriter();
+        instanceConfig.getProperties().store(writer, "Auto-generated by Exhibitor");
+
+        lock.acquireLock(lockTimeoutMs, TimeUnit.MILLISECONDS);
+        try {
+            kv.putValue(propertiesPath, writer.toString());
+            kv.putValue(versionPath, String.valueOf(currentVersion + 1));
+        }
+        finally {
+            lock.releaseLock();
+        }
+
+        return new LoadedInstanceConfig(instanceConfig, currentVersion + 1);
+    }
+
+    @Override
+    public PseudoLock newPseudoLock() throws Exception {
+        return new ConsulPseudoLock(consul, pseudoLockPath);
+    }
+
+    private String getString(String path) {
+        return consul.keyValueClient().getValueAsString(path).orNull();
+    }
+
+    private Long getLong(String path) {
+        return Long.valueOf(consul.keyValueClient().getValueAsString(path).or("0"));
+    }
+
+    private ConsulVersionedProperties loadProperties() throws Exception {
+        Long version = getLong(versionPath);
+
+        Properties properties = new Properties();
+        String rawProperties = getString(propertiesPath);
+        if (rawProperties != null) {
+            StringReader reader = new StringReader(getString(propertiesPath));
+            properties.load(reader);
+        }
+
+        return new ConsulVersionedProperties(properties, version);
+    }
+}

exhibitor-core/src/main/java/com/netflix/exhibitor/core/config/consul/ConsulKvLock.java

@@ -0,0 +1,92 @@
+package com.netflix.exhibitor.core.config.consul;
+
+import com.google.common.base.Optional;
+import com.orbitz.consul.Consul;
+import com.orbitz.consul.KeyValueClient;
+import com.orbitz.consul.model.kv.Value;
+import com.orbitz.consul.model.session.ImmutableSession;
+import com.orbitz.consul.option.QueryOptions;
+
+import java.math.BigInteger;
+import java.util.concurrent.TimeUnit;
+
+public class ConsulKvLock {
+    private final Consul consul;
+    private final String path;
+    private final String name;
+    private final String ttl;
+    private String sessionId;
+
+    /**
+     * @param consul consul client instance for connecting to consul cluster
+     * @param path consul key-value path to lock
+     * @param name a descriptive name for the lock
+     * @param ttl TTL, in seconds, for the consul session underpinning the lock
+     */
+    public ConsulKvLock(Consul consul, String path, String name, Integer ttl) {
+        this.consul = consul;
+        this.path = path;
+        this.name = name;
+        this.ttl = ttl != null ? String.format("%ds", ttl) : null;
+        this.sessionId = null;
+    }
+
+    /**
+     * @param consul consul client instance for connecting to consul cluster
+     * @param path consul key-value path to lock
+     * @param name a descriptive name for the lock
+     */
+    public ConsulKvLock(Consul consul, String path, String name) {
+        this(consul, path, name, 60);
+    }
+
+    private String createSession() {
+        final ImmutableSession session = ImmutableSession.builder()
+                .name(name)
+                .ttl(Optional.fromNullable(ttl))
+                .build();
+        return consul.sessionClient().createSession(session).getId();
+    }
+
+    private void destroySession() {
+        consul.sessionClient().destroySession(sessionId);
+        sessionId = null;
+    }
+
+    public boolean acquireLock(long maxWait, TimeUnit unit) {
+        KeyValueClient kv = consul.keyValueClient();
+        sessionId = createSession();
+
+        Optional<Value> value = kv.getValue(path);
+
+        if (kv.acquireLock(path, sessionId)) {
+            return true;
+        }
+
+        BigInteger index = BigInteger.valueOf(value.get().getModifyIndex());
+        kv.getValue(path, QueryOptions.blockMinutes((int) unit.toMinutes(maxWait), index).build());
+
+        if (!kv.acquireLock(path, sessionId)) {
+            destroySession();
+            return false;
+        } else {
+            return true;
+        }
+    }
+
+    public void releaseLock() {
+        try {
+            KeyValueClient kv = consul.keyValueClient();
+            Optional<Value> value = kv.getValue(path);
+
+            if (value.isPresent()) {
+                Optional<String> session = value.get().getSession();
+                if (session.isPresent()) {
+                    kv.releaseLock(path, session.get());
+                }
+            }
+        } finally {
+            destroySession();
+        }
+    }
+}

exhibitor-core/src/main/java/com/netflix/exhibitor/core/config/consul/ConsulPseudoLock.java

@@ -0,0 +1,33 @@
+package com.netflix.exhibitor.core.config.consul;
+
+import com.netflix.exhibitor.core.activity.ActivityLog;
+import com.netflix.exhibitor.core.config.PseudoLock;
+import com.orbitz.consul.Consul;
+
+import java.util.concurrent.TimeUnit;
+
+public class ConsulPseudoLock implements PseudoLock {
+
+    private final ConsulKvLock lock;
+
+    public ConsulPseudoLock(Consul consul, String prefix) {
+        String path = prefix.endsWith("/") ? prefix + "pseudo-lock" : prefix + "/pseudo-lock";
+        this.lock = new ConsulKvLock(consul, path, "pseudo-lock");
+    }
+
+    @Override
+    public boolean lock(ActivityLog log, long maxWait, TimeUnit unit) throws Exception {
+        if (!lock.acquireLock(maxWait, unit)) {
+            log.add(ActivityLog.Type.ERROR,
+                    String.format("Could not acquire lock within %d ms", unit.toMillis(maxWait)));
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public void unlock() throws Exception {
+        lock.releaseLock();
+    }
+}

exhibitor-core/src/main/java/com/netflix/exhibitor/core/config/consul/ConsulVersionedProperties.java

@@ -0,0 +1,21 @@
+package com.netflix.exhibitor.core.config.consul;
+
+import java.util.Properties;
+
+public class ConsulVersionedProperties {
+    private final Properties properties;
+    private final Long version;
+
+    public ConsulVersionedProperties(Properties properties, Long version) {
+        this.properties = properties;
+        this.version = version;
+    }
+
+    public Properties getProperties() {
+        return properties;
+    }
+
+    public Long getVersion() {
+        return version;
+    }
+}

exhibitor-core/src/test/java/com/netflix/exhibitor/core/config/consul/TestConsulConfigProvider.java

@@ -0,0 +1,70 @@
+package com.netflix.exhibitor.core.config.consul;
+
+import com.google.common.net.HostAndPort;
+import com.netflix.exhibitor.core.config.LoadedInstanceConfig;
+import com.netflix.exhibitor.core.config.PropertyBasedInstanceConfig;
+import com.netflix.exhibitor.core.config.StringConfigs;
+import com.orbitz.consul.Consul;
+import com.orbitz.consul.model.session.SessionInfo;
+import com.pszymczyk.consul.ConsulProcess;
+import com.pszymczyk.consul.ConsulStarterBuilder;
+import org.apache.curator.test.Timing;
+import org.apache.curator.utils.CloseableUtils;
+import org.testng.Assert;
+import org.testng.annotations.*;
+
+import java.util.List;
+import java.util.Properties;
+
+
+public class TestConsulConfigProvider {
+    private Timing timing;
+    private ConsulProcess consul;
+    private Consul client;
+
+    @BeforeClass
+    public void setupClass() throws Exception {
+        consul = ConsulStarterBuilder.consulStarter().build().start();
+    }
+
+    @AfterClass
+    public void tearDownClass()
+    {
+        consul.close();
+    }
+
+    @BeforeMethod
+    public void setup() throws Exception {
+        timing = new Timing();
+
+        consul.reset();
+        client = Consul.builder()
+                .withHostAndPort(HostAndPort.fromParts("localhost", consul.getHttpPort()))
+                .build();
+    }
+
+    @Test
+    public void testBasic() throws Exception {
+        ConsulConfigProvider config = new ConsulConfigProvider(client, "prefix", new Properties());
+
+        try {
+            config.start();
+            config.loadConfig();
+
+            Properties properties = new Properties();
+            properties.setProperty(PropertyBasedInstanceConfig.toName(StringConfigs.ZOO_CFG_EXTRA, PropertyBasedInstanceConfig.ROOT_PROPERTY_PREFIX), "1,2,3");
+            config.storeConfig(new PropertyBasedInstanceConfig(properties, new Properties()), 0);
+
+            timing.sleepABit();
+
+            LoadedInstanceConfig instanceConfig = config.loadConfig();
+            Assert.assertEquals(instanceConfig.getConfig().getRootConfig().getString(StringConfigs.ZOO_CFG_EXTRA), "1,2,3");
+
+            List<SessionInfo> sessions = client.sessionClient().listSessions();
+            Assert.assertEquals(sessions.size(), 0, "Consul session still exists!");
+        }
+        finally {
+            CloseableUtils.closeQuietly(config);
+        }
+    }
+}