Burlesque

Burlesque is a message queue server writen in Go. It gives access to queues using the pub/sub HTTP API.

This server's main purpose is to provide an inter-process comunication tool with a memory efficient persistent storage for messages. These messages usually are delayed job descriptions serialized in JSON that are published by the application server and later on retrieved by application workers.

Subscription uses long polling technique. When application worker subscribes to a queue which is empty at the moment, connection is kept open until a client publishes a message to this queue, or subscription timeout is reached. If there is already a message in the queue it is removed from the queue and returned to the worker.

To store messages Burlesque uses Kyoto Cabinet, which is a powerful DIY database. Usage of Kyoto Cabinet is thoroughly described in the storage section of this document.

Contents

• Installation
  • Building on OS X
• Starting
• Storage
  • In-memory databases
  • Persistent databases
  • Tuning parameters
  • Support of tuning parameters by databases
• What storage to choose
  • Production
  • Development
• API
  • Publish
  • Subscribe
  • Status
  • Debug

Installation

Download and extract the latest release. That's it.

Building on OS X

First install Homebrew. Using Homebrew install Go language compiler and tools. Then install Kyoto Cabinet library.

brew install go
brew install kyoto-cabinet
go get github.com/KosyanMedia/burlesque

Starting

The following arguments are supported by the burlesque executable:

Argument	Description	Defaults
-storage	Kyoto Cabinet storage path (e.g. storage.kch#msiz=524288000)	-
-environment	Process environment: development or production	development
-port	Server HTTP port	4401
-rollbar	Rollbar token

Example

wget -O burlesque.zip https://github.com/KosyanMedia/burlesque/archive/1.0.0.zip
unzip burlesque.zip
./burlesque

By default, Burlesque starts on port 4401 and uses in-memory database ProtoHashDB.

Storage

-storage argument defines the way data is stored in the database. You can read more on Kyoto Cabinet database types here.

In-memory databases

If you need a temporary in-memory storage use the following symbols as the -storage value:

Value	Database Type
-	ProtoHashDB Prototype hash database. In-memory database implemented with std::unorderd_map
+	ProtoTreeDB Prototype tree database. In-memory database implemented with std::map
:	StashDB Stash database. In-memory database saving memory
*	CacheDB Cache hash database. In-memory database featuring LRU deletion
%	GrassDB Cache tree database. In-memory database of B+ tree: cache with order

Example: -

Persistent databases

In order to use a persistent database, use the path to the database file (or directory) as the -storage argument value. File extension in the database path defines the type of the database created.

File Extension	Database Type
kch	HashDB File hash database. File database of hash table: typical DBM
kct	TreeDB File tree database. File database of B+ tree: DBM with order
kcd	DirDB Directory hash database. Respective files in a directory of the file system
kcf	ForestDB Directory tree database. Directory database of B+ tree: huge DBM with order
kcx	TextDB Plain text database. Emulation to handle a plain text file as a database

Example: /path/to/my/storage.kch

Tuning parameters

When the database type is defined, you can also add tuning parameters to the -storage argument. Tuning parameters are separated by the # symbol, parameters' name and value are separated by the = symbol.

The table below describes tuning parameters.

Parameter	Description
apow	Power of the record size alignment
bnum	Base hash table size (number of buckets of the hash table)
capcnt	Capacity limit by the number of records (#capcnt=10000 means "keep in memory 10,000 records maximum")
capsiz	Capacity limit by the size of records (#capsiz=536870912 means "keep in memory all the records that fit into 512 megabytes")
dfunit	Unit step number of auto defragmentation (#dfunit=8 means "run defragmentation every 8 fragmentations detected").
fpow	Power of the free block pool capacity
log	Path to the log file. Use - for the STDOUT, or + for the STDERR
logkinds	Kinds of logged messages. The value can be debug, info, warn or error
logpx	Prefix of each log message
msiz	Expected database memory usage
opts	Additional options: s, l and c (can be specified together, e.g lc). s stands for "small" and reduces the width of record address from 6 bytes to 4 bytes. As a result, the footprint for each record is reduced from 16 bytes to 12 bytes. However, it limits the maximum size of the database file to 16GB. l stands for "linear" and changes the data structure of the collision chain of hash table from binary tree to linear linked list. c enables compression of the record values. If the value is bigger than 1KB compression is effective.
pccap	Capacity size of the page cache
psiz	Page size
rcomp	Comparator used to compare key names. lex for the lexical comparator, dec for the decimal comparator, lexdesc for the lexical descending comparator, or decdesc for the decimal descending comparator
zcomp	Compression library: zlib for the ZLIB raw compressor, def for the ZLIB deflate compressor, gz for the ZLIB gzip compressor, lzo for the LZO compressor, lzma for the LZMA compressor, or arc for the Arcfour cipher
zkey	Cipher keyword used with compression

Example: storage.kch#opts=c#zcomp=gz#msiz=524288000

Support of tuning parameters by databases

The table below describes support of these parameters by the in-memory database types.

Parameter	ProtoHashDB	ProtoTreeDB	StashDB	CacheDB	GrassDB
bnum	—	—	Yes	Yes	Yes
capcnt	—	—	—	Yes	—
capsiz	—	—	—	Yes	—
log	Yes	Yes	Yes	Yes	Yes
logkinds	Yes	Yes	Yes	Yes	Yes
logpx	Yes	Yes	Yes	Yes	Yes
opts	—	—	—	Yes	Yes
pccap	—	—	—	—	Yes
psiz	—	—	—	—	Yes
rcomp	—	—	—	—	Yes
zcomp	—	—	—	Yes	Yes
zkey	—	—	—	Yes	Yes

The table below describes support of these parameters by the persistent database types.

Parameter	HashDB	TreeDB	DirDB	ForestDB	TextDB
apow	Yes	Yes	—	—	—
bnum	Yes	Yes	—	—	—
dfunit	Yes	Yes	—	—	—
fpow	Yes	Yes	—	—	—
log	Yes	Yes	Yes	Yes	Yes
logkinds	Yes	Yes	Yes	Yes	Yes
logpx	Yes	Yes	Yes	Yes	Yes
msiz	Yes	Yes	—	—	—
opts	Yes	Yes	Yes	Yes	—
pccap	—	Yes	—	Yes	—
psiz	—	Yes	—	Yes	—
rcomp	—	Yes	—	Yes	—
zcomp	Yes	Yes	Yes	Yes	—
zkey	Yes	Yes	Yes	Yes	—

What storage to choose

Production

For production usage it is strongly recommended to choose a persistent database. Burlesque uses Kyoto Cabinet as a persistent hash-table, which means HashDB would be a smart choice.

If the average message size is expected to be more than 1KB then compression should be considered as an option. To enable compression you need to pass opts tuning parameter to the database path with value c (#opts=c) in it, you also need to define compression algorithm using the zcomp parameter (e.g #zcomp=gz).

You can define maximum memory limit; when the limit is reached new records are swapped to disk. Memory limit is defined by value of msiz parameter in bytes (e.g #msiz=524288000)

So, to use a persistent hash database with enabled compression and 512MB memory limit the -storage argument value should be storage.kch#opts=c#zcomp=gz#msiz=524288000.

Further tuning

If queues are kept empty or relatively small, bnum option might be considered (e.g #bnum=1000)

Development

If development database doesn't need to be persisted consider using ProtoHashDB (which locks the whole table), StashDB (locks record) or CacheDB (locks record using a mutex). By default ProtoHashDB is used.

API

All endpoints exposed by the API are described below.

Publish

This endpoint is used to publish messages to a queue. If there is a connection waiting to recieve a message from this queue, the message will be handed directly to the awaiting worker.

Publication can be done via both GET and POST methods. Both methods use queue argument to pass queue name. When using GET method pass message body with msg argument. To publish a message via POST method pass message body via request body instead of the msg argument.

In case of success, server will respond with status 200 and OK message. Otherwise, there will be status 500 and FAIL message.

Example

curl '127.0.0.1:4401/publish?queue=urgent' -d 'Process this message as soon as possible!'

Response

OK

Subscribe

This endpoint is used to try and fetch a message from one of the queues given. If at least one of these queues contains a message, this message will be removed from the queue and returned as a response body. The name of the queue where this message was taken from will be provided as a Queue response header.

Subscription is always done via GET method. To fetch a message from a queue use the name of the queue as the queues argument value. Multiple queue names could be passed separated with the comma character.

Example

curl '127.0.0.1:4401/subscribe?queues=urgent,someday'

Response

Process this message as soon as possible!

Status

This endpoint is used to display information about the queues, their messages and current subscriptions encoded in JSON format.

Example

curl 127.0.0.1:4401/status

Response

{
    "urgent": {
        "messages": 0,
        "subscriptions": 0
    },
    "someday": {
        "messages": 0,
        "subscriptions": 0
    }
}

Debug

This endpoint is used to display debug information about Burlesque process. Currenty displays the number of goroutines only.

Example

curl 127.0.0.1:4401/debug

Response

{
    "goroutines": 13
}