Circuit Breaker¶
Circuit breaker policies protect your backend services when a performance issue occurs. If the backend service of an API times out for N consecutive times or if the latency is long, the downgrade mechanism of a circuit breaker policy is triggered to return an error to the API caller or forward requests to a specified backend. After the backend service recovers, the circuit breaker closes and requests become normal.
Note
If your gateway does not support this policy, contact technical support to upgrade the gateway to the latest version.
Prerequisites¶
You have understood the guidelines for policy creation and API binding.
Parameter Description¶
Parameter | Description |
|---|---|
Policy Type |
|
Circuit Breaker Type | Triggering type of the circuit breaker.
|
Condition Type | Triggering mode of the circuit breaker.
|
Match Condition | This parameter is required only when Circuit Breaker Type is set to Condition downgrade. Configure triggering conditions for the circuit breaker.
|
Time Window (s) | The period for determining how many times have the conditions been met. Use this parameter together with Threshold or Min Percentage. If the threshold or percentage is reached, the circuit breaker is triggered. |
Threshold | This parameter is required only when Condition Type is set to Count. Set the threshold for triggering the circuit breaker. Use this parameter together with Time Window. Once the number of backend requests that meet the conditions within the time window reaches the threshold, the circuit breaker is triggered. Note A circuit breaker policy is triggered for a single gateway component. If your gateway has multiple components, the triggering for each component is determined separately. If the threshold is reached within the time window for a gateway component, requests sent to the component trigger the circuit breaker, and other gateway components still forward requests normally. A gateway component is a connection address of your gateway. To view the number of gateway components, go to the Gateway Information page of the gateway and view the number of IP addresses in Private Network Access IP. |
Min Calls | This parameter is required only when Condition Type is set to Percentage. Set the minimum number of API calls that will trigger the circuit breaker within the time period. The circuit breaker will not be triggered if the number of API calls within the time period is less than this value. |
Min Percentage (%) | This parameter is required only when Condition Type is set to Percentage. Set the threshold for triggering the circuit breaker. Use this parameter together with Time Window. Once the percentage of backend requests that meet the conditions within the time window reaches the threshold, the circuit breaker is triggered. |
Control Duration (s) | Time for which the circuit breaker will be on. When the time is reached, the circuit breaker will be off. |
Backend Downgrade | Determine whether to enable backend downgrade.
|
Backend Type | This parameter is required only when Backend Downgrade is enabled. Specify the backend type to which requests will be forwarded when the circuit breaker is on.
|
Downgrade Parameter Settings | Determine whether to enable downgrade parameter configuration. After this option is enabled, custom rules take precedence over the default triggering conditions and downgrade settings configured above.
|
Parameters | Define parameters for rule matching.
By default, the system provides the reqPath (request path) and method (request method) parameters. Click Add Parameter to add parameters. |
Rules | Customize matching rules for the circuit breaker. Click Add Rule to add rules. The system matches rules from top to bottom. Adjust the rule priority by moving the rules up or down.
Example: You have enabled Downgrade Parameter Settings and added rules rule01 and rule02 in sequence. And you have disabled Trigger Configuration and enabled Backend Downgrade for rule01, and have enabled both options for rule02. With these settings, the circuit breaker first checks whether the conditions of rule01 are met. If yes, the circuit breaker is turned on based on the default settings because no triggering condition has been defined in rule01, and backend downgrade configured in rule01 is executed. If no, the check is continued for rule02. |
to set condition expressions. If there are three or more expressions, you can layer them by clicking Set Lower Level.Example Script¶
{
"breaker_condition":{
"breaker_type":"timeout",
"breaker_mode":"counter",
"unhealthy_threshold":30,
"time_window":15,
"open_breaker_time":15,
"unhealthy_percentage":51,
"min_call_threshold":20
},
"scope":"share",
"downgrade_default":{
"type":"http",
"passthrough_infos":null,
"func_info":null,
"mock_info":null,
"http_info":{
"isVpc":false,
"vpc_channel_id":"",
"address":"10.10.10.10",
"scheme":"HTTP",
"method":"GET",
"path":"/demo",
"timeout":5000
},
"http_vpc_info":null
},
"downgrade_parameters":[
{
"name":"reqPath",
"type":"path",
"value":"path",
"disabled":true,
"focused":true,
"id":"92002eqbpilg6g"
},
{
"name":"method",
"type":"method",
"value":"method",
"disabled":true,
"focused":true,
"id":"tuvxetsdqvcos8"
}],
"downgrade_rules":[
{
"rule_name":"rule-test1",
"parameters":[
"reqPath",
"method"
],
"match_regex":"[\"reqPath\",\"==\",\"/test\"]",
"downgrade_backend":{
"type":"mock",
"passthrough_infos":null,
"func_info":null,
"mock_info":{
"status_code":200,
"result_content":"{status: ok}",
"headers":[]
},
"http_info":null,
"http_vpc_info":null
},
"breaker_condition":{
"breaker_type":"timeout",
"breaker_mode":"percentage",
"unhealthy_threshold":30,
"time_window":15,
"open_breaker_time":15,
"unhealthy_percentage":51,
"min_call_threshold":20
}
}]
}