docs: multi client

docs/_ldi-nifi/index.md

@@ -15,28 +15,61 @@ The processors can be imported into a NiFi docker instance via volume binding:
 1. Create a `docker-compose.yml` file with the following content in a new directory
     ````yaml
     services:
-      nifi:
-        image: apache/nifi:2.0.0
-        environment:
-          SINGLE_USER_CREDENTIALS_USERNAME: admin
-          SINGLE_USER_CREDENTIALS_PASSWORD: ctsBtRBKHRAx69EqUghvvgEvjnaLjFEB
-        ports:
-          - 8443:8443
-        volumes:
-          - ./nifi-ext:/opt/nifi/nifi-current/nar_extensions:rw
+        nifi:
+            image: apache/nifi:2.0.0
+            environment:
+              SINGLE_USER_CREDENTIALS_USERNAME: admin
+              SINGLE_USER_CREDENTIALS_PASSWORD: ctsBtRBKHRAx69EqUghvvgEvjnaLjFEB
+            ports:
+              - 8443:8443
+            volumes:
+              - ./nifi-ext:/opt/nifi/nifi-current/nar_extensions:rw
+              - ./nifi-drivers:/opt/nifi/nifi-current/lib_temp:rw
+            entrypoint: [ "/bin/bash",
+                          "-c",
+                          "cp -r /opt/nifi/nifi-current/lib_temp/* /opt/nifi/nifi-current/lib/ && exec /opt/nifi/scripts/start.sh" ]
     ````
 2. Create a directory `nifi-ext` in your current directory.
 3. Download either the `...-nar-bundle.jar` and unpack this or download the individual required processors (.nar extension) from the [nexus repository].
    Next, place the required processors in the `nifi-ext` directory.
-4. Finally, start your instance.
+4. Additionally, for using any processor with a persistence layer, you will need to download the needed drivers.
+   Create a `nifi-drivers` directory and place these drivers inside.
+   Possible drivers are:
+    - [PostgreSQL driver](https://jdbc.postgresql.org/download)
+   - [SQLite driver](https://mvnrepository.com/artifact/org.xerial/sqlite-jdbc)
+5. Finally, start your instance.
     ````shell
     docker compose up
     ````
-5. Log in at `https://localhost:8443/nifi` with the credentials mentioned in step 1
-6. All downloaded extensions are available under the ``be.vlaanderen.informatievlaanderen.ldes.ldi.nifi`` group.
+6. Log in at `https://localhost:8443/nifi` with the credentials mentioned in step 1
+7. All downloaded extensions are available under the ``be.vlaanderen.informatievlaanderen.ldes.ldi.nifi`` group.
 
 {: .note }
 All documentation and notes about configuration are available in the NiFi component itself.
 
+## Setting up Database Connection Pools
+
+As of LDI 2.13.0, some processors require a database connection pool to be set up.
+Although this is a pure NiFi configuration, a minimal explanation will be mentioned here. \
+For more details, please refer to
+the [NiFi documentation on DBCP](https://nifi.apache.org/components/org.apache.nifi.dbcp.DBCPConnectionPool/).
+This can be done by following these steps:
+
+1. Go to the `Controller Services` tab in the NiFi UI.
+2. Click on the `Create new service` button.
+3. Select the `DBCPConnectionPool` service.
+4. Configure the service with the required properties:
+   - `Database Connection URL`,
+      - `jdbc:sqlite:/path/to/database.db` for SQLite
+      - `jdbc:postgresql://localhost:5432/database` for PostgreSQL,
+   - `Database Driver Class Name`
+      - `org.sqlite.JDBC` for SQLite
+      - `org.postgresql.Driver` for PostgreSQL,
+   - `Database User`,
+   - `Password`,
+5. Save the service.
+6. Enable the service.
+7. Use the service in the processors that require it.
+
 [Apache NiFi]: https://nifi.apache.org/
 [nexus repository]: https://s01.oss.sonatype.org/#nexus-search;quick~be.vlaanderen.informatievlaanderen.ldes.ldi.nifi