Packages

  • package root
    Definition Classes
    root
  • package com
    Definition Classes
    root
  • package twitter

    Start with com.twitter.finagle.

    Definition Classes
    com
  • package finagle

    Finagle is an extensible RPC system.

    Finagle is an extensible RPC system.

    Services are represented by class com.twitter.finagle.Service. Clients make use of com.twitter.finagle.Service objects while servers implement them.

    Finagle contains a number of protocol implementations; each of these implement Client and/or com.twitter.finagle.Server. For example, Finagle's HTTP implementation, com.twitter.finagle.Http (in package finagle-http), exposes both.

    Thus a simple HTTP server is built like this:

    import com.twitter.finagle.{Http, Service}
    import com.twitter.finagle.http.{Request, Response}
    import com.twitter.util.{Await, Future}
    
    val service = new Service[Request, Response] {
      def apply(req: Request): Future[Response] =
        Future.value(Response())
    }
    val server = Http.server.serve(":8080", service)
    Await.ready(server)

    We first define a service to which requests are dispatched. In this case, the service returns immediately with a HTTP 200 OK response, and with no content.

    This service is then served via the Http protocol on TCP port 8080. Finally we wait for the server to stop serving.

    We can now query our web server:

    % curl -D - localhost:8080
    HTTP/1.1 200 OK

    Building an HTTP client is also simple. (Note that type annotations are added for illustration.)

    import com.twitter.finagle.{Http, Service}
    import com.twitter.finagle.http.{Request, Response}
    import com.twitter.util.{Future, Return, Throw}
    
    val client: Service[Request, Response] = Http.client.newService("localhost:8080")
    val f: Future[Response] = client(Request()).respond {
      case Return(rep) =>
        printf("Got HTTP response %s\n", rep)
      case Throw(exc) =>
        printf("Got error %s\n", exc)
    }

    Http.client.newService("localhost:8080") constructs a new com.twitter.finagle.Service instance connected to localhost TCP port 8080. We then issue a HTTP/1.1 GET request to URI "/". The service returns a com.twitter.util.Future representing the result of the operation. We listen to this future, printing an appropriate message when the response arrives.

    The Finagle homepage contains useful documentation and resources for using Finagle.

    Definition Classes
    twitter
  • package addr
    Definition Classes
    finagle
  • package builder
    Definition Classes
    finagle
  • package client
    Definition Classes
    finagle
  • package context
    Definition Classes
    finagle
  • package core
    Definition Classes
    finagle
  • package dispatch
    Definition Classes
    finagle
  • package exp

    Package exp contains experimental code.

    Package exp contains experimental code. This can be removed or stabilized (moved elsewhere) at any time.

    Definition Classes
    finagle
  • package factory
    Definition Classes
    finagle
  • package filter
    Definition Classes
    finagle
  • package http
    Definition Classes
    finagle
  • package http2
    Definition Classes
    finagle
  • package liveness
    Definition Classes
    finagle
  • package loadbalancer

    This package implements client side load balancing algorithms.

    This package implements client side load balancing algorithms.

    As an end-user, see the Balancers API to create instances which can be used to configure a Finagle client with various load balancing strategies.

    As an implementor, each algorithm gets its own subdirectory and is exposed via the Balancers object. Several convenient traits are provided which factor out common behavior and can be mixed in (i.e. Balancer, DistributorT, NodeT, and Updating).

    Definition Classes
    finagle
  • package logging
    Definition Classes
    finagle
  • package memcached
    Definition Classes
    finagle
  • package mux

    Package mux implements a generic RPC multiplexer with a rich protocol.

    Package mux implements a generic RPC multiplexer with a rich protocol. Mux is itself encoding independent, so it is meant to use as the transport for other RPC systems (eg. thrift). In OSI terminology, it is a pure session layer.

    In the below description, all numeric values are unsigned and in big-endian byte order. The schema size:4 body:10 defines the field size to be 4 bytes, followed by 10 bytes of the field body. The schema key~4 defines the field key to be defined by 4 bytes interpreted as the size of the field, followed by that many bytes comprising the field itself--it is shorthand for keysize:4 key:keysize. Groups are denoted by parenthesis; * denotes repetition of the previous schema 0 or more times, while {n} indicates repetition exactly n times. Unspecified sizes consume the rest of the frame: they may be specified only as the last field in the message.

    All strings in Mux are Utf-8 encoded, and are never null-terminated.

    Message framing

    Messages in mux are framed with a 4-byte big-endian size header, followed by 1 byte describing the message type and a 3-byte tag; or, diagrammatically: size:4 type:1 tag:3. The remainder of the frame (size-4 bytes) contains the body. Its format depends on the message type, documented below.

    Tag 0 designates a "marker" T message that expects no reply. Some messages may be split into an ordered sequence of fragments. Tag MSB=0 denotes the last message in such a sequence, making the tag namespace 23 bits. The tag is otherwise arbitrary, and is chosen by the sender of the T message.

    Currently, only Tdispatch and Rdispatch messages may be split into an ordered sequence of fragments. TdispatchError message ends a Tdispatch sequence and an Rerr ends an Rdispatch sequence.

    Message types, interpreted as a two's complement, 1-byte integer are numbered as follows: positive numbers are T-messages; their negative complement is the corresponding R message. T-messages greater than 63 (correspondingly R-messages smaller than -63) are session messages. The message number -128 is reserved for Rerr. All other messages are application messages. Middle boxes may forward application messages indiscriminately. Because of an early implementation bug, two aliases exist: 127 is Rerr, and -62 is Tdiscarded.

    The protocol is full duplex: both the server and client may send T messages initiating an exchange.

    Exchanges

    Messages are designated as "T messages" or "R messages", T and R being stand-ins for transmit and receive. A T message initiates an exchange and is assigned a free tag by the sender. A reply is either an R message of the same type (Rx replies to Tx for some x), or an Rerr, indicating a session layer error. R messages are matched to their T messages by tag, and the reply concludes the exchange and frees the tag for future use. Implementations should reuse small tag numbers.

    Messages

    size:4 Tinit:1 tag:3 version:2 (key~4 value~4)* reinitializes a session. Clients typically send this at the beginning of the session. When doing so, the sender may issue no more T messages until the corresponding size:4 Rinit:1 tag:3 version:2 (key~4 value~4)* has been received. After the Rinit was received, all connection state has been reset (outstanding tags are invalidated) and the stream is resumed according to the newly negotiated parameters. Prior to the first Tinit, the session operates at version 1. Rinit's version field is the accepted version of the session (which may be lower than the one requested by Tinit).

    size:4 Treq:1 tag:3 n:1 (key:1 value~1){n} body: initiates the request described by its body. The request body is delivered to the application. The request header contains a number of key-value pairs that describe request metadata.

    Keys for Treq messages are as follows:

    1. traceid: a 24-byte value describing the full Dapper trace id assigned by the client. The value's format is spanid:8 parentid:8 traceid:8.

    2. traceflag: a bitmask describing trace flags. Currently, the only defined flag is bit 0 which enables "debug mode", asking the server to force trace sampling.

    size:4 Tdispatch:1 tag:3 nctx:2 (ckey~2 cval~2){nc} dst~2 nd:2 (from~2 to~2){nd} body: implements destination dispatch. Tdispatch messages carry a set of keyed request contexts, followed by a logical destination encoded as a UTF-8 string. A delegation table follows describing rewrite rules that apply to this request.

    size:4 Rreq:1 tag:3 status:1 body: replies to a request. Status codes are as follows: 0=OK; the body contains the reply. 1=ERROR; the body contains a string describing the error. 2=NACK; a negative acknowledgment, the body contains a string describing the reason.

    size:4 Rdispatch:1 tag:3 status:1 nctx:2 (key~2 value~2){nctx} body: replies to a Tdispatch request. Status codes are as in Rreq. Replies can include request contexts. MuxFailure flags are currently sent via Rdispatch contexts under the "MuxFailure" key. See the MuxFailure flags section below.

    size:4 Rerr:1 tag:3 why: indicates that the corresponding T message produced an error. Rerr is specifically for server errors: the server failed to interpret or act on the message. The body carries a string describing the error.

    size:4 Tdrain:1 tag:3 is a request sent by the server telling the client to stop sending new requests. A client acknowledges this with an Rdrain message.

    size:4 Tping:1 tag:3 is sent by either party to check the liveness of its peer; these should be responded to immediately with a Rping message.

    size:4 Tdiscarded:1 tag:3 discard_tag:3 why: is a marker message and therefore has a tag value of 0. discard_tag indicates the tag of the Tdispatch to be discarded by the client. This can be used as a hint for early termination. Why is a string describing why the request was discarded. Note that it does *not* free the server from the obligation of replying to the original Treq.

    size:4 Tlease:1 tag:3 unit:1 howmuch:8 is a marker message indicating that a lease has been issued for howmuch units. As a marker message, its tag value must be 0. Unit '0' is reserved for duration in milliseconds. Whenever a lease has not been issued, a client can assume it holds an indefinite lease. Adhering to the lease is optional, but the server may reject requests or provide degraded service should the lease expire. This is used by servers to implement features like garbage collection avoidance.

    MuxFailure Flags

    Failure flags are read and written as an 8 byte integer. Unrecognized flags will be ignored silently, but should all be considered reserved for future use.

    Flag Value Meaning Restartable 1 << 0 Request is safe to re-issue Rejected 1 << 1 Request was rejected/Nacked by the server NonRetryable 1 << 2 Request should not be retried

    Security

    TLS is supported via three mechanisms: - Explicit and exclusive TLS. This pathway involves requiring the establishment of TLS immediately after establishing the socket connection. This is configured by adding TLS configuration to the client or server and not configuring opportunistic TLS or TLS snooping (see below).

    - Negotiated Opportunistic TLS. This pathway involves starting the connection as cleartext and the client and server subsequently negotiate a TLS level via the handshake. Based on that handshake the connection is either left as cleartext or upgraded to TLS. This is configured by adding TLS configuration and also configuring an opportunistic TLS level but not configuring TLS snooping.

    In this pathway there are three configuration options:

    • Off signals that TLS is not supported by this peer
    • Desired signals that TLS is preferred but not required by this peer
    • Required signals that this peer will only allow the session to continue over TLS

    - TLS snooping. This pathway allows a server to use TLS either by performing a TLS handshake immediately after the socket is established or by starting the session as cleartext or using the negotiated pathway described above. If the session is started as a TLS session the headers that drive the opportunistic TLS pathway are ignored.

    Note that the server may still require TLS but leaves the option to start TLS immediately after establishing the socket or starting cleartext and requiring TLS via the opportunistic TLS pathway described above.

    Definition Classes
    finagle
  • package mysql
    Definition Classes
    finagle
  • package namer
    Definition Classes
    finagle
  • package naming
    Definition Classes
    finagle
  • package netty4

    Package netty4 implements the bottom finagle primitives: com.twitter.finagle.Server and a client transport in terms of the netty4 event loop.

    Package netty4 implements the bottom finagle primitives: com.twitter.finagle.Server and a client transport in terms of the netty4 event loop.

    Definition Classes
    finagle
  • package offload
    Definition Classes
    finagle
  • package param

    Defines common com.twitter.finagle.Stack.Param's shared between finagle clients and servers.

    Defines common com.twitter.finagle.Stack.Param's shared between finagle clients and servers.

    Definition Classes
    finagle
  • package partitioning
    Definition Classes
    finagle
  • package pool
    Definition Classes
    finagle
  • package postgresql
    Definition Classes
    finagle
  • package pushsession
    Definition Classes
    finagle
  • package redis
    Definition Classes
    finagle
  • package scribe
    Definition Classes
    finagle
  • package server
    Definition Classes
    finagle
  • package serverset2
    Definition Classes
    finagle
  • package service
    Definition Classes
    finagle
  • package ssl
    Definition Classes
    finagle
  • package stats
    Definition Classes
    finagle
  • package thrift

    Please use the new interface, com.twitter.finagle.Thrift, for constructing Thrift clients and servers.

    Deprecation

    Please use the new interface, com.twitter.finagle.Thrift, for constructing Thrift clients and servers.

    Thrift codecs

    We provide client and server protocol support for the framed protocol. The public implementations are defined on the Thrift object:

    The type of the server codec is Service[Array[Byte], Array[Byte]] and the client codecs are Service[ThriftClientRequest, Array[Byte]]. The service provided is that of a "transport" of thrift messages (requests and replies) according to the protocol chosen. This is why the client codecs need to have access to a thrift ProtocolFactory.

    These transports are used by the services produced by the finagle thrift codegenerator.

    val service: Service[ThriftClientRequest, Array[Byte]] = ClientBuilder()
      .hosts("foobar.com:123")
      .stack(Thrift.client)
      .build()
    
    // Wrap the raw Thrift transport in a Client decorator. The client
    // provides a convenient procedural interface for accessing the Thrift
    // server.
    val client = new Hello.ServiceToClient(service, protocolFactory)

    In this example, Hello is the thrift interface, and the inner class ServiceToClient is provided by the finagle thrift code generator.

    Definition Classes
    finagle
  • package thriftmux
    Definition Classes
    finagle
  • package toggle
    Definition Classes
    finagle
  • package tracing
    Definition Classes
    finagle
  • package transport
    Definition Classes
    finagle
  • package tunable
    Definition Classes
    finagle
  • package util
    Definition Classes
    finagle
  • package zipkin
    Definition Classes
    finagle
  • package zookeeper
    Definition Classes
    finagle
  • AbstractFailureFlags
  • AbstractNamer
  • AbstractResolver
  • Addr
  • Address
  • Addresses
  • Addrs
  • Announcement
  • Announcer
  • AnnouncerForumInvalid
  • AnnouncerNotFoundException
  • ApiException
  • Backoff
  • CanStackFrom
  • CancelledConnectionException
  • CancelledRequestException
  • ChannelBufferUsageException
  • ChannelClosedException
  • ChannelException
  • ChannelWriteException
  • Client
  • ClientConnection
  • ClientParamsInjector
  • ClientStackTransformer
  • ConnectionFailedException
  • ConnectionRefusedException
  • Dentry
  • DroppedWriteException
  • Dtab
  • DtabBuilder
  • DtabFlags
  • FactoryToService
  • FailResolver
  • FailedFastException
  • Failure
  • FailureFlags
  • Filter
  • FinagleInit
  • FixedInetResolver
  • GlobalRequestTimeoutException
  • HasRemoteInfo
  • Http
  • HttpRichClient
  • InconsistentStateException
  • IndividualRequestTimeoutException
  • InetResolver
  • JavaFailureFlags
  • ListeningServer
  • Memcached
  • MemcachedRichClient
  • MultipleAnnouncersPerSchemeException
  • MultipleResolversPerSchemeException
  • Mux
  • Mysql
  • MysqlRichClient
  • Name
  • NameTree
  • Namer
  • Names
  • NegResolver
  • NilResolver
  • NoBrokersAvailableException
  • NotServableException
  • NullServer
  • Path
  • PostgreSql
  • ProxyAnnouncement
  • ProxyConnectException
  • ReadTimedOutException
  • Redis
  • RedisRichClient
  • RefusedByRateLimiter
  • RequestException
  • RequestTimeoutException
  • Resolver
  • ResolverAddressInvalid
  • ResolverNotFoundException
  • Resolvers
  • Server
  • ServerErrorMonitor
  • ServerParamsInjector
  • ServerStackTransformer
  • Service
  • ServiceClosedException
  • ServiceException
  • ServiceFactory
  • ServiceFactoryProxy
  • ServiceFactoryWrapper
  • ServiceNamer
  • ServiceNotAvailableException
  • ServiceProxy
  • ServiceReturnedToPoolException
  • ServiceTimeoutException
  • ShardNotAvailableException
  • SimpleFilter
  • SourcedException
  • SslException
  • SslVerificationFailedException
  • Stack
  • StackBuilder
  • StackParams
  • Stackable
  • Stacks
  • Status
  • StreamClosedException
  • Thrift
  • ThriftMux
  • TimeoutException
  • TooManyConcurrentRequestsException
  • TooManyWaitersException
  • TransportException
  • UnknownChannelException
  • WriteException
  • WriteTimedOutException
  • stack

sealed abstract class Backoff extends AnyRef

A recursive ADT to define various backoff strategies, where duration returns the current backoff, and next returns a new Backoff.

All Backoffs are infinite unless it isExhausted (an empty Backoff), in this case, calling duration will return a NoSuchElementException, calling next will return an UnsupportedOperationException.

Finagle provides the following backoff strategies:

  1. BackoffFunction
    • Create backoffs based on a given function, can be created via Backoff.apply.
  2. BackoffFromGeneration
    • Create backoffs based on a generation function, can be created via Backoff.fromFunction.
  3. Const
    • Return a constant backoff, can be created via Backoff.const.
  4. Exponential
    • Create backoffs that grow exponentially, can be created via Backoff.exponential.
  5. Linear
    • Create backoffs that grow linearly, can be created via Backoff.linear.
  6. DecorrelatedJittered
    • Create backoffs that jitter randomly between a start value and 3 times of that value, can be created via Backoff.decorrelatedJittered.
  7. EqualJittered
    • Create backoffs that jitter between 0 and half of the exponential growth. Can be created via Backoff.equalJittered.
  8. ExponentialJittered
    • Create backoffs that jitter randomly between 0 and a value that grows exponentially by 2. Can be created via Backoff.exponentialJittered.
Note

A new Backoff will be created only when next is called.

,

None of the Backoffs are memoized, for strategies that involve randomness (DecorrelatedJittered, EqualJittered and ExponentialJittered), there is no way to foresee the next backoff value.

,

All Backoffs are infinite unless using take(Int) to create a strategy with limited number of iterations.

,

You can combine one or more Backoffs with take(Int) and concat(Backoff).

,

If the backoff returned from any Backoffs overflowed, all succeeding backoffs will be Duration.Top.

Linear Supertypes
Known Subclasses
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. Backoff
  2. AnyRef
  3. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Abstract Value Members

  1. abstract def duration: Duration

    return the current backoff

  2. abstract def isExhausted: Boolean

    return true if this is Backoff.empty, when true, calling duration will return a NoSuchElementException, calling next will return an UnsupportedOperationException.

    return true if this is Backoff.empty, when true, calling duration will return a NoSuchElementException, calling next will return an UnsupportedOperationException. This is used to terminate backoff supplies.

  3. abstract def next: Backoff

    return a new Backoff to get the next backoff

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##: Int
    Definition Classes
    AnyRef → Any
  3. final def ++(that: Backoff): Backoff

    An alias for Backoff concatenation.

  4. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  5. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  6. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
  7. final def concat(that: Backoff): Backoff

    Start creating backoffs from that once the current Backoff isExhausted.

    Start creating backoffs from that once the current Backoff isExhausted. You can combine one or more Backoffs by:

    Backoff.const(1.second).take(5)
      .concat(Backoff.linear(2.millis, 1.millis).take(7))
      .concat(Backoff.const(9.millis))
    Note

    The Backoffs are invoked in the same order as they are concatenated. The former Backoff needs to be finite in order to invoke the succeeding strategies.

    See also

    take on how to create a finite Backoff.

  8. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  9. def equals(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef → Any
  10. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
  11. final def getClass(): Class[_ <: AnyRef]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  12. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  13. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  14. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  15. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  16. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  17. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  18. final def take(attempt: Int): Backoff

    Only create backoffs for attempt number of times.

    Only create backoffs for attempt number of times. When attempt is reached, a Backoff.empty will be returned.

    Note

    Calling take with a non-positive attempt will return a Backoff.empty, where calling duration and next will throw exceptions.

  19. final def takeUntil(maxCumulativeBackoff: Duration): Backoff

    Only create backoffs until the sum of all previous backoffs is less than or equal to maxCumulativeBackoff.

    Only create backoffs until the sum of all previous backoffs is less than or equal to maxCumulativeBackoff. When maxCumulativeBackoff is reached, a Backoff.empty will be returned.

    Note

    Calling takeUntil with a non-positive maxCumulativeBackoff will return a Backoff.empty, where calling duration and next will throw exceptions.

  20. final def toJavaIterator: Iterator[Duration]

    Convert a Backoff into a Java-friendly representation of iterator.

  21. final def toStream: Stream[Duration]

    Convert the Backoff to a Stream[Duration]

    Convert the Backoff to a Stream[Duration]

    Note

    This API is only recommended to be used for migrating from Stream to Backoff.

    ,

    Every element of the returned Stream will be memorized due to the nature of Stream, when using this method, your service is at risk of memory leaks.

  22. def toString(): String
    Definition Classes
    Backoff → AnyRef → Any
  23. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  24. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  25. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()

Inherited from AnyRef

Inherited from Any

Ungrouped