fluent-plugin-mongo provides input and output plugins for Fluentd (GitHub)

|fluent-plugin-mongo|   fluentd  |  ruby  |
|-------------------|------------|--------|
|     >= 1.0.0      | >= 0.14.12 | >= 2.1 |
|     <  1.0.0      | >= 0.12.0  | >= 1.9 |

The gem is hosted at Rubygems.org. You can install the gem as follows:

$ fluent-gem install fluent-plugin-mongo

Store Fluentd event to MongoDB database.

Use mongo type in match.

<match mongo.**>
  @type mongo

  # You can choose two approaches, connection_string or each parameter
  # 1. connection_string for MongoDB URI
  connection_string mongodb://fluenter:10000/fluent

  # 2. specify each parameter
  database fluent
  host fluenter
  port 10000

  # collection name to insert
  collection test

  # Set 'user' and 'password' for authentication.
  # These options are not used when use connection_string parameter.
  user handa
  password shinobu

  # Set 'capped' if you want to use capped collection
  capped
  capped_size 100m

  # Specify date fields in record to use MongoDB's Date object (Optional) default: nil
  # Supported data types are String/Integer/Float/Fuentd EventTime.
  # For Integer type, milliseconds epoch and seconds epoch are supported.
  # eg: updated_at: "2020-02-01T08:22:23.780Z" or updated_at: 1580546457010
  date_keys updated_at

  # Specify id fields in record to use MongoDB's BSON ObjectID (Optional) default: nil
  # eg: my_id: "507f1f77bcf86cd799439011"
  object_id_keys my_id

  # Other buffer configurations here
</match>

For connection_string parameter, see docs.mongodb.com/manual/reference/connection-string/ article for more detail.

fluent-plugin-mongo support built-in placeholders. database and collection parameters can handle them.

Here is an example to use built-in placeholders:

<match mongo.**>
  @type mongo

  database ${tag[0]}

  # collection name to insert
  collection ${tag[1]}-%Y%m%d

  # Other buffer configurations here
  <buffer tag, time>
    @type memory
    timekey 3600
  </buffer>
</match>

In more detail, please refer to the officilal document for built-in placeholders: docs.fluentd.org/v1.0/articles/buffer-section#placeholders

Tag mapped to MongoDB collection automatically.

Use tag_mapped parameter in match of mongo type.

If tag name is “foo.bar”, auto create collection “foo.bar” and insert data.

<match forward.*>
  @type mongo
  database fluent

  # Set 'tag_mapped' if you want to use tag mapped mode.
  tag_mapped

  # If tag is "forward.foo.bar", then prefix "forward." is removed.
  # Collection name to insert is "foo.bar".
  remove_tag_prefix forward.

  # This configuration is used if tag not found. Default is 'untagged'.
  collection misc

  # Other configurations here
</match>

Replica Set version of mongo.

<match mongo.**>
  @type mongo_replset
  database fluent
  collection logs

  nodes localhost:27017,localhost:27018

  # The replica set name
  replica_set myapp

  # num_retries is threshold at failover, default is 60.
  # If retry count reached this threshold, mongo plugin raises an exception.
  num_retries 30

  # following optional parameters passed to mongo-ruby-driver.
  # See mongo-ruby-driver docs for more detail: https://docs.mongodb.com/ruby-driver/master/tutorials/ruby-driver-create-client/
  # Specifies the read preference mode
  #read secondary
</match>

Use mongo_replset type in match.

<match mongo.**>
  @type mongo_replset
  database fluent
  collection logs

  # each node separated by ','
  nodes localhost:27017,localhost:27018,localhost:27019

  # following optional parameters passed to mongo-ruby-driver.
  #name replset_name
  #read secondary
  #refresh_mode sync
  #refresh_interval 60
  #num_retries 60
</match>

Tail capped collection to input data.

Use mongo_tail type in source.

<source>
  @type mongo_tail
  database fluent
  collection capped_log

  tag app.mongo_log

  # waiting time when there is no next document. default is 1s.
  wait_time 5

  # Convert 'time'(BSON's time) to fluent time(Unix time).
  time_key time

  # Convert ObjectId to string
  object_id_keys ["id_key"]
</source>

You can also use url to specify the database to connect.

<source>
  @type mongo_tail
  url mongodb://user:password@192.168.0.13:10249,192.168.0.14:10249/database
  collection capped_log
  ...
</source>

This allows the plugin to read data from a replica set.

You can save last ObjectId to tail over server’s shutdown to file.

<source>
  ...

  id_store_file /Users/repeatedly/devel/fluent-plugin-mongo/last_id
</source>

Or Mongo collection can be used to keep last ObjectID.

<source>
  ...

  id_store_collection last_id
</source>

Make sure the collection is capped. The plugin inserts records but does not remove at all.

BSON records which include ‘.’ or start with ‘$’ are invalid and they will be stored as broken data to MongoDB. If you want to sanitize keys, you can use replace_dot_in_key_with and replace_dollar_in_key_with.

<match forward.*>
  ...
  # replace '.' in keys with '__dot__'
  replace_dot_in_key_with __dot__

  # replace '$' in keys with '__dollar__'
  # Note: This replaces '$' only on first character
  replace_dollar_in_key_with __dollar__
  ...
</match>

NOTE: This feature will be removed since v0.8

Fluentd event sometimes has an invalid record as a BSON. In such case, Mongo plugin marshals an invalid record using Marshal.dump and re-inserts its to same collection as a binary.

If passed following invalid record:

{"key1": "invalid value", "key2": "valid value", "time": ISODate("2012-01-15T21:09:53Z") }

then Mongo plugin converts this record to following format:

{"__broken_data": BinData(0, Marshal.dump result of {"key1": "invalid value", "key2": "valid value"}), "time": ISODate("2012-01-15T21:09:53Z") }

Mongo-Ruby-Driver cannot detect an invalid attribute, so Mongo plugin marshals all attributes excluding Fluentd keys(“tag_key” and “time_key”).

You can deserialize broken data using Mongo and Marshal.load. Sample code is below:

# _collection_ is an instance of Mongo::Collection
collection.find({'__broken_data' => {'$exists' => true}}).each do |doc|
  p Marshal.load(doc['__broken_data'].to_s) #=> {"key1": "invalid value", "key2": "valid value"}
end

If you want to ignore an invalid record, set true to ignore_invalid_record parameter in match.

<match forward.*>
  ...

  # ignore invalid documents at write operation
  ignore_invalid_record true

  ...
</match>

If you want to exclude some fields from broken data marshaling, use exclude_broken_fields to specfiy the keys.

<match forward.*>
  ...

  # key2 is excluded from __broken_data.
  # e.g. {"__broken_data": BinData(0, Marshal.dump result of {"key1": "invalid value"}), "key2": "valid value", "time": ISODate("2012-01-15T21:09:53Z")
  exclude_broken_fields key2

  ...
</match>

Specified value is a comma separated keys(e.g. key1,key2,key3). This parameter is useful for excluding shard keys in shard environment.

Mongo plugin has the limitation of buffer size. Because MongoDB and mongo-ruby-driver checks the total object size at each insertion. If total object size gets over the size limitation, then MongoDB returns error or mongo-ruby-driver raises an exception.

So, Mongo plugin resets buffer_chunk_limit if configurated value is larger than above limitation:

• Before v1.8, max of buffer_chunk_limit is 2MB

• After v1.8, max of buffer_chunk_limit is 8MB

You can tail mongo capped collection.

$ mongo-tail -f

Run following command:

$ bundle exec rake test

You can use ‘mongod’ environment variable for specified mongod:

$ mongod=/path/to/mongod bundle exec rake test

Note that source code in test/tools are from mongo-ruby-driver.

Copyright

Copyright © 2011- Masahiro Nakagawa

License

Apache License, Version 2.0