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本文主要研究一下elasticsearch的SeedHostsProvider
SeedHostsProvider
elasticsearch-7.0.0/server/src/main/java/org/elasticsearch/discovery/SeedHostsProvider.java
/**
* A pluggable provider of the list of seed hosts to use for discovery.
*/
public interface SeedHostsProvider {
/**
* Returns a list of seed hosts to use for discovery. Called repeatedly while discovery is active (i.e. while there is no master)
* so that this list may be dynamic.
*/
List<TransportAddress> getSeedAddresses(HostsResolver hostsResolver);
/**
* Helper object that allows to resolve a list of hosts to a list of transport addresses.
* Each host is resolved into a transport address (or a collection of addresses if the
* number of ports is greater than one)
*/
interface HostsResolver {
List<TransportAddress> resolveHosts(List<String> hosts, int limitPortCounts);
}
}
複製程式碼- SeedHostsProvider介面定義了getSeedAddresses方法，該方法引數型別為HostsResolver；HostsResolver介面定義了resolveHosts方法；它有幾個實現類，分別是SettingsBasedSeedHostsProvider、FileBasedSeedHostsProvider、GceSeedHostsProvider、AwsEc2SeedHostsProvider、AzureSeedHostsProvider
SettingsBasedSeedHostsProvider
elasticsearch-7.0.0/server/src/main/java/org/elasticsearch/discovery/SettingsBasedSeedHostsProvider.java
public class SettingsBasedSeedHostsProvider implements SeedHostsProvider {
private static final Logger logger = LogManager.getLogger(SettingsBasedSeedHostsProvider.class);
public static final Setting<List<String>> LEGACY_DISCOVERY_ZEN_PING_UNICAST_HOSTS_SETTING =
Setting.listSetting("discovery.zen.ping.unicast.hosts", emptyList(), Function.identity(), Property.NodeScope, Property.Deprecated);
public static final Setting<List<String>> DISCOVERY_SEED_HOSTS_SETTING =
Setting.listSetting("discovery.seed_hosts", emptyList(), Function.identity(), Property.NodeScope);
// these limits are per-address
private static final int LIMIT_FOREIGN_PORTS_COUNT = 1;
private static final int LIMIT_LOCAL_PORTS_COUNT = 5;
private final List<String> configuredHosts;
private final int limitPortCounts;
public SettingsBasedSeedHostsProvider(Settings settings, TransportService transportService) {
if (LEGACY_DISCOVERY_ZEN_PING_UNICAST_HOSTS_SETTING.exists(settings)) {
if (DISCOVERY_SEED_HOSTS_SETTING.exists(settings)) {
throw new IllegalArgumentException("it is forbidden to set both ["
+ DISCOVERY_SEED_HOSTS_SETTING.getKey() + "] and ["
+ LEGACY_DISCOVERY_ZEN_PING_UNICAST_HOSTS_SETTING.getKey() + "]");
}
configuredHosts = LEGACY_DISCOVERY_ZEN_PING_UNICAST_HOSTS_SETTING.get(settings);
// we only limit to 1 address, makes no sense to ping 100 ports
limitPortCounts = LIMIT_FOREIGN_PORTS_COUNT;
} else if (DISCOVERY_SEED_HOSTS_SETTING.exists(settings)) {
configuredHosts = DISCOVERY_SEED_HOSTS_SETTING.get(settings);
// we only limit to 1 address, makes no sense to ping 100 ports
limitPortCounts = LIMIT_FOREIGN_PORTS_COUNT;
} else {
// if unicast hosts are not specified, fill with simple defaults on the local machine
configuredHosts = transportService.getLocalAddresses();
limitPortCounts = LIMIT_LOCAL_PORTS_COUNT;
}
logger.debug("using initial hosts {}", configuredHosts);
}
@Override
public List<TransportAddress> getSeedAddresses(HostsResolver hostsResolver) {
return hostsResolver.resolveHosts(configuredHosts, limitPortCounts);
}
}
複製程式碼- SettingsBasedSeedHostsProvider主要是讀取discovery.seed_hosts或discovery.zen.ping.unicast.hosts配置
FileBasedSeedHostsProvider
elasticsearch-7.0.0/server/src/main/java/org/elasticsearch/discovery/FileBasedSeedHostsProvider.java
public class FileBasedSeedHostsProvider implements SeedHostsProvider {
private static final Logger logger = LogManager.getLogger(FileBasedSeedHostsProvider.class);
public static final String UNICAST_HOSTS_FILE = "unicast_hosts.txt";
private final Path unicastHostsFilePath;
public FileBasedSeedHostsProvider(Path configFile) {
this.unicastHostsFilePath = configFile.resolve(UNICAST_HOSTS_FILE);
}
private List<String> getHostsList() {
if (Files.exists(unicastHostsFilePath)) {
try (Stream<String> lines = Files.lines(unicastHostsFilePath)) {
return lines.filter(line -> line.startsWith("#") == false) // lines starting with `#` are comments
.collect(Collectors.toList());
} catch (IOException e) {
logger.warn(() -> new ParameterizedMessage("failed to read file [{}]", unicastHostsFilePath), e);
return Collections.emptyList();
}
}
logger.warn("expected, but did not find, a dynamic hosts list at [{}]", unicastHostsFilePath);
return Collections.emptyList();
}
@Override
public List<TransportAddress> getSeedAddresses(HostsResolver hostsResolver) {
final List<TransportAddress> transportAddresses = hostsResolver.resolveHosts(getHostsList(), 1);
logger.debug("seed addresses: {}", transportAddresses);
return transportAddresses;
}
}
複製程式碼- FileBasedSeedHostsProvider主要是從指定位置讀取unicast_hosts.txt檔案解析hostsList
SeedHostsProvider.HostsResolver
UnicastZenPing.createHostsResolver
elasticsearch-7.0.0/server/src/main/java/org/elasticsearch/discovery/zen/UnicastZenPing.java
private SeedHostsProvider.HostsResolver createHostsResolver() {
return (hosts, limitPortCounts) -> SeedHostsResolver.resolveHostsLists(unicastZenPingExecutorService, logger, hosts,
limitPortCounts, transportService, resolveTimeout);
}
複製程式碼- UnicastZenPing的createHostsResolver方法建立了一個匿名的SeedHostsProvider.HostsResolver類，其實現是委託為SeedHostsResolver.resolveHostsLists方法
SeedHostsResolver
elasticsearch-7.0.0/server/src/main/java/org/elasticsearch/discovery/SeedHostsResolver.java
public class SeedHostsResolver extends AbstractLifecycleComponent implements ConfiguredHostsResolver {
//......
public static List<TransportAddress> resolveHostsLists(
final ExecutorService executorService,
final Logger logger,
final List<String> hosts,
final int limitPortCounts,
final TransportService transportService,
final TimeValue resolveTimeout) {
Objects.requireNonNull(executorService);
Objects.requireNonNull(logger);
Objects.requireNonNull(hosts);
Objects.requireNonNull(transportService);
Objects.requireNonNull(resolveTimeout);
if (resolveTimeout.nanos() < 0) {
throw new IllegalArgumentException("resolve timeout must be non-negative but was [" + resolveTimeout + "]");
}
// create tasks to submit to the executor service; we will wait up to resolveTimeout for these tasks to complete
final List<Callable<TransportAddress[]>> callables =
hosts
.stream()
.map(hn -> (Callable<TransportAddress[]>) () -> transportService.addressesFromString(hn, limitPortCounts))
.collect(Collectors.toList());
final List<Future<TransportAddress[]>> futures;
try {
futures = executorService.invokeAll(callables, resolveTimeout.nanos(), TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return Collections.emptyList();
}
final List<TransportAddress> transportAddresses = new ArrayList<>();
final Set<TransportAddress> localAddresses = new HashSet<>();
localAddresses.add(transportService.boundAddress().publishAddress());
localAddresses.addAll(Arrays.asList(transportService.boundAddress().boundAddresses()));
// ExecutorService#invokeAll guarantees that the futures are returned in the iteration order of the tasks so we can associate the
// hostname with the corresponding task by iterating together
final Iterator<String> it = hosts.iterator();
for (final Future<TransportAddress[]> future : futures) {
final String hostname = it.next();
if (!future.isCancelled()) {
assert future.isDone();
try {
final TransportAddress[] addresses = future.get();
logger.trace("resolved host [{}] to {}", hostname, addresses);
for (int addressId = 0; addressId < addresses.length; addressId++) {
final TransportAddress address = addresses[addressId];
// no point in pinging ourselves
if (localAddresses.contains(address) == false) {
transportAddresses.add(address);
}
}
} catch (final ExecutionException e) {
assert e.getCause() != null;
final String message = "failed to resolve host [" + hostname + "]";
logger.warn(message, e.getCause());
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
// ignore
}
} else {
logger.warn("timed out after [{}] resolving host [{}]", resolveTimeout, hostname);
}
}
return Collections.unmodifiableList(transportAddresses);
}
//......
}
複製程式碼- SeedHostsResolver的resolveHostsLists靜態方法主要是利用多執行緒並行執行transportService.addressesFromString方法
小結
- SeedHostsProvider介面定義了getSeedAddresses方法，該方法引數型別為HostsResolver；HostsResolver介面定義了resolveHosts方法；它有幾個實現類，分別是SettingsBasedSeedHostsProvider、FileBasedSeedHostsProvider、GceSeedHostsProvider、AwsEc2SeedHostsProvider、AzureSeedHostsProvider
- SettingsBasedSeedHostsProvider主要是讀取discovery.seed_hosts或discovery.zen.ping.unicast.hosts配置；FileBasedSeedHostsProvider主要是從指定位置讀取unicast_hosts.txt檔案解析hostsList
- UnicastZenPing的createHostsResolver方法建立了一個匿名的SeedHostsProvider.HostsResolver類，其實現是委託為SeedHostsResolver.resolveHostsLists方法；SeedHostsResolver的resolveHostsLists靜態方法主要是利用多執行緒並行執行transportService.addressesFromString方法