jsun98 commented on a change in pull request #6431: Add Kinesis Indexing Service to core Druid URL: https://github.com/apache/incubator-druid/pull/6431#discussion_r243043758
########## File path: docs/content/development/extensions-core/kinesis-ingestion.md ########## @@ -0,0 +1,399 @@ +<!-- + ~ Licensed to the Apache Software Foundation (ASF) under one + ~ or more contributor license agreements. See the NOTICE file + ~ distributed with this work for additional information + ~ regarding copyright ownership. The ASF licenses this file + ~ to you 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. + --> + +--- +layout: doc_page +--- + +# Kinesis Indexing Service + +Similar to the [Kafka indexing service](./kafka-ingestion.html), the Kinesis indexing service enables the configuration of *supervisors* on the Overlord, which facilitate ingestion from +Kinesis by managing the creation and lifetime of Kinesis indexing tasks. These indexing tasks read events using Kinesis's own +Shards and Sequence Number mechanism and are therefore able to provide guarantees of exactly-once ingestion. They are also +able to read non-recent events from Kinesis and are not subject to the window period considerations imposed on other +ingestion mechanisms using Tranquility. The supervisor oversees the state of the indexing tasks to coordinate handoffs, manage failures, +and ensure that the scalability and replication requirements are maintained. + +The Kinesis indexing service is provided as the `druid-kinesis-indexing-service` core extension (see +[Including Extensions](../../operations/including-extensions.html)). Please note that this is +currently designated as an *experimental feature* and is subject to the usual +[experimental caveats](../experimental.html). + +## Submitting a Supervisor Spec + +The Kinesis indexing service requires that the `druid-kinesis-indexing-service` extension be loaded on both the overlord +and the middle managers. A supervisor for a dataSource is started by submitting a supervisor spec via HTTP POST to +`http://<OVERLORD_IP>:<OVERLORD_PORT>/druid/indexer/v1/supervisor`, for example: + +``` +curl -X POST -H 'Content-Type: application/json' -d @supervisor-spec.json http://localhost:8090/druid/indexer/v1/supervisor +``` + +A sample supervisor spec is shown below: + +```json +{ + "type": "kinesis", + "dataSchema": { + "dataSource": "metrics-kinesis", + "parser": { + "type": "string", + "parseSpec": { + "format": "json", + "timestampSpec": { + "column": "timestamp", + "format": "auto" + }, + "dimensionsSpec": { + "dimensions": [], + "dimensionExclusions": [ + "timestamp", + "value" + ] + } + } + }, + "metricsSpec": [ + { + "name": "count", + "type": "count" + }, + { + "name": "value_sum", + "fieldName": "value", + "type": "doubleSum" + }, + { + "name": "value_min", + "fieldName": "value", + "type": "doubleMin" + }, + { + "name": "value_max", + "fieldName": "value", + "type": "doubleMax" + } + ], + "granularitySpec": { + "type": "uniform", + "segmentGranularity": "HOUR", + "queryGranularity": "NONE" + } + }, + "tuningConfig": { + "type": "kinesis", + "maxRowsPerSegment": 5000000 + }, + "ioConfig": { + "stream": "metrics", + "endpoint": "kinesis.us-east-1.amazonaws.com", + "taskCount": 1, + "replicas": 1, + "taskDuration": "PT1H", + "recordsPerFetch": 2000, + "fetchDelayMillis": 1000 + } +} +``` + +## Supervisor Configuration + +|Field|Description|Required| +|--------|-----------|---------| +|`type`|The supervisor type, this should always be `kinesis`.|yes| +|`dataSchema`|The schema that will be used by the Kinesis indexing task during ingestion, see [Ingestion Spec DataSchema](../../ingestion/ingestion-spec.html#dataschema).|yes| +|`ioConfig`|A KinesisSupervisorIOConfig to configure the supervisor and indexing tasks, see below.|yes| +|`tuningConfig`|A KinesisSupervisorTuningConfig to configure the supervisor and indexing tasks, see below.|no| + +### KinesisSupervisorTuningConfig + +The tuningConfig is optional and default parameters will be used if no tuningConfig is specified. + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|`type`|String|The indexing task type, this should always be `kinesis`.|yes| +|`maxRowsInMemory`|Integer|The number of rows to aggregate before persisting. This number is the post-aggregation rows, so it is not equivalent to the number of input events, but the number of aggregated rows that those events result in. This is used to manage the required JVM heap size. Maximum heap memory usage for indexing scales with maxRowsInMemory * (2 + maxPendingPersists).|no (default == 100000)| +|`maxBytesInMemory`|Long|The number of bytes to aggregate in heap memory before persisting. This is based on a rough estimate of memory usage and not actual usage. Normally this is computed internally and user does not need to set it. The maximum heap memory usage for indexing is maxBytesInMemory * (2 + maxPendingPersists). |no (default == One-sixth of max JVM memory)| +|`maxRowsPerSegment`|Integer|The number of rows to aggregate into a segment; this number is post-aggregation rows. Handoff will happen either if `maxRowsPerSegment` or `maxTotalRows` is hit or every `intermediateHandoffPeriod`, whichever happens earlier.|no (default == 5000000)| +|`maxTotalRows`|Long|The number of rows to aggregate across all segments; this number is post-aggregation rows. Handoff will happen either if `maxRowsPerSegment` or `maxTotalRows` is hit or every `intermediateHandoffPeriod`, whichever happens earlier.|no (default == unlimited)| +|`intermediatePersistPeriod`|ISO8601 Period|The period that determines the rate at which intermediate persists occur.|no (default == PT10M)| +|`maxPendingPersists`|Integer|Maximum number of persists that can be pending but not started. If this limit would be exceeded by a new intermediate persist, ingestion will block until the currently-running persist finishes. Maximum heap memory usage for indexing scales with maxRowsInMemory * (2 + maxPendingPersists).|no (default == 0, meaning one persist can be running concurrently with ingestion, and none can be queued up)| +|`indexSpec`|Object|Tune how data is indexed, see 'IndexSpec' below for more details.|no| +|`reportParseExceptions`|Boolean|If true, exceptions encountered during parsing will be thrown and will halt ingestion; if false, unparseable rows and fields will be skipped.|no (default == false)| +|`handoffConditionTimeout`|Long|Milliseconds to wait for segment handoff. It must be >= 0, where 0 means to wait forever.|no (default == 0)| +|`resetOffsetAutomatically`|Boolean|Whether to reset the consumer sequence numbers if the next sequence number that it is trying to fetch is less than the earliest available sequence number for that particular shard. The sequence number will be reset to either the earliest or latest sequence number depending on `useEarliestOffset` property of `KinesisSupervisorIOConfig` (see below). This situation typically occurs when messages in Kinesis are no longer available for consumption and therefore won't be ingested into Druid. If set to false then ingestion for that particular shard will halt and manual intervention is required to correct the situation, please see `Reset Supervisor` API below.|no (default == false)| +|`skipSequenceNumberAvailabilityCheck`|Boolean|Whether to enable checking if the current sequence number is still available in a particular Kinesis shard. If set to false, the indexing task will attempt to reset the current sequence number (or not), depending on the value of `resetOffsetAutomatically`. |no (default == false)| +|`workerThreads`|Integer|The number of threads that will be used by the supervisor for asynchronous operations.|no (default == min(10, taskCount))| +|`chatThreads`|Integer|The number of threads that will be used for communicating with indexing tasks.|no (default == min(10, taskCount * replicas))| +|`chatRetries`|Integer|The number of times HTTP requests to indexing tasks will be retried before considering tasks unresponsive.|no (default == 8)| +|`httpTimeout`|ISO8601 Period|How long to wait for a HTTP response from an indexing task.|no (default == PT10S)| +|`shutdownTimeout`|ISO8601 Period|How long to wait for the supervisor to attempt a graceful shutdown of tasks before exiting.|no (default == PT80S)| +|`recordBufferSize`|Integer|Size of the buffer (number of events) used between the Kinesis fetch threads and the main ingestion thread.|no (default == 10000)| +|`recordBufferOfferTimeout`|Integer|Length of time in milliseconds to wait for space to become available in the buffer before timing out.|no (default == 5000)| +|`recordBufferFullWait`|Integer|Length of time in milliseconds to wait for the buffer to drain before attempting to fetch records from Kinesis again.|no (default == 5000)| +|`fetchSequenceNumberTimeout`|Integer|Length of time in milliseconds to wait for Kinesis to return the earliest or latest sequence number for a shard. Kinesis will not return the latest sequence number if no data is actively being written to that shard. In this case, this fetch call will repeatedly timeout and retry until fresh data is written to the stream.|no (default == 60000)| +|`fetchThreads`|Integer|Size of the pool of threads fetching data from Kinesis. There is no benefit in having more threads than Kinesis shards.|no (default == max(1, {numProcessors} - 1))| +|`segmentWriteOutMediumFactory`|Object|Segment write-out medium to use when creating segments. See below for more information.|no (not specified by default, the value from `druid.peon.defaultSegmentWriteOutMediumFactory.type` is used)| +|`intermediateHandoffPeriod`|ISO8601 Period|How often the tasks should hand off segments. Handoff will happen either if `maxRowsPerSegment` or `maxTotalRows` is hit or every `intermediateHandoffPeriod`, whichever happens earlier.|no (default == P2147483647D)| +|`logParseExceptions`|Boolean|If true, log an error message when a parsing exception occurs, containing information about the row where the error occurred.|no, default == false| +|`maxParseExceptions`|Integer|The maximum number of parse exceptions that can occur before the task halts ingestion and fails. Overridden if `reportParseExceptions` is set.|no, unlimited default| +|`maxSavedParseExceptions`|Integer|When a parse exception occurs, Druid can keep track of the most recent parse exceptions. "maxSavedParseExceptions" limits how many exception instances will be saved. These saved exceptions will be made available after the task finishes in the [task completion report](../../ingestion/reports.html). Overridden if `reportParseExceptions` is set.|no, default == 0| +|`maxRecordsPerPoll`|Integer| The maximum number of records/events to be fetched from buffer per poll. The actual maximum will be `Max(maxRecordsPerPoll, Max(bufferSize, 1)) |no, default == 100| + +#### IndexSpec + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|bitmap|Object|Compression format for bitmap indexes. Should be a JSON object; see below for options.|no (defaults to Concise)| +|dimensionCompression|String|Compression format for dimension columns. Choose from `LZ4`, `LZF`, or `uncompressed`.|no (default == `LZ4`)| +|metricCompression|String|Compression format for metric columns. Choose from `LZ4`, `LZF`, `uncompressed`, or `none`.|no (default == `LZ4`)| +|longEncoding|String|Encoding format for metric and dimension columns with type long. Choose from `auto` or `longs`. `auto` encodes the values using sequence number or lookup table depending on column cardinality, and store them with variable size. `longs` stores the value as is with 8 bytes each.|no (default == `longs`)| + +##### Bitmap types + +For Concise bitmaps: + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|`type`|String|Must be `concise`.|yes| + +For Roaring bitmaps: + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|`type`|String|Must be `roaring`.|yes| +|`compressRunOnSerialization`|Boolean|Use a run-length encoding where it is estimated as more space efficient.|no (default == `true`)| + +#### SegmentWriteOutMediumFactory + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|`type`|String|See [Additional Peon Configuration: SegmentWriteOutMediumFactory](../../configuration/index.html#segmentwriteoutmediumfactory) for explanation and available options.|yes| + +### KinesisSupervisorIOConfig + +|Field|Type|Description|Required| +|-----|----|-----------|--------| +|`stream`|String|The Kinesis stream to read.|yes| +|`endpoint`|String|The AWS Kinesis stream endpoint for a region. You can find a list of endpoints [here](http://docs.aws.amazon.com/general/latest/gr/rande.html#ak_region).|no (default == kinesis.us-east-1.amazonaws.com)| +|`replicas`|Integer|The number of replica sets, where 1 means a single set of tasks (no replication). Replica tasks will always be assigned to different workers to provide resiliency against node failure.|no (default == 1)| +|`taskCount`|Integer|The maximum number of *reading* tasks in a *replica set*. This means that the maximum number of reading tasks will be `taskCount * replicas` and the total number of tasks (*reading* + *publishing*) will be higher than this. See 'Capacity Planning' below for more details. The number of reading tasks will be less than `taskCount` if `taskCount > {numKinesisshards}`.|no (default == 1)| +|`taskDuration`|ISO8601 Period|The length of time before tasks stop reading and begin publishing their segment. Note that segments are only pushed to deep storage and loadable by historical nodes when the indexing task completes.|no (default == PT1H)| +|`startDelay`|ISO8601 Period|The period to wait before the supervisor starts managing tasks.|no (default == PT5S)| +|`period`|ISO8601 Period|How often the supervisor will execute its management logic. Note that the supervisor will also run in response to certain events (such as tasks succeeding, failing, and reaching their taskDuration) so this value specifies the maximum time between iterations.|no (default == PT30S)| +|`useEarliestSequenceNumber`|Boolean|If a supervisor is managing a dataSource for the first time, it will obtain a set of starting sequence numbers from Kinesis. This flag determines whether it retrieves the earliest or latest sequence numbers in Kinesis. Under normal circumstances, subsequent tasks will start from where the previous segments ended so this flag will only be used on first run.|no (default == false)| +|`completionTimeout`|ISO8601 Period|The length of time to wait before declaring a publishing task as failed and terminating it. If this is set too low, your tasks may never publish. The publishing clock for a task begins roughly after `taskDuration` elapses.|no (default == PT6H)| +|`lateMessageRejectionPeriod`|ISO8601 Period|Configure tasks to reject messages with timestamps earlier than this period before the task was created; for example if this is set to `PT1H` and the supervisor creates a task at *2016-01-01T12:00Z*, messages with timestamps earlier than *2016-01-01T11:00Z* will be dropped. This may help prevent concurrency issues if your data stream has late messages and you have multiple pipelines that need to operate on the same segments (e.g. a realtime and a nightly batch ingestion pipeline).|no (default == none)| +|`earlyMessageRejectionPeriod`|ISO8601 Period|Configure tasks to reject messages with timestamps later than this period after the task reached its taskDuration; for example if this is set to `PT1H`, the taskDuration is set to `PT1H` and the supervisor creates a task at *2016-01-01T12:00Z*, messages with timestamps later than *2016-01-01T14:00Z* will be dropped. **Note:** Tasks sometimes run past their task duration, for example, in cases of supervisor failover. Setting earlyMessageRejectionPeriod too low may cause messages to be dropped unexpectedly whenever a task runs past its originally configured task duration.|no (default == none)| +|`recordsPerFetch`|Integer|The number of records to request per GetRecords call to Kinesis. See 'Determining Fetch Settings' below.|no (default == 2000)| +|`fetchDelayMillis`|Integer|Time in milliseconds to wait between subsequent GetRecords calls to Kinesis. See 'Determining Fetch Settings' below.|no (default == 1000)| +|`awsAssumedRoleArn`|String|The AWS assumed role to use for additional permissions.|no| +|`awsExternalId`|String|The AWS external id to use for additional permissions.|no| +|`deaggregate`|Boolean|Whether to use the de-aggregate function of the KCL. See below for details.|no| + +## Operations + +This section gives descriptions of how some supervisor APIs work specifically in Kinesis Indexing Service. +For all supervisor APIs, please check [Supervisor APIs](../../operations/api-reference.html#supervisors). + +### AWS Authentication +To authenticate with AWS, you must provide your AWS access key and AWS secret key via environment properties, for example: +``` +-Ddruid.kinesis.accessKey=123 -Ddruid.kinesis.secretKey=456 +``` +- The AWS access key ID is used for Kinesis API requests. If this is not provided, the service will look for credentials set in system properties, in the default profile configuration file, and from the EC2 instance profile provider (in this order). +- The AWS secret access key is used for Kinesis API requests. + +### Getting Supervisor Status Report + +`GET /druid/indexer/v1/supervisor/<supervisorId>/status` returns a snapshot report of the current state of the tasks managed by the given supervisor. This includes the latest +sequence numbers as reported by Kinesis. Unlike the Kafka Indexing Service, stats about lag is not yet supported. + +### Getting Supervisor Ingestion Stats Report + +`GET /druid/indexer/v1/supervisor/<supervisorId>/stats` returns a snapshot of the current ingestion row counters for each task being managed by the supervisor, along with moving averages for the row counters. + +See [Task Reports: Row Stats](../../ingestion/reports.html#row-stats) for more information. + +### Updating Existing Supervisors + +`POST /druid/indexer/v1/supervisor` can be used to update existing supervisor spec. +Calling this endpoint when there is already an existing supervisor for the same dataSource will cause: + +- The running supervisor to signal its managed tasks to stop reading and begin publishing. +- The running supervisor to exit. +- A new supervisor to be created using the configuration provided in the request body. This supervisor will retain the +existing publishing tasks and will create new tasks starting at the sequence numbers the publishing tasks ended on. + +Seamless schema migrations can thus be achieved by simply submitting the new schema using this endpoint. + +### Suspending and Resuming Supervisors + +You can suspend and resume a supervisor using `POST /druid/indexer/v1/supervisor/<supervisorId>/suspend` and `POST /druid/indexer/v1/supervisor/<supervisorId>/resume`, respectively. + +Note that the supervisor itself will still be operating and emitting logs and metrics, +it will just ensure that no indexing tasks are running until the supervisor is resumed. + +### Resetting Supervisors + +To reset a running supervisor, you can use `POST /druid/indexer/v1/supervisor/<supervisorId>/reset`. + +The indexing service keeps track of the latest persisted Kinesis sequence number in order to provide exactly-once ingestion +guarantees across tasks. Subsequent tasks must start reading from where the previous task completed in order for the +generated segments to be accepted. If the messages at the expected starting sequence numbers are no longer available in Kinesis +(typically because the message retention period has elapsed or the topic was removed and re-created) the supervisor will +refuse to start and in-flight tasks will fail. + +This endpoint can be used to clear the stored sequence numbers which will cause the supervisor to start reading from +either the earliest or latest sequence numbers in Kinesis (depending on the value of `useEarliestOffset`). The supervisor must be +running for this endpoint to be available. After the stored sequence numbers are cleared, the supervisor will automatically kill +and re-create any active tasks so that tasks begin reading from valid sequence numbers. + +Note that since the stored sequence numbers are necessary to guarantee exactly-once ingestion, resetting them with this endpoint +may cause some Kinesis messages to be skipped or to be read twice. + +### Terminating Supervisors + +`POST /druid/indexer/v1/supervisor/<supervisorId>/terminate` terminates a supervisor and causes all associated indexing +tasks managed by this supervisor to immediately stop and begin +publishing their segments. This supervisor will still exist in the metadata store and it's history may be retrieved +with the supervisor history api, but will not be listed in the 'get supervisors' api response nor can it's configuration +or status report be retrieved. The only way this supervisor can start again is by submitting a functioning supervisor +spec to the create api. + +### Capacity Planning + +Kinesis indexing tasks run on middle managers and are thus limited by the resources available in the middle manager +cluster. In particular, you should make sure that you have sufficient worker capacity (configured using the +`druid.worker.capacity` property) to handle the configuration in the supervisor spec. Note that worker capacity is +shared across all types of indexing tasks, so you should plan your worker capacity to handle your total indexing load +(e.g. batch processing, realtime tasks, merging tasks, etc.). If your workers run out of capacity, Kinesis indexing tasks +will queue and wait for the next available worker. This may cause queries to return partial results but will not result +in data loss (assuming the tasks run before Kinesis purges those sequence numbers). + +A running task will normally be in one of two states: *reading* or *publishing*. A task will remain in reading state for +`taskDuration`, at which point it will transition to publishing state. A task will remain in publishing state for as long +as it takes to generate segments, push segments to deep storage, and have them be loaded and served by a historical node +(or until `completionTimeout` elapses). + +The number of reading tasks is controlled by `replicas` and `taskCount`. In general, there will be `replicas * taskCount` +reading tasks, the exception being if taskCount > {numKinesisShards} in which case {numKinesisShards} tasks will +be used instead. When `taskDuration` elapses, these tasks will transition to publishing state and `replicas * taskCount` +new reading tasks will be created. Therefore to allow for reading tasks and publishing tasks to run concurrently, there +should be a minimum capacity of: + +``` +workerCapacity = 2 * replicas * taskCount +``` + +This value is for the ideal situation in which there is at most one set of tasks publishing while another set is reading. +In some circumstances, it is possible to have multiple sets of tasks publishing simultaneously. This would happen if the +time-to-publish (generate segment, push to deep storage, loaded on historical) > `taskDuration`. This is a valid +scenario (correctness-wise) but requires additional worker capacity to support. In general, it is a good idea to have +`taskDuration` be large enough that the previous set of tasks finishes publishing before the current set begins. + +### Supervisor Persistence + +When a supervisor spec is submitted via the `POST /druid/indexer/v1/supervisor` endpoint, it is persisted in the +configured metadata database. There can only be a single supervisor per dataSource, and submitting a second spec for +the same dataSource will overwrite the previous one. + +When an overlord gains leadership, either by being started or as a result of another overlord failing, it will spawn +a supervisor for each supervisor spec in the metadata database. The supervisor will then discover running Kinesis indexing +tasks and will attempt to adopt them if they are compatible with the supervisor's configuration. If they are not +compatible because they have a different ingestion spec or shard allocation, the tasks will be killed and the +supervisor will create a new set of tasks. In this way, the supervisors are persistent across overlord restarts and +fail-overs. + +A supervisor is stopped via the `POST /druid/indexer/v1/supervisor/<supervisorId>/shutdown` endpoint. 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