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feat(filter): add CPU load-based request control with HTTP 429 (#3037)
Introduce LoadControlFilter that monitors OpenSearch CPU usage and returns HTTP 429 (Too Many Requests) when thresholds are exceeded. Web and API requests have independent configurable thresholds. - Add LoadControlFilter servlet filter with configurable CPU thresholds - Add LoadControlMonitorTarget for periodic OpenSearch CPU monitoring - Add ErrorBusyAction and busy.jsp for user-friendly 429 error page - Add web.xml filter registration and 429 error-page mapping - Add FessConfig properties: web.load.control, api.load.control, load.control.monitor.interval (disabled by default with threshold=100) - Add i18n labels for busy page across all supported languages - Add comprehensive unit tests for LoadControlFilter Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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‎src/main/java/org/codelibs/fess/app/web/error/ErrorBusyAction.java‎

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/*
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* Copyright 2012-2025 CodeLibs Project and the Others.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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* either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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package org.codelibs.fess.app.web.error;
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import org.codelibs.fess.app.web.base.FessSearchAction;
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import org.lastaflute.web.Execute;
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import org.lastaflute.web.response.HtmlResponse;
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/**
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* Action class for handling HTTP 429 Too Many Requests error pages.
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* This action displays error pages when the server is under high load.
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*/
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public class ErrorBusyAction extends FessSearchAction {
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/**
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* Default constructor for ErrorBusyAction.
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*/
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public ErrorBusyAction() {
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super();
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}
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/**
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* Displays the busy error page.
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*
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* @param form the error form containing error information
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* @return HTML response for the busy error page
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*/
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@Execute
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public HtmlResponse index(final ErrorForm form) {
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return asHtml(virtualHost(path_Error_BusyJsp));
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}
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}

‎src/main/java/org/codelibs/fess/filter/LoadControlFilter.java‎

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/*
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* Copyright 2012-2025 CodeLibs Project and the Others.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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* either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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package org.codelibs.fess.filter;
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import java.io.IOException;
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import java.util.Arrays;
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import java.util.Set;
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import java.util.stream.Collectors;
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import org.apache.logging.log4j.LogManager;
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import org.apache.logging.log4j.Logger;
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import org.codelibs.fess.mylasta.direction.FessConfig;
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import org.codelibs.fess.util.ComponentUtil;
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import jakarta.servlet.Filter;
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import jakarta.servlet.FilterChain;
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import jakarta.servlet.ServletException;
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import jakarta.servlet.ServletRequest;
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import jakarta.servlet.ServletResponse;
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import jakarta.servlet.http.HttpServletRequest;
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import jakarta.servlet.http.HttpServletResponse;
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/**
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* Filter for CPU load-based request control.
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* Returns HTTP 429 (Too Many Requests) when CPU usage exceeds configurable thresholds.
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* Web and API requests have independent threshold settings.
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*/
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public class LoadControlFilter implements Filter {
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private static final Logger logger = LogManager.getLogger(LoadControlFilter.class);
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private static final int RETRY_AFTER_SECONDS = 60;
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private static final Set<String> STATIC_EXTENSIONS =
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Arrays.stream(new String[] { ".css", ".js", ".png", ".jpg", ".gif", ".ico", ".svg", ".woff", ".woff2", ".ttf", ".eot" })
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.collect(Collectors.toSet());
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/**
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* Creates a new instance of LoadControlFilter.
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*/
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public LoadControlFilter() {
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// Default constructor
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}
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@Override
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public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
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throws IOException, ServletException {
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if (!ComponentUtil.available()) {
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chain.doFilter(request, response);
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return;
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}
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final HttpServletRequest httpRequest = (HttpServletRequest) request;
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final HttpServletResponse httpResponse = (HttpServletResponse) response;
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final String path = httpRequest.getRequestURI().substring(httpRequest.getContextPath().length());
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if (isExcludedPath(path)) {
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chain.doFilter(request, response);
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return;
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}
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final boolean isApiPath = path.startsWith("/api/");
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final FessConfig fessConfig = ComponentUtil.getFessConfig();
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final int threshold = isApiPath ? fessConfig.getApiLoadControlAsInteger() : fessConfig.getWebLoadControlAsInteger();
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if (threshold >= 100) {
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chain.doFilter(request, response);
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return;
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}
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final short cpuPercent = ComponentUtil.getSystemHelper().getSearchEngineCpuPercent();
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if (cpuPercent < threshold) {
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chain.doFilter(request, response);
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return;
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}
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if (logger.isInfoEnabled()) {
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logger.info("Rejecting request due to high CPU load: path={}, cpu={}%, threshold={}%", path, cpuPercent, threshold);
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}
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if (isApiPath) {
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sendApiResponse(httpResponse);
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} else {
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httpResponse.sendError(429);
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}
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}
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/**
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* Checks if the given path should be excluded from load control.
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* @param path the request path
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* @return true if the path should be excluded
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*/
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protected boolean isExcludedPath(final String path) {
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if (path.startsWith("/admin") || path.startsWith("/error") || path.startsWith("/login")) {
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return true;
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}
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final int dotIndex = path.lastIndexOf('.');
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if (dotIndex >= 0) {
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final String extension = path.substring(dotIndex);
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return STATIC_EXTENSIONS.contains(extension);
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}
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return false;
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}
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/**
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* Sends a 429 JSON response for API requests.
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* @param response the HTTP response
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* @throws IOException if an I/O error occurs
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*/
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protected void sendApiResponse(final HttpServletResponse response) throws IOException {
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response.setStatus(429);
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response.setContentType("application/json;charset=UTF-8");
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response.setHeader("Retry-After", String.valueOf(RETRY_AFTER_SECONDS));
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response.getWriter()
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.write("{\"response\":{\"status\":9,\"message\":\"Server is busy. Please retry after " + RETRY_AFTER_SECONDS
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+ " seconds.\",\"retry_after\":" + RETRY_AFTER_SECONDS + "}}");
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}
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}

‎src/main/java/org/codelibs/fess/helper/SystemHelper.java‎

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import org.codelibs.core.lang.StringUtil;
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import org.codelibs.core.lang.ThreadUtil;
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import org.codelibs.core.misc.Pair;
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import org.codelibs.core.timer.TimeoutManager;
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import org.codelibs.core.timer.TimeoutTask;
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import org.codelibs.fess.Constants;
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import org.codelibs.fess.crawler.util.CharUtil;
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import org.codelibs.fess.exception.FessSystemException;
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import org.codelibs.fess.mylasta.action.FessMessages;
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import org.codelibs.fess.mylasta.action.FessUserBean;
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import org.codelibs.fess.mylasta.direction.FessConfig;
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import org.codelibs.fess.timer.LoadControlMonitorTarget;
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import org.codelibs.fess.util.ComponentUtil;
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import org.codelibs.fess.util.GsaConfigParser;
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import org.codelibs.fess.util.IpAddressUtil;
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private long systemCpuCheckInterval = 1000L;
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private volatile short searchEngineCpuPercent;
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private volatile TimeoutTask loadControlMonitorTask;
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/** A map of listeners for configuration updates. */
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protected Map<String, Supplier<String>> updateConfigListenerMap = new HashMap<>();
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return systemCpuPercent;
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}
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/**
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* Gets the current system CPU usage percentage.
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*
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* @return The system CPU usage percentage.
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*/
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public short currentSystemCpuPercent() {
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return getSystemCpuPercent();
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}
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/**
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* Gets the search engine CPU usage percentage.
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*
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* @return The search engine CPU usage percentage.
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*/
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public short getSearchEngineCpuPercent() {
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ensureLoadControlMonitorStarted();
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return searchEngineCpuPercent;
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}
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/**
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* Sets the search engine CPU usage percentage.
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*
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* @param percent The search engine CPU usage percentage.
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*/
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public void setSearchEngineCpuPercent(final short percent) {
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searchEngineCpuPercent = percent;
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}
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private void ensureLoadControlMonitorStarted() {
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if (loadControlMonitorTask == null) {
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final FessConfig fessConfig = ComponentUtil.getFessConfig();
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if (fessConfig.getWebLoadControlAsInteger() < 100 || fessConfig.getApiLoadControlAsInteger() < 100) {
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synchronized (this) {
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if (loadControlMonitorTask == null) {
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final int interval = fessConfig.getLoadControlMonitorIntervalAsInteger();
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loadControlMonitorTask =
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TimeoutManager.getInstance().addTimeoutTarget(new LoadControlMonitorTarget(this), interval, true);
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}
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}
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}
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}
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}
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/**
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* Gets a map of filtered environment variables.
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*

‎src/main/java/org/codelibs/fess/mylasta/action/FessHtmlPath.java‎

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/** The path of the HTML: /error/badRequest.jsp */
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HtmlNext path_Error_BadRequestJsp = new HtmlNext("/error/badRequest.jsp");
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/** The path of the HTML: /error/busy.jsp */
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HtmlNext path_Error_BusyJsp = new HtmlNext("/error/busy.jsp");
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/** The path of the HTML: /error/error.jsp */
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HtmlNext path_Error_ErrorJsp = new HtmlNext("/error/error.jsp");
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‎src/main/java/org/codelibs/fess/mylasta/action/FessLabels.java‎

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/** The key of the message: Please check the URL. */
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public static final String LABELS_check_url = "{labels.check_url}";
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/** The key of the message: Service Temporarily Unavailable */
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public static final String LABELS_busy_title = "{labels.busy_title}";
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/** The key of the message: The server is currently experiencing high load. Please try again later. */
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public static final String LABELS_busy_message = "{labels.busy_message}";
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/** The key of the message: Username */
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public static final String LABELS_user_name = "{labels.user_name}";
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‎src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java‎

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/** The key of the configuration. e.g. 50 */
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String ADAPTIVE_LOAD_CONTROL = "adaptive.load.control";
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/** The key of the configuration. e.g. 100 */
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String WEB_LOAD_CONTROL = "web.load.control";
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/** The key of the configuration. e.g. 100 */
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String API_LOAD_CONTROL = "api.load.control";
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/** The key of the configuration. e.g. 1 */
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String LOAD_CONTROL_MONITOR_INTERVAL = "load.control.monitor.interval";
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/** The key of the configuration. e.g. js */
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String SUPPORTED_UPLOADED_JS_EXTENTIONS = "supported.uploaded.js.extentions";
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*/
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Integer getAdaptiveLoadControlAsInteger();
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/**
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* Get the value for the key 'web.load.control'. <br>
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* The value is, e.g. 100 <br>
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* comment: CPU threshold (%) for web request load control. Returns 429 when CPU &gt;= this value. (100: disabled)
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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*/
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String getWebLoadControl();
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/**
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* Get the value for the key 'web.load.control' as {@link Integer}. <br>
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* The value is, e.g. 100 <br>
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* comment: CPU threshold (%) for web request load control. Returns 429 when CPU &gt;= this value. (100: disabled)
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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* @throws NumberFormatException When the property is not integer.
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*/
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Integer getWebLoadControlAsInteger();
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/**
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* Get the value for the key 'api.load.control'. <br>
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* The value is, e.g. 100 <br>
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* comment: CPU threshold (%) for API request load control. Returns 429 when CPU &gt;= this value. (100: disabled)
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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*/
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String getApiLoadControl();
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/**
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* Get the value for the key 'api.load.control' as {@link Integer}. <br>
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* The value is, e.g. 100 <br>
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* comment: CPU threshold (%) for API request load control. Returns 429 when CPU &gt;= this value. (100: disabled)
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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* @throws NumberFormatException When the property is not integer.
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*/
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Integer getApiLoadControlAsInteger();
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/**
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* Get the value for the key 'load.control.monitor.interval'. <br>
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* The value is, e.g. 1 <br>
2584+
* comment: Interval (seconds) for monitoring OpenSearch CPU load.
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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*/
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String getLoadControlMonitorInterval();
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/**
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* Get the value for the key 'load.control.monitor.interval' as {@link Integer}. <br>
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* The value is, e.g. 1 <br>
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* comment: Interval (seconds) for monitoring OpenSearch CPU load.
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* @return The value of found property. (NotNull: if not found, exception but basically no way)
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* @throws NumberFormatException When the property is not integer.
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*/
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Integer getLoadControlMonitorIntervalAsInteger();
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/**
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* Get the value for the key 'supported.uploaded.js.extentions'. <br>
25402600
* The value is, e.g. js <br>
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return getAsInteger(FessConfig.ADAPTIVE_LOAD_CONTROL);
97809840
}
97819841

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public String getWebLoadControl() {
9843+
return get(FessConfig.WEB_LOAD_CONTROL);
9844+
}
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9846+
public Integer getWebLoadControlAsInteger() {
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return getAsInteger(FessConfig.WEB_LOAD_CONTROL);
9848+
}
9849+
9850+
public String getApiLoadControl() {
9851+
return get(FessConfig.API_LOAD_CONTROL);
9852+
}
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9854+
public Integer getApiLoadControlAsInteger() {
9855+
return getAsInteger(FessConfig.API_LOAD_CONTROL);
9856+
}
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9858+
public String getLoadControlMonitorInterval() {
9859+
return get(FessConfig.LOAD_CONTROL_MONITOR_INTERVAL);
9860+
}
9861+
9862+
public Integer getLoadControlMonitorIntervalAsInteger() {
9863+
return getAsInteger(FessConfig.LOAD_CONTROL_MONITOR_INTERVAL);
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}
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97829866
public String getSupportedUploadedJsExtentions() {
97839867
return get(FessConfig.SUPPORTED_UPLOADED_JS_EXTENTIONS);
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}
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1318813272
defaultMap.put(FessConfig.USE_OWN_TMP_DIR, "true");
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defaultMap.put(FessConfig.MAX_LOG_OUTPUT_LENGTH, "4000");
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defaultMap.put(FessConfig.ADAPTIVE_LOAD_CONTROL, "50");
13275+
defaultMap.put(FessConfig.WEB_LOAD_CONTROL, "100");
13276+
defaultMap.put(FessConfig.API_LOAD_CONTROL, "100");
13277+
defaultMap.put(FessConfig.LOAD_CONTROL_MONITOR_INTERVAL, "1");
1319113278
defaultMap.put(FessConfig.SUPPORTED_UPLOADED_JS_EXTENTIONS, "js");
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defaultMap.put(FessConfig.SUPPORTED_UPLOADED_CSS_EXTENTIONS, "css");
1319313280
defaultMap.put(FessConfig.SUPPORTED_UPLOADED_MEDIA_EXTENTIONS, "jpg,jpeg,gif,png,swf");

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