druid/docs/development/extensions-core/protobuf.md

id	title
protobuf	Protobuf

This Apache Druid (incubating) extension enables Druid to ingest and understand the Protobuf data format. Make sure to include druid-protobuf-extensions as an extension.

Protobuf Parser

Field	Type	Description	Required
type	String	This should say protobuf.	no
descriptor	String	Protobuf descriptor file name in the classpath or URL.	yes
protoMessageType	String	Protobuf message type in the descriptor. Both short name and fully qualified name are accepted. The parser uses the first message type found in the descriptor if not specified.	no
parseSpec	JSON Object	Specifies the timestamp and dimensions of the data. The format must be JSON. See JSON ParseSpec for more configuration options. Please note timeAndDims parseSpec is no longer supported.	yes

Example: Load Protobuf messages from Kafka

This example demonstrates how to load Protobuf messages from Kafka. Please read the Load from Kafka tutorial first. This example will use the same "metrics" dataset.

Files used in this example are found at ./examples/quickstart/protobuf in your Druid directory.

• We will use Kafka Indexing Service instead of Tranquility.
• Kafka broker host is localhost:9092.
• Kafka topic is metrics_pb instead of metrics.
• datasource name is metrics-kafka-pb instead of metrics-kafka to avoid the confusion.

Here is the metrics JSON example.

{
  "unit": "milliseconds",
  "http_method": "GET",
  "value": 44,
  "timestamp": "2017-04-06T02:36:22Z",
  "http_code": "200",
  "page": "/",
  "metricType": "request/latency",
  "server": "www1.example.com"
}

Proto file

The proto file should look like this. Save it as metrics.proto.

syntax = "proto3";
message Metrics {
  string unit = 1;
  string http_method = 2;
  int32 value = 3;
  string timestamp = 4;
  string http_code = 5;
  string page = 6;
  string metricType = 7;
  string server = 8;
}

Descriptor file

Using the protoc Protobuf compiler to generate the descriptor file. Save the metrics.desc file either in the classpath or reachable by URL. In this example the descriptor file was saved at /tmp/metrics.desc.

protoc -o /tmp/metrics.desc metrics.proto

Supervisor spec JSON

Below is the complete Supervisor spec JSON to be submitted to the Overlord. Please make sure these keys are properly configured for successful ingestion.

• descriptor for the descriptor file URL.
• protoMessageType from the proto definition.
• parseSpec format must be json.
• topic to subscribe. The topic is "metrics_pb" instead of "metrics".
• bootstrap.server is the Kafka broker host.

{
  "type": "kafka",
  "dataSchema": {
    "dataSource": "metrics-kafka2",
    "parser": {
      "type": "protobuf",
      "descriptor": "file:///tmp/metrics.desc",
      "protoMessageType": "Metrics",
      "parseSpec": {
        "format": "json",
        "timestampSpec": {
          "column": "timestamp",
          "format": "auto"
        },
        "dimensionsSpec": {
          "dimensions": [
            "unit",
            "http_method",
            "http_code",
            "page",
            "metricType",
            "server"
          ],
          "dimensionExclusions": [
            "timestamp",
            "value"
          ]
        }
      }
    },
    "metricsSpec": [
      {
        "name": "count",
        "type": "count"
      },
      {
        "name": "value_sum",
        "fieldName": "value",
        "type": "doubleSum"
      },
      {
        "name": "value_min",
        "fieldName": "value",
        "type": "doubleMin"
      },
      {
        "name": "value_max",
        "fieldName": "value",
        "type": "doubleMax"
      }
    ],
    "granularitySpec": {
      "type": "uniform",
      "segmentGranularity": "HOUR",
      "queryGranularity": "NONE"
    }
  },
  "tuningConfig": {
    "type": "kafka",
    "maxRowsPerSegment": 5000000
  },
  "ioConfig": {
    "topic": "metrics_pb",
    "consumerProperties": {
      "bootstrap.servers": "localhost:9092"
    },
    "taskCount": 1,
    "replicas": 1,
    "taskDuration": "PT1H"
  }
}

Kafka Producer

Here is the sample script that publishes the metrics to Kafka in Protobuf format.

1. Run protoc again with the Python binding option. This command generates metrics_pb2.py file.

 protoc -o metrics.desc metrics.proto --python_out=.

2. Create Kafka producer script.

This script requires protobuf and kafka-python modules.

#!/usr/bin/env python

import sys
import json

from kafka import KafkaProducer
from metrics_pb2 import Metrics

producer = KafkaProducer(bootstrap_servers='localhost:9092')
topic = 'metrics_pb'
metrics = Metrics()

for row in iter(sys.stdin):
    d = json.loads(row)
    for k, v in d.items():
        setattr(metrics, k, v)
    pb = metrics.SerializeToString()
    producer.send(topic, pb)

3. run producer

./bin/generate-example-metrics | ./pb_publisher.py

4. test

kafka-console-consumer --zookeeper localhost --topic metrics_pb

It should print messages like this

millisecondsGETR"2017-04-06T03:23:56Z*2002/list:request/latencyBwww1.example.com