| Event bus | Total number of system event buses | A maximum of one system event bus is allowed. |
| Total number of custom event buses | A maximum of 50 custom event buses are allowed. |
| Number of event rules for an event bus | A maximum of 50 event rules are allowed. |
| Name of an event bus | - The name can be up to 127 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
- The reserved keyword "default" cannot be used as the name of an event bus.
- The name cannot be a string that is prefixed with
eventbridge-reserved-.
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| Frequency of calling the PutEvents API operation | A maximum of 3,000 queries per second (QPS) are allowed for each bus. |
| Event rule | Event targets of an event rule | - A maximum of five event targets are allowed.
- An event target must reside in the region where EventBridge is activated.
- An event target must be a service instance in your Alibaba Cloud account.
- The ID of an event target must be unique.
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| Pattern of an event rule | In the stringExpression pattern, each field can contain up to five expressions in the map data structure. |
| Name of an event rule | - The name can be up to 127 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
- The name cannot be a string that is prefixed with
eventbridge-reserved-.
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| Transformation of the event content | template: Its value can be up to 10,240 characters in length. value: Its value can be up to 1,024 characters in length.
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| Event | Event message | - An event message cannot exceed 256 KB in size.
- A maximum of 16 event messages can be sent at a time.
- The total size of event messages that are sent in a batch cannot exceed 1 MB.
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| Event field | - id: Its value can be up to 128 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
- source: Its value can be up to 128 characters in length.
- subject: Its value can be up to 512 characters in length.
- type: Its value can be up to 64 characters in length.
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| Schema | Schema name | - The name can contain only letters, digits, hyphens (-), underscores (_), and periods (.).
- The name can be up to 128 characters in length. If the name that you specify is more than 128 characters in length, excess characters are deleted.
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| Number of schema versions | A maximum of 1,000 schema versions are allowed. |
| Event stream | Event stream name | - The name must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
- The name can be up to 127 characters in length. If the name that you specify is more than 127 characters in length, excess characters are deleted.
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| Number of event streams | A maximum of 50 event streams are allowed. |
| Pattern of an event rule | In the stringExpression pattern, each field can contain up to five expressions in the map data structure. |
| Transformation of the event content | template: Its value can be up to 10,240 characters in length. value: Its value can be up to 1,024 characters in length.
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| Event source | Name of an event source | - The name can contain letters, digits, hyphens (-), and periods (.).
- The name can be up to 127 characters in length. If the name that you specify is more than 127 characters in length, excess characters are deleted.
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