## Event Overview
An event is an information carrier, which describes a change to a specific object at a specific time. An event is associated with a unique moment and a unique object. For example, an event occurs when the status of a computer changes from running to shutdown, when a program starts or stops running, or when a power failure occurs in an office building. An event records the moment when an object changes between different states.
The monitoring service helps find, locate, and solve problems to ensure the overall stability and performance of the system and services. Information and data are core drivers for OPS and monitoring.
As the main information source for monitoring, metric describes the value and trend of an object's specific variable over time in a threshold–like, periodic, and persistent manner. It shows the usage of resources and environment, while reflecting their health status. For example, the metric can show the CPU utilization of a Cloud Virtual Machine (CVM) instance and the number of slow query log of a database instance.
The metric covers most scenarios where problems are detected during monitoring. However, using metric as the only information source for monitoring has the following disadvantages:
Using event as a carrier of monitoring information can describe the running status of resources and underlying infrastructure and services in a more accurate and direct manner. This helps discover, locate, and solve problems more efficiently.
Advantage: events are result-oriented and can improve information accuracy, reduce delay, transmit more information, and enrich the dimension of monitoring information.
As the event information hub of Tencent Cloud, the Cloud Monitor (CM) Event Center packages important event information in the lifecycle and operation of Tencent Cloud resources and underlying infrastructure and services into a product, which constructs a complete event consumption channel and process to help customers with monitoring and OPS on the cloud.
The packaged event information provided by the Event Center is obtained from Tencent Cloud product modules and underlying infrastructure services. It is then aggregated, analyzed, condensed, and ultimately presented. Information sources are system logs and monitoring items under each module, which ensure the accuracy and value of the information passed on to customers.
Based on information sources, causes, characteristics, and forms, events are categorized by the event center as product events and platform events, which are carried by two independent product pages and consumption processes.
|Item||Product Event||Platform Event|
|Event source||Resource instances and products that are purchased and used by customers in Tencent Cloud||Underlying infrastructure and services of Tencent Cloud|
|Event cause||Directly or indirectly triggered by customers during use||Generated or caused by the infrastructure and services of Tencent Cloud|
|Event dimension||Resource instance||Underlying service|
|Event processing||Can be controlled and managed by customers||Cannot be controlled by customers and must be managed by Tencent Cloud|
|Event object granularity||Resource instances affected by and associated with events can be explicitly determined||Services or product modules affected by and associated with events can be determined,
but the affected and associated resource instances cannot always be determined
|Event subscription||The entry is in **Alarm Configuration** > **Alarm Policy**, and resource instances need to be bound||The entry is in **Alarm Configuration** > **Platform Event Subscription**|
Based on event information, the Event Center plans and provides comprehensive event consumption channels and capabilities.