5.3 Health Check

Background

The purpose of health checks is to obtain the status of an application throughout its lifecycle, including the operational and runtime phases, so that users can make decisions based on this status. For instance, if the application status is DOWN, it indicates a malfunction in the application, and the user may choose to restart or replace the machine.

In the case of a single application, health checks are relatively simple:

Operational phase status:
- If it’s starting up, the status is UNKNOWN;
- If startup fails, the status is DOWN;
- If startup is successful, the status is UP.
Runtime phase status:
- If all health checkpoints of the application are healthy, the status is UP;
- If any health checkpoint of the application is not healthy, the status is DOWN.

In multi-application scenarios, the situation can be much more complex. We need to consider the impact of the multi-application’s status during both the operational phase and the runtime phase on the overall application health. When designing health checks, we need to consider the following two issues:

During the module operational phase, should the module start-up status affect the overall application health status?

In different operational scenarios, users have different expectations. koupleless module operations have three scenarios:

Scenario	Impact of the Module on the Overall Application Health Status
Module Hot-Deployment	Provide configuration to let users decide whether the hot-deployment result should affect the overall application health status (default configuration is: does not affect the original health status of the application)
Static Merge Deployment	Module deployment occurs during the base startup, so the module startup status should directly affect the overall health status of the application
Module Replay	Module replay occurs during the base startup, thus the module startup status should directly affect the overall health status of the application

During the module runtime phase, should the module running status affect the overall application health status?
The module runtime phase status should have a direct impact on the overall application health status.

Under this context, we have designed a health check approach for multi-application scenarios.

Usage

Requirements

Koupleless version >= 1.1.0
sofa-ark version >= 2.2.9

Obtain the overall health status of the application

There are 3 types of health status for the base:

Status	Meaning
UP	Healthy, indicating readiness
UNKNOWN	Currently starting up
DOWN	Unhealthy (may be due to startup failure or unhealthy running state)

Since Koupleless supports hot deployment of modules, while obtaining the overall health status of the application, users may wish for the module deployment result to impact the overall application health status or not.

Module launch result does not affect the overall application health status (default)

Features: For a healthy base, if the module installation fails, it will not affect the overall application health status.
Usage: Same as the health check configuration for regular Spring Boot, configure in the base’s application.properties:

# or do not configure management.endpoints.web.exposure.include
management.endpoints.web.exposure.include=health
# If you need to display all information, configure the following content
management.endpoint.health.show-components=always
management.endpoint.health.show-details=always

Access: {baseIp:port}/actuator/health
Result:

{
    // Overall health status of the application
    "status": "UP",
    "components": {
        // Aggregated health status of the modules
        "arkBizAggregate": {
            "status": "UP",
            "details": {
                "biz1:0.0.1-SNAPSHOT": {
                    "status": "UP",
                    // Can see the health status of all active HealthIndicators in the modules
                    "details": {
                        "diskSpace": {
                          "status": "UP",
                          "details": {
                            "total": 494384795648,
                            "free": 272435396608,
                            "threshold": 10485760,
                            "exists": true
                            }
                        },
                        "pingHe": {
                          "status": "UP",
                          "details": {}
                        }
                    }
                }
            }
        },
        // Startup health status of base and modules
        "masterBizStartUp": {
            "status": "UP",
            // Including the startup status of each module.
            "details": {
                "base:1.0.0": {
                    "status": "UP"
                },
                "biz1:0.0.1-SNAPSHOT": {
                    "status": "UP"
                },
                "biz2:0.0.1-SNAPSHOT": {
                    "status": "DOWN"
                }
            }
        }
    }
}

Overall Health Status in Different Scenarios

Scenario 1: Start base

Status	Meaning
UP	Base is healthy
UNKNOWN	Base is starting up
DOWN	Base is unhealthy

Scenario 2: Start base and install modules with static merge deployment

Status	Meaning
UP	Base and module are healthy
UNKNOWN	Base or module is starting up
DOWN	Base startup failed / base is unhealthy / module startup failed / module is unhealthy

Scenario 3: After base starts, install modules with hot deployment

Provide configuration to let users decide whether the result of module hot deployment affects the overall health status of the application (The default configuration is: Does not affect the original health status of the application)

Default Configuration: In the scenario of hot deployment, whether or not a module is successfully installed does not affect the overall health status of the application, as follows:

Status	Meaning
UP	Base and module are healthy
UNKNOWN	Base is starting up
DOWN	Base startup failed / base is unhealthy / module is unhealthy

Scenario 4: Base running

Status	Meaning
UP	Base and module are healthy
UNKNOWN	-
DOWN	Base is unhealthy or module is unhealthy

Scenario 5: After base started, reinstall module

Reinstall module refers to automatically pulling the module baseline and installing the module after the base is started.

Reinstall module is not supported at the moment

Status	Meaning
UP	Base and module are healthy
UNKNOWN	Base or module is starting up
DOWN	Base is unhealthy or module startup failed or module is unhealthy

Module launch result affects the overall application health status

Features: For a healthy base, if a module installation fails, the overall application health status will also fail.
Usage: In addition to the above configuration, you need to configure koupleless.healthcheck.base.readiness.withAllBizReadiness=true, that is, configure in the base’s application.properties:

# Alternatively, do not configure management.endpoints.web.exposure.include
management.endpoints.web.exposure.include=health
# If you need to display all information, configure the following content
management.endpoint.health.show-components=always
management.endpoint.health.show-details=always
# Do not ignore module startup status
koupleless.healthcheck.base.readiness.withAllBizReadiness=true

Access: {baseIp:port}/actuator/health
Result:

{
    // Overall health status of the application
    "status": "UP",
    "components": {
        // Aggregated health status of the modules
        "arkBizAggregate": {
            "status": "UP",
            "details": {
                "biz1:0.0.1-SNAPSHOT": {
                    "status": "UP",
                    // Can see the health status of all active HealthIndicators in the modules
                    "details": {
                        "diskSpace": {
                          "status": "UP",
                          "details": {
                            "total": 494384795648,
                            "free": 272435396608,
                            "threshold": 10485760,
                            "exists": true
                            }
                        },
                        "pingHe": {
                          "status": "UP",
                          "details": {}
                        }
                    }
                }
            }
        },
        // Startup health status of base and modules
        "masterBizStartUp": {
            "status": "UP",
            // Including the startup status of each module.
            "details": {
                "base:1.0.0": {
                    "status": "UP"
                },
                "biz1:0.0.1-SNAPSHOT": {
                    "status": "UP"
                }
            }
        }
    }
}

Overall Health Status in Different Scenarios

Scenario 1: Start base

Status	Meaning
UP	Base is healthy
UNKNOWN	Base is starting up
DOWN	Base is unhealthy

Scenario 2: Start base and install modules with static merge deployment

Status	Meaning
UP	Base and module are healthy
UNKNOWN	Base or module is starting up
DOWN	Base startup failed / base is unhealthy / module startup failed / module is unhealthy

Scenario 3: After base starts, install modules with hot deployment

When configuring as koupleless.healthcheck.base.readiness.withAllBizReadiness=true:

Status	Meaning
UP	Base and module are healthy
UNKNOWN	Base or module is starting up
DOWN	Base startup failed / Module startup failed / base is unhealthy / module is unhealthy

Scenario 4: Base running

Status	Meaning
UP	Base and module are healthy
UNKNOWN	-
DOWN	Base is unhealthy or module is unhealthy

Scenario 5: After base started, reinstall module

Reinstall module refers to automatically pulling the module baseline and installing the module after the base is started.

Reinstall module is not supported at the moment.

Obtaining the Health Status of a Single Module

Usage: Consistent with the normal springboot health check configuration, enable the health node, i.e. configure in the module’s application.properties:

# or do not configure management.endpoints.web.exposure.include
management.endpoints.web.exposure.include=health

Access: {baseIp:port}/{bizWebContextPath}/actuator/info
Result:

{
    "status": "UP",
    "components": {
        "diskSpace": {
            "status": "UP",
            "details": {
                "total": 494384795648,
                "free": 270828220416,
                "threshold": 10485760,
                "exists": true
            }
        },
        "ping": {
            "status": "UP"
        }
    }
}

Get information about base, modules, and plugins

Usage: Same as the regular springboot health check configuration, enable the info endpoint, i.e., configure in the base’s application.properties:

# Note: If the user configures management.endpoints.web.exposure.include on their own, they need to include the health endpoint, otherwise the health endpoint cannot be accessed
management.endpoints.web.exposure.include=health,info

Access: {baseIp:port}/actuator/info
Result:

{
    "arkBizInfo": [
      {
        "bizName": "biz1",
        "bizVersion": "0.0.1-SNAPSHOT",
        "bizState": "ACTIVATED",
        "webContextPath": "biz1"
      },
      {
        "bizName": "base",
        "bizVersion": "1.0.0",
        "bizState": "ACTIVATED",
        "webContextPath": "/"
      }
    ],
    "arkPluginInfo": [
        {
            "pluginName": "koupleless-adapter-log4j2",
            "groupId": "com.alipay.sofa.koupleless",
            "artifactId": "koupleless-adapter-log4j2",
            "pluginVersion": "1.0.1-SNAPSHOT",
            "pluginUrl": "file:/Users/lipeng/.m2/repository/com/alipay/sofa/koupleless/koupleless-adapter-log4j2/1.0.1-SNAPSHOT/koupleless-adapter-log4j2-1.0.1-SNAPSHOT.jar!/",
            "pluginActivator": "com.alipay.sofa.koupleless.adapter.Log4j2AdapterActivator"
        },
        {
            "pluginName": "web-ark-plugin",
            "groupId": "com.alipay.sofa",
            "artifactId": "web-ark-plugin",
            "pluginVersion": "2.2.9-SNAPSHOT",
            "pluginUrl": "file:/Users/lipeng/.m2/repository/com/alipay/sofa/web-ark-plugin/2.2.9-SNAPSHOT/web-ark-plugin-2.2.9-SNAPSHOT.jar!/",
            "pluginActivator": "com.alipay.sofa.ark.web.embed.WebPluginActivator"
        },
        {
            "pluginName": "koupleless-base-plugin",
            "groupId": "com.alipay.sofa.koupleless",
            "artifactId": "koupleless-base-plugin",
            "pluginVersion": "1.0.1-SNAPSHOT",
            "pluginUrl": "file:/Users/lipeng/.m2/repository/com/alipay/sofa/koupleless/koupleless-base-plugin/1.0.1-SNAPSHOT/koupleless-base-plugin-1.0.1-SNAPSHOT.jar!/",
            "pluginActivator": "com.alipay.sofa.koupleless.plugin.ServerlessRuntimeActivator"
        }
    ]
}

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Last modified 2024.14.11: Update module-startup.md (39aeb80)