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MongoDB Output Plugin

The out_mongo Buffered Output plugin writes records into MongoDB, the emerging document-oriented database system.

If you're using ReplicaSet, please see the out_mongo_replset article instead.

Table of Contents

Why Fluentd with MongoDB?

Fluentd enables your apps to insert records to MongoDB asynchronously with batch-insertion, unlike direct insertion of records from your apps. This has the following advantages:

  1. less impact on application performance
  2. higher MongoDB insertion throughput while maintaining JSON record structure

Install

out_mongo is included in td-agent by default. Fluentd gem users will need to install the fluent-plugin-mongo gem using the following command.

$ fluent-gem install fluent-plugin-mongo

Example Configuration

# Single MongoDB
<match mongo.**>
  type mongo
  host fluentd
  port 27017
  database fluentd
  collection test

  # for capped collection
  capped
  capped_size 1024m

  # authentication
  user michael
  password jordan

  # flush
  flush_interval 10s
</match>

Please see the Store Apache Logs into MongoDB article for real-world use cases.

Please see the Config File article for the basic structure and syntax of the configuration file.

Parameters

type (required)

The value must be mongo.

host (required)

The MongoDB hostname.

port (required)

The MongoDB port.

database (required)

The database name.

collection (required, if not tag_mapped)

The collection name.

capped

This option enables capped collection. This is always recommended because MongoDB is not suited to storing large amounts of historical data.

capped_size

Sets the capped collection size.

user

The username to use for authentication.

password

The password to use for authentication.

tag_mapped

This option will allow out_mongo to use Fluentd’s tag to determine the destination collection. For example, if you generate records with tags ‘mongo.foo’, the records will be inserted into the foo collection within the fluentd database.

<match mongo.*>
  type mongo
  host fluentd
  port 27017
  database fluentd

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

  # If the tag is "mongo.foo", then the prefix "mongo." is removed.
  # The inserted collection name is "foo".
  remove_tag_prefix mongo.

  # This configuration is used if the tag is not found. The default is 'untagged'.
  collection misc
</match>

This option is useful for flexible log collection.

Buffer Parameters

For advanced usage, you can tune Fluentd’s internal buffering mechanism with these parameters.

buffer_type

The buffer type is memory by default (buf_memory). The file (buf_file) buffer type can be chosen as well. The path parameter is used as buffer_path in this plugin.

buffer_queue_limit, buffer_chunk_limit

The length of the chunk queue and the size of each chunk, respectively. Please see the Buffer Plugin Overview article for the basic buffer structure. The default values are 64 and 8m, respectively. The suffixes “k” (KB), “m” (MB), and “g” (GB) can be used for buffer_chunk_limit.

flush_interval

The interval between data flushes. The default is 60s. The suffixes “s” (seconds), “m” (minutes), and “h” (hours) can be used.

retry_wait, max_retry_wait

The initial and maximum intervals between write retries. The default values are 1.0 and unset (no limit). The interval doubles (with +/-12.5% randomness) every retry until max_retry_wait is reached. In the default configuration the last retry waits for approximately 131072 sec, roughly 36 hours.

retry_limit, disable_retry_limit

The limit on the number of retries before buffered data is discarded, and an option to disable that limit (if true, the value of retry_limit is ignored and there is no limit). The default values are 17 and false (not disabled). If the limit is reached, buffered data is discarded and the retry interval is reset to its initial value (retry_wait).

disable_retry_limit is available for v0.10.53 and above.

num_threads

The number of threads to flush the buffer. This option can be used to parallelize writes into the output(s) designated by the output plugin. The default is 1.

log_level option (Fluentd v0.10.43 and above)

The log_level option allows the user to set different levels of logging for each plugin. The supported log levels are: fatal, error, warn, info, debug, and trace.

Please see the logging article for further details.

Further Reading

Last updated: 2014-02-14 05:08:15 UTC

Available languages | en | ja |

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