com.twitter.common.net.http.handlers.TimeSeriesDataSource.java Source code

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Here is the source code for com.twitter.common.net.http.handlers.TimeSeriesDataSource.java

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// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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 com.twitter.common.net.http.handlers;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.annotation.Nullable;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.base.Splitter;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.net.MediaType;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import com.google.inject.Inject;

import com.twitter.common.collections.Iterables2;
import com.twitter.common.stats.TimeSeries;
import com.twitter.common.stats.TimeSeriesRepository;

/**
 * A servlet that provides time series data in JSON format.
 */
public class TimeSeriesDataSource extends HttpServlet {

    @VisibleForTesting
    static final String TIME_METRIC = "time";

    private static final String METRICS = "metrics";
    private static final String SINCE = "since";

    private final TimeSeriesRepository timeSeriesRepo;
    private final Gson gson = new Gson();

    @Inject
    public TimeSeriesDataSource(TimeSeriesRepository timeSeriesRepo) {
        this.timeSeriesRepo = Preconditions.checkNotNull(timeSeriesRepo);
    }

    @VisibleForTesting
    String getResponse(@Nullable String metricsQuery, @Nullable String sinceQuery) throws MetricException {

        if (metricsQuery == null) {
            // Return metric listing.
            return gson.toJson(ImmutableList.copyOf(timeSeriesRepo.getAvailableSeries()));
        }

        List<Iterable<Number>> tsData = Lists.newArrayList();
        tsData.add(timeSeriesRepo.getTimestamps());
        // Ignore requests for "time" since it is implicitly returned.
        Iterable<String> names = Iterables.filter(Splitter.on(",").split(metricsQuery),
                Predicates.not(Predicates.equalTo(TIME_METRIC)));
        for (String metric : names) {
            TimeSeries series = timeSeriesRepo.get(metric);
            if (series == null) {
                JsonObject response = new JsonObject();
                response.addProperty("error", "Unknown metric " + metric);
                throw new MetricException(gson.toJson(response));
            }
            tsData.add(series.getSamples());
        }

        final long since = Long.parseLong(Optional.fromNullable(sinceQuery).or("0"));
        Predicate<List<Number>> sinceFilter = new Predicate<List<Number>>() {
            @Override
            public boolean apply(List<Number> next) {
                return next.get(0).longValue() > since;
            }
        };

        ResponseStruct response = new ResponseStruct(
                ImmutableList.<String>builder().add(TIME_METRIC).addAll(names).build(),
                FluentIterable.from(Iterables2.zip(tsData, 0)).filter(sinceFilter).toList());
        return gson.toJson(response);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        resp.setContentType(MediaType.JSON_UTF_8.toString());
        PrintWriter out = resp.getWriter();
        try {
            out.write(getResponse(req.getParameter(METRICS), req.getParameter(SINCE)));
        } catch (MetricException e) {
            resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
            out.write(e.getMessage());
        }
    }

    @VisibleForTesting
    static class ResponseStruct {
        // Fields must be non-final for deserialization.
        List<String> names;
        List<List<Number>> data;

        ResponseStruct(List<String> names, List<List<Number>> data) {
            this.names = names;
            this.data = data;
        }
    }

    @VisibleForTesting
    static class MetricException extends Exception {
        MetricException(String message) {
            super(message);
        }
    }
}