couch-daemon provides high-level interface as well as low-level streams. couch-daemon is built as a pipeline of six streams:
_pipeline//Create a stream of databases, filtered via black- and white lists.dbscouch opts// Fetch and emit design docs.ddocscouch opts// Create a global stream of changes.changescouch opts// Compile functions defined in ddocs.compilecouch optsyour_workercouch opts// Store last seq in checkpoint docs.checkpointcouch opts// Print log events.loggercouch opts;
he idea is to store per database daemon configuration in design documents in an object under the daemon name. The configuration cana have functions, like filters or processors (see couchmagick and massage-couch). couch-daemon looks at those configurations and evaluates each function in a sandbox. The actual daemon code is modelled as through stream. It receives configuration as well as changes of each database it is configured for. You can do anything you want inside that stream - make http calls to the outside, query the database or run long computations. When you're done you emit the original event to have couch-daemon store the checkpoint. Do not hesitate to open a ticket if something is unclear - this was written a bit in a hussle.
When using the high-level interface you do not need to handle
os_daemon communication with
CouchDB, commandline option parsing nor set up the pipeline yourself. Just call
couch-daemon with (optional) defaults and your worker stream and you're fine:
require'couch-daemon' include_docs: true// url comes from daemon configuration,// as well as the optionsreturnreturn sourcefiltergroupzipwhatever;;
The last stream in the couch-daemon pipeline is one that logs either to CouchDB's log or, when running in CLI mode, prints to console.
You can instruct the logger to respect your message by emitting a special log event from your worker stream:
type: 'log'level: 'debug' // Default is 'info'. Also possible: 'error'message: 'And the stars look very different today'
See examples/logger.js for a concrete example.
The daemon is set up in the
os_daemons config section (eg. in local.ini):
[os_daemons]mydaemon = mydaemon
The actual configuration is done under its own config section:
[mydaemon]; Optional username and password, used by the workers to access the databaseusername = mein-userpassword = secure; Only documents in the databases below are processed (separate with comma).; Regular expressions are allowed:;whitelist = mydb,otherdb,/^special-.*/; Ignore the following databases (again comma separated list); Regular expressions are again allowed:blacklist = /^_/
couch-daemon makes it easy to test your daemon via commandline. couch-daemon
detects if it has been started interactively.
--daemon argument for testing CouchDB os daemon interaction.)
When running interactively couch-daemon parses commandline options and prints out log messages to console.
- Massage Couch
- TBD: worker-fetch-tweets
- TBD: worker-generate-stills
- TBD: worker-fetch-json
Send me a pull to add yours.
An example daemon is included. It just prints out each change in all dbs:
./examples/logger.js --name my-daemon --blacklist _users
Write tests with tap,
then test your code with
Specify CouchDB url and credentials via
COUCH environment variable:
COUCH=http://user:password@localhost:5984 npm test
Copyright (c) 2014 Johannes J. Schmidt, null2 GmbH
Licensed under the MIT license.