Take AM feedbacks

Author: Arlevoy

ops/health-check-route.s.md

@@ -4,14 +4,13 @@
 
 # Why
 
-In order to monitor correctly their environments, some Cloud services require a HealthCheck route which returns a status depending on how the API is running.
+In order to monitor correctly their environments, backend services require a HealthCheck route which returns a status depending on how the API is running.
 
 ## Checks
 
-- [ ] Do a call to every DB used by the API
+- [ ] Make a call to every database used by the API
 - [ ] Send a 2xx status code status in case of API running correctly and 5xx status code if not
-- [ ] Do the less data usage DB calls
-- [ ] Include a timestamp in order not to reduce the number of successive calls
+- [ ] Make the less data usage database calls: the health check route is likely to be called very often in short period of time
 
 ## Examples
 
@@ -27,14 +26,13 @@ app.get("/health-check", (req, res) => {
 
 - There is no call to any of the two databases
 - There is no 5xx status code if the API is not running
-- There is not timestamp hence the route may be called successively every seconds
 
 ### Example 2: Bad example
 
 ```javascript
 app.get("/health", async (req, res) => {
   try {
-    await findAllDataCollectors(); //  DataCollectors ~ 100 entries
+    await RDS.getAllEntries();
     res.status(200).send({ status: "OK" });
   } catch (error) {
     res.status(503).send({ status: "KO" });
@@ -44,25 +42,32 @@ app.get("/health", async (req, res) => {
 
 - There is a call to one of the database but not the other
 - The call is using too much data
-- There is no timestamp
 - There is a 503 if the DB is down
 
 ### Example 3: Good example
 
 ```javascript
 app.get("/health", async (req, res) => {
   try {
-    if (nextFetchingDate && nextFetchingDate > Date.now()) {
-      return res.status(200).send({ status: 200, message: "OK" });
-    }
-
-    nextFetchingDate = Date.now() + TIME_CHECKING_INTERVAL;
-    await Promise.all([AppsDynamoRepo.getDynamoHealth(), getHealth()]);
-
+    await Promise.all([DynamoDB.getDynamoHealth(), RDS.getHealth()]);
     res.status(200).send({ status: 200, message: "OK" });
   } catch (error) {
-    nextFetchingDate = Date.now();
     handleError(res, error, { status: 503, error: error.message, message: "KO" });
   }
 });
+
+RDS.getHealth = async () => {
+  await knex.raw("select 1+1 as result");
+};
+
+DynamoDB.getDynamoHealth = (): Promise<Array<Object>> => {
+  return new Promise((resolve, reject) => {
+    dynamodb.describeTable({ TableName: dynamodbTableName }, (error, data) => {
+      if (error) {
+        return reject(error);
+      }
+      resolve(data);
+    });
+  });
+};
 ```