mirror of https://github.com/apache/druid.git
92 lines
3.9 KiB
Markdown
92 lines
3.9 KiB
Markdown
---
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layout: doc_page
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---
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# Tutorial: Configuring data retention
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This tutorial demonstrates how to configure retention rules on a datasource to set the time intervals of data that will be retained or dropped.
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For this tutorial, we'll assume you've already downloaded Druid as described in
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the [single-machine quickstart](index.html) and have it running on your local machine.
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It will also be helpful to have finished [Tutorial: Loading a file](../tutorials/tutorial-batch.html) and [Tutorial: Querying data](../tutorials/tutorial-query.html).
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## Load the example data
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For this tutorial, we'll be using the Wikipedia edits sample data, with an ingestion task spec that will create a separate segment for each hour in the input data.
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The ingestion spec can be found at `quickstart/retention-index.json`. Let's submit that spec, which will create a datasource called `retention-tutorial`:
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```bash
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bin/post-index-task --file quickstart/tutorial/retention-index.json
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```
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After the ingestion completes, go to http://localhost:8081 in a browser to access the Coordinator console.
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In the Coordinator console, go to the `datasources` tab at the top of the page.
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This tab shows the available datasources and a summary of the retention rules for each datasource:
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Currently there are no rules set for the `retention-tutorial` datasource. Note that there are default rules, currently set to `load Forever 2 in _default_tier`.
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This means that all data will be loaded regardless of timestamp, and each segment will be replicated to two nodes in the default tier.
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In this tutorial, we will ignore the tiering and redundancy concepts for now.
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Let's click the `retention-tutorial` datasource on the left.
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The next page (http://localhost:8081/#/datasources/retention-tutorial) provides information about what segments a datasource contains. On the left, the page shows that there are 24 segments, each one containing data for a specific hour of 2015-09-12:
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## Set retention rules
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Suppose we want to drop data for the first 12 hours of 2015-09-12 and keep data for the later 12 hours of 2015-09-12.
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Click the `edit rules` button with a pencil icon at the upper left corner of the page.
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A rule configuration window will appear. Enter `tutorial` for both the user and changelog comment field.
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Now click the `+ Add a rule` button twice.
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In the `rule #1` box at the top, click `Load`, `Interval`, enter `2015-09-12T12:00:00.000Z/2015-09-13T00:00:00.000Z` in the interval box, and click `+ _default_tier replicant`.
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In the `rule #2` box at the bottom, click `Drop` and `Forever`.
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The rules should look like this:
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Now click `Save all rules`, wait for a few seconds, and refresh the page.
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The segments for the first 12 hours of 2015-09-12 are now gone:
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The resulting retention rule chain is the following:
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1. loadByInterval 2015-09-12T12/2015-09-13 (12 hours)
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2. dropForever
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3. loadForever (default rule)
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The rule chain is evaluated from top to bottom, with the default rule chain always added at the bottom.
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The tutorial rule chain we just created loads data if it is within the specified 12 hour interval.
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If data is not within the 12 hour interval, the rule chain evaluates `dropForever` next, which will drop any data.
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The `dropForever` terminates the rule chain, effectively overriding the default `loadForever` rule, which will never be reached in this rule chain.
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Note that in this tutorial we defined a load rule on a specific interval.
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If instead you want to retain data based on how old it is (e.g., retain data that ranges from 3 months in the past to the present time), you would define a Period load rule instead.
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## Further reading
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* [Load rules](../operations/rule-configuration.html)
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