Clickhouse

Before starting

• In most cases, you will want to send data from the central server. It is also possible to send it from a remote server or a poller (e.g. if you want to avoid the central server being a SPOF, or if you are an MSP and you install the stream connector on a poller or a remote server within your customer's infrastructure).
• By default, the Clickhouse stream connector sends data from host_status and service_status Broker events. These metrics are contained in the perf_data field of the events. The event format is shown here.
• These events are sent each time a host or a service is checked. Various parameters let you filter out events.

Prerequisites

• The Clickhouse HTTP interface must be enabled. (Clickhouse Documentation).
• You must have a valid user/password that can INSERT data into the desired table.
• You must create a table in Clickhouse to receive Centreon data. Here is the table schema (you can change the database and table name. They are both configurable in the stream connector configuration).

Standard table schema

This is the default schema that should be used.

CREATE TABLE centreon_stream.metrics
(
  host String,
  service String,
  metric_id String,
  metric_name String,
  metric_unit String,
  metric_value Decimal,
  metric_min Decimal,
  metric_max Decimal,
  timestamp DateTime,
  hostgroups Array(String)
)
ENGINE = MergeTree()
PRIMARY KEY (timestamp, host, service, metric_name, metric_id)

Alternative table schema

Disclaimer: you should not use this schema unless you absolutely want the internal metric_id of Centreon. This comes with the loss of many possibilities such as having access to metric units, min, max.... To use this schema, please refer to the use_deprecated_metric_system parameter documentation below.

CREATE TABLE centreon_stream.metrics
(
  host String,
  service String,
  metric_id BIGINT,
  metric_name String,
  metric_value Decimal,
  timestamp DateTime,
  hostgroups Array(String)
)
ENGINE = MergeTree()
PRIMARY KEY (timestamp, host, service, metric_name, metric_id)

Installation

Perform the installation on the server that will send data to Clickhouse (central server, remote server, poller).

Alma / RHEL / Oracle Linux 8

1. Login as root using your favorite SSH client.

2. Install the Epel repository.

dnf install epel-release

3. Install the Centreon lua modules.

dnf install centreon-stream-connectors-lib

4. Download the Clickhouse metrics stream connector:

wget -O /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua https://raw.githubusercontent.com/centreon/centreon-stream-connector-scripts/develop/centreon-certified/clickhouse/clickhouse-metrics-apiv2.lua
chmod 644 /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua

Alma / RHEL / Oracle Linux 9

1. Login as root using your favorite SSH client.

2. Install the Epel repository.

dnf install epel-release

3. Install the Centreon lua modules.

dnf install centreon-stream-connectors-lib

4. Download the Clickhouse metrics stream connector:

wget -O /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua https://raw.githubusercontent.com/centreon/centreon-stream-connector-scripts/develop/centreon-certified/clickhouse/clickhouse-metrics-apiv2.lua
chmod 644 /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua

Debian 12

1. Login as root using your favorite SSH client.

2. Install the Centreon lua modules.

dnf install centreon-stream-connectors-lib

3. Download the Clickhouse metrics stream connector:

wget -O /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua https://raw.githubusercontent.com/centreon/centreon-stream-connector-scripts/develop/centreon-certified/clickhouse/clickhouse-metrics-apiv2.lua
chmod 644 /usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua

Configuring your Clickhouse equipment

You may need to configure your Clickhouse equipment so that it can receive data from Centreon. Please refer to Clickhouse's documentation. Make sure Clickhouse is able to receive data sent by Centreon: flows must not be blocked by Clickhouse's configuration or by a security equipment.

Configuring the stream connector in Centreon

1. On your central server, go to Configuration > Pollers > Broker configuration.
2. Click on central-broker-master (or the appropriate broker configuration if it is a poller or a remote server that will send events).
3. On the Output tab, select Generic - Stream connector from the list and then click Add. A new output appears in the list.
4. Fill in the fields as follows:

Field	Value
Name	Clickhouse metrics
Path	/usr/share/centreon-broker/lua/clickhouse-metrics-apiv2.lua
Filter category	Neb

5. To enable Centreon to connect to your Clickhouse equipment, fill in the following mandatory parameters. The fields for the first entry are already present. Click on the +Add a new entry link located below the Filter category table to add another one.

Type	Name	Value explanation	Value exemple
string	user	Clickhouse user that will be used	centreon
string	password	Password for this user	centreon
string	http_server_url	Address of the Clickhouse server (include the protocol and the port)	https://myclickhouse.local:8123

6. Fill in any optional parameters you want (using the +Add a new entry link):

Type	Name	Value explanation	default value
string	clickhouse_database	Name of the database in which the desired table is stored	centreon_stream
string	clickhouse_table	Table in which metrics are written	metrics
number	use_deprecated_metric_system	Allows you to use the alternative table schema when set to 1	0

7. Use the stream connector's optional parameters to filter or adapt the data you want Centreon to send to Clickhouse.

8. Deploy the configuration.

9. Restart centengine on all pollers:

   systemctl restart centengine

   Clickhouse should now receive data from Centreon. To test if it is working, see Curl commands: testing the stream connector.

Filtering or adapting the data you want to send to Clickhouse

All stream connectors have a set of optional parameters, that allow you to filter the data you will send to your Clickhouse equipment, to reformat the data, to define a proxy...

Each optional parameter has a default value, that is indicated in the corresponding documentation.

• To override the default value of a parameter, click the +Add a new entry link located below the Filter category table to add a custom parameter. For example, if you want to only send to Clickhouse the events handled by a poller named "poller-1", enter:

  type = string
  name = accepted_pollers
  value = poller-1

• For the Clickhouse stream connector, the following values always override the default values, you do not need to define them in the interface.

Type	Name	Default value for the stream connector	Additional notes
string	accepted_categories	neb
string	accepted_elements	host_status,service_status
string	max_buffer_size	1000	You should lower this value to about a hundred if you have less than 10 000 services. If you are performing troubleshooting operations with log_curl_commands and/or send_data_test parameters, you can lower this value to less than 10.
number	hard_only	0
number	enable_host_status_dedup	0
number	enable_service_status_dedup	0

Event bulking

This stream connector is compatible with event bulking: it is able to send more that one event in each call to the Clickhouse REST API.

To use this feature you must add the max_buffer_size parameter in your stream connector configuration.

Event format

This stream connector will send event with the following format.

service_status event

INSERT INTO centreon_stream.metrics (host, timestamp, metric_name, metric_value, service, hostgroups, metric_id, metric_unit, metric_min, metric_max) VALUES ('central_1',1702910747,'rtmin',0.005,'Ping',['hg'],'10-8-rtmin','ms',,),('central_1',1702910747,'rta',0.061,'Ping',['hg'],'10-8-rta','ms',0.0,),('central_1',1702910747,'pl',0.0,'Ping',['hg'],'10-8-pl','%',0.0,100.0)

host_status event

INSERT INTO centreon_stream.metrics (host, timestamp, metric_name, metric_value, service, hostgroups, metric_id, metric_unit, metric_min, metric_max) VALUES ('central_3',1702910932,'rtmin',0.0,'Ping',['hg'],'12-10-rtmin','ms',,),('central_3',1702910932,'rta',0.0,'Ping',['hg'],'12-10-rta','ms',0.0,),('central_3',1702910932,'pl',100.0,'Ping',['hg'],'12-10-pl','%',0.0,100.0)

Results inside Clickhouse

┌─host────┬─service─┬─metric_name─┬─metric_unit─┬─metric_value─┬─metric_min─┬─metric_max─┬───────────timestamp─┬─hostgroups─────────────┐
│ central │         │ pl          │ %           │            0 │          0 │        100 │ 2023-11-27 14:23:31 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rta         │ ms          │        0.052 │          0 │          0 │ 2023-11-27 14:23:31 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rtmax       │ ms          │        0.052 │          0 │          0 │ 2023-11-27 14:23:31 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rtmin       │ ms          │        0.052 │          0 │          0 │ 2023-11-27 14:23:31 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ pl          │ %           │            0 │          0 │        100 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ pl          │ %           │            0 │          0 │        100 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rta         │ ms          │        0.013 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rta         │ ms          │        0.013 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rtmax       │ ms          │        0.049 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rtmax       │ ms          │        0.049 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rtmin       │ ms          │        0.004 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │ Ping    │ rtmin       │ ms          │        0.004 │          0 │          0 │ 2023-11-27 14:26:51 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ pl          │ %           │            0 │          0 │        100 │ 2023-11-27 14:28:11 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rta         │ ms          │        0.027 │          0 │          0 │ 2023-11-27 14:28:11 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rtmax       │ ms          │        0.027 │          0 │          0 │ 2023-11-27 14:28:11 │ ['hg_1','hg_2','hg_3'] │
│ central │         │ rtmin       │ ms          │        0.027 │          0 │          0 │ 2023-11-27 14:28:11 │ ['hg_1','hg_2','hg_3'] │
└─────────┴─────────┴─────────────┴─────────────┴──────────────┴────────────┴────────────┴─────────────────────┴────────────────────────┘

Custom event format

You can't change the format of the event for metrics oriented stream connectors. This means you cannot send other Broker events that contain performance data.

Curl commands: testing the stream connector

Sending events

If you want to test that events are sent to Clickhouse correctly:

1. Log in to the server that you configured to send events to Clickhouse (your central server, a remote server or a poller).
2. Run the following command:

curl -X POST -H 'X-ClickHouse-User: <user>' -H 'X-ClickHouse-Key: <password>' <http_server_url>' -d 'INSERT INTO <clickhouse_database>.<clickhouse_table> (host, timestamp, metric_name, metric_value, service, hostgroups, metric_id, metric_unit, metric_min, metric_max) VALUES ('central_2',1702910872,'rtmin',0.0,'Ping',['hg'],'11-9-rtmin','ms',,),('central_2',1702910872,'rta',0.0,'Ping',['hg'],'11-9-rta','ms',0.0,),('central_2',1702910872,'pl',100.0,'Ping',['hg'],'11-9-pl','%',0.0,100.0)'

You must replace all the <xxxx> inside the below commands with their appropriate value. For example, <clickhouse_database> may become centreon_stream.

3. Check that the event has been received by Clickhouse.