Implementing Request Rate Limiting in Moco with a Custom LimitHandler

When using the Moco API, some required testing features are not available out‑of‑the‑box, so a custom solution is needed; this article introduces a LimitHandler that limits the number of accesses regardless of session or user.

The limit functionality is useful for scenarios such as lottery draws in mini‑games, order submissions, or any operation that should not be invoked repeatedly within a short time window.

package com.fun.moco.support; import com.fun.utils.Time; import com.github.dreamhead.moco.HttpRequest; import com.github.dreamhead.moco.MocoConfig; import com.github.dreamhead.moco.ResponseHandler; import com.github.dreamhead.moco.handler.AbstractResponseHandler; import com.github.dreamhead.moco.internal.SessionContext; import com.github.dreamhead.moco.model.MessageContent; import com.google.common.base.Function; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; @SuppressWarnings("all") public class LimitHandle extends AbstractResponseHandler { private final ResponseHandler limit; private final ResponseHandler unlimit; private Map tatal = new ConcurrentHashMap<>(); private int interval; private LimitHandle(final ResponseHandler limit, final ResponseHandler unLimit, int interval) { this.limit = limit; this.unlimit = unLimit; this.interval = interval; } public static ResponseHandler newSeq(final ResponseHandler limit, final ResponseHandler unLimit, int interval) { return new LimitHandle(limit, unLimit, interval); } @Override public void writeToResponse(final SessionContext context) { HttpRequest request = (HttpRequest) context.getRequest(); String uri = request.getUri(); MessageContent content = request.getContent(); (limited(uri + content) ? limit : unlimit).writeToResponse(context); } @Override public ResponseHandler apply(final MocoConfig config) { if (config.isFor(MocoConfig.RESPONSE_ID)) { return super.apply(config); } return new LimitHandle(limit, unlimit, interval); } private Function applyConfig(final MocoConfig config) { return new Function () { @Override public ResponseHandler apply(final ResponseHandler input) { return input.apply(config); } }; } /** * Determine whether the request is limited. * By recording the timestamp of each response, the method checks if the interval between two requests exceeds the configured limit. */ public boolean limited(String info) { long fresh = Time.getTimeStamp(); long old = tatal.containsKey(info) ? tatal.get(info) : 0L; tatal.put(info, fresh); return fresh - old > interval; } }

The handler can be used through a set of static limit methods that accept either plain strings, JSON objects, or other ResponseHandler instances, with an optional interval parameter (default 1000 ms):

/** * Limit request frequency, default 1000 ms */ static ResponseHandler limit(String limited, String unlimited) { limit(contentResponse(limited), contentResponse(unlimited)); } static ResponseHandler limit(JSONObject limited, JSONObject unlimited) { limit(jsonResponse(limited), jsonResponse(unlimited)); } static ResponseHandler limit(ResponseHandler limited, ResponseHandler unlimited) { limit(limited, unlimited, 1000); } /** * Limit request frequency with custom interval (ms) */ static ResponseHandler limit(String limited, String unlimited, int interval) { limit(contentResponse(limited), contentResponse(unlimited), interval); } static ResponseHandler limit(JSONObject limited, JSONObject unlimited, int interval) { limit(limited.toString(), unlimited.toString(), interval); } static ResponseHandler limit(ResponseHandler limit, ResponseHandler unlimit, int interval) { return LimitHandle.newSeq(limit, unlimit, interval); }

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