Package io.grpc.internal

Class DnsNameResolver

java.lang.Object

io.grpc.NameResolver

io.grpc.internal.DnsNameResolver

Direct Known Subclasses:

GrpclbNameResolver

public class DnsNameResolver
extends NameResolver

A DNS-based NameResolver.

Each A or AAAA record emits an EquivalentAddressGroup in the list passed to NameResolver.Listener2.onResult2(ResolutionResult).

See Also:

DnsNameResolverProvider

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	DnsNameResolver.AddressResolver	AddressResolver resolves a hostname into a list of addresses.
protected static class	DnsNameResolver.InternalResolutionResult	Used as a DNS-based name resolver's internal representation of resolution result.
private static class	DnsNameResolver.JdkAddressResolver
private class	DnsNameResolver.Resolve
static interface	DnsNameResolver.ResourceResolver	DnsNameResolver.ResourceResolver is a Dns ResourceRecord resolver.
(package private) static interface	DnsNameResolver.ResourceResolverFactory	DnsNameResolver.ResourceResolverFactory is a factory for making resource resolvers.
static class	DnsNameResolver.SrvRecord	Describes a parsed SRV record.

Nested classes/interfaces inherited from class io.grpc.NameResolver

NameResolver.Args, NameResolver.ConfigOrError, NameResolver.Factory, NameResolver.Listener, NameResolver.Listener2, NameResolver.ResolutionResult, NameResolver.ResolutionResultAttr, NameResolver.ServiceConfigParser

Field Summary

Fields

Modifier and Type	Field	Description
protected DnsNameResolver.AddressResolver	addressResolver
private java.lang.String	authority
private long	cacheTtlNanos
(package private) static long	DEFAULT_NETWORK_CACHE_TTL_SECONDS	Default DNS cache duration if network cache ttl value is not specified (null).
(package private) static boolean	enableJndi
(package private) static boolean	enableJndiLocalhost
protected static boolean	enableTxt
private java.util.concurrent.Executor	executor
private SharedResourceHolder.Resource<java.util.concurrent.Executor>	executorResource	Executor that will be used if an Executor is not provide via NameResolver.Args.
private java.lang.String	host
private static java.lang.String	JNDI_LOCALHOST_PROPERTY
private static java.lang.String	JNDI_PROPERTY
private static java.lang.String	JNDI_TXT_PROPERTY
private NameResolver.Listener2	listener
private static java.lang.String	localHostname	Access through getLocalHostname().
private static java.util.logging.Logger	logger
(package private) static java.lang.String	NETWORKADDRESS_CACHE_TTL_PROPERTY	Java networking system properties name for caching DNS result.
private int	port
(package private) ProxyDetector	proxyDetector
private java.util.Random	random
protected boolean	resolved
private boolean	resolving
private java.util.concurrent.atomic.AtomicReference<DnsNameResolver.ResourceResolver>	resourceResolver
private static DnsNameResolver.ResourceResolverFactory	resourceResolverFactory
private static java.lang.String	SERVICE_CONFIG_CHOICE_CLIENT_HOSTNAME_KEY
private static java.lang.String	SERVICE_CONFIG_CHOICE_CLIENT_LANGUAGE_KEY
private static java.util.Set<java.lang.String>	SERVICE_CONFIG_CHOICE_KEYS
private static java.lang.String	SERVICE_CONFIG_CHOICE_PERCENTAGE_KEY
private static java.lang.String	SERVICE_CONFIG_CHOICE_SERVICE_CONFIG_KEY
private static java.lang.String	SERVICE_CONFIG_NAME_PREFIX
(package private) static java.lang.String	SERVICE_CONFIG_PREFIX
private NameResolver.ServiceConfigParser	serviceConfigParser
private boolean	shutdown
private com.google.common.base.Stopwatch	stopwatch
private SynchronizationContext	syncContext
private boolean	usingExecutorResource	True if using an executor resource that should be released after use.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DnsNameResolver(java.lang.String nsAuthority, java.lang.String name, NameResolver.Args args, SharedResourceHolder.Resource<java.util.concurrent.Executor> executorResource, com.google.common.base.Stopwatch stopwatch, boolean isAndroid)

Method Summary

Modifier and Type	Method	Description
private boolean	cacheRefreshRequired()
private EquivalentAddressGroup	detectProxy()
protected DnsNameResolver.InternalResolutionResult	doResolve(boolean forceTxt)	Main logic of name resolution.
private static java.util.List<java.lang.String>	getClientLanguagesFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)
protected java.lang.String	getHost()
private static java.util.List<java.lang.String>	getHostnamesFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)
private static java.lang.String	getLocalHostname()
private static long	getNetworkAddressCacheTtlNanos(boolean isAndroid)	Returns value of network address cache ttl property if not Android environment.
private static java.lang.Double	getPercentageFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)
(package private) int	getPort()
protected DnsNameResolver.ResourceResolver	getResourceResolver()
(package private) static DnsNameResolver.ResourceResolverFactory	getResourceResolverFactory(java.lang.ClassLoader loader)
java.lang.String	getServiceAuthority()	Returns the authority used to authenticate connections to servers.
(package private) static java.util.Map<java.lang.String,?>	maybeChooseServiceConfig(java.util.Map<java.lang.String,?> choice, java.util.Random random, java.lang.String hostname)	Determines if a given Service Config choice applies, and if so, returns it.
(package private) static NameResolver.ConfigOrError	parseServiceConfig(java.util.List<java.lang.String> rawTxtRecords, java.util.Random random, java.lang.String localHostname)
(package private) static java.util.List<java.util.Map<java.lang.String,?>>	parseTxtResults(java.util.List<java.lang.String> txtRecords)	Parse TXT service config records as JSON.
void	refresh()	Re-resolve the name.
private void	resolve()
private java.util.List<EquivalentAddressGroup>	resolveAddresses()
private NameResolver.ConfigOrError	resolveServiceConfig()
protected void	setAddressResolver(DnsNameResolver.AddressResolver addressResolver)
protected void	setResourceResolver(DnsNameResolver.ResourceResolver resourceResolver)
protected static boolean	shouldUseJndi(boolean jndiEnabled, boolean jndiLocalhostEnabled, java.lang.String target)
void	shutdown()	Stops the resolution.
void	start(NameResolver.Listener2 listener)	Starts the resolution.

Methods inherited from class io.grpc.NameResolver

start

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

private static final java.util.logging.Logger logger

SERVICE_CONFIG_CHOICE_CLIENT_LANGUAGE_KEY

private static final java.lang.String SERVICE_CONFIG_CHOICE_CLIENT_LANGUAGE_KEY

See Also:

Constant Field Values

SERVICE_CONFIG_CHOICE_PERCENTAGE_KEY

private static final java.lang.String SERVICE_CONFIG_CHOICE_PERCENTAGE_KEY

See Also:

Constant Field Values

SERVICE_CONFIG_CHOICE_CLIENT_HOSTNAME_KEY

private static final java.lang.String SERVICE_CONFIG_CHOICE_CLIENT_HOSTNAME_KEY

See Also:

Constant Field Values

SERVICE_CONFIG_CHOICE_SERVICE_CONFIG_KEY

private static final java.lang.String SERVICE_CONFIG_CHOICE_SERVICE_CONFIG_KEY

See Also:

Constant Field Values

SERVICE_CONFIG_PREFIX

static final java.lang.String SERVICE_CONFIG_PREFIX

See Also:

Constant Field Values

SERVICE_CONFIG_CHOICE_KEYS

private static final java.util.Set<java.lang.String> SERVICE_CONFIG_CHOICE_KEYS

SERVICE_CONFIG_NAME_PREFIX

private static final java.lang.String SERVICE_CONFIG_NAME_PREFIX

See Also:

Constant Field Values

JNDI_PROPERTY

private static final java.lang.String JNDI_PROPERTY

JNDI_LOCALHOST_PROPERTY

private static final java.lang.String JNDI_LOCALHOST_PROPERTY

JNDI_TXT_PROPERTY

private static final java.lang.String JNDI_TXT_PROPERTY

NETWORKADDRESS_CACHE_TTL_PROPERTY

static final java.lang.String NETWORKADDRESS_CACHE_TTL_PROPERTY

Java networking system properties name for caching DNS result.

Default value is -1 (cache forever) if security manager is installed. If security manager is not installed, the ttl value is null which falls back to gRPC default value.

For android, gRPC doesn't attempt to cache; this property value will be ignored.

See Also:

Constant Field Values

DEFAULT_NETWORK_CACHE_TTL_SECONDS

static final long DEFAULT_NETWORK_CACHE_TTL_SECONDS

Default DNS cache duration if network cache ttl value is not specified (null).

See Also:

Constant Field Values

enableJndi

static boolean enableJndi

enableJndiLocalhost

static boolean enableJndiLocalhost

enableTxt

protected static boolean enableTxt

resourceResolverFactory

private static final DnsNameResolver.ResourceResolverFactory resourceResolverFactory

proxyDetector

final ProxyDetector proxyDetector

localHostname

private static java.lang.String localHostname

Access through getLocalHostname().

random

private final java.util.Random random

addressResolver

protected volatile DnsNameResolver.AddressResolver addressResolver

resourceResolver

private final java.util.concurrent.atomic.AtomicReference<DnsNameResolver.ResourceResolver> resourceResolver

authority

private final java.lang.String authority

host

private final java.lang.String host

port

private final int port

executorResource

private final SharedResourceHolder.Resource<java.util.concurrent.Executor> executorResource

Executor that will be used if an Executor is not provide via NameResolver.Args.

cacheTtlNanos

private final long cacheTtlNanos

syncContext

private final SynchronizationContext syncContext

stopwatch

private final com.google.common.base.Stopwatch stopwatch

resolved

protected boolean resolved

shutdown

private boolean shutdown

executor

private java.util.concurrent.Executor executor

usingExecutorResource

private final boolean usingExecutorResource

True if using an executor resource that should be released after use.

serviceConfigParser

private final NameResolver.ServiceConfigParser serviceConfigParser

resolving

private boolean resolving

listener

private NameResolver.Listener2 listener

Constructor Detail

DnsNameResolver

protected DnsNameResolver(@Nullable
                          java.lang.String nsAuthority,
                          java.lang.String name,
                          NameResolver.Args args,
                          SharedResourceHolder.Resource<java.util.concurrent.Executor> executorResource,
                          com.google.common.base.Stopwatch stopwatch,
                          boolean isAndroid)

Method Detail

getServiceAuthority

public java.lang.String getServiceAuthority()

Description copied from class: NameResolver

Returns the authority used to authenticate connections to servers. It must be from a trusted source, because if the authority is tampered with, RPCs may be sent to the attackers which may leak sensitive user data.

An implementation must generate it without blocking, typically in line, and must keep it unchanged. NameResolvers created from the same factory with the same argument must return the same authority.

Specified by:

getServiceAuthority in class NameResolver

getHost

protected java.lang.String getHost()

start

public void start(NameResolver.Listener2 listener)

Description copied from class: NameResolver

Starts the resolution. The method is not supposed to throw any exceptions. That might cause the Channel that the name resolver is serving to crash. Errors should be propagated through NameResolver.Listener2.onError(io.grpc.Status).

An instance may not be started more than once, by any overload of this method, even after an intervening call to NameResolver.shutdown().

Overrides:

start in class NameResolver

Parameters:

listener - used to receive updates on the target

refresh

public void refresh()

Description copied from class: NameResolver

Re-resolve the name.

Can only be called after NameResolver.start(io.grpc.NameResolver.Listener) has been called.

This is only a hint. Implementation takes it as a signal but may not start resolution immediately. It should never throw.

The default implementation is no-op.

Overrides:

refresh in class NameResolver

resolveAddresses

private java.util.List<EquivalentAddressGroup> resolveAddresses()

resolveServiceConfig

@Nullable
private NameResolver.ConfigOrError resolveServiceConfig()

detectProxy

@Nullable
private EquivalentAddressGroup detectProxy()
                                    throws java.io.IOException

Throws:

java.io.IOException

doResolve

protected DnsNameResolver.InternalResolutionResult doResolve(boolean forceTxt)

Main logic of name resolution.

parseServiceConfig

@Nullable
static NameResolver.ConfigOrError parseServiceConfig(java.util.List<java.lang.String> rawTxtRecords,
                                                     java.util.Random random,
                                                     java.lang.String localHostname)

resolve

private void resolve()

cacheRefreshRequired

private boolean cacheRefreshRequired()

shutdown

public void shutdown()

Description copied from class: NameResolver

Stops the resolution. Updates to the Listener will stop.

Specified by:

shutdown in class NameResolver

getPort

final int getPort()

parseTxtResults

static java.util.List<java.util.Map<java.lang.String,?>> parseTxtResults(java.util.List<java.lang.String> txtRecords)
                                                                        throws java.io.IOException

Parse TXT service config records as JSON.

Throws:

java.io.IOException - if one of the txt records contains improperly formatted JSON.

getPercentageFromChoice

@Nullable
private static final java.lang.Double getPercentageFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)

getClientLanguagesFromChoice

@Nullable
private static final java.util.List<java.lang.String> getClientLanguagesFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)

getHostnamesFromChoice

@Nullable
private static final java.util.List<java.lang.String> getHostnamesFromChoice(java.util.Map<java.lang.String,?> serviceConfigChoice)

getNetworkAddressCacheTtlNanos

private static long getNetworkAddressCacheTtlNanos(boolean isAndroid)

Returns value of network address cache ttl property if not Android environment. For android, DnsNameResolver does not cache the dns lookup result.

maybeChooseServiceConfig

@Nullable
static java.util.Map<java.lang.String,?> maybeChooseServiceConfig(java.util.Map<java.lang.String,?> choice,
                                                                        java.util.Random random,
                                                                        java.lang.String hostname)

Determines if a given Service Config choice applies, and if so, returns it.

Parameters:

choice - The service config choice.

Returns:

The service config object or null if this choice does not apply.

See Also:

Service Config in DNS

setAddressResolver

protected void setAddressResolver(DnsNameResolver.AddressResolver addressResolver)

setResourceResolver

protected void setResourceResolver(DnsNameResolver.ResourceResolver resourceResolver)

getResourceResolver

@Nullable
protected DnsNameResolver.ResourceResolver getResourceResolver()

getResourceResolverFactory

@Nullable
static DnsNameResolver.ResourceResolverFactory getResourceResolverFactory(java.lang.ClassLoader loader)

getLocalHostname

private static java.lang.String getLocalHostname()

shouldUseJndi

protected static boolean shouldUseJndi(boolean jndiEnabled,
                                       boolean jndiLocalhostEnabled,
                                       java.lang.String target)