113 lines
5 KiB
Markdown
113 lines
5 KiB
Markdown
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---
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layout: post
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title: rdb-rs - fast and efficient RDB parsing utility
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date: 15.01.2015 23:50
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---
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Ever since I started looking into [Rust][] I knew I needed a bigger project for which I could use it.
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I released a [few][lzf] [small][crc] [libraries][redlock], all based on Redis code/tools, so I figured:
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Why not a bigger project focused on Redis as well?
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We already have a nice [client library][redis-rs], so I did not need to write one myself.
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I then thought about writing a Cluster-aware library on top of that, but before I got any real code written I faced some difficulties in how I want the API to look like, so I abandonded the idea for now as well.
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The next idea was to have another implementation of the Cluster configuration utility `redis-trib`. Problem though: I did not even finish my attempt [in Go][redis-trib].
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I looked around for more ideas and then I came across the [redis-rdb-tools][tools] again.
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This small Python utility can parse, format and analyze Redis' dump files.
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Its author Sripathi Krishnan also documented the [file format][old-wiki] and version history of RDB.
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Sripathi didn't pay much attention to his project anymore, and so some bugs and feature requests remained unsolved.
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With the current changes for Redis 3.0 like the Quicklist and a new RDB version, the redis-rdb-tools can't be used anymore for new dump files without patches.
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So on last year's 31c3 I took some time and started reading and implementing a RDB parser in Rust based on the documentation.
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While reading the documentation, the Python code as well as Redis' own [rdb.c][] I took notes and later rewrote and reformatted Sripathi's documentation to be up to date and to also include the latest changes.
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Today I release this updated documentation. It's available online at [rdb.fnordig.de][site]:
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* [RDB File Format][file-format]
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* [RDB Version History][version-history]
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I will keep it updated, should there be need and of course I will improve it if necessary.
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At the same time I also open source my port of the redis-rdb-tools to Rust:
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## [rdb-rs][code]
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---
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`rdb-rs` is a library and tool to parse RDB and dump it into another format like JSON or the [Redis protocol](http://redis.io/topics/protocol).
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`rdb-rs` is offered both as a library and as a stand-alone command line tool.
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The command line tool can be used to dump an existing RDB file in one of the provided formats:
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~~~bash
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$ rdb --format json dump.rdb
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[{"key":"value"}]
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$ rdb --format protocol dump.rdb
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*2
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$6
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SELECT
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$1
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0
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*3
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$3
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SET
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$3
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key
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$5
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value
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~~~
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For now it is nothing too fancy, but it gets the job done.
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Over the next days and weeks I will improve it, add missing features such as filter options and hopefully also a memory reporter.
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### Library
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Using the library is as easy as calling the `rdb::parse` function and pass it a stream to read from and a formatter to use.
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~~~rust
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use std::io::{BufferedReader, File};
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let file = File::open(&Path::new("dump.rdb"));
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let reader = BufferedReader::new(file);
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rdb::parse(reader, rdb::JSONFormatter::new());
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~~~
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`rdb-rs` brings 4 pre-defined formatters, which can be used:
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* `PlainFormatter`: Just plain output for testing
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* `JSONFormatter`: JSON-encoded output
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* `NilFormatter`: Surpresses all output
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* `ProtocolFormatter`: Formats the data in [RESP](http://redis.io/topics/protocol), the Redis Serialization Protocol
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Adding your own formatter is as easy as implementing the [RdbParseFormatter][RdbParseFormatter] trait.
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Over the next weeks I will rework parts of the library. Currently I'm not too happy with the API offered, especially proper return values and error handling.
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The code also needs to be refactored to allow for filtering and memory reporting.
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For the `redis-rdb-tools` Sripathi also reverse-engineered and documented the memory usage of key-value pairs, which needs updates as well.
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This will take me some time to bring into the same format.
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---
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Finally, I want to say thanks to Sripathi Krishnan for building the rdb-tools and for the proper and very well written documentation. It helped a lot getting this done.
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Also thanks to [Matt][], [Andy][] and [Itamar][] for some input and comments on the small parts of the project I showed them.
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[redis-trib]: https://github.com/badboy/redis-trib.go
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[rust]: http://rust-lang.org/
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[lzf]: https://github.com/badboy/lzf-rs
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[crc]: https://github.com/badboy/crc64-rs
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[redlock]: https://github.com/badboy/redlock-rs
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[redis-rs]: https://github.com/mitsuhiko/redis-rs
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[old-wiki]: https://github.com/sripathikrishnan/redis-rdb-tools/wiki/Redis-RDB-Dump-File-Format
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[rdb.c]: https://github.com/antirez/redis/blob/unstable/src/rdb.c
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[site]: http://rdb.fnordig.de/
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[code]: https://github.com/badboy/rdb-rs
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[tools]: https://github.com/sripathikrishnan/redis-rdb-tools
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[file-format]: http://rdb.fnordig.de/file_format.html
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[version-history]: http://rdb.fnordig.de/version_history.html
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[RdbParseFormatter]: http://rdb.fnordig.de/doc/rdb/formatter/trait.RdbParseFormatter.html
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[Matt]: https://twitter.com/mattsta
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[Andy]: https://twitter.com/andygrunwald
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[Itamar]: https://twitter.com/itamarhaber
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