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// Copyright (C) 2018 The Android Open Source Project
//
// 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.google.gerrit.server.git;
import com.google.gerrit.server.logging.TraceContext;
import java.util.List;
import java.util.Optional;
import org.eclipse.jgit.transport.FetchV2Request;
import org.eclipse.jgit.transport.LsRefsV2Request;
import org.eclipse.jgit.transport.ProtocolV2Hook;
/**
* Git hook for ls-refs and fetch that enables Gerrit request tracing if the user sets the 'trace'
* server option.
*
* <p>This hook is only invoked if Git protocol v2 is used.
*
* <p>If the 'trace' server option is specified without value, this means without providing a trace
* ID, a trace ID is generated, but it's not returned to the client. Hence users are advised to
* always provide a trace ID.
*/
public class TracingHook implements ProtocolV2Hook, AutoCloseable {
private TraceContext traceContext;
@Override
public void onLsRefs(LsRefsV2Request req) {
maybeStartTrace(req.getServerOptions());
}
@Override
public void onFetch(FetchV2Request req) {
maybeStartTrace(req.getServerOptions());
}
@Override
public void close() {
if (traceContext != null) {
traceContext.close();
}
}
/**
* Starts request tracing if 'trace' server option is set.
*
* @param serverOptionList list of provided server options
*/
private void maybeStartTrace(List<String> serverOptionList) {
if (traceContext != null) {
// Trace was already started
return;
}
Optional<String> traceOption = parseTraceOption(serverOptionList);
traceContext =
TraceContext.newTrace(
traceOption.isPresent(),
traceOption.orElse(null),
(tagName, traceId) -> {
// TODO(ekempin): Return trace ID to client
});
}
private Optional<String> parseTraceOption(List<String> serverOptionList) {
if (serverOptionList == null || serverOptionList.isEmpty()) {
return Optional.empty();
}
Optional<String> traceOption =
serverOptionList.stream().filter(o -> o.startsWith("trace")).findAny();
if (!traceOption.isPresent()) {
return Optional.empty();
}
int e = traceOption.get().indexOf('=');
if (e > 0) {
// trace option was specified with trace ID: "--trace=<trace-ID>"
return Optional.of(traceOption.get().substring(e + 1));
}
// trace option was specified without trace ID: "--trace",
// return an empty string so that a trace ID is generated
return Optional.of("");
}
}