Improve the APIs exposed to the client

[VincenzoFerme]

Clearly define and improve the APIs exposed to the client, so that we return JSON responses and errors (see #14 (diff)), in case it is needed.

Some notes on the mysql monitor

Uniform the API accepting the query to perform and uniform the response sent to the client, at least for a subset of types of possible query. This way we can uniform the way we allow the users to use the equal and notequal we offer, by always getting back as response true (1) or false (0).

Still not done: Then we also let the user to perform arbitrary queries with arbitrary responses that the user is in charge to parse.

[VincenzoFerme]

@Cerfoglg Document here the design on which #19 is based on.

[Cerfoglg]

@VincenzoFerme

Mysql Monitor:

To perform a query, we call the API on /data, passing as query parameters:

• query: the mysql query to perform
• value: the value to compare the result to
• method: the method to use for comparison, either "equal" or "equal"

The response if successful is a JSON with a boolean field called "Result", and a field called "Query_response" containing the response from the database. If the query is invalid, it will return a BadRequest response.

Example response on a count query with value 1 and method equal: `

{"Result":true,"Query_response":"1"}

Cpu Monitor:

To start monitoring we call /start, to stop we call /stop. If either is called when the monitoring is already running or not running respectively, it will return a 409 response (invalid method). We can call /data to get the monitored data, with query:

• select: which container to get, either "all" or a container name.
  The response if successful is a JSON containing a list of the containers' cpu usage for the past 5, 30 and 60 seconds.

Example response:

 {"Name": db, "ID":"35de9dd9b323fe44288fbd5a43b3a351dde218a51f6fa80da354e48d89741a35",  "last5":73332, "last5D":43, "last5Time": "2016-03-08T21:57:31.547920715Z", "last30":34434244, "last30D":4334, "last30Time":"2016-03-08T21:57:56.547920715Z","last60":3243654244, "last60D":466334, "last60Time":"2016-03-08T21:58:24.547920715Z"}

[VincenzoFerme]

@Cerfoglg I would change it to accept container name or container id. Moreover, how the response is structured? Provide examples of the actual response.

[VincenzoFerme]

@Cerfoglg document also the types of query the MySQL monitor handles. Moreover, what are the numbers (e.g., last30) you show in the example of the CPU Monitor response? Then I also miss the name of the container in the response, why only the id?

[Cerfoglg]

@VincenzoFerme The monitor can handle any query that returns a single row with a single column as a result, so a count or a select with a single column selected.

The numbers for CPU all show absolute CPU usage, both absolute (last5 for example) and relative (last5D).

The response actually shows both ID and Name, let me correct that.

[VincenzoFerme]

@Cerfoglg for CPU we should have percentages. Open a new issue for that.

[VincenzoFerme]

@VincenzoFerme

For cpu monitor:

• /start to start monitoring
• /stop to stop monitoring
• /data to get data, with query select which is either a container name/ID, or "all" for all monitored containers. Response is a list of JSON objects with Name, ID, last5, last5D, last5Time, last30, last30D, last30Time, last60, last60D, last60Time (where D is for delta).

For mysql monitor:

• /data to get data, with query values: query for a mysql query to return, method either "equal" or "nequal" for comparison, and value for the value to compare to. Response is a JSON object containing Result and Query_response