AstarteExport: Add Cassandra host/port and update README

- Modified export_realm_data/3 to accept db_host_and_port as an argument.
- Set Cassandra host and port as env variables
- Updated the run/1 function to reflect the new parameters for exporting.
- Enhanced documentation to include the new db_host_and_port argument.
- Updated README to reflect the changes in function usage and parameters.

Signed-off-by: Jusuf <jusuf.avdic@secomind.com>

Author: Jusuf95

tools/astarte_export/README.md

@@ -3,7 +3,7 @@
 Astarte Export is an easy to use tool that allows to exporting all the devices and data from an existing Astarte realm to XML format.
 
 ```iex
-iex(astarte_export@127.0.0.1)6> Astarte.Export.export_realm_data("test", "test.xml")
+iex(astarte_export@127.0.0.1)6> Astarte.Export.export_realm_data("localhost:9042" "test", "test.xml")
 level=info ts=2020-02-03T03:57:21.412+00:00 msg="Export started." module=Astarte.Export function=generate_xml/2 realm=test tag=export_started
 level=info ts=2020-02-03T03:57:21.413+00:00 msg="Connecting to \"172.23.0.3\":\"9042\" cassandra database." module=Astarte.Export.FetchData.Queries function=get_connection/0
 level=info ts=2020-02-03T03:57:21.414+00:00 msg="Connected to database." module=Astarte.Export.FetchData.Queries function=get_connection/0

tools/astarte_export/lib/astarte/export.ex

@@ -29,18 +29,25 @@ defmodule Astarte.Export do
   """
 
   @doc """
-    The export_realm_data/2 function required 2 arguments to export
+    The export_realm_data/2 function required 3 arguments to export
     the realm data into XML format.
     the arguments are
+    - db-host-and-port -> -> A string in the format "hostname:port",
+      used to set the environment variables for Cassandra database connection.
     - realm-name -> This is a string format of input
     - file      -> file where to export the realm data.
     - options   -> options to export the realm data.
   """
 
-  @spec export_realm_data(String.t(), String.t(), keyword()) ::
+  @spec export_realm_data(String.t(), String.t(), String.t(), keyword()) ::
           :ok | {:error, :invalid_parameters} | {:error, any()}
 
-  def export_realm_data(realm, file, opts \\ []) do
+  def export_realm_data(db_host_and_port, realm, file, opts \\ []) do
+    [db_host, db_port] = String.split(db_host_and_port, ":")
+
+    System.put_env("CASSANDRA_DB_HOST", db_host)
+    System.put_env("CASSANDRA_DB_PORT", db_port)
+
     file = Path.expand(file) |> Path.absname()
 
     with {:ok, fd} <- File.open(file, [:write]) do

tools/astarte_export/lib/mix/tasks/astarte_export.ex

@@ -8,18 +8,18 @@ defmodule Mix.Tasks.Astarte.Export do
   @shortdoc "export data from an existing Astarte realm"
   def run(args) do
     case args do
-      [realm, file_name] ->
+      [db_host_and_port, realm, file_name] ->
         Logger.info("Exporting data from realm #{realm} to file #{file_name}")
 
         case Application.ensure_all_started(:astarte_export) do
           {:ok, _} ->
-            Export.export_realm_data(realm, file_name)
+            Export.export_realm_data(db_host_and_port, realm, file_name)
 
           {:error, reason} ->
             Logger.error("Cannot start applications: #{inspect(reason)}")
         end
 
-      [realm, file_name, device_id] ->
+      [db_host_and_port, realm, file_name, device_id] ->
         Logger.info(
           "Exporting data for device #{device_id} from realm #{realm} to file #{file_name}"
         )
@@ -28,7 +28,7 @@ defmodule Mix.Tasks.Astarte.Export do
 
         case Application.ensure_all_started(:astarte_export) do
           {:ok, _} ->
-            Export.export_realm_data(realm, file_name, options)
+            Export.export_realm_data(db_host_and_port, realm, file_name, options)
 
           {:error, reason} ->
             Logger.error("Cannot start applications: #{inspect(reason)}")

tools/astarte_export/test/astarte_export_test.exs

@@ -5,6 +5,7 @@ defmodule Astarte.ExportTest do
   alias Astarte.Export.FetchData
   alias Astarte.DatabaseTestdata
   @realm "test"
+  @db_host_and_port "localhost:9042"
 
   @expected_xml """
   <?xml version="1.0" encoding="UTF-8"?>
@@ -72,14 +73,14 @@ defmodule Astarte.ExportTest do
 
   test "export realm data to xmlfile" do
     DatabaseTestdata.initialize_database()
-    assert {:ok, :export_completed} == Export.export_realm_data(@realm, "test.xml")
+    assert {:ok, :export_completed} == Export.export_realm_data(@db_host_and_port, @realm, "test.xml")
     file = Path.expand("test.xml") |> Path.absname()
     assert @expected_xml == File.read!(file)
   end
 
   test "export realm data to xmlfile in a absolute path " do
     file = File.cwd!() <> "/test.xml"
-    assert {:ok, :export_completed} == Export.export_realm_data(@realm, file)
+    assert {:ok, :export_completed} == Export.export_realm_data(@db_host_and_port, @realm, file)
     assert @expected_xml == File.read!(file)
   end