Method getChanges

fdbserver/ConfigNode.actor.cpp:196–225

	}

	ACTOR static Future<Void> getChanges(ConfigNodeImpl* self, ConfigFollowerGetChangesRequest req) {
		Version lastCompactedVersion = wait(getLastCompactedVersion(self));
		if (req.lastSeenVersion < lastCompactedVersion) {
			++self->failedChangeRequests;
			req.reply.sendError(version_already_compacted());
			return Void();
		}
		state Version committedVersion =
		    wait(map(getGeneration(self), [](auto const& gen) { return gen.committedVersion; }));
		if (committedVersion < req.mostRecentVersion) {
			// Handle a very rare case where a ConfigNode loses data between
			// responding with a committed version and responding to the
			// subsequent get changes request.
			CODE_PROBE(true, "ConfigNode data loss occurred on a minority of coordinators");
			req.reply.sendError(process_behind()); // Reuse the process_behind error
			return Void();
		}
		state Standalone<VectorRef<VersionedConfigMutationRef>> versionedMutations =
		    wait(getMutations(self, req.lastSeenVersion + 1, committedVersion));
		state Standalone<VectorRef<VersionedConfigCommitAnnotationRef>> versionedAnnotations =
		    wait(getAnnotations(self, req.lastSeenVersion + 1, committedVersion));
		TraceEvent(SevDebug, "ConfigNodeSendingChanges", self->id)
		    .detail("ReqLastSeenVersion", req.lastSeenVersion)
		    .detail("CommittedVersion", committedVersion)
		    .detail("NumMutations", versionedMutations.size())
		    .detail("NumCommits", versionedAnnotations.size());
		++self->successfulChangeRequests;
		req.reply.send(ConfigFollowerGetChangesReply{ committedVersion, versionedMutations, versionedAnnotations });
		return Void();
	}

	// New transactions increment the database's current live version. This effectively serves as a lock, providing
	// serializability