Class CachingRlsLbClient

rls/src/main/java/io/grpc/rls/CachingRlsLbClient.java:87–1104

A CachingRlsLbClient is a core implementation of RLS loadbalancer supports dynamic request routing by fetching the decision from route lookup server. Every single request is routed by the server's decision. To reduce the performance penalty, LruCache is used.

 * the server's decision. To reduce the performance penalty, {@link LruCache} is used.
 */
@ThreadSafe
final class CachingRlsLbClient {

  private static final Converter<RouteLookupRequest, io.grpc.lookup.v1.RouteLookupRequest>
      REQUEST_CONVERTER = new RlsProtoConverters.RouteLookupRequestConverter().reverse();
  private static final Converter<RouteLookupResponse, io.grpc.lookup.v1.RouteLookupResponse>
      RESPONSE_CONVERTER = new RouteLookupResponseConverter().reverse();
  public static final long MIN_EVICTION_TIME_DELTA_NANOS = TimeUnit.SECONDS.toNanos(5);
  public static final int BYTES_PER_CHAR = 2;
  public static final int STRING_OVERHEAD_BYTES = 38;
  /** Minimum bytes for a Java Object. */
  public static final int OBJ_OVERHEAD_B = 16;

  private static final LongCounterMetricInstrument DEFAULT_TARGET_PICKS_COUNTER;
  private static final LongCounterMetricInstrument TARGET_PICKS_COUNTER;
  private static final LongCounterMetricInstrument FAILED_PICKS_COUNTER;
  private static final LongGaugeMetricInstrument CACHE_ENTRIES_GAUGE;
  private static final LongGaugeMetricInstrument CACHE_SIZE_GAUGE;
  private final Registration gaugeRegistration;
  private final String metricsInstanceUuid = UUID.randomUUID().toString();

  // All cache status changes (pending, backoff, success) must be under this lock
  private final Object lock = new Object();
  // LRU cache based on access order (BACKOFF and actual data will be here)
  @GuardedBy("lock")
  private final RlsAsyncLruCache linkedHashLruCache;
  private final Future<?> periodicCleaner;
  // any RPC on the fly will cached in this map
  @GuardedBy("lock")
  private final Map<RouteLookupRequestKey, PendingCacheEntry> pendingCallCache = new HashMap<>();

  private final ScheduledExecutorService scheduledExecutorService;
  private final Ticker ticker;
  private final Throttler throttler;

  private final LbPolicyConfiguration lbPolicyConfig;
  private final BackoffPolicy.Provider backoffProvider;
  private final long maxAgeNanos;
  private final long staleAgeNanos;
  private final long callTimeoutNanos;

  private final RlsLbHelper helper;
  private final ManagedChannel rlsChannel;
  private final RouteLookupServiceStub rlsStub;
  private final RlsPicker rlsPicker;
  private final ResolvedAddressFactory childLbResolvedAddressFactory;
  @GuardedBy("lock")
  private final RefCountedChildPolicyWrapperFactory refCountedChildPolicyWrapperFactory;
  private final ChannelLogger logger;
  private final ChildPolicyWrapper fallbackChildPolicyWrapper;

  static {
    MetricInstrumentRegistry metricInstrumentRegistry
        = MetricInstrumentRegistry.getDefaultRegistry();
    DEFAULT_TARGET_PICKS_COUNTER = metricInstrumentRegistry.registerLongCounter(
        "grpc.lb.rls.default_target_picks",
        "EXPERIMENTAL. Number of LB picks sent to the default target", "{pick}",
        Arrays.asList("grpc.target", "grpc.lb.rls.server_target",