JingsongLi commented on a change in pull request #12283: URL: https://github.com/apache/flink/pull/12283#discussion_r429905623
########## File path: docs/dev/table/connectors/filesystem.md ########## @@ -0,0 +1,340 @@ +--- +title: "FileSystem Connector" +nav-title: FileSystem Connector +nav-parent_id: connectors +nav-pos: 5 +--- +<!-- +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. +--> + +This connector provides access to partitioned files in filesystems +supported by the [Flink FileSystem abstraction]({{ site.baseurl}}/ops/filesystems/index.html). + +* This will be replaced by the TOC +{:toc} + +The file system connector itself is included in Flink and does not require an additional dependency. +A corresponding format needs to be specified for reading and writing rows from and to a file system. + +The file system connector allows for reading and writing from a local or distributed filesystem. A filesystem can be defined as: + +<div class="codetabs" markdown="1"> +<div data-lang="DDL" markdown="1"> +{% highlight sql %} +CREATE TABLE MyUserTable ( + column_name1 INT, + column_name2 STRING, + ... + part_name1 INT, + part_name2 STRING +) PARTITIONED BY (part_name1, part_name2) WITH ( + 'connector' = 'filesystem', -- required: specify to connector type + 'path' = 'file:///path/to/whatever', -- required: path to a directory + 'format' = '...', -- required: file system connector requires to specify a format, + -- Please refer to Table Formats + -- section for more details.s + 'partition.default-name' = '...', -- optional: default partition name in case the dynamic partition + -- column value is null/empty string. + + -- optional: the option to enable shuffle data by dynamic partition fields in sink phase, this can greatly + -- reduce the number of file for filesystem sink but may lead data skew, the default value is disabled. + 'sink.shuffle-by-partition.enable' = '...', + ... +) +{% endhighlight %} +</div> +</div> + +<span class="label label-danger">Attention</span> Make sure to include [Flink File System specific dependencies]({{ site.baseurl }}/ops/filesystems/index.html). + +<span class="label label-danger">Attention</span> File system sources for streaming is still under development. In the future, the community will add support for common streaming use cases, i.e., partition and directory monitoring. + +## Partition Files + +Flink's file system partition support uses the standard hive format. However, it does not require partitions to be pre-registered with a table catalog. Partitions are discovered and inferred based on directory structure. For example, a table partitioned based on the directory below would be inferred to contain `datetime` and `hour` partitions. + +``` +path +└── datetime=2019-08-25 + └── hour=11 + ├── part-0.parquet + ├── part-1.parquet + └── hour=12 + ├── part-0.parquet +└── datetime=2019-08-26 + └── hour=6 + ├── part-0.parquet +``` + +The file system table supports both partition inserting and overwrite inserting. See [INSERT Statement]({{ site.baseurl }}/table/sql/insert.html). When you insert overwrite to a partitioned table, only the corresponding partition will be overwritten, not the entire table. + +## File Formats + +The file system connector supports multiple formats: + + - CSV: [RFC-4180](https://tools.ietf.org/html/rfc4180). Uncompressed. + - JSON: Note JSON format for file system connector is not a typical JSON file but uncompressed [newline delimited JSON](http://jsonlines.org/). + - Avro: [Apache Avro](http://avro.apache.org). Support compression by configuring `avro.codec`. + - Parquet: [Apache Parquet](http://parquet.apache.org). Compatible with Hive. + - Orc: [Apache Orc](http://orc.apache.org). Compatible with Hive. + +## Streaming Sink + +The file system connector supports streaming writes, based on Flink's [Streaming File Sink]({{ site.baseurl }}/connectors/streamfile_sink.html) +to write records to file. Row-encoded Formats are csv and json. Bulk-encoded Formats are parquet, orc and avro. + +### Rolling Policy + +Data within the partition directories are split into part files. Each partition will contain at least one part file for +each subtask of the sink that has received data for that partition. The in-progress part file will be closed and additional +part file will be created according to the configurable rolling policy. The policy rolls part files based on size, +a timeout that specifies the maximum duration for which a file can be open. + +<table class="table table-bordered"> + <thead> + <tr> + <th class="text-left" style="width: 20%">Key</th> + <th class="text-left" style="width: 15%">Default</th> + <th class="text-left" style="width: 10%">Type</th> + <th class="text-left" style="width: 55%">Description</th> + </tr> + </thead> + <tbody> + <tr> + <td><h5>sink.rolling-policy.file-size</h5></td> + <td style="word-wrap: break-word;">1024L * 1024L * 128L</td> + <td>Long</td> + <td>The maximum part file size before rolling.</td> + </tr> + <tr> + <td><h5>sink.rolling-policy.time-interval</h5></td> + <td style="word-wrap: break-word;">30 m</td> + <td>Duration</td> + <td>The maximum time duration a part file can stay open before rolling (by default 30 min to avoid to many small files).</td> + </tr> + </tbody> +</table> + +**NOTE:** For bulk formats (parquet, orc, avro), the rolling policy in combination with the checkpoint interval(pending files +become finished on the next checkpoint) control the size and number of these parts. + +**NOTE:** For row formats (csv, json), you can reduce the time interval appropriately to avoid too long delay. + +### Partition Commit + +After writing a partition, it is often necessary to notify downstream applications. For example, add the partition to a Hive metastore or writing a `_SUCCESS` file in the directory. The file system sink contains a partition commit feature that allows configuring custom policies. Commit actions are based on a combination of `triggers` and `policies`. + +- Trigger: The timing of the commit of the partition can be determined by the watermark with the time extracted from the partition, or by processing time. +- Policy: How to commit a partition, built-in policies support for the commit of success files and metastore, you can also implement your own policies, such as triggering hive's analysis to generate statistics, or merging small files, etc. + +#### Partition commit trigger + +To define when to commit a partition, providing partition commit trigger: + +<table class="table table-bordered"> + <thead> + <tr> + <th class="text-left" style="width: 20%">Key</th> + <th class="text-left" style="width: 15%">Default</th> + <th class="text-left" style="width: 10%">Type</th> + <th class="text-left" style="width: 55%">Description</th> + </tr> + </thead> + <tbody> + <tr> + <td><h5>sink.partition-commit.trigger</h5></td> + <td style="word-wrap: break-word;">partition-time</td> + <td>String</td> + <td>Trigger type for partition commit: 'partition-time': extract time from partition, if 'watermark' > 'partition-time' + 'delay', will commit the partition. 'process-time': use processing time, if 'current processing time' > 'partition directory creation time' + 'delay', will commit the partition.</td> + </tr> + <tr> + <td><h5>sink.partition-commit.delay</h5></td> + <td style="word-wrap: break-word;">0 s</td> + <td>Duration</td> + <td>The partition will not commit until the delay time. If it is a daily partition, should be '1 d', if it is a hourly partition, should be '1 h'.</td> + </tr> + </tbody> +</table> + +There are two types of trigger: +- The first is to judge the time of partition commit according to the partition time and watermark. +This requires that your job is using event time, and the partition is divided according to time, such as +hourly partition or daily partition. +- The second is partition processing time. The time of partition commit according to partition +creation time and current time. This trigger is more universal, but not so precise. For example, +data delay or failover will lead to premature partition commit. + +#### Partition Time Extractor + +Time extractors define extracting time from partition values. + +<table class="table table-bordered"> + <thead> + <tr> + <th class="text-left" style="width: 20%">Key</th> + <th class="text-left" style="width: 15%">Default</th> + <th class="text-left" style="width: 10%">Type</th> + <th class="text-left" style="width: 55%">Description</th> + </tr> + </thead> + <tbody> + <tr> + <td><h5>partition.time-extractor.kind</h5></td> + <td style="word-wrap: break-word;">default</td> + <td>String</td> + <td>Time extractor to extract time from partition values. Support default and custom. For default, can configure timestamp pattern. For custom, should configure extractor class.</td> + </tr> + <tr> + <td><h5>partition.time-extractor.class</h5></td> + <td style="word-wrap: break-word;"></td> + <td>String</td> + <td>The extractor class for implement PartitionTimeExtractor interface.</td> + </tr> + <tr> + <td><h5>partition.time-extractor.timestamp-pattern</h5></td> + <td style="word-wrap: break-word;"></td> + <td>String</td> + <td>The 'default' construction way allows users to use partition fields to get a legal timestamp pattern. Default support 'yyyy-mm-dd hh:mm:ss' from first field. If timestamp in partition is single field 'dt', can configure: '$dt'. If timestamp in partition is year, month, day, hour, can configure: '$year-$month-$day $hour:00:00'. If timestamp in partition is dt and hour, can configure: '$dt $hour:00:00'.</td> + </tr> + </tbody> +</table> + +The default extractor is based on a timestamp pattern composed of your partition fields. You can also specify an implementation for fully custom partition extraction based on the `PartitionTimeExtractor` interface. + +<div class="codetabs" markdown="1"> +<div data-lang="java" markdown="1"> +{% highlight java %} + +public class HourPartTimeExtractor implements PartitionTimeExtractor { + @Override + public LocalDateTime extract(List<String> keys, List<String> values) { + String dt = values.get(0); + String hour = values.get(1); + return Timestamp.valueOf(dt + " " + hour + ":00:00").toLocalDateTime(); + } +} + +{% endhighlight %} +</div> +</div> + +#### Partition Commit Policy + +The partition commit policy defines what action is taken when partitions are committed. + +- The first is metastore, only hive table supports metastore policy, file system manages partitions through directory structure. +- The second is the success file, which will write an empty file in the directory corresponding to the partition. + +<table class="table table-bordered"> + <thead> + <tr> + <th class="text-left" style="width: 20%">Key</th> + <th class="text-left" style="width: 15%">Default</th> + <th class="text-left" style="width: 10%">Type</th> + <th class="text-left" style="width: 55%">Description</th> + </tr> + </thead> + <tbody> + <tr> + <td><h5>sink.partition-commit.policy.kind</h5></td> + <td style="word-wrap: break-word;"></td> + <td>String</td> + <td>Policy to commit a partition is to notify the downstream application that the partition has finished writing, the partition is ready to be read. metastore: add partition to metastore. Only work with hive table, it is empty implementation for file system table. success-file: add '_success' file to directory. Both can be configured at the same time: 'metastore,success-file'. custom: use policy class to create a commit policy. Support to configure multiple policies: 'metastore,success-file'.</td> + </tr> + <tr> + <td><h5>sink.partition-commit.policy.class</h5></td> + <td style="word-wrap: break-word;"></td> + <td>String</td> + <td>The partition commit policy class for implement PartitionCommitPolicy interface. Only work in custom commit policy.</td> + </tr> + <tr> + <td><h5>sink.partition-commit.success-file.name</h5></td> + <td style="word-wrap: break-word;"></td> + <td>String</td> + <td>The file name for success-file partition commit policy, default is '_SUCCESS'.</td> + </tr> + </tbody> +</table> + +You can extend the implementation of commit policy, The custom commit policy implementation like: + +<div class="codetabs" markdown="1"> +<div data-lang="java" markdown="1"> +{% highlight java %} + +public class AnalysisCommitPolicy implements PartitionCommitPolicy { + private HiveShell hiveShell; + @Override + public void commit(Context context) throws Exception { + if (hiveShell == null) { + hiveShell = createHiveShell(context.catalogName()); + } + hiveShell.execute(String.format("ALTER TABLE %s ADD PARTITION (%s = '%s') location '%s'", + context.tableName(), + context.partitionKeys().get(0), + context.partitionValues().get(0), + context.partitionPath())); + hiveShell.execute(String.format( + "ANALYZE TABLE %s PARTITION (%s = '%s') COMPUTE STATISTICS FOR COLUMNS", + context.tableName(), + context.partitionKeys().get(0), + context.partitionValues().get(0))); + } +} + +{% endhighlight %} +</div> +</div> + +## Full Example + +The below shows how the file system connector can be used to write a streaming query to write data from Kafka into a file system and runs a batch query to read that data back out. + +{% highlight sql %} + +CREATE TABLE kafka_table ( + user_id STRING, + order_amount DOUBLE, + log_ts TIMESTAMP(3), + WATERMARK FOR log_ts AS log_ts - INTERVAL '5' SECOND +) WITH (...); + +CREATE TABLE fs_table ( + user_id STRING, + order_amount DOUBLE, + dt STRING, + hour STRING +) PARTITIONED BY (dt, hour) WITH ( + ’connector’=’filesystem’, + ’path’=’...’, Review comment: Good catch ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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