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本文主要研究一下storm trident的operations
function filter projection
Function
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/operation/Function.java
public interface Function extends EachOperation { /** * Performs the function logic on an individual tuple and emits 0 or more tuples. * * @param tuple The incoming tuple * @param collector A collector instance that can be used to emit tuples */ void execute(TridentTuple tuple, TridentCollector collector);} - Function定义了execute方法，它发射的字段会追加到input tuple中
Filter
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/operation/Filter.java
public interface Filter extends EachOperation { /** * Determines if a tuple should be filtered out of a stream * * @param tuple the tuple being evaluated * @return `false` to drop the tuple, `true` to keep the tuple */ boolean isKeep(TridentTuple tuple);} - Filter提供一个isKeep方法，用来决定该tuple是否输出
projection
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * Filters out fields from a stream, resulting in a Stream containing only the fields specified by `keepFields`. * * For example, if you had a Stream `mystream` containing the fields `["a", "b", "c","d"]`, calling" * * ```java * mystream.project(new Fields("b", "d")) * ``` * * would produce a stream containing only the fields `["b", "d"]`. * * * @param keepFields The fields in the Stream to keep * @return */ public Stream project(Fields keepFields) { projectionValidation(keepFields); return _topology.addSourcedNode(this, new ProcessorNode(_topology.getUniqueStreamId(), _name, keepFields, new Fields(), new ProjectedProcessor(keepFields))); } - 这里使用了ProjectedProcessor来进行projection操作
repartitioning operations
partition
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * @param partitioner * @return */ public Stream partition(CustomStreamGrouping partitioner) { return partition(Grouping.custom_serialized(Utils.javaSerialize(partitioner))); } - 这里使用了CustomStreamGrouping
partitionBy
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * @param fields * @return */ public Stream partitionBy(Fields fields) { projectionValidation(fields); return partition(Grouping.fields(fields.toList())); } - 这里使用Grouping.fields
identityPartition
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * @return */ public Stream identityPartition() { return partition(new IdentityGrouping()); } - 这里使用IdentityGrouping
shuffle
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * Use random round robin algorithm to evenly redistribute tuples across all target partitions * * @return */ public Stream shuffle() { return partition(Grouping.shuffle(new NullStruct())); } - 这里使用Grouping.shuffle
localOrShuffle
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * Use random round robin algorithm to evenly redistribute tuples across all target partitions, with a preference * for local tasks. * * @return */ public Stream localOrShuffle() { return partition(Grouping.local_or_shuffle(new NullStruct())); } - 这里使用Grouping.local_or_shuffle
global
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * All tuples are sent to the same partition. The same partition is chosen for all batches in the stream. * @return */ public Stream global() { // use this instead of storm's built in one so that we can specify a singleemitbatchtopartition // without knowledge of storm's internals return partition(new GlobalGrouping()); } - 这里使用GlobalGrouping
batchGlobal
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * All tuples in the batch are sent to the same partition. Different batches in the stream may go to different * partitions. * * @return */ public Stream batchGlobal() { // the first field is the batch id return partition(new IndexHashGrouping(0)); } - 这里使用IndexHashGrouping，是对整个batch维度的repartition
broadcast
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Repartitioning Operation * * Every tuple is replicated to all target partitions. This can useful during DRPC – for example, if you need to do * a stateQuery on every partition of data. * * @return */ public Stream broadcast() { return partition(Grouping.all(new NullStruct())); } - 这里使用Grouping.all
groupBy
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
/** * ## Grouping Operation * * @param fields * @return */ public GroupedStream groupBy(Fields fields) { projectionValidation(fields); return new GroupedStream(this, fields); } - 这里返回的是GroupedStream
aggregators
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/Stream.java
//partition aggregate public Stream partitionAggregate(Aggregator agg, Fields functionFields) { return partitionAggregate(null, agg, functionFields); } public Stream partitionAggregate(CombinerAggregator agg, Fields functionFields) { return partitionAggregate(null, agg, functionFields); } public Stream partitionAggregate(Fields inputFields, CombinerAggregator agg, Fields functionFields) { projectionValidation(inputFields); return chainedAgg() .partitionAggregate(inputFields, agg, functionFields) .chainEnd(); } public Stream partitionAggregate(ReducerAggregator agg, Fields functionFields) { return partitionAggregate(null, agg, functionFields); } public Stream partitionAggregate(Fields inputFields, ReducerAggregator agg, Fields functionFields) { projectionValidation(inputFields); return chainedAgg() .partitionAggregate(inputFields, agg, functionFields) .chainEnd(); } //aggregate public Stream aggregate(Fields inputFields, Aggregator agg, Fields functionFields) { projectionValidation(inputFields); return chainedAgg() .aggregate(inputFields, agg, functionFields) .chainEnd(); } public Stream aggregate(Fields inputFields, CombinerAggregator agg, Fields functionFields) { projectionValidation(inputFields); return chainedAgg() .aggregate(inputFields, agg, functionFields) .chainEnd(); } public Stream aggregate(Fields inputFields, ReducerAggregator agg, Fields functionFields) { projectionValidation(inputFields); return chainedAgg() .aggregate(inputFields, agg, functionFields) .chainEnd(); } //persistent aggregate public TridentState persistentAggregate(StateFactory stateFactory, CombinerAggregator agg, Fields functionFields) { return persistentAggregate(new StateSpec(stateFactory), agg, functionFields); } public TridentState persistentAggregate(StateSpec spec, CombinerAggregator agg, Fields functionFields) { return persistentAggregate(spec, null, agg, functionFields); } public TridentState persistentAggregate(StateFactory stateFactory, Fields inputFields, CombinerAggregator agg, Fields functionFields) { return persistentAggregate(new StateSpec(stateFactory), inputFields, agg, functionFields); } public TridentState persistentAggregate(StateSpec spec, Fields inputFields, CombinerAggregator agg, Fields functionFields) { projectionValidation(inputFields); // replaces normal aggregation here with a global grouping because it needs to be consistent across batches return new ChainedAggregatorDeclarer(this, new GlobalAggScheme()) .aggregate(inputFields, agg, functionFields) .chainEnd() .partitionPersist(spec, functionFields, new CombinerAggStateUpdater(agg), functionFields); } public TridentState persistentAggregate(StateFactory stateFactory, ReducerAggregator agg, Fields functionFields) { return persistentAggregate(new StateSpec(stateFactory), agg, functionFields); } public TridentState persistentAggregate(StateSpec spec, ReducerAggregator agg, Fields functionFields) { return persistentAggregate(spec, null, agg, functionFields); } public TridentState persistentAggregate(StateFactory stateFactory, Fields inputFields, ReducerAggregator agg, Fields functionFields) { return persistentAggregate(new StateSpec(stateFactory), inputFields, agg, functionFields); } public TridentState persistentAggregate(StateSpec spec, Fields inputFields, ReducerAggregator agg, Fields functionFields) { projectionValidation(inputFields); return global().partitionPersist(spec, inputFields, new ReducerAggStateUpdater(agg), functionFields); } - trident的aggregators主要分为三类，分别是partitionAggregate、aggregate、persistentAggregate；aggregator操作会改变输出
- partitionAggregate其作用的粒度为每个partition，而非整个batch
- aggregrate操作作用的粒度为batch，对每个batch，它先使用global操作将该batch的tuple从所有partition合并到一个partition，最后再对batch进行aggregation操作；这里提供了三类参数，分别是Aggregator、CombinerAggregator、ReducerAggregator；调用stream.aggregrate方法时，相当于一次global aggregation，此时使用Aggregator或ReducerAggregator时，stream会先将tuple划分到一个partition，然后再进行aggregate操作；而使用CombinerAggregator时，trident会进行优化，先对每个partition进行局部的aggregate操作，然后再划分到一个partition，最后再进行aggregate操作，因而相对Aggregator或ReducerAggregator可以节省网络传输耗时
- persistentAggregate操作会对stream上所有batch的tuple进行aggretation，然后将结果存储在state中
Aggregator
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/operation/Aggregator.java
public interface Aggregatorextends Operation { T init(Object batchId, TridentCollector collector); void aggregate(T val, TridentTuple tuple, TridentCollector collector); void complete(T val, TridentCollector collector);}
- Aggregator首先会调用init进行初始化，然后通过参数传递给aggregate以及complete方法
- 对于batch partition中的每个tuple执行一次aggregate；当batch partition中的tuple执行完aggregate之后执行complete方法
- 假设自定义Aggregator为累加操作，那么对于[4]、[7]、[8]这批tuple，init为0，对于[4]，val=0，0+4=4；对于[7]，val=4，4+7=11；对于[8]，val=11，11+8=19；然后batch结束，val=19，此时执行complete，可以使用collector发射数据
CombinerAggregator
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/operation/CombinerAggregator.java
public interface CombinerAggregatorextends Serializable { T init(TridentTuple tuple); T combine(T val1, T val2); T zero();}
- CombinerAggregator每收到一个tuple，就调用init获取当前tuple的值，调用combine操作使用前一个combine的结果(
没有的话取zero的值)与init取得的值进行新的combine操作，如果该partition中没有tuple，则返回zero方法的值 - 假设combine为累加操作，zero返回0，那么对于[4]、[7]、[8]这批tuple，init值分别是4、7、8，对于[4]，没有前一个combine结果，于是val1=0，val2=4，combine结果为4；对于[7]，val1=4，val2=7，combine结果为11；对于[8]，val1为11，val2为8，combine结果为19
- CombinerAggregator操作的网络开销相对较低，因此性能比其他两类aggratator好
ReducerAggregator
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/operation/ReducerAggregator.java
public interface ReducerAggregatorextends Serializable { T init(); T reduce(T curr, TridentTuple tuple);}
- ReducerAggregator在对一批tuple进行计算时，先调用一次init获取初始值，然后再执行reduce操作，curr值为前一次reduce操作的值，没有的话，就是init值
- 假设reduce为累加操作，init返回0，那么对于[4]、[7]、[8]这批tuple，对于[4]，init为0，然后curr=0，先是0+4=4；对于[7]，curr为4，就是4+7=11；对于[8]，curr为11，最后就是11+8=19
topology stream operations
join
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/TridentTopology.java
public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields); } public Stream join(List streams, List joinFields, Fields outFields) { return join(streams, joinFields, outFields, JoinType.INNER); } public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields, JoinType type) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields, type); } public Stream join(List streams, List joinFields, Fields outFields, JoinType type) { return join(streams, joinFields, outFields, repeat(streams.size(), type)); } public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields, List mixed) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields, mixed); } public Stream join(List streams, List joinFields, Fields outFields, List mixed) { return join(streams, joinFields, outFields, mixed, JoinOutFieldsMode.COMPACT); } public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields, JoinOutFieldsMode mode) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields, mode); } public Stream join(List streams, List joinFields, Fields outFields, JoinOutFieldsMode mode) { return join(streams, joinFields, outFields, JoinType.INNER, mode); } public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields, JoinType type, JoinOutFieldsMode mode) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields, type, mode); } public Stream join(List streams, List joinFields, Fields outFields, JoinType type, JoinOutFieldsMode mode) { return join(streams, joinFields, outFields, repeat(streams.size(), type), mode); } public Stream join(Stream s1, Fields joinFields1, Stream s2, Fields joinFields2, Fields outFields, List mixed, JoinOutFieldsMode mode) { return join(Arrays.asList(s1, s2), Arrays.asList(joinFields1, joinFields2), outFields, mixed, mode); } public Stream join(List streams, List joinFields, Fields outFields, List mixed, JoinOutFieldsMode mode) { switch (mode) { case COMPACT: return multiReduce(strippedInputFields(streams, joinFields), groupedStreams(streams, joinFields), new JoinerMultiReducer(mixed, joinFields.get(0).size(), strippedInputFields(streams, joinFields)), outFields); case PRESERVE: return multiReduce(strippedInputFields(streams, joinFields), groupedStreams(streams, joinFields), new PreservingFieldsOrderJoinerMultiReducer(mixed, joinFields.get(0).size(), getAllOutputFields(streams), joinFields, strippedInputFields(streams, joinFields)), outFields); default: throw new IllegalArgumentException("Unsupported out-fields mode: " + mode); } } - 可以看到join最后调用了multiReduce，对于COMPACT类型使用的GroupedMultiReducer是JoinerMultiReducer，对于PRESERVE类型使用的GroupedMultiReducer是PreservingFieldsOrderJoinerMultiReducer
merge
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/TridentTopology.java
public Stream merge(Fields outputFields, Stream... streams) { return merge(outputFields, Arrays.asList(streams)); } public Stream merge(Stream... streams) { return merge(Arrays.asList(streams)); } public Stream merge(List streams) { return merge(streams.get(0).getOutputFields(), streams); } public Stream merge(Fields outputFields, List streams) { return multiReduce(streams, new IdentityMultiReducer(), outputFields); } - 可以看到merge最后是调用了multiReduce，使用的MultiReducer是IdentityMultiReducer
multiReduce
storm-core-1.2.2-sources.jar!/org/apache/storm/trident/TridentTopology.java
public Stream multiReduce(Stream s1, Stream s2, MultiReducer function, Fields outputFields) { return multiReduce(Arrays.asList(s1, s2), function, outputFields); } public Stream multiReduce(Fields inputFields1, Stream s1, Fields inputFields2, Stream s2, MultiReducer function, Fields outputFields) { return multiReduce(Arrays.asList(inputFields1, inputFields2), Arrays.asList(s1, s2), function, outputFields); } public Stream multiReduce(GroupedStream s1, GroupedStream s2, GroupedMultiReducer function, Fields outputFields) { return multiReduce(Arrays.asList(s1, s2), function, outputFields); } public Stream multiReduce(Fields inputFields1, GroupedStream s1, Fields inputFields2, GroupedStream s2, GroupedMultiReducer function, Fields outputFields) { return multiReduce(Arrays.asList(inputFields1, inputFields2), Arrays.asList(s1, s2), function, outputFields); } public Stream multiReduce(List streams, MultiReducer function, Fields outputFields) { return multiReduce(getAllOutputFields(streams), streams, function, outputFields); } public Stream multiReduce(List streams, GroupedMultiReducer function, Fields outputFields) { return multiReduce(getAllOutputFields(streams), streams, function, outputFields); } public Stream multiReduce(List inputFields, List groupedStreams, GroupedMultiReducer function, Fields outputFields) { List fullInputFields = new ArrayList<>(); List streams = new ArrayList<>(); List fullGroupFields = new ArrayList<>(); for(int i=0; i inputFields, List streams, MultiReducer function, Fields outputFields) { List names = new ArrayList<>(); for(Stream s: streams) { if(s._name!=null) { names.add(s._name); } } Node n = new ProcessorNode(getUniqueStreamId(), Utils.join(names, "-"), outputFields, outputFields, new MultiReducerProcessor(inputFields, function)); return addSourcedNode(streams, n); } - multiReduce方法有个MultiReducer参数，join与merge虽然都调用了multiReduce，但是他们传的MultiReducer值不一样
小结
- trident的操作主要有几类，一类是基本的function、filter、projection操作；一类是repartitioning操作，主要是一些grouping；一类是aggregate操作，包括aggregate、partitionAggregate、persistentAggregate；一类是在topology对stream的join、merge操作
- function的话，若有emit字段会追加到原始的tuple上；filter用于过滤tuple；projection用于提取字段
- repartitioning操作有Grouping.local_or_shuffle、Grouping.shuffle、Grouping.all、GlobalGrouping、CustomStreamGrouping、IdentityGrouping、IndexHashGrouping等；partition操作可以理解为将输入的tuple分配到task上，也可以理解为是对stream进行grouping
- aggregate操作的话，普通的aggregate操作有3类接口，分别是Aggregator、CombinerAggregator、ReducerAggregator，其中Aggregator是最为通用的，它继承了Operation接口，而且在方法参数里头可以使用到collector，这是CombinerAggregator与ReducerAggregator所没有的；而CombinerAggregator与Aggregator及ReducerAggregator不同的是，调用stream.aggregrate方法时，trident会优先在partition进行局部聚合，然后再归一到一个partition做最后聚合，相对来说比较节省网络传输耗时，但是如果将CombinerAggregator与非CombinerAggregator的进行chaining的话，就享受不到这个优化；partitionAggregate主要是在partition维度上进行操作；而persistentAggregate则是在整个stream的维度上对所有batch的tuple进行操作，结果持久化在state上
- 对于stream的join及merge操作，其最后都是依赖multiReduce来实现，只是传递的MultiReducer值不一样；join的话join的话需要字段来进行匹配(
字段名可以不一样)，可以选择JoinType，是INNER还是OUTER，不过join是对于spout的small batch来进行join的；merge的话，就是纯粹的几个stream进行tuple的归总。