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97 lines
4.4 KiB
97 lines
4.4 KiB
1 year ago
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# Rocksdb Tuning Advisor
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## Motivation
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The performance of Rocksdb is contingent on its tuning. However,
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because of the complexity of its underlying technology and a large number of
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configurable parameters, a good configuration is sometimes hard to obtain. The aim of
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the python command-line tool, Rocksdb Advisor, is to automate the process of
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suggesting improvements in the configuration based on advice from Rocksdb
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experts.
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## Overview
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Experts share their wisdom as rules comprising of conditions and suggestions in the INI format (refer
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[rules.ini](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/rules.ini)).
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Users provide the Rocksdb configuration that they want to improve upon (as the
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familiar Rocksdb OPTIONS file —
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[example](https://github.com/facebook/rocksdb/blob/main/examples/rocksdb_option_file_example.ini))
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and the path of the file which contains Rocksdb logs and statistics.
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The [Advisor](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/rule_parser_example.py)
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creates appropriate DataSource objects (for Rocksdb
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[logs](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/db_log_parser.py),
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[options](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/db_options_parser.py),
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[statistics](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/db_stats_fetcher.py) etc.)
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and provides them to the [Rules Engine](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/rule_parser.py).
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The Rules uses rules from experts to parse data-sources and trigger appropriate rules.
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The Advisor's output gives information about which rules were triggered,
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why they were triggered and what each of them suggests. Each suggestion
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provided by a triggered rule advises some action on a Rocksdb
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configuration option, for example, increase CFOptions.write_buffer_size,
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set bloom_bits to 2 etc.
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## Usage
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### Prerequisites
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The tool needs the following to run:
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* python3
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### Running the tool
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An example command to run the tool:
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```shell
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cd rocksdb/tools/advisor
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python3 -m advisor.rule_parser_example --rules_spec=advisor/rules.ini --rocksdb_options=test/input_files/OPTIONS-000005 --log_files_path_prefix=test/input_files/LOG-0 --stats_dump_period_sec=20
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```
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### Command-line arguments
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Most important amongst all the input that the Advisor needs, are the rules
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spec and starting Rocksdb configuration. The configuration is provided as the
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familiar Rocksdb Options file (refer [example](https://github.com/facebook/rocksdb/blob/main/examples/rocksdb_option_file_example.ini)).
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The Rules spec is written in the INI format (more details in
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[rules.ini](https://github.com/facebook/rocksdb/blob/main/tools/advisor/advisor/rules.ini)).
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In brief, a Rule is made of conditions and is triggered when all its
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constituent conditions are triggered. When triggered, a Rule suggests changes
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(increase/decrease/set to a suggested value) to certain Rocksdb options that
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aim to improve Rocksdb performance. Every Condition has a 'source' i.e.
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the data source that would be checked for triggering that condition.
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For example, a log Condition (with 'source=LOG') is triggered if a particular
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'regex' is found in the Rocksdb LOG files. As of now the Rules Engine
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supports 3 types of Conditions (and consequently data-sources):
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LOG, OPTIONS, TIME_SERIES. The TIME_SERIES data can be sourced from the
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Rocksdb [statistics](https://github.com/facebook/rocksdb/blob/main/include/rocksdb/statistics.h)
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or [perf context](https://github.com/facebook/rocksdb/blob/main/include/rocksdb/perf_context.h).
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For more information about the remaining command-line arguments, run:
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```shell
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cd rocksdb/tools/advisor
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python3 -m advisor.rule_parser_example --help
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```
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### Sample output
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Here, a Rocksdb log-based rule has been triggered:
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```shell
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Rule: stall-too-many-memtables
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LogCondition: stall-too-many-memtables regex: Stopping writes because we have \d+ immutable memtables \(waiting for flush\), max_write_buffer_number is set to \d+
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Suggestion: inc-bg-flush option : DBOptions.max_background_flushes action : increase suggested_values : ['2']
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Suggestion: inc-write-buffer option : CFOptions.max_write_buffer_number action : increase
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scope: col_fam:
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{'default'}
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```
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## Running the tests
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Tests for the code have been added to the
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[test/](https://github.com/facebook/rocksdb/tree/main/tools/advisor/test)
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directory. For example, to run the unit tests for db_log_parser.py:
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```shell
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cd rocksdb/tools/advisor
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python3 -m unittest -v test.test_db_log_parser
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```
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