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108 lines
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<title>Spring Cloud Function</title><link rel="stylesheet" type="text/css" href="css/manual-singlepage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book"><div class="titlepage"><div><div><h1 class="title"><a name="d0e3"></a>Spring Cloud Function</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="preface"><a href="#d0e9"></a></span></dt><dt><span class="chapter"><a href="#_introduction">1. Introduction</a></span></dt><dt><span class="chapter"><a href="#_getting_started">2. Getting Started</a></span></dt><dt><span class="chapter"><a href="#_building_and_running_a_function">3. Building and Running a Function</a></span></dt><dt><span class="chapter"><a href="#_dynamic_compilation">4. Dynamic Compilation</a></span></dt><dd><dl><dt><span class="section"><a href="#_start_the_function_registry_service">4.1. Start the Function Registry Service:</a></span></dt><dt><span class="section"><a href="#_register_a_function">4.2. Register a Function:</a></span></dt><dt><span class="section"><a href="#_run_a_rest_microservice_using_that_function">4.3. Run a REST Microservice using that Function:</a></span></dt><dt><span class="section"><a href="#_register_a_supplier">4.4. Register a Supplier:</a></span></dt><dt><span class="section"><a href="#_run_a_rest_microservice_using_that_supplier">4.5. Run a REST Microservice using that Supplier:</a></span></dt><dt><span class="section"><a href="#_register_a_consumer">4.6. Register a Consumer:</a></span></dt><dt><span class="section"><a href="#_run_a_rest_microservice_using_that_consumer">4.7. Run a REST Microservice using that Consumer:</a></span></dt><dt><span class="section"><a href="#_run_stream_processing_microservices">4.8. Run Stream Processing Microservices:</a></span></dt></dl></dd><dt><span class="chapter"><a href="#_function_catalog_and_flexible_function_signatures">5. Function Catalog and Flexible Function Signatures</a></span></dt><dt><span class="chapter"><a href="#_standalone_web_applications">6. Standalone Web Applications</a></span></dt><dt><span class="chapter"><a href="#_standalone_streaming_applications">7. Standalone Streaming Applications</a></span></dt><dt><span class="chapter"><a href="#_serverless_platform_adapters">8. Serverless Platform Adapters</a></span></dt><dt><span class="chapter"><a href="#_deploying_a_packaged_function">9. Deploying a Packaged Function</a></span></dt></dl></div><div class="preface"><div class="titlepage"><div><div><h1 class="title"><a name="d0e9" href="#d0e9"></a></h1></div></div></div><p>Mark Fisher, Dave Syer</p><p></p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_introduction" href="#_introduction"></a>1. Introduction</h1></div></div></div><p>Spring Cloud Function is a project with the following high-level goals:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="emphasis"><em>Promote the implementation of business logic via functions.</em></span></li><li class="listitem"><span class="emphasis"><em>Decouple the development lifecycle of business logic from any specific runtime target so that the same code can run as a web endpoint, a stream processor, or a task.</em></span></li><li class="listitem"><span class="emphasis"><em>Support a uniform programming model across serverless providers, as well as the ability to run standalone (locally or in a PaaS).</em></span></li><li class="listitem"><span class="emphasis"><em>Enable Spring Boot features (auto-configuration, dependency injection, metrics) on serverless providers.</em></span></li></ul></div><p>It abstracts away all of the transport details and
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infrastructure, allowing the developer to keep all the familiar tools
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and processes, and focus firmly on business logic.</p><p>Here’s a complete, executable, testable Spring Boot application
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(implementing a simple string manipulation):</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@SpringBootApplication</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> Application {
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<em><span class="hl-annotation" style="color: gray">@Bean</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> Function<Flux<String>, Flux<String>> uppercase() {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> flux -> flux.map(value -> value.toUpperCase());
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}
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">static</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> main(String[] args) {
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SpringApplication.run(Application.<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span>, args);
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}
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}</pre><p>It’s just a Spring Boot application, so it can be built, run and
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tested, locally and in a CI build, the same way as any other Spring
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Boot application. The <code class="literal">Function</code> is from <code class="literal">java.util</code> and <code class="literal">Flux</code> is a
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<a class="link" href="http://www.reactive-streams.org/" target="_top">Reactive Streams</a> <code class="literal">Publisher</code> from
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<a class="link" href="https://projectreactor.io/" target="_top">Project Reactor</a>. The function can be
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accessed over HTTP or messaging.</p><p>Spring Cloud Function has 4 main features:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">Wrappers for <code class="literal">@Beans</code> of type <code class="literal">Function</code>, <code class="literal">Consumer</code> and
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<code class="literal">Supplier</code>, exposing them to the outside world as either HTTP
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endpoints and/or message stream listeners/publishers with RabbitMQ, Kafka etc.</li><li class="listitem">Compiling strings which are Java function bodies into bytecode, and
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then turning them into <code class="literal">@Beans</code> that can be wrapped as above.</li><li class="listitem">Deploying a JAR file containing such an application context with an
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isolated classloader, so that you can pack them together in a single
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JVM.</li><li class="listitem">Adapters for <a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-aws" target="_top">AWS Lambda</a>, <a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-azure" target="_top">Azure</a>, <a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-openwhisk" target="_top">Apache OpenWhisk</a> and possibly other "serverless" service providers.</li></ol></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>Spring Cloud is released under the non-restrictive Apache 2.0 license. If you would like to contribute to this section of the documentation or if you find an error, please find the source code and issue trackers in the project at <a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/docs/src/main/asciidoc" target="_top">github</a>.</p></td></tr></table></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_getting_started" href="#_getting_started"></a>2. Getting Started</h1></div></div></div><p>Build from the command line (and "install" the samples):</p><pre class="screen">$ ./mvnw clean install</pre><p>(If you like to YOLO add <code class="literal">-DskipTests</code>.)</p><p>Run one of the samples, e.g.</p><pre class="screen">$ java -jar spring-cloud-function-samples/function-sample/target/*.jar</pre><p>This runs the app and exposes its functions over HTTP, so you can
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convert a string to uppercase, like this:</p><pre class="screen">$ curl -H "Content-Type: text/plain" localhost:8080/uppercase -d Hello
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HELLO</pre><p>You can convert multiple strings (a <code class="literal">Flux<String></code>) by separating them
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with new lines</p><pre class="screen">$ curl -H "Content-Type: text/plain" localhost:8080/uppercase -d 'Hello
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> World'
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HELLOWORLD</pre><p>(You can use <code class="literal"><sup>Q</sup>J</code> in a terminal to insert a new line in a literal
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string like that.)</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_building_and_running_a_function" href="#_building_and_running_a_function"></a>3. Building and Running a Function</h1></div></div></div><p>The sample <code class="literal">@SpringBootApplication</code> above has a function that can be
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decorated at runtime by Spring Cloud Function to be an HTTP endpoint,
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or a Stream processor, for instance with RabbitMQ, Apache Kafka or
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JMS.</p><p>The <code class="literal">@Beans</code> can be <code class="literal">Function</code>, <code class="literal">Consumer</code> or <code class="literal">Supplier</code> (all from
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<code class="literal">java.util</code>), and their parametric types can be String or POJO. A
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<code class="literal">Function</code> is exposed as a Spring Cloud Stream <code class="literal">Processor</code> if
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<code class="literal">spring-cloud-function-stream</code> is on the classpath.
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A <code class="literal">Consumer</code> is also exposed as a Stream
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<code class="literal">Sink</code> and a <code class="literal">Supplier</code> translates to a Stream <code class="literal">Source</code>.
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HTTP endpoints are exposed if the Stream binder is <code class="literal">spring-cloud-stream-binder-servlet</code>.</p><p>Functions can be of <code class="literal">Flux<String></code> or <code class="literal">Flux<Pojo></code> and Spring Cloud
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Function takes care of converting the data to and from the desired
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types, as long as it comes in as plain text or (in the case of the
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POJO) JSON. TBD: support for <code class="literal">Flux<Message<Pojo>></code> and maybe plain
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<code class="literal">Pojo</code> types (Fluxes implied and implemented by the framework).</p><p>Functions can be grouped together in a single application, or deployed
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one-per-jar. It’s up to the developer to choose. An app with multiple
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functions can be deployed multiple times in different "personalities",
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exposing different functions over different physical transports.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_dynamic_compilation" href="#_dynamic_compilation"></a>4. Dynamic Compilation</h1></div></div></div><p>There is a sample app that uses the function compiler to create a
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function from a configuration property. The vanilla "function-sample"
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also has that feature. And there are some examples that you can run to
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see the compilation happening at run time. To run these examples,
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change into the <code class="literal">scripts</code> directory:</p><pre class="screen">cd scripts</pre><p>Also, start a RabbitMQ server locally (e.g. execute <code class="literal">rabbitmq-server</code>).</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_start_the_function_registry_service" href="#_start_the_function_registry_service"></a>4.1 Start the Function Registry Service:</h2></div></div></div><pre class="screen">./function-registry.sh</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_register_a_function" href="#_register_a_function"></a>4.2 Register a Function:</h2></div></div></div><pre class="screen">./registerFunction.sh -n uppercase -f "f->f.map(s->s.toString().toUpperCase())"</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_run_a_rest_microservice_using_that_function" href="#_run_a_rest_microservice_using_that_function"></a>4.3 Run a REST Microservice using that Function:</h2></div></div></div><pre class="screen">./web.sh -f uppercase -p 9000
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curl -H "Content-Type: text/plain" -H "Accept: text/plain" localhost:9000/uppercase -d foo</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_register_a_supplier" href="#_register_a_supplier"></a>4.4 Register a Supplier:</h2></div></div></div><pre class="screen">./registerSupplier.sh -n words -f "()->Flux.just(\"foo\",\"bar\")"</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_run_a_rest_microservice_using_that_supplier" href="#_run_a_rest_microservice_using_that_supplier"></a>4.5 Run a REST Microservice using that Supplier:</h2></div></div></div><pre class="screen">./web.sh -s words -p 9001
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curl -H "Accept: application/json" localhost:9001/words</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_register_a_consumer" href="#_register_a_consumer"></a>4.6 Register a Consumer:</h2></div></div></div><pre class="screen">./registerConsumer.sh -n print -t String -f "System.out::println"</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_run_a_rest_microservice_using_that_consumer" href="#_run_a_rest_microservice_using_that_consumer"></a>4.7 Run a REST Microservice using that Consumer:</h2></div></div></div><pre class="screen">./web.sh -c print -p 9002
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curl -X POST -H "Content-Type: text/plain" -d foo localhost:9002/print</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_run_stream_processing_microservices" href="#_run_stream_processing_microservices"></a>4.8 Run Stream Processing Microservices:</h2></div></div></div><p>First register a streaming words supplier:</p><pre class="screen">./registerSupplier.sh -n wordstream -f "()->Flux.interval(Duration.ofMillis(1000)).map(i->\"message-\"+i)"</pre><p>Then start the source (supplier), processor (function), and sink (consumer) apps
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(in reverse order):</p><pre class="screen">./stream.sh -p 9103 -i uppercaseWords -c print
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./stream.sh -p 9102 -i words -f uppercase -o uppercaseWords
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./stream.sh -p 9101 -s wordstream -o words</pre><p>The output will appear in the console of the sink app (one message per second, converted to uppercase):</p><pre class="screen">MESSAGE-0
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MESSAGE-1
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MESSAGE-2
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MESSAGE-3
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MESSAGE-4
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MESSAGE-5
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MESSAGE-6
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MESSAGE-7
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MESSAGE-8
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MESSAGE-9
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...</pre></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_function_catalog_and_flexible_function_signatures" href="#_function_catalog_and_flexible_function_signatures"></a>5. Function Catalog and Flexible Function Signatures</h1></div></div></div><p>One of the main features of Spring Cloud Function is to adapt and
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support a range of type signatures for user-defined functions. So
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users can supply a bean of type <code class="literal">Function<String,String></code>, for
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instance, and the <code class="literal">FunctionCatalog</code> will wrap it into a
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<code class="literal">Function<Flux<String>,Flux<String>></code>. Users don’t normally have to
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care about the <code class="literal">FunctionCatalog</code> at all, but it is useful to know what
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kind of functions are supported in user code.</p><p>Generally speaking users can expect that if they write a function for
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a plain old Java type (or primitive wrapper), then the function
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catalog will wrap it to a <code class="literal">Flux</code> of the same type. If the user writes
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a function using <code class="literal">Message</code> (from spring-messaging) it will receive and
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transmit headers from any adapter that supports key-value metadata
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(e.g. HTTP headers). Here are the details.</p><div class="informaltable"><table style="border-collapse: collapse;border-top: 0.5pt solid ; border-bottom: 0.5pt solid ; border-left: 0.5pt solid ; border-right: 0.5pt solid ; "><colgroup><col class="col_1"><col class="col_2"><col class="col_3"></colgroup><thead><tr><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">User Function</th><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">Catalog Registration</th><th style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </th></tr></thead><tbody><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<S,T></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<S>, Flux<T>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Message<S>,Message<T>></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<Message<S>>, Flux<Message<T>>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<S>, Flux<T>></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<S>, Flux<T>></code> (pass through)</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Supplier<T></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Supplier<Flux<T>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Supplier<Flux<T>></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Supplier<Flux<T>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Consumer<T></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<T>, Mono<Void>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Consumer<Message<T>></code></p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Function<Flux<Message<T>>, Mono<Void>></code></p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"> </td></tr><tr><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Consumer<Flux<T>></code></p></td><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p><code class="literal">Consumer<Flux<T>></code></p></td><td style="" align="left" valign="top"> </td></tr></tbody></table></div><p>Consumer is a little bit special because it has a <code class="literal">void</code> return type,
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which implies blocking, at least potentially. Most likely you will not
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need to write <code class="literal">Consumer<Flux<?>></code>, but if you do need to do that,
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remember to subscribe to the input flux. If you declare a <code class="literal">Consumer</code>
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of a non publisher type (which is normal), it will be converted to a
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function that returns a publisher, so that it can be subscribed to in
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a controlled way.</p><p>A function catalog can contain a <code class="literal">Supplier</code> and a <code class="literal">Function</code> (or
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<code class="literal">Consumer</code>) with the same name (like a GET and a POST to the same
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resource). It can even contain a <code class="literal">Consumer<Flux<>></code> with the same name
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as a <code class="literal">Function</code>, but it cannot contain a <code class="literal">Consumer<T></code> and a
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<code class="literal">Function<T,S></code> with the same name when <code class="literal">T</code> is not a <code class="literal">Publisher</code>
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because the consumer would be converted to a <code class="literal">Function</code> and only one
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of them can be registered.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_standalone_web_applications" href="#_standalone_web_applications"></a>6. Standalone Web Applications</h1></div></div></div><p>The <code class="literal">spring-cloud-function-web</code> module has autoconfiguration that
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activates when it is included in a Spring Boot web application (with
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MVC support). There is also a <code class="literal">spring-cloud-starter-function-web</code> to
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collect all the optional dependnecies in case you just want a simple
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getting started experience.</p><p>With the web configurations activated your app will have an MVC
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endpoint (on "/" by default, but configurable with
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<code class="literal">spring.cloud.function.web.path</code>) that can be used to access the
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functions in the application context. The supported content types are
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plain text and JSON.</p><div class="informaltable"><table style="border-collapse: collapse;border-top: 0.5pt solid ; border-bottom: 0.5pt solid ; border-left: 0.5pt solid ; border-right: 0.5pt solid ; "><colgroup><col class="col_1"><col class="col_2"><col class="col_3"><col class="col_4"><col class="col_5"></colgroup><thead><tr><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">Method</th><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">Path</th><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">Request</th><th style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top">Response</th><th style="border-bottom: 0.5pt solid ; " align="left" valign="top">Status</th></tr></thead><tbody><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>GET</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>/{supplier}</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>-</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>Items from the named supplier</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"><p>200 OK</p></td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>POST</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>/{consumer}</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>JSON object or text</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>Mirrors input and pushes request body into consumer</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"><p>202 Accepted</p></td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>POST</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>/{consumer}</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>JSON array or text with new lines</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>Mirrors input and pushes body into consumer one by one</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"><p>202 Accepted</p></td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>POST</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>/{function}</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>JSON object or text</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>The result of applying the named function</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"><p>200 OK</p></td></tr><tr><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>POST</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>/{function}</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>JSON array or text with new lines</p></td><td style="border-right: 0.5pt solid ; border-bottom: 0.5pt solid ; " align="left" valign="top"><p>The result of applying the named function</p></td><td style="border-bottom: 0.5pt solid ; " align="left" valign="top"><p>200 OK</p></td></tr><tr><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p>GET</p></td><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p>/{function}/{item}</p></td><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p>-</p></td><td style="border-right: 0.5pt solid ; " align="left" valign="top"><p>Convert the item into an object and return the result of applying the function</p></td><td style="" align="left" valign="top"><p>200 OK</p></td></tr></tbody></table></div><p>As the table above shows the behaviour of the endpoint depends on the method and also the type of incoming request data. When the incoming data is single valued, and the target function is declared as obviously single valued (i.e. not returning a collection or <code class="literal">Flux</code>), then the response will also contain a single value. For multi-valued responses the client can ask for a server-sent event stream by sending `Accept: text/event-stream". If there is only one function (consumer etc.) then the name in the path is optional. Composite functions can be addressed using pipes or commas to separate function names (pipes are legal in URL paths, but a bit awkward to type on the command line).</p><p>Functions and consumers that are declared with input and output in <code class="literal">Message<?></code> will see the request headers on the input messages, and the output message headers will be converted to HTTP headers.</p><p>When POSTing text the response format might be different with Spring Boot 2.0 and older versions, depending on the content negotiation (provide content type and accpt headers for the best results).</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_standalone_streaming_applications" href="#_standalone_streaming_applications"></a>7. Standalone Streaming Applications</h1></div></div></div><p>To send or receive messages from a broker (such as RabbitMQ or Kafka) you can use the <code class="literal">spring-cloud-function-stream</code> adapter. Add the adapter to your classpath along with the appropriate binder from Spring Cloud Stream. The adapter will bind to the message broker as a <code class="literal">Processor</code> (input and output streams) unless the user explicitly disables one or the other using <code class="literal">spring.cloud.function.stream.{source,sink}.enabled=false</code>.</p><p>An incoming message is routed to a function (or consumer). If there is only one, then the choice is obvious. If there are multiple functions that can accept an incoming message, the message is inspected to see if there is a <code class="literal">stream_routekey</code> header containing the name of a function. Routing headers or function names can be composed using a comma- or pipe-separated name. The header is also added to outgoing messages from a supplier. Messages with no route key can be routed exclusively to a function or consumer by specifying <code class="literal">spring.cloud.function.stream.{processor,sink}.name</code>. If a single function cannot be identified to process an incoming message there will be an error, unless you set <code class="literal">spring.cloud.function.stream.shared=true</code>, in which case such messages will be sent to all compatible functions. A single supplier can be chosen for output messages from a supplier (if more than one is available) using the <code class="literal">spring.cloud.function.stream.source.name</code>.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>some binders will fail on startup if the message broker is not available and the function catalog contains suppliers that immediately produce messages when accessed. You can switch off the automatic publishing from suppliers on startup using the <code class="literal">spring.cloud.function.strean.supplier.enabled=false</code> flag.</p></td></tr></table></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_serverless_platform_adapters" href="#_serverless_platform_adapters"></a>8. Serverless Platform Adapters</h1></div></div></div><p>As well as being able to run as a standalone process, a Spring Cloud
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Function application can be adapted to run one of the existing
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servlerless platforms. In the project there are adapters for
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<a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-aws" target="_top">AWS
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Lambda</a>,
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<a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-azure" target="_top">Azure</a>,
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and
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<a class="link" href="https://github.com/spring-cloud/spring-cloud-function/tree/master/spring-cloud-function-adapters/spring-cloud-function-adapter-openwhisk" target="_top">Apache
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OpenWhisk</a>. The Oracle Fn platform has its own Spring Cloud Function adapter.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_deploying_a_packaged_function" href="#_deploying_a_packaged_function"></a>9. Deploying a Packaged Function</h1></div></div></div><p>Spring Cloud Function provides a "deployer" library that allows you to launch a jar file (or exploded archive, or set of jar files) with an isolated class loader and expose the functions defined in it. This is quite a powerful tool that would allow you to, for instance, adapt a function to a range of different input-output adapters without changing the target jar file. Serverless platforms often have this kind of feature built in, so you could see it as a building block for a function invoker in such a platform (indeed the <a class="link" href="https://projectriff.io" target="_top">Riff</a> Java function invoker uses this library).</p><p>The standard entry point of the API is the Spring configuration annotation <code class="literal">@EnableFunctionDeployer</code>. If that is used in a Spring Boot application the deployer kicks in and looks for some configuration to tell it where to find the function jar. At a minimum the user has to provide a <code class="literal">function.location</code> which is a URL or resource location for the archive containing the functions. It can optionally use a <code class="literal">maven:</code> prefix to locate the artifact via a dependency lookup (see <code class="literal">FunctionProperties</code> for complete details). A Spring Boot application is bootstrapped from the jar file, using the <code class="literal">MANIFEST.MF</code> to locate a start class, so that a standard Spring Boot fat jar works well, for example. If the target jar can be launched successfully then the result is a function registered in the main application’s <code class="literal">FunctionCatalog</code>. The registered function can be applied by code in the main application, even though it was created in an isolated class loader (by default).</p></div></div></body></html> |