Vivo Exporter

Vivo Exporter is an output plugin that exposes logs, metrics, and traces through an HTTP endpoint. This plugin aims to be used in conjunction with Vivo project .

Configuration Parameters

Key	Description	Default
empty_stream_on_read	If enabled, when an HTTP client consumes the data from a stream, the stream content will be removed.	Off
stream_queue_size	Specify the maximum queue size per stream. Each specific stream for logs, metrics and traces can hold up to stream_queue_size bytes.	20M
http_cors_allow_origin	Specify the value for the HTTP Access-Control-Allow-Origin header (CORS).

Getting Started

Here is a simple configuration of Vivo Exporter, note that this example is not based on defaults.

[INPUT]
    name  dummy
    tag   events
    rate  2

[OUTPUT]
    name                   vivo_exporter
    empty_stream_on_read   off
    stream_queue_size      20M
    http_cors_allow_origin *

How it works

Vivo Exporter provides buffers that serve as streams for each telemetry data type, in this case, logs, metrics, and traces. Each buffer contains a fixed capacity in terms of size (20M by default). When the data arrives at a stream, it’s appended to the end. If the buffer is full, it removes the older entries to make room for new data.

The data that arrives is a chunk. A chunk is a group of events that belongs to the same type (logs, metrics or traces) and contains the same tag. Every chunk placed in a stream is assigned with an auto-incremented id.

Requesting data from the streams

By using a simple HTTP request, you can retrieve the data from the streams. The following are the endpoints available:

endpoint	Description
/logs	Exposes log events in JSON format. Each event contains a timestamp, metadata and the event content.
/metrics	Exposes metrics events in JSON format. Each metric contains name, metadata, metric type and labels (dimensions).
/traces	Exposes traces events in JSON format. Each trace contains a name, resource spans, spans, attributes, events information, and so on.

The example below will generate dummy log events which will be consuming by using curl HTTP command line client:

Configure and start Calyptia Core Agent

[INPUT]
    name  dummy
    tag   events
    rate  2

[OUTPUT]
    name   vivo_exporter

Retrieve the data

curl -i http://127.0.0.1:2025/logs

We are using the -i curl option to print also the HTTP response headers.

Curl output would look like this:

HTTP/1.1 200 OK
Server: Monkey/1.7.0
Date: Tue, 21 Mar 2023 16:42:28 GMT
Transfer-Encoding: chunked
Content-Type: application/json
Vivo-Stream-Start-ID: 0
Vivo-Stream-End-ID: 3

[[1679416945459254000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416945959398000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416946459271000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416946959943000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416947459806000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416947958777000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416948459391000,{"_tag":"events"}],{"message":"dummy"}]

Streams and IDs

As mentioned above, on each stream we buffer a chunk that contains N events, each chunk contains it own ID which is unique inside the stream.

When we receive the HTTP response, Vivo Exporter also reports the range of chunk IDs that were served in the response via the HTTP headers Vivo-Stream-Start-ID and Vivo-Stream-End-ID.

The values of these headers can be used by the client application to specify a range between IDs or set limits for the number of chunks to retrieve from the stream.

Retrieve ranges and use limits

A client might be interested into always retrieve the latest chunks available and skip previous one that already processed. In a first request without any given range, Vivo Exporter will provide all the content that exists in the buffer for the specific stream, on that response the client might want to keep the last ID (Vivo-Stream-End-ID) that was received.

To query ranges or starting from specific chunks IDs, remember that they are incremental, you can use a mix of the following options:

Query string option	Description
from	Specify the first chunk ID that is desired to be retrieved. Note that if the chunk ID does not exists the next one in the queue will be provided.
to	The last chunk ID is desired. If not found, the whole stream will be provided (starting from from if was set).
limit	Limit the output to a specific number of chunks. The default value is 0, which means: send everything.

The following example specifies the range from chunk ID 1 to chunk ID 3 and only 1 chunk:

curl -i "http://127.0.0.1:2025/logs?from=1&to=3&limit=1"

Output:

HTTP/1.1 200 OK
Server: Monkey/1.7.0
Date: Tue, 21 Mar 2023 16:45:05 GMT
Transfer-Encoding: chunked
Content-Type: application/json
Vivo-Stream-Start-ID: 1
Vivo-Stream-End-ID: 1

[[1679416945959398000,{"_tag":"events"}],{"message":"dummy"}]
[[1679416946459271000,{"_tag":"events"}],{"message":"dummy"}]