Merge pull request #3 from Financial-Times/addConfigurableHealthChecks

Add configurable healthchecks

ReadMe.md

@@ -137,3 +137,36 @@ parameters:
 
 ## Useful links
 - [FT health check formatter for viewing healthchecks in chrome ](https://github.com/Financial-Times/health-status-formatter)
+
+## Configurable health checks
+Configurable health checks can be used in place of regular health checks. These healthchecks can be modified through parameter values loaded during a cache clear.
+To make a healthcheck configurable define the health check as you normally would but use the `health_check.configurable` tag instead.
+
+```yml
+services:
+    # Health Checks
+    app.placeholder.health_check:
+        class: YourBundle\HealthCheck\PlaceholderHealthCheck
+        tags: [{ name: health_check.configurable, priority: 20 }]
+```
+
+Configurable health checks can have various parts of themselves overridden by using parameters. Parameters are given in the form `${serviceId}.${config}`. 
+For instance:
+```yml
+parameters:
+    # Override the name of the healthcheck
+    app.placeholder.health_check.name: "A new name"
+    # Override the healthcheck severity 
+    app.placeholder.health_check.severity: 2
+``` 
+Would configure the `app.placeholder.health_check` to have a new name and priority.
+
+| Config attribute  | Description                                                                                                                                                    | Default (If applicable) |
+|-------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------|
+| priority          | The priority of the healthcheck (in the order in which they run)                                                                                               | N/A                     |
+| run               | If the health check should be run or not.  In the event false is given the service definition for the health check is removed and the health check is not run. | true                    |
+| name              | Gives the option to override the health check name (Equivalent to calling `withName` on health check).                                                         | N/A                     |
+| severity          | Gives the option to override the health check severity (Equivalent of calling `withSeverity` on health check).                                                 | N/A                     |
+| business_impact   | Gives the option to override the health check business impact entry (Equivalent of calling `withBusinessImpact` on health check).                              | N/A                     |
+| panic_guide       | Gives the option to override the health check panic guide (Equivalent of calling `withPanicGuide` on health check).                                            | N/A                     |
+| technical_summary | Gives the option to override the health check technical summary  (Equivalent of calling `withTechnicalSummary` on health check).                               | N/A                     |

src/HealthCheckBundle/Controller/HealthCheckController.php

@@ -66,7 +66,7 @@ public function healthCheckAction()
                     ->withBusinessImpact("A healthcheck failed to run. It is unknown what effects this would have for users or the editorial team.")
                     ->withPanicGuide("Read the output of the check to find where the fatal error was thrown. Note that this healthcheck failing might be a symptom of a larger problem and more serious health check failures should be looked into first.")
                     ->withTechnicalSummary("This is a placeholder for the ". get_class($healthCheckHandle) ." heath check that failed to run successfully.")
-                    ->withCheckOutput(get_class($e).": {$e->getMessage()} in {$e->getFile()}:{$e->getLine()} ");
+                    ->withCheckOutputException($e);
             }
             return $healthCheck;
         }, $this->healthCheckHandles);

src/HealthCheckBundle/DependencyInjection/HealthCheckPass.php

@@ -3,6 +3,7 @@
 namespace FT\HealthCheckBundle\DependencyInjection;
 
 use FT\HealthCheckBundle\EventListener\HealthCheckListener;
+use FT\HealthCheckBundle\HealthCheck\ConfigurableHealthCheckHandler;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Reference;
@@ -16,20 +17,60 @@ public function process(ContainerBuilder $container)
             return;
         }
         $healthCheckController = $container->getDefinition('health_check.controller');
+
         // Get health checks.
         $healthChecks = $container->findTaggedServiceIds('health_check');
+
+        // Get Configurable healthchecks
+        $configurableHealthChecks = $container->findTaggedServiceIds('health_check.configurable');
 
-        if(empty($healthChecks)){
+        // Terminate compiler pass if there are no healthchecks to register
+        if(empty($healthChecks) && empty($configurableHealthChecks)){
             return;
         }
 
-        $converterIdsByPriority = array();
+        $converterIdsByPriority = [];
+
+        foreach ($configurableHealthChecks as $id => $tags) {
+            if($container->hasParameter($id.'.run') && $container->getParameter($id.'.run') === false ){
+                //In the event a health check should not be run entirely remove it's service definition from the container and don't register it
+                $container->removeDefinition($id);
+                continue;
+            } 
+
+            //Create and inject a decorated service definition each definition tagged with a configurable health check
+            $container
+                ->register($id.'.decorated', ConfigurableHealthCheckHandler::class)
+                ->addArgument(new Reference('service_container'))
+                ->addArgument(new Reference($id.".decorated.inner"))
+                ->addArgument($id)
+                ->setDecoratedService($id);
+
+            //Try to pull service priority from a user set priority
+            $priority = $container->hasParameter($id.'.priority') ? $container->getParameter($id.'.priority') : null;
+
+            //In the event that that fails or the priority is invalid use the original services priority
+            if (!is_int($priority)) {
+                foreach ($tags as $tag) {
+                    $priority = isset($tag['priority']) ? (int) $tag['priority'] : 0;
+                }
+            }
+
+            $converterIdsByPriority[$priority][] = $id;
+        }
+
         foreach ($healthChecks as $id => $tags) {
             foreach ($tags as $tag) {
                 $priority = isset($tag['priority']) ? (int) $tag['priority'] : 0;
                 $converterIdsByPriority[$priority][] = $id;
             }
         }
+
+        if(empty($converterIdsByPriority)){
+            //Abort in the case that we have no health checks
+            return;
+        }
+
         $converterIdsByPriority = $this->sortConverterIds($converterIdsByPriority);
         foreach ($converterIdsByPriority as $referenceId) {
             $healthCheckController->addMethodCall('addHealthCheck', array(new Reference($referenceId)));
@@ -42,7 +83,7 @@ public function process(ContainerBuilder $container)
      *
      * @param array $converterIdsByPriority
      *
-     * @return \Symfony\Component\DependencyInjection\Reference[]
+     * @return string[]
      */
     protected function sortConverterIds(array $converterIdsByPriority)
     {

src/HealthCheckBundle/HealthCheck/ConfigurableHealthCheckHandler.php

@@ -0,0 +1,113 @@
+<?php
+
+namespace FT\HealthCheckBundle\HealthCheck;
+
+use Symfony\Component\DependencyInjection\Container;
+
+/**
+ * This class is used to wrap health check handles that expose themeselves as being be configurable.
+ */
+class ConfigurableHealthCheckHandler implements HealthCheckHandlerInterface
+{
+    const CONFIG_OVERRIDE_MAPPINGS = [
+        'name' => 'withName',
+        'severity' => 'withSeverity',
+        'business_impact' => 'withBusinessImpact',
+        'panic_guide' => 'withPanicGuide',
+        'technical_summary' => 'withTechnicalSummary',
+    ];
+
+    /**
+     * @var HealthCheckHandlerInterface
+     */
+    protected $healthCheckHandle;
+
+    /**
+     * @var Container
+     */
+    protected $container;
+
+    /**
+     * @var string
+     */
+    private $serviceId;
+
+    /**
+     * @param Container $container
+     * @param HealthCheckHandlerInterface $healthCheckHandle
+     * @param string $serviceId
+     */
+    public function __construct(Container $container, HealthCheckHandlerInterface $healthCheckHandle, string $serviceId)
+    {
+        $this->container = $container;
+        $this->healthCheckHandle = $healthCheckHandle;
+        $this->serviceId =  $serviceId;
+    }
+
+    /**
+     * Decorates the {@see \FT\HealthCheckBundle\HealthCheck\HealthCheck::runHealthCheck()} method by accepting parameters to override health check values.
+     *
+     * @return HealthCheck
+     */
+    public function runHealthCheck(): HealthCheck
+    {
+        $healthCheck = $this->healthCheckHandle->runHealthCheck();
+
+        //Override health check parts that can be overidden with there given props
+        foreach (self::CONFIG_OVERRIDE_MAPPINGS as $parameterName => $methodName) {
+            if ($this->hasParameter($parameterName)) {
+                $healthCheck->{$methodName}($this->getParameter($parameterName));
+            }
+        }
+
+        return $healthCheck;
+    }
+
+    /**
+     * Proxies the internal instance of the healthCheckHandle checking for if configuration overrides the interval set in the healthcheck.
+     *
+     * @return int|null
+     */
+    public function getHealthCheckInterval(): ?int
+    {
+        $interval = $this->hasParameter('interval') ?
+            $this->getParameter('interval') :
+            false;
+
+        return (\is_int($interval) || null === $interval) ?
+            $interval :
+            $this->healthCheckHandle->getHealthCheckInterval();
+    }
+
+    /**
+     * Retrieves the health check from config if possible, returning the id from the internal healthCheckHandle instance if not.
+     *
+     * @return string
+     */
+    public function getHealthCheckId(): string
+    {
+        return $this->hasParameter('id') ?
+            $this->getParameter('interval') :
+            $this->healthCheckHandle->getHealthCheckId();
+    }
+
+    /**
+     * Gets if parameter is defined in the context of healthcheck override.
+     *
+     * @param string $paramName
+     * @return bool
+     */
+    protected function hasParameter(string $paramName): bool
+    {
+        return $this->container->hasParameter($this->serviceId. '.' . $paramName);
+    }
+
+    /**
+     * @param string $paramName
+     * @return string
+     */
+    protected function getParameter(string $paramName): string
+    {
+        return $this->container->getParameter($this->serviceId . '.' . $paramName);
+    }
+}