svc-loader-yaml

service

Load and reload processors at runtime from YAML or Java source. Hot-reload graphs without restarting the server.

<dependency>
    <groupId>com.telamin</groupId>
    <artifactId>svc-loader-yaml</artifactId>
    <version>1.0.35</version>
</dependency>

When to use

• You ship processor topologies as YAML config and want operators to swap them at runtime.
• You need a "compile + load" admin command that builds a new processor from source.
• You're prototyping topologies and want fast iteration without server restarts.

Modes

Mode	Source	Speed at runtime	Best for
Compiled	Java source	Fast	Production-grade dynamic loading
Interpreted	YAML	Slower at first event, fast steady-state	Pure-config topologies

Sample

Register the loader as a service and point it at one or more processor topologies to instantiate at boot:

services:
  - name: yamlLoaderService
    service: !!com.telamin.mongoose.plugin.loader.yaml.EventHandlerLoader
      loadAtStartup:
        - { yamlFile: "config/log-processor.yaml", compile: true }

Or, programmatically from Java:

EventHandlerLoader.EventLoadAtStartup load = new EventHandlerLoader.EventLoadAtStartup();
load.setYamlFile("config/log-processor.yaml");
load.setCompile(true);

EventHandlerLoader loader = new EventHandlerLoader();
loader.setLoadAtStartup(Set.of(load));

MongooseServerConfig.builder()
    .addService(ServiceConfig.<EventHandlerLoader>builder()
        .service(loader)
        .serviceClass(EventHandlerLoader.class)
        .name("yamlLoaderService")
        .build())
    .build();

The processor YAML uses namedNodes or nodes plus SnakeYAML's !!ClassName tag:

namedNodes:
  logHandler: !!com.example.MyHandler
    prefix: "INCOMING:"
enableAudit: true

MyHandler is a plain ObjectEventHandlerNode — no start() override or explicit subscribeToNamedFeed(...) call required. Under broadcast=true feeds (the catalogue's default), the dispatcher wires the dynamically-loaded processor through the same subscription path as a statically-registered one.

When svc-admin-rest, svc-admin-telnet, or svc-admin-web is on the classpath, the loader also registers four admin commands:

• yamlLoader.compileProcessor <yamlFile> [group] — compile and add a YAML topology
• yamlLoader.interpretProcessor <yamlFile> [group] — same, via the Fluxtion interpreter (no codegen)
• javaLoader.compileProcessor <javaFile> [group] — compile and add a Java FluxtionGraphBuilder source file
• javaLoader.interpretProcessor <javaFile> [group] — same, via the interpreter

Examples

• plugins/yaml-service-loader-example — EventHandlerLoader registered as a service with loadAtStartup; instantiates a handler from log-processor.yaml, feeds it events from an in-memory source, prints them through the YAML-injected prefix.
• getting-started/five-minute-yaml-tutorial — full YAML config flow into a booting server. Same config shape svc-loader-yaml consumes at runtime.
• getting-started/app-integration-tutorial — multi-process YAML config across a data-generator + PnL calculator.

Gotchas

• SnakeYAML 2.x blocks !!ClassName tags by default. Until the plugin ships a release that installs a permissive TagInspector, pin org.yaml:snakeyaml:1.33 in the consumer pom.
• mongoose >= 1.0.9 required. Earlier versions miss event-processor agents that the loader registers during its own start() hook — the processor would init but never receive events. Fixed by a late-start pass in MongooseServer.start().

Source

mongoose-plugins/service/svc-loader-yaml