Treasure Data Summer Internship 2016

Internship Final ReportSep 30, 2016 Yuta Iwama

Who am I

• Yuma Iwama (@ganmacs)

• Master’s student, The University of Tokyo

• Research: Programming languages (My theme is extending language syntax)

• Group: Chiba Shigeru Group

What I did in summer intern

• Add features and enhancements to Fluentd v0.14.x

What I did in summer intern

• 6 features • Counter API (Not merged yet) • Data compression in buffer plugins and forward plugins • New out_file plugin only for <secondary> section • A CLI tool to read dumped event data • Log rotation • `filter_with_time` method in filter plugins

• 2 enhancements • Optimizing multiple filter calls • Add event size to options in a forward protocol

• Some small tasks

I’ll talk about

• Counter API • Data compression in buffer plugins and

forward plugins • New out_file plugin only for <secondary>

section • A CLI tool to read dumped event data • Log rotation • Optimizing multiple filter calls

I’ll talk about




Data Compression in buffer plugins and

forward plugins

Current buffer plugins and forward plugins in Fluentd• Buffer plugins have data as a string (formatted

with MessagePack or user custom formats)

• Forward plugins send data as a string (format is same as buffer plugins)

• Although data is serialized with MessagePack, its footprint is large

• Current way consumes many memory resources and bandwidth of the network

New buffer plugins and forward plugins• String data in buffer plugins can be compressed

• Forward plugins can send and receive compressed data

• Things to be able to

• Save the bandwidth across the datacenter

• Accelerate the transfer speed and save the time

• Reduce memory consumptions and costs of IaaS (EC2 , etc.)

Implementation

• I used “zlib” in Ruby to implement a compression/decompression method

• It’s hard to work both compressed version and raw version (To solve this problem, I used `extend` in Ruby not to break existing interface)

New out_file plugin only for <secondary> section

Background

• Many users use out_file plugin to dump buffer with <secondary> sections when primary buffered output plugins are failing flush

• But out_file is too complex and has too many features for such purpose

• => We need simple out_file only for <secondary> section just to dump buffer

New plugin: secondary_out_file

• Only four attributes • directory: the directory dumped data saved • basename: the file name of dumped data (default value is

dump.bin) • append: the flushed data is appended to an existing file or

not (default false) • compress: The type of the file ( gzip or txt, default is txt)

• Users can use this plugin only to set directory<match > @type forward ... <secondary> type secondary_file directory log/secondary/ </secondary> </match>

A CLI tool which is used for reading dump data

Background

• Dumped data are created by secondary plugins (e.g. secondary_out_file) when primary plugins are failing flush

• We can't read dumped data because dumped data is binary format(MessagePack) in most case

• => Provide a CLI tool to read dumped data

fluent-binlog-reader

• fluent-buinlog-reader is bundled in Fluent • It reads dumped data and outputs readable

format • Users can use fluent’s formatter plugins as an

output format$ fluent-binlog-reader --help Usage: fluent-binlog-reader <command> [<args>]

Commands of fluent-binlog-reader: cat : Read files sequentially, writing them to standard output. head : Display the beginning of a text file. format : Display plugins that you can use. See 'fluent-binlog-reader <command> --help' for more information on a specific command.

fluent-binlog-reader

$ fluent-binlog-reader head packed.log 2016-08-12T17:24:18+09:00 packed.log {"message":"dummy"} 2016-08-12T17:24:18+09:00 packed.log {"message":"dummy"} 2016-08-12T17:24:18+09:00 packed.log {"message":"dummy"} 2016-08-12T17:24:18+09:00 packed.log {"message":"dummy"} 2016-08-12T17:24:18+09:00 packed.log {"message":"dummy"}

Default format is json format

Using a “csv formatter” to output dumped data

$ fluent-binlog-reader cat --formats=csv -e fields=message packed.log "dummy" ... "dummy"

Log rotation

Background

• Fluentd can’t do log rotation • As the file size of log increases, it becomes

difficult to handle the log file.

• => Fluentd supports log rotation to keep log files down to a manageable size

Log rotation

• Two options • log-rotate-age: The number of old log files

to keep • log-rotate-size: Maximum log file size

• Use serverengine log rotation (Fluentd uses serverengine logger to one’s log)

Optimise multiple filter calls

Background

• If users apply multiple filters to incoming events, Fluentd creates a lot of EventStream object and calls its add method

• => Removing useless instantiations of EventStream and the `add` method calls

Filter 11. Create an EventStream object (1 time) 2. Apply a filter to each event (5 times) 3. Add a filtered event to an EventStream object (5times)

[e1, e2, e3, e4, e5]

If 10 filters are applied 1. call 10 times 2. call 50 times 3. call 50 times

[e1’, e2’, e3’, e4’, e5’]

[e1x, e2x, e3x, e4x, e5x]

Filter n

Current filters

Filter 1

1. Create an EventStream object (1 time) 2. Apply each filters to each event (n * 5 times) 3. Add a filtered event to an EventStream object (5times)

[e1, e2, e3, e4, e5]

if 10 filters are applied 1. call 1 time 2. call 50 times 3. call 5 times

[e1x, e2x, e3x, e4x, e5x]

Filter n+

Constraint: These filters must not be implemented `filter_stream` method

Optimised case

Performance

Tool : ruby-prof ProductName: Mac OS X ProductVersion: 10.11.6 BuildVersion: 15G31 PROCESSOR: 2.7 GHz Intel Core i5 MEMORY: 8 GB 1867 MHz DDR3

Not optimized Optimised

0.063186 0.051646

1.2 times faster when it is using 10 filters and 1000 events per sec

I’ll talk about




Counter API

Motivations

• To get metrics of Fluentd itself between processes

• To provide counter API to 3rd party plugins

• It is useful to implement counter plugins (e.g. fluent-plugin-datacounter and fluent-plugin-flowcounter)

What’s the counter

• The counter:

• A key-value store

• Used for storing the number of occurrences of a particular event in the specified time

• Provides API to users to operate its value(e.g. inc, reset , etc.)

• shared between processes

Counter

key value

key1 5

key2 1.2

key3 3

CounterProcess 1 inc(key1 => 2)

Process 2 reset(key2)

What’s the counter (cont.)

Counter

Counter

What’s the counter (cont.)

key value

key1 7

key2 1.2

key3 0

Process 1 inc(key1 => 2)

Process 2 reset(key2)

Implementation

• RPC server and client

• All operators should be thread safe

• Cleaning mutex objects for keys

Implementation




RPC server and client

• Because the counter is shared between processes. We need a server and clients (Store counter values in server and clients manipulate them by RPC )

• I designed RPC server and client for counter • I use cool.io to implement RPC server and client

• cool.io is providing a high-performance event framework for Ruby (https://coolio.github.io/)

http://cool.io

https://coolio.github.io/

API to operate counter values

• init: create new value • reset: reset a counter value • delete: delete a counter value • inc: increment or decrement a counter value • get: fetch a counter value

Implementation




All operations should be a thread safe

• Counter works in multi threads

• You need to get a lock per keys when you change a counter value

• Counter stores mutex objects in hash (key_name => mutex_object)

How an inc method works

key valuekey1 2

Counter server

client in worker1inc( key1 => 2)

1. Call an inc method

key value

key1 mutex obj

Mutex hash


key valuekey1 2

Counter server

key value

key1 mutex obj

Mutex hashclient in worker1inc( key1 => 2)

1. Call an inc method 2. Get a lock for a mutex hash

locked


key valuekey1 2

Counter server

key value

key1 locked


1. Call an inc method 2. Get a lock for a mutex hash 3. Get a lock for a key

locked


key valuekey1 2

Counter server

key value

key1 locked


1. Call an inc method 2. Get a lock for a mutex hash 3. Get a lock for a key 4. Unlock a mutex hash


key valuekey1 4

Counter server

key value

key1 locked


1. Call an inc method 2. Get a lock for a mutex hash 3. Get a lock for a key 4. Unlock a mutex hash 5. Change a counter value


key valuekey1 4

Counter server

key value

key1 unlock


1. Call an inc method 2. Get a lock for a mutex hash 3. Get a lock for a key 4. Unlock a mutex hash 5. Change a counter value 6. Unlock a key lock

Implementation




Mutex objects for keys

• To avoid storing mutex objects for all keys, I implement a cleanup thread which removes unused key’s mutex object (like GC)

• This thread removes mutex objects which are not used for a certain period

Cleaning up a mutex hash

key valuekey1 2

Counter serverkey value

key1 mutex obj

Mutex hash

• If “key1” are not modified for a long period, “key1” may be unused after this


key value

key1 mutex obj

Mutex hash


1. Start a cleaning thread (once in 15 min)


key value

key1 mutex obj

Mutex hash


1. Start a cleaning thread (once in 15 min) 2. Get a lock for a mutex hash locked


key value

Mutex hash


1. Start a cleaning thread (once in 15 min) 2. Get a lock for a mutex hash 3. Remove a mutex for an unused key

locked


key value

Mutex hash


1. Start a cleaning thread (once in 15 min) 2. Get a lock for a mutex hash 3. Remove a mutex for an unused key 4. Try to get a lock for the same key

If this thread can’t get a lock restore a key-value

locked


key value

Mutex hash


1. Start a cleaning thread (once in 15 min) 2. Get a lock for a mutex hash 3. Remove a mutex for an unused key 4. Try to get a lock for the same key 5. Unlock a mutex hash

Summary

• Add six features and two enhancements to Fluentd v0.14.x

• Counter API is not merged yet

• Other PRs have been merged

Impression of intern

• The hardest thing for me is to design about counter API(It takes over 1 week)

• I have learned about the development of middleware which is used by many people

• I want to became more careful to code written by myself (typo, description, comment etc.)

Treasure Data Summer Internship 2016

Engineering