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Package io.vertx.ext.healthchecks

= Vert.x Health Checks This component provides a simple way to expose health checks.

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Package io.vertx.ext.healthchecks Description

= Vert.x Health Checks This component provides a simple way to expose health checks. Health checks are used to express the current state of the application in very simple terms: _UP_ or _DOWN_. The health checks can be used individually, or in combination to Vert.x Web or the event bus. This component provides a Vert.x Web handler on which you can register procedure testing the health of the application. The handler computes the final state and returns the result as JSON. == Using Vert.x Health Checks Notice that you generally need Vert.x Web to use this component. In addition add the following dependency: * Maven (in your `pom.xml`): [source,xml,subs="+attributes"] ---- ${maven.groupId} ${maven.artifactId} ${maven.version} ---- * Gradle (in your `build.gradle` file): [source,groovy,subs="+attributes"] ---- compile '${maven.groupId}:${maven.artifactId}:${maven.version}' ---- === Creating the health check object. The central object is HealthChecks. You can create a new instance using: [source, $lang] ---- examples.Examples#example1(io.vertx.core.Vertx) ---- Once you have created this object you can register and unregister procedures. See more about this below. === Registering the Vert.x Web handler To create the Vert.x Web handler managing your health check you can either: * using an existing instance of HealthChecks * let the handler create one instance for you. [source, $lang] ---- examples.Examples#example2(io.vertx.core.Vertx) ---- Procedure registration can be directly made on the HealthCheckHandler instance. Alternatively, if you have created the HealthChecks instance beforehand, you can register the procedure on this object directly. Registrations and unregistrations can be done at anytime, even after the route registration: [source, $lang] ---- examples.Examples#example2(io.vertx.core.Vertx, io.vertx.ext.web.Router) ---- == Procedures A procedure is a function checking some aspect of the system to deduce the current health. It reports a Status indicating whether or not the test has passed or failed. This function must not block and report to the given Future whether or not it succeed. When you register a procedure, you give a name, and the function (handler) executing the check. Rules deducing the status are the following * if the future is mark as failed, the check is considered as _KO_ * if the future is completed successfully but without a Status, the check is considered as _OK_. * if the future is completed successfully with a Status marked as _OK_, the check is considered as _OK_. * if the future is completed successfully with a Status marked as _KO_, the check is considered as _KO_. Status can also provide additional data: [source, $lang] ---- examples.Examples#example4(io.vertx.core.Vertx, io.vertx.ext.web.Router) ---- Procedures can be organised by groups. The procedure name indicates the group. The procedures are organized as a tree and the structure is mapped to HTTP urls (see below). [source, $lang] ---- examples.Examples#example3(io.vertx.core.Vertx, io.vertx.ext.web.Router) ---- == HTTP responses and JSON Output When using the Vert.x web handler, the overall health check is retrieved using a HTTP GET or POST (depending on the route you registered) on the route given when exposing the HealthCheckHandler. If no procedure are registered, the response is `204 - NO CONTENT`, indicating that the system is _UP_ but no procedures has been executed. The response does not contain a payload. If there is at least one procedure registered, this procedure is executed and the outcome status is computed. The response would use the following status code: * `200` : Everything is fine * `503` : At least one procedure has reported a non-healthy state * `500` : One procedure has thrown an error or has not reported a status in time The content is a JSON document indicating the overall result (`outcome`). It's either `UP` or `DOWN`. A `checks` array is also given indicating the result of the different executed procedures. If the procedure has reported additional data, the data is also given: [source] ---- { "checks" : [ { "id" : "A", "status" : "UP" }, { "id" : "B", "status" : "DOWN", "data" : { "some-data" : "some-value" } } ], "outcome" : "DOWN" } ---- In case of groups/ hierarchy, the `checks` array depicts this structure: [source] ---- { "checks" : [ { "id" : "my-group", "status" : "UP", "checks" : [ { "id" : "check-2", "status" : "UP", }, { "id" : "check-1", "status" : "UP" }] }], "outcome" : "UP" } ---- If a procedure throws an error, reports a failure (exception), the JSON document provides the `cause` in the `data` section. If a procedure does not report back before a timeout, the indicated cause is `Timeout`. == Examples of procedures This section provides example of common health checks. === JDBC This check reports whether or not a connection to the database can be established: [source, $lang] ---- examples.Examples#jdbc(io.vertx.ext.jdbc.JDBCClient, HealthCheckHandler) ---- === Service availability This check reports whether or not a service (here a HTTP endpoint) is available in the service discovery: [source, $lang] ---- examples.Examples#service ---- === Event bus This check reports whether a consumer is ready on the event bus. The protocol, in this example, is a simple ping/pong, but it can be more sophisticated. This check can be used to check whether or not a verticle is ready if it's listening on a specific event address. [source, $lang] ---- examples.Examples#eventbus(io.vertx.core.Vertx, HealthCheckHandler) ---- == Authentication When using the Vert.x web handler, you can pass a AuthProvider use to authenticate the request. Check Vert.x Auth for more details about available authentication providers. The Vert.x Web handler creates a JSON object containing: * the request headers * the request params * the form param if any * the content as JSON if any and if the request set the content type to `application/json`. The resulting object is passed to the auth provider to authenticate the request. If the authentication failed, it returns a `403 - FORBIDDEN` response. == Exposing health checks on the event bus While exposing the health checks using HTTP with the Vert.x web handler is convenient, it can be useful to expose the data differently. This section gives an example to expose the data on the event bus: [source, $lang] ---- examples.Examples#publishOnEventBus(io.vertx.core.Vertx, HealthChecks) ----
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