The out_http Output plugin writes records via HTTP/HTTPS.

This plugin is introduced since fluentd v1.7.0.

It is included in Fluentd's core.

Example Configuration

<match pattern>
  @type http
​
  endpoint http://logserver.com:9000/api
  open_timeout 2
​
  <format>
    @type json
  </format>
  <buffer>
    flush_interval 10s
  </buffer>
</match>

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

For <buffer>, refer to Buffer Section Configuration.

Parameters

@type

The value must be http.

endpoint

The endpoint for HTTP request. If you want to use HTTPS, use https prefix.

# Use HTTP
endpoint http://example.com/api
​
# USe HTTPS. You can set additional HTTPS parameters like tls_xxx
endpoint https://example.com/api

The endpoint parameter supports placeholders, so you can embed time, tag and record fields in the endpoint. Placeholders also require the buffer section in order to work. Here is an example:

endpoint http://example.com/api/${tag}-${key}
<buffer tag,key>
  # buffer parameters
</buffer>

See Buffer Section Configurations for more details.

http_method

The method for HTTP request.

proxy

The proxy for HTTP request.

content_type

Content-Type for HTTP request. out_http automatically set Content-Type for built-in formatters when this parameter is not specified.

Here is a table:

• json with json_array false: application/x-ndjson

• json with json_array true: application/json

• csv: text/csv

• tsv, ltsv: text/tab-separated-values

• msgpack: application/x-msgpack

• out_file, single_value, stdout, hash: text/plain

json_array

Using the array format of JSON. This parameter is used and valid only for json format. When json_array as true, Content-Type should be application/json and be able to use JSON data for the HTTP request body.

• json_array true

[
  {"key":"value", ...},
  {"key":"value", ...},
  ...
]

• json_array false

{"key":"value", ...}
{"key":"value", ...}
...

<format> Directive

The format of the payload. The default @type is json.

Here is single_value example:

<format>
  @type single_value
</format>

See formatter article for more detail.

headers

Additional headers for HTTP request.

headers {"key1":"value1", "key2":"value2"}

headers_from_placeholders

Additional placeholder based headers for HTTP request. If you want to use tag or record field, use this parameter instead of headers.

headers_from_placeholders {"x-foo-bar":"${$.foo.bar}","x-tag":"app-${tag}"}
<buffer tag,$.foo.bar>
  # buffer parameters...
</buffer>

open_timeout

The connection open timeout in seconds.

See also Ruby document.

read_timeout

The read timeout in seconds.

See also Ruby document.

ssl_timeout

The TLS timeout in seconds.

tls_ca_cert_path

The CA certificate path for TLS.

tls_client_cert_path

The client certificate path for TLS.

tls_private_key_path

The client private key path for TLS.

tls_private_key_passphrase

The client private key passphrase for TLS.

tls_verify_mode

The verify mode of TLS.

tls_version

The default version of TLS.

tls_ciphers

The cipher suites configuration of TLS.

error_response_as_unrecoverable

Raise UnrecoverableError when the response code is not SUCCESS, 1xx/3xx/4xx/5xx. If false, out_http logs error message instead of raising UnrecoverableError.

See also Handling Unrecoverable Errors.

retryable_response_codes

The list of retryable response codes. If the response code is included in this list, out_http retries the buffer flush.

<auth> Section

Specifies HTTP authentication:

<auth>
  method basic
  username fluentd
  password hello
</auth>

method

The method for HTTP authentication. Now only basic.

username

The username for basic authentication.

password

The password for basic authentication.

Common Output / Buffer parameters

For common output / buffer parameters, please check the following articles:

• ​Output Plugin Overview​

• ​Buffer Section Configuration​

The Payload Content

out_http's request body depends on <format> configuration. For example, the default setting generates newline delimited JSON like this:

# \n is added by `add_newline true` parameter in <format>
{"key1":"value1","key2":"value2",...}\n
{"key1":"value1","key2":"value2",...}\n
{"key1":"value1","key2":"value2",...}\n
{"key1":"value1","key2":"value2",...}\n
...

With @type single_value:

log line1\n
log line2\n
log line3\n
log line4\n
...

Troubleshooting

400 Bad request between out_http and in_http

When getting the following error:

#0 got unrecoverable error in primary and no secondary error_class=Fluent::UnrecoverableError error="400 Bad Request 400 Bad Request\n'json' or 'msgpack' parameter is required\n"
#0 bad chunk is moved to /tmp/fluent/backup/worker0/object_3ff8a73edae8/5a71a08ca19b1b343c8dce1b74c9a963.log

Users should specify json format with json_array as true for out_http configuration:

<match **>
  @type http
  endpoint http://some.your.http.endpoint:9811/your-awesome-path
  <format>
    @type json
  </format>
  json_array true
  <buffer>
    flush_interval 2s
  </buffer>
</match>

And receiver in_http configuration should be:

<source>
  @type http
  port 9811
  bind 0.0.0.0
  <parse>
    @type json
  </parse>
</source>

Or specify msgpack format:

<match **>
  @type http
  endpoint http://some.your.http.endpoint:9882/your-awesome-path
  <format>
    @type msgpack
  </format>
  <buffer>
    flush_interval 2s
  </buffer>
</match>

And, receiver in_http configuration should be:

<source>
  @type http
  port 9882
  bind 0.0.0.0
  <parse>
    @type msgpack
  </parse>
  <format>
    @type json
  </format>
</source>

But, we recommend to use in/out forward plugin to communicate with two Fluentd instances due to at-most-once and at-least-once semantics for rigidity.

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open article- source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.