HTTP
This module defines the ServiceTalk client and server API for the HTTP/1.x protocol. This module supports all the different Programming Paradigms for client and server. Here is a quick start example of the blocking and aggregated paradigm:
Blocking Client
try (BlockingHttpClient client = HttpClients.forSingleAddress("localhost", 8080).buildBlocking()) {
HttpResponse response = client.request(client.get("/sayHello"));
// use the response
}Blocking Server
HttpServers.forPort(8080)
.listenBlockingAndAwait((ctx, request, responseFactory) ->
responseFactory.ok().payloadBody("Hello World!", textSerializer()))
.awaitShutdown();Extensibility and Filters
The design of this protocol involves configuring builders for core protocol concerns, and then appending Filters for
extensibility. Filters are described in more detail below (e.g. Service Filters, Client Filters) but in
general they facilitate user code to filter/intercept/modify the request/response processing. Filters can be used for
cross-cutting concerns such as authentication, authorization, logging, metrics, tracing, etc…
Server
The server side is built around the concept of Service. A Service is where your business logic lives. ServiceTalk’s
HTTP module will interact with a single service which is provided by the user via HttpServers. The flow of data from
the socket to the HTTP Service is visualized as follows:
+--------+ request +---------+ +---------+ | |--------->| HTTP |------>| HTTP | | Socket | | Decoder | | Service | | |<---------| Encoder |<------| | +--------+ response +---------+ +---------+
Each Service has access to a
HttpServiceContext
which provides additional context
(via ConnectionContext)
into the Connection/transport details for each request/response. This means that the HttpService may be invoked
for multiple connections, from different threads, and even concurrently.
Service Filters
Filters provide a means to filter/intercept and modify each request/response life cycle. Service Filters are used to
implement
tracing
metrics, logging,
basic auth,
and any other extension that needs request/response level visibility. The diagram below describes the control flow
as related to Service filters:
+--------+ request +---------+ +---------+ +---------+ +---------+ | |--------->| HTTP |------>| HTTP |------>| HTTP |------>| HTTP | | Socket | | Decoder | | Service | | Service | | Service | | |<---------| Encoder |<------| Filter 1|<------| Filter n|<------| | +--------+ response +---------+ +---------+ +---------+ +---------+
To implement a Service filter you should implement the
Service Filter Factory and append it
on the HttpServerBuilder via
HttpServerBuilder#appendServiceFilter(..).
Currently we only support writing Filters for the
Asynchronous and Streaming
programming paradigm. An
Asynchronous and Streaming
filter can be used with a Service in any other programming paradigm.
|
Routers
In practice it is common for a HTTP Service to handle many different types of request(s) that all have unique
processing requirements. The control flow in ServiceTalk is represented by a "Router". A "Router" is a Service that
owns the responsibility of multiplexing the control flow. ServiceTalk does not mandate a specific "Router"
implementation but provides a couple reference implementations for common use cases (e.g.
Predicate Router and
JAX-RS via Jersey). The general component diagram of a "Router"
is as follows:
+---------+
/------>| Route 1 |
| +---------+
+--------+ request +---------+ +---------+ |
| |--------->| HTTP |------>| HTTP | | +---------+
| Socket | | Decoder | | Service |<------+------>| Route 2 |
| |<---------| Encoder |<------| Router | | +---------+
+--------+ response +---------+ +---------+ |
| +---------+
\------>| Route n |
+---------+
Client
A Client is generally responsible for managing multiple Connections. There are a few flavors of HTTP Clients:
SingleAddress Client
This Client will connect to a single unresolved address, that is provided while creating the client. The unresolved
address is resolved via an asynchronous DNS resolver by default (see Service Discovery). This Client is for use
cases where you want to issue requests to a single service (that may have multiple instances).
MultiAddress Client
This Client parses the request-target to determine the remote
address for each request. This Client simulates a browser type of use case.
Each of the above Clients can be created via the
HttpClients static factory.
The Client manages multiple Connections via a
LoadBalancer. The control flow
of a request/response can be visualized in the below diagram:
+--------------+ +----------------------+ +--------+
/--->| Connection 1 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| +--------------+ +----------------------+ +--------+
+--------+ request +--------------+ |
| |--------->| | | +--------------+ +----------------------+ +--------+
| Client | | LoadBalancer |<---+--->| Connection 2 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| |<---------| | | +--------------+ +----------------------+ +--------+
+--------+ response +--------------+ |
| +--------------+ +----------------------+ +--------+
\--->| Connection x |<--->| HTTP Decoder/Encoder |<--->| Socket |
+--------------+ +----------------------+ +--------+
The LoadBalancer is consulted
for each request to determine which connection should be used. The LoadBalancer interface is extensible and
the reference implementation provides a
Round Robin algorithm.
Client Filters
Filters provide a means to filter/intercept and modify each request/response life cycle. Client Filters are used to
implement
tracing
metrics, logging, authorization, and any other extension that needs request/response level visibility.
+--------------+ +----------------------+ +--------+
/--->| Connection 1 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| +--------------+ +----------------------+ +--------+
+--------+ request +---------+ +---------+ +--------------+ |
| |--------->| |---->| |---->| | | +--------------+ +----------------------+ +--------+
| Client | | Client | | Client | | LoadBalancer |<---+--->| Connection 2 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| |<---------| Filter 1|<----| Filter n|<----| | | +--------------+ +----------------------+ +--------+
+--------+ response +---------+ +---------+ +--------------+ |
| +--------------+ +----------------------+ +--------+
\--->| Connection x |<--->| HTTP Decoder/Encoder |<--->| Socket |
+--------------+ +----------------------+ +--------+
To implement a Client filter you should implement the
Client Filter Factory and append it on
the HttpClientBuilder via
HttpClientBuilder#appendClientFilter(..).
Currently we only support writing Filters for the
Asynchronous and Streaming
programming paradigm. An
Asynchronous and Streaming
filter can be used with a Client in any other programming paradigm.
|
Connection Filters
The Client doesn’t have visibility into Connection specific information. For example, the Connection layer knows
about transport details such as connected remote address and other elements in the
ConnectionContext.
If you have use cases that require this information in the request/response control flow you can use a
Connection Filter. The diagram below illustrates how the Connection Filter interacts with the request/response
control flow.
+---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
/--->| Connection Filter 1 |<--->| Connection Filter n |<--->| Connection 1 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| +---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
+--------+ request +--------------+ |
| |--------->| | | +---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
| Client | | LoadBalancer |<---+--->| Connection Filter 1 |<--->| Connection Filter n |<--->| Connection 2 |<--->| HTTP Decoder/Encoder |<--->| Socket |
| |<---------| | | +---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
+--------+ response +--------------+ |
| +---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
\--->| Connection Filter 1 |<--->| Connection Filter n |<--->| Connection x |<--->| HTTP Decoder/Encoder |<--->| Socket |
+---------------------+ +---------------------+ +--------------+ +----------------------+ +--------+
Service Discovery
Another core component of the Client is the
ServiceDiscoverer. The
ServiceDiscoverer is responsible for resolving a service address into a set of resolved addresses used to create
Connection(s) by the LoadBalancer. The default implementation for HTTP is DNS and will resolve the IP addresses of
each service address every TTL seconds. ServiceDiscoverers
are typically not invoked in the request/response path and addresses are resolved "out of band", a.k.a in the
background.
+------------+
| Service |
| Discoverer |
+------------+
^
|
| +--------------+
| /--->| Connection 1 |
V | +--------------+
+--------+ request +--------------+ |
| |--------->| | | +--------------+
| Client | | LoadBalancer |<---+--->| Connection 2 |
| |<---------| | | +--------------+
+--------+ response +--------------+ |
| +--------------+
\--->| Connection x |
+--------------+
Serialization
Serialization factories are made available in the HttpSerializationProviders static factory class.
The core abstractions
HttpDeserializer and
HttpSerializer are designed to be coupled to a
specific Java type T and accessed via a
HttpSerializationProvider. The
HttpDeserializer and
HttpSerializer are also designed to handle the HTTP
headers data behind the scenes. This means either checking if content-type format is compatible with the
deserialization format and also adding a content-type header identifying the resulting serialization format.