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Posted to dev@camel.apache.org by Luca Burgazzoli <lb...@gmail.com> on 2017/09/04 14:01:18 UTC

Health Check API

Hello,

I've been working a little on the Health Check API [1] implementation an
the code is available in my Apache Camel fork [2]. There is now a a new
package [3] that defines the following concepts:

- HealthCheck

this represent an health check and defines the some basic contract i.e
the response;

- HealthCheckConfiguration

this is a basic coonfiguration object that holds some basic settings
like the minimum delay between calls, the number of time a service may
be reported as unhealthy before meking the check as failed; beside
those simple options, is then responsability of the check impl. to
eventually implement further limitations;

- HealthCheckRegistry

this is just a registry, it doesn't have any method to trigger checks
and it has intentionally been kept simple as in the future it may be
superseeded by an internal camel registry [4];

- HealthCheckRepository

this is a simple interface to define health check providers and by
default there is one that grabs all the checks available in the
registry so you can add your own check i.e. istantiating your bean
in spring/spring-boot; components can provide theirs own repository.

- HealthCheckService

this is a simple service that runs in the background and invokes the
checks according to a schedule.

The default camel context sets-up a default implementation of the health
check registry which you can override by putting your own implementation
in the camel registry as usual. Check are not active by default so you
need to explicit enable/configure them.

The current implementation has a number of limitations:

- it is spring-boot oriented for demostration purpose so you can't
access health checks using JMX (but it is planned);
- it is focused on monitoring the status of external systems so there
are a few implementations based on the Component verifier extension:

1. a ServiceNow instance check to report if an instances is alive
2. a simple undertow based http check that issue an http get to an
http endpoint

There is also a simple consul repository that let you to reuse consul
checks [5] so i.e. you can have a single check to monitor the status
of twitter and reuse it in all your microservices.

An example can be found in my fork [6]

My next goals are:

1. define some core checks to monitor the health of the camel context
i.e. fail if there is an excessive number of errors, if the latency
is too high, etc.
2. expose check through JMX.
3. use health checks for ServiceCall EIP
4. use health checks in Clustering/Superving route controller

Any feedback is very welcome,
Luca

[1] https://issues.apache.org/jira/browse/CAMEL-10026
[2] https://github.com/lburgazzoli/apache-camel/tree/CAMEL-10026-hc
[3] https://github.com/lburgazzoli/apache-camel/tree/CAMEL-10026-hc/camel-core/src/main/java/org/apache/camel/health
[4] https://issues.apache.org/jira/browse/CAMEL-10792
[5] https://www.consul.io/docs/agent/checks.html
[6] https://github.com/lburgazzoli/apache-camel/tree/CAMEL-10026-hc/examples/camel-example-spring-boot-health-checks

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Luca Burgazzoli