org.apache.aurora.scheduler.http.LeaderRedirectFilter.java Source code

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Here is the source code for org.apache.aurora.scheduler.http.LeaderRedirectFilter.java

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/**
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.aurora.scheduler.http;

import java.io.IOException;
import java.util.Objects;

import javax.inject.Inject;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.core.HttpHeaders;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.io.Resources;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.aurora.gen.apiConstants.BYPASS_LEADER_REDIRECT_HEADER_NAME;
import static org.apache.aurora.scheduler.http.LeaderRedirect.LeaderStatus;

/**
 * An HTTP filter that will redirect the request to the leading scheduler.
 */
public class LeaderRedirectFilter extends AbstractFilter {
    private static final Logger LOG = LoggerFactory.getLogger(LeaderRedirectFilter.class);

    @VisibleForTesting
    static final String NO_LEADER_PAGE = "no-leader.html";

    private final LeaderRedirect redirector;

    @Inject
    LeaderRedirectFilter(LeaderRedirect redirector) {
        this.redirector = Objects.requireNonNull(redirector);
    }

    private void sendServiceUnavailable(HttpServletResponse response) throws IOException {
        response.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
        Resources.asByteSource(Resources.getResource(LeaderRedirectFilter.class, NO_LEADER_PAGE))
                .copyTo(response.getOutputStream());
    }

    @Override
    public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        if (request.getHeader(BYPASS_LEADER_REDIRECT_HEADER_NAME) != null) {
            LOG.info(BYPASS_LEADER_REDIRECT_HEADER_NAME + " header was present on the request, bypassing "
                    + "leader redirection.");
            chain.doFilter(request, response);
            return;
        }

        LeaderStatus leaderStatus = redirector.getLeaderStatus();
        switch (leaderStatus) {
        case LEADING:
            chain.doFilter(request, response);
            return;
        case NO_LEADER:
            sendServiceUnavailable(response);
            return;
        case NOT_LEADING:
            Optional<String> leaderRedirect = redirector.getRedirectTarget(request);
            if (leaderRedirect.isPresent()) {
                response.setStatus(HttpServletResponse.SC_TEMPORARY_REDIRECT);
                response.setHeader(HttpHeaders.LOCATION, leaderRedirect.get());
                return;
            }

            LOG.warn("Got no leader redirect contrary to leader status, treating as if no leader " + "was found.");
            sendServiceUnavailable(response);
            return;
        default:
            throw new IllegalArgumentException("Encountered unknown LeaderStatus: " + leaderStatus);
        }
    }
}