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/*
 *  Copyright 2017 Expedia, Inc.
 *
 *     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 com.expedia.www.haystack.agent.span.service;

import com.codahale.metrics.Meter;
import com.codahale.metrics.Timer;
import com.expedia.open.tracing.Span;
import com.expedia.open.tracing.agent.api.DispatchResult;
import com.expedia.open.tracing.agent.api.SpanAgentGrpc;
import com.expedia.www.haystack.agent.core.Dispatcher;
import com.expedia.www.haystack.agent.core.RateLimitException;
import com.expedia.www.haystack.agent.core.metrics.SharedMetricRegistry;
import com.expedia.www.haystack.agent.span.enricher.Enricher;
import io.grpc.stub.StreamObserver;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;

public class SpanAgentGrpcService extends SpanAgentGrpc.SpanAgentImplBase {

    private final Logger LOGGER = LoggerFactory.getLogger(SpanAgentGrpcService.class);

    private final List dispatchers;
    private final Timer dispatchTimer;
    private final Meter dispatchFailureMeter;
    private final List enrichers;

    public SpanAgentGrpcService(final List dispatchers, final List enrichers) {
        Validate.notEmpty(dispatchers, "Dispatchers can't be empty");
        this.dispatchers = dispatchers;
        this.enrichers = enrichers;
        dispatchTimer = SharedMetricRegistry.newTimer("span.agent.dispatch.timer");
        dispatchFailureMeter = SharedMetricRegistry.newMeter("span.agent.dispatch.failures");
    }

    @Override
    public void dispatch(final Span span, final StreamObserver responseObserver) {
        final DispatchResult.Builder result = DispatchResult.newBuilder().setCode(DispatchResult.ResultCode.SUCCESS);
        final StringBuilder failedDispatchers = new StringBuilder();

        final Timer.Context timer = dispatchTimer.time();

        final Span enrichedSpan = enrichSpan(span);

        for(final Dispatcher d : dispatchers) {
            try {
                d.dispatch(enrichedSpan.getTraceId().getBytes("utf-8"), enrichedSpan.toByteArray());
            } catch (RateLimitException r) {
                result.setCode(DispatchResult.ResultCode.RATE_LIMIT_ERROR);
                dispatchFailureMeter.mark();
                LOGGER.error("Fail to dispatch the span record due to rate limit errors", r);
                failedDispatchers.append(d.getName()).append(',');
            }
            catch (Exception ex) {
                result.setCode(DispatchResult.ResultCode.UNKNOWN_ERROR);
                dispatchFailureMeter.mark();
                LOGGER.error("Fail to dispatch the span record to the dispatcher with name={}", d.getName(), ex);
                failedDispatchers.append(d.getName()).append(',');
            }
        }

        if(failedDispatchers.length() > 0) {
            result.setErrorMessage("Fail to dispatch the span record to the dispatchers=" +
                    StringUtils.removeEnd(failedDispatchers.toString(), ","));
        }

        timer.close();
        responseObserver.onNext(result.build());
        responseObserver.onCompleted();
    }

    private Span enrichSpan(final Span span) {
        if(enrichers.isEmpty()) {
            return span;
        } else {
            final Span.Builder transformedSpanBuilder = span.toBuilder();
            for (final Enricher enricher : enrichers) {
                enricher.apply(transformedSpanBuilder);
            }
            return transformedSpanBuilder.build();
        }
    }
}