Cacti can support from one to many Data Collectors. There are two types of Data Collectors they are:
- Main Data Collector - This is essentially your core Cacti server and database. The Main Data Collector is also referred to as the Primary Server.
- Remote Data Collector - These Data Collectors are located in distant locations, or where reaching devices is blocked due to firewall or security policies. The Remote Data Collectors are also referred to as Remote Pollers.
Due to the design of the Cacti Remote Data Collector, someone at the remote site, can actually login to that Data Collector and interact with it as if their Data Collector was the Main Data Collector. Additionally, if for some reason the Main Data Collector becomes unavailable due to a WAN outage for example, the data for the Devices it manages will be cached locally until such time as the Main Data Collector is reachable again.
When connectivity returns, the remote collector forwards cached results to the main collector. This provides continuity during some network outages; it is not automatic failover of the main server, database, or RRD storage. Size local storage for the expected outage and monitor the delivery backlog.
Remote collection uses Cacti's built-in Boost functionality. Review its configuration before deploying additional collectors.
Main and remote systems exchange data over the configured web and database connections. Permit only the required hosts and configured ports, use HTTPS, and secure database connections according to the installation's policy. Confirm connectivity in both directions where configuration replication and remote-agent operations require it. Additional dependencies such as DNS, SNMP, and device availability checks have their own network requirements.
The image below shows the current online collector (aka pollers). On this page,
we can see the current, average, and max data collection times, the
Data Collector processes and threads used, the number of Devices as well
as what those Devices are polling. The Actions drop-down allows your to
Enable, Disable, and Delete Remote Data Collectors. There is also a
Full Sync option there. The Full Sync option will replicate key Cacti
tables to the selected Remote Data Collectors for things like
authentication,
global settings, etc.
In the current Cacti design, you should not have to perform a Full Sync
very often. It would mainly be used to push the user database and global
settings to the remotes, after an outage if there were database changes
during that outage.
The Main Data Collector resides on the central Cacti server. It also serves as the master Data Collector performing key maintenance operations for the entire system.
In the edit page below, you can see what options are available when editing the Main Data Collector. It is important that the hostname used is resolvable by the Remote Data Collectors.
When editing the Remote Data Collector in the images below, you can see that
it shares many of the settings of the Main Data Collector with the addition
of a TimeZone setting and MySQL/MariaDB credentials and a Test Connection
button. Generally, these setting are only use during the initial setup
of Cacti, and afterwards for diagnostics only.
Use the same Cacti version on the main and remote systems. Follow How To Setup Remote Pollers, and select New Remote Poller when installing the remote system.
Create a database account restricted to the remote collector's address, using the account name consistently for both grants. Run the following in an interactive database administration session after replacing the address and password placeholders:
CREATE USER 'cacti_remote'@'192.0.2.20' IDENTIFIED BY 'REPLACE_WITH_UNIQUE_PASSWORD';
GRANT ALL PRIVILEGES ON cacti.* TO 'cacti_remote'@'192.0.2.20';
GRANT SELECT ON mysql.time_zone_name TO 'cacti_remote'@'192.0.2.20';Configure the database listener, firewall, TLS, and host restrictions for your network. Do not expose database access publicly or grant global privileges. Use separate accounts where collectors require different access policies.
On the remote system, include/config.php uses $database_* settings for its
local database and $rdatabase_* settings for the main database. Populate the
remote settings during installation using that release's config.php.dist.
Verify the main hostname, database name, credentials, port, and TLS settings;
do not copy the main database address into the remote's local database fields.
Protect the configuration file because it contains credentials.
After installation, assign a test device to the collector, run a polling cycle, and verify both local collection and delivery to the main system. Confirm that graph timestamps advance before moving additional devices.
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