discord4j.rest.request.RequestStream Maven / Gradle / Ivy
/*
* This file is part of Discord4J.
*
* Discord4J is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Discord4J is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Discord4J. If not, see
* The flow of a request through the stream is as follows:
*
* 
*/
class RequestStream {
private static final Logger log = Loggers.getLogger(RequestStream.class);
private final BucketKey id;
private final RequestQueue> requestQueue;
private final GlobalRateLimiter globalRateLimiter;
private final Scheduler timedTaskScheduler;
private final List responseFunctions;
private final DiscordWebClient httpClient;
private final RateLimitStrategy rateLimitStrategy;
private final RateLimitRetryOperator rateLimitRetryOperator;
RequestStream(BucketKey id, RouterOptions routerOptions, DiscordWebClient httpClient,
RateLimitStrategy rateLimitStrategy) {
this.id = id;
this.requestQueue = routerOptions.getRequestQueueFactory().create();
this.globalRateLimiter = routerOptions.getGlobalRateLimiter();
this.timedTaskScheduler = routerOptions.getReactorResources().getTimerTaskScheduler();
this.responseFunctions = routerOptions.getResponseTransformers();
this.httpClient = httpClient;
this.rateLimitStrategy = rateLimitStrategy;
this.rateLimitRetryOperator = new RateLimitRetryOperator(timedTaskScheduler);
}
/**
* This retry function is used for reading and completing HTTP requests in the event of a server error (codes
* 500, 502, 503 and 504). The delay is calculated using exponential backoff with jitter.
*/
private Retry serverErrorRetryFactory() {
return Retry.onlyIf(ClientException.isRetryContextStatusCode(500, 502, 503, 504))
.withBackoffScheduler(timedTaskScheduler)
.exponentialBackoffWithJitter(Duration.ofSeconds(2), Duration.ofSeconds(30))
.doOnRetry(ctx -> {
if (log.isDebugEnabled()) {
log.debug("Retry {} in bucket {} due to {} for {}",
ctx.iteration(), id.toString(), ctx.exception().toString(), ctx.backoff());
}
});
}
void push(RequestCorrelation request) {
requestQueue.push(request);
}
void start() {
requestQueue.requests()
.doOnDiscard(RequestCorrelation.class, this::onDiscard)
.subscribe(new RequestSubscriber(rateLimitStrategy));
}
private void onDiscard(RequestCorrelation requestCorrelation) {
requestCorrelation.getResponse().onError(new DiscardedRequestException(requestCorrelation.getRequest()));
}
/**
* Reads and completes one request from the stream at a time. If a request fails, it is retried according a retry
* strategy. The reader may wait in between each request if preemptive rate limiting is necessary according to the
* response headers.
*/
private class RequestSubscriber extends BaseSubscriber> {
private volatile Duration sleepTime = Duration.ZERO;
private final Function> responseFunction;
public RequestSubscriber(RateLimitStrategy strategy) {
this.responseFunction = response -> {
HttpClientResponse httpResponse = response.getHttpResponse();
if (log.isDebugEnabled()) {
Instant requestTimestamp =
Instant.ofEpochMilli(httpResponse.currentContext().get(DiscordWebClient.KEY_REQUEST_TIMESTAMP));
Duration responseTime = Duration.between(requestTimestamp, Instant.now());
LogUtil.traceDebug(log, trace -> format(httpResponse.currentContext(),
"Read " + httpResponse.status() + " in " + responseTime + (!trace ? "" :
" with headers: " + httpResponse.responseHeaders())));
}
Duration nextReset = strategy.apply(httpResponse);
if (!nextReset.isZero()) {
if (log.isDebugEnabled()) {
log.debug(format(httpResponse.currentContext(), "Delaying next request by {}"), nextReset);
}
sleepTime = nextReset;
}
boolean global = Boolean.parseBoolean(httpResponse.responseHeaders().get("X-RateLimit-Global"));
Mono action = Mono.empty();
if (global) {
long retryAfter = Long.parseLong(httpResponse.responseHeaders().get("Retry-After"));
Duration fixedBackoff = Duration.ofMillis(retryAfter);
action = globalRateLimiter.rateLimitFor(fixedBackoff)
.doOnTerminate(() -> log.debug(format(httpResponse.currentContext(),
"Globally rate limited for {}"), fixedBackoff));
}
if (httpResponse.status().code() >= 400) {
return action.then(response.createException().flatMap(Mono::error));
} else {
return action.thenReturn(response);
}
};
}
@Override
protected void hookOnSubscribe(Subscription subscription) {
request(1);
}
@Override
protected void hookOnNext(RequestCorrelation correlation) {
DiscordWebRequest request = correlation.getRequest();
ClientRequest clientRequest = new ClientRequest(request);
MonoProcessor callback = correlation.getResponse();
if (log.isDebugEnabled()) {
log.debug("[B:{}, R:{}] {}", id.toString(), clientRequest.getId(), clientRequest.getDescription());
}
Mono.just(clientRequest)
.doOnEach(s -> log.trace(format(s.getContext(), ">> {}"), s))
.flatMap(req -> globalRateLimiter.withLimiter(httpClient.exchange(req)
.flatMap(responseFunction))
.next())
.doOnEach(s -> log.trace(format(s.getContext(), "<< {}"), s))
.subscriberContext(ctx -> ctx.putAll(correlation.getContext())
.put(LogUtil.KEY_REQUEST_ID, clientRequest.getId())
.put(LogUtil.KEY_BUCKET_ID, id.toString()))
.retryWhen(rateLimitRetryOperator::apply)
.transform(getResponseTransformers(request))
.retryWhen(serverErrorRetryFactory())
.doFinally(this::next)
.checkpoint("Request to " + clientRequest.getDescription() + " [RequestStream]")
.subscribeWith(callback)
.subscribe(null, t -> log.trace("Error while processing {}: {}", request, t));
}
private Function, Mono> getResponseTransformers(DiscordWebRequest discordRequest) {
return responseFunctions.stream()
.map(rt -> rt.transform(discordRequest)
.andThen(mono -> mono.checkpoint("Apply " + rt + " to " +
discordRequest.getDescription() + " [RequestStream]")))
.reduce(Function::andThen)
.orElse(mono -> mono);
}
private void next(SignalType signal) {
Mono timer = sleepTime.isZero() ? Mono.just(0L) : Mono.delay(sleepTime, timedTaskScheduler);
timer.subscribe(l -> {
if (log.isDebugEnabled()) {
log.debug("[B:{}] Ready to consume next request after {}", id.toString(), signal);
}
sleepTime = Duration.ZERO;
request(1);
}, t -> log.error("[B:{}] Error while scheduling next request", id.toString(), t));
}
}
}