ingester

ClickHouse Ingester

The ClickHouse ingester can be used to write logs from Kafka into ClickHouse. To write the logs from Fluent Bit into Kafka the official Kafka output plugin can be used.

Configuration

An example Deployment for the ClickHouse ingester can be found in the ingester.yaml file. The following command-line flags and environment variables can be used to configure the ingester:

Command-Line Flag	Environment Variable	Description	Default
--metrics-server.address	METRICS_SERVER_ADDRESS	The address, where the metrics server should listen on.	:2021
--clickhouse.address	CLICKHOUSE_ADDRESS	ClickHouse address to connect to.
--clickhouse.database	CLICKHOUSE_DATABASE	ClickHouse database name.	logs
--clickhouse.username	CLICKHOUSE_USERNAME	ClickHouse username for the connection.
--clickhouse.password	CLICKHOUSE_PASSWORD	ClickHouse password for the connection.
--clickhouse.dial-timeout	CLICKHOUSE_DIAL_TIMEOUT	ClickHouse dial timeout.	10s
--clickhouse.conn-max-lifetime	CLICKHOUSE_CONN_MAX_LIFETIME	ClickHouse maximum connection lifetime.	1h
--clickhouse.max-idle-conns	CLICKHOUSE_MAX_IDLE_CONNS	ClickHouse maximum number of idle connections.	1
--clickhouse.max-open-conns	CLICKHOUSE_MAX_OPEN_CONNS	ClickHouse maximum number of open connections.	1
--clickhouse.async-insert	CLICKHOUSE_ASYNC_INSERT	Enable async inserts.	false
--clickhouse.wait-for-async-insert	CLICKHOUSE_WAIT_FOR_ASYNC_INSERT	Wait for async inserts.	false
--clickhouse.batch-size	CLICKHOUSE_BATCH_SIZE	The size for how many log lines should be buffered, before they are written to ClickHouse.	100000
--clickhouse.flush-interval	CLICKHOUSE_FLUSH_INTERVAL	The maximum amount of time to wait, before logs are written to ClickHouse.	60s
--clickhouse.force-number-fields	CLICKHOUSE_FORCE_NUMBER_FIELDS	A list of fields which should be parsed as number.	[]
--clickhouse.force-underscores	CLICKHOUSE_FORCE_UNDERSCORES	Replace all . with _ in keys.	false
--kafka.brokers	KAFKA_BROKERS	Kafka bootstrap brokers to connect to, as a comma separated list
--kafka.group	KAFKA_GROUP	Kafka consumer group definition	kafka-clickhouse
--kafka.version	KAFKA_VERSION	Kafka cluster version	2.1.1
--kafka.topics	KAFKA_TOPICS	Kafka topics to be consumed, as a comma separated list	fluent-bit
--log.format	LOG_FORMAT	The log format. Must be console or json.	console
--log.level	LOG_LEVEL	The log level. Must be debug, info, warn, error, fatal or panic.	info

Development

We are using kind for local development. To create a new Kubernetes cluster using kind you can run the cluster/cluster.sh script, which will create such a cluster with a Docker registry:

./cluster/cluster.sh

Once the cluster is running we can build and push the Docker image for Fluent Bit:

docker build -f cmd/ingester/Dockerfile -t localhost:5000/klogs:latest-ingester .
docker push localhost:5000/klogs:latest-ingester

# To run the Docker image locally, the following command can be used:
docker run -it --rm localhost:5000/klogs:latest-ingester

In the next step we have to create our ClickHouse cluster via the ClickHouse Operator. To do that we can deploy all the files from the cluster/clickhouse-operator and cluster/clickhouse folder:

k apply -f cluster/clickhouse-operator
k apply -f cluster/clickhouse

Once ClickHouse is running we have to connect to one ClickHouse instance to create our SQL schema. The schema can be found in the schema.sql file, just execute each SQL command one by one on the ClickHouse instance:

k exec -n clickhouse -it chi-clickhouse-sharded-0-0-0 -c clickhouse -- clickhouse-client

Before we can deploy Fluent Bit and the ingester, we have to deploy Kafka using the following command:

k apply -f cluster/kafka

Now we can deploy Fluent Bit to ingest all logs into Kafka and the ingester to write the logs from Kafka into ClickHouse:

k apply -f cluster/fluent-bit/ingester
k logs -n fluent-bit -l app=fluent-bit -f

To check if the logs are arriving in ClickHouse you can use the following SQL commands:

SELECT count(*) FROM logs.logs;
SELECT * FROM logs.logs LIMIT 10;

SELECT count(*) FROM logs.logs_local;
SELECT * FROM logs.logs_local LIMIT 10;

To clean up all the created resources run the following commands:

kind delete cluster --name fluent-bit-clickhouse
docker stop kind-registry
docker rm kind-registry