The document discusses the migration of services to Armeria, highlighting the benefits of using Armeria for managing large requests and combining it with Spring. It outlines the migration steps, including quick wins and must-have features that improve performance and simplify service architecture. The challenges of migrating existing blocking code to a fully asynchronous model are also addressed, alongside performance improvements achieved through the transition.

1. HelloArmeria,ByeSpring
GihwanKim,LINE
KyeongsuYim,LINE
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2. TableofContent
1.Why Armeriamigration?
2.Migrationsteps
Quick-win(Spring+ArmeriaClient)
Must-have(ArmeriaServer+TomcatService)
FinalGoal(ArmeriaOnly+SpringforDI)
Challenges
3.PerformanceHighlight-Streaminglargebodywithoutexhaustingresources
Spring'swayofuploading/downloadingabinary
Goingreactivewith Armeria!
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3. WhyArmeriamigration?
ChannelGateway-APIGatewayserverforLINEfamilyservices&3rdpartyapps
Hasmanyupstreamservices
Serves8billion+requestsaday
Before:
SpringBoot+Tomcat(HTTP/1.1)
ApacheHttpClient
Thewholesystemgetseailyoverloadedevenonatinyupstreamfailure
Manyhackstoisolatetheissuestowheretheybelongto(e.g.dedicatedthreadpoolorservergroups)
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4. WhyArmeriaMigration?
AfterArmeriamigration:
Asyncclient+microservicepatternimplementedviadecorators
Circuitbreaker,client-sideloadbalancingwithautomaticupstreamhealth
check
Upstreamfailurenolongerpropagatestotheotherservices..!
Servergetsmoreversatile
NativelyspeaksHTTP/2incleartext
Largebinarystreamingwithoutaffectingthelatencyofotherservices
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5. Startingamigrationisabreeze..
..sinceArmeriaallowstokeepyourlegacywhilegettingthemostoutofit..!
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6. Migration:Quick-win(SpringApp+ArmeriaClient)
JustaddArmeriacoredependencyanduseitspowerfulclienteverywhere!
@Bean
public WebClient lineAPIClient() {
return WebClient.builder("https://api.line.me")
.decorator(LoggingClient.newDecorator())
.decorator(ContentPreviewingClient.newDecorator(2048))
.decorator(RetryingClient.newDecorator(RetryRule.failsafe()))
.decorator(CircuitBreakerClient.newDecorator(..))
.build();
}
final AggregateHttpResponse res = lineAPIClient.get("/v2/profile").aggregate().join();
Microservicepatternwithoutintroducinganotherlayer
Failsaferetry,circuitbreaker,client-sideloadbalancing,metriccollectingandmuchmore..!
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7. Migration:Must-have(ArmeriaServer+TomcatService)
ReplacethewholenetworklayerwithArmeria!
..byaddingjustfewlinesofcode.
@Bean
public ArmeriaServerConfigurator serverConfigurator(ServletWebServerApplicationContext context) {
TomcatWebServer container = (TomcatWebServer) context.getWebServer();
container.start();
return sb -> {
sb.serviceUnder("/", TomcatService.of(container.getTomcat()));
}
}
Youcanaddasync gRPC , Thrift servicestothesameportwithyourRESTservices
withoutTomcatoverhead
Yourservernativelyspeaks HTTP/2 bothonTLSandcleartext
...still,youkeepservingyour Tomcat legacyasisvia TomcatService
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8. Migration:FinalGoal(ArmeriaOnly&SpringforDI)
Replace @Controller swithArmeria's AnnotatedService .
@RestController("/coffee")
class CoffeeController {
private final CoffeeService coffeeService;
public CoffeeController(CoffeeService coffeeService) {
this.coffeeService = coffeeService;
}
@PostMapping("/brew")
public void brewCoffee() {
coffeeService.brew();
}
}
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9. Migration:FinalGoal(ArmeriaOnly&SpringforDI)
Replace @Controller swithArmeria's AnnotatedService .
@ConsumesJson
@ProducesJson
@PathPrefix("/coffee")
class CoffeeRouter {
private final CoffeeService coffeeService;
public CoffeeRouter(CoffeeService coffeeService) {
this.coffeeService = coffeeService;
}
@Post("/brew")
public CompletableFuture<Void> brewCoffee() {
coffeeService.brew();
}
}
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10. Migration:FinalGoal(ArmeriaOnly&SpringforDI)
Register AnnotatedService toArmeriaserver.
@Bean
public ArmeriaServerConfigurator configureServer(CoffeeService coffeeService) {
return sb -> {
sb.annotatedService(new CoffeeRouter(coffeeService));
};
}
Nowyourserverrunsfullyasynchronous..!
Armeriahandlesthewhole request - response pipeline.
SupportsvariousJVMasynctechnologies.
kotlin-coroutine , RxJava , Reactor , CompletableFuture
but,youstillbenefitfromSpring's auto-configuration &DI..!
Allspringfeatures&integrationsrunjustfine (e.g.spring-starters).
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11. Migration:Challenges
RunningblockingcodeinArmeriaapplication
// Your blocking code..
public void brew() {
coffeeJdbcRepository.save(new Coffee("cold brew"));
}
@Post("/brew")
@Blocking // Should always run in a blocking thread.
public void brewCoffee() {
coffeeService.brew();
}
Veryeasytoshootyourownfootbyblockingeventloops
Youshouldalwaysbecarefulofthethreadsthatyourlegacyblockingcoderunson
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12. Migration:Challenges
Managing RequestContext hoppingthreads
public CompletableFuture<Void> brewAsync() {
return CompletableFuture
.supplyAsync(() -> coffeeJdbcRepository.save(new Coffee()))
.thenApply(() -> {
RequestContext.current(); // This will throw an error.
});
}
Areqeustishandledonvariousthreads
Oldwayofrelyingon ThreadLocal doesn'tworkanymore..
RequestContextHooks comestotherescue
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13. PerformanceHighlight
WemigratedanAPIfordownloadingamessage'smediacontent(imageorvideo)
Withcustomizedauth,additionalHTTPcallduringdownload
NGINXwiththeOpenRestywasourfirstbet,butstoppedthemigrationsince:
AdditionalcostoflearningLua
DuplicatecodebetweenJavaandLua
DifficultyoftestingNGINX
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14. PerformanceHighlight
Armeriacomestotherescue
UseexistingwebapplicationserverrunningonArmeria&Tomcat(SpringMVC)
OtherAPIsareservedonTomcat,butthecontentdownloadAPIisonArmeria
only
About25%performancegaininlatencycomparedtoSpringMVC
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15. StreamingMadeEasywithArmeria
Spring'swayofservinglargepayload
@GetMapping("/download")
public ResponseEntity<byte[]> downloadImage() {
byte[] image = restTemplate.get("https://example.com");
return ResponseEntity.ok(image);
}
Whathappensif...:
therearemanyrequestsoraburst?
somerequeststaketoolongtimetoserve?
Threadpoolgetsexhaustedbecauseservletshouldallocateadedicatedthreadforarequest
OutOfMemoryException maybeobservedsincethewholecontentshouldbeloadedonJVM
heapbeforesendingaresponse
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16. StreamingMadeEasywithArmeria
Armeriacanbeasilverbullet
Armeriaiscompletelyasynchronousandreactive
Wedon'tneedadedicatedthreadanymore
RelaysmallchunkofHTTPdataone-by-onetoclient/upstreamassoonasreceive
fromupstream/client
AllisdonewithoutcopyingcontentontheJVMheap
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17. StreamingMadeEasywithArmeria
GoingReactive
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18. StreamingMadeEasywithArmeria
Downloadandcustomizeresponseheaders
private WebClient upstreamClient = WebClient.of("https://example.com");
public HttpResponse serve(ServiceRequestContext ctx, HttpRequest req) {
// You can do anything (such as request validation)
HttpResponse res = upstreamClient.get("/a-very-big-file")
.mapHeaders(headers -> {
HttpHeaders customizedHeaders = ...
return customizedHeaders;
});
// You can do anything
return res;
}
Downloadafilefromhttps://example.com/a-very-big-fileandcustomizeHTTP
headers(e.g.sanitizing,additionalheaders) 18

19. StreamingMadeEasywithArmeria
Uploadingisalsojustaseasy
private WebClient upstreamClient = WebClient.of("https://example.com");
public HttpResponse serve(ServiceRequestContext ctx, HttpRequest req) {
// You can do anything (such as request validation)
HttpResponse res = upstreamClient.execute(req);
// You can do anything
return res;
}
RelaythegivenHTTPrequesttohttps://example.comregardlessofthesizeofbody
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20. StreamingMadeEasywithArmeria
Intherealworld
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21. Thankyou
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