Add FAQs about server migrating (#106)

docs/faq.md

@@ -14,6 +14,8 @@ title: FAQ
 * [Can I store the model configuration file as well?](#store-model-configuration)
 * [I am training multiple models at the same time, but I only see one of them. What happened?](#only-last-model-appears)
 * [Can I log input and output models manually?](#manually-log-models)
+* [Models are not accessible from the UI after I migrated ClearML Server to a new domain. How do I fix this?](#migrate_server_models)
+* [Models are not accessible from the UI after I moved them (different bucket / server). How do I fix this?](#relocate_models)
 
 **Experiments**
 
@@ -44,6 +46,7 @@ title: FAQ
 * [Is there something ClearML can do about uncommitted code running?](#help-uncommitted-code)
 * [I read there is a feature for centralized model storage. How do I use it?](#centralized-model-storage)
 * [When using PyCharm to remotely debug a machine, the Git repo is not detected. Do you have a solution?](#pycharm-remote-debug-detect-git)
+* [Debug images and / or artifacts are not loading in the UI after I migrated ClearML Server to a new domain. How do I fix this?](#migrate_server_debug)
 
 
 **Remote Debugging (ClearML PyCharm Plugin)**
@@ -201,6 +204,68 @@ method to manually connect a model weights file.
 For more information about models, see [InputModel](references/sdk/model_inputmodel.md) 
 and [OutputModel](references/sdk/model_outputmodel.md) classes.
 
+<br/>
+
+**Models are not accessible the UI after I migrated ClearML Server to a new domain. How do I fix this?** <a id="migrate_server_models"></a>
+
+This can happen if your models were uploaded to the ClearML files server, since the value registered was their full URL 
+at the time of registration (e.g. `https://files.<OLD_DOMAIN>/path/to/model`).
+
+To fix this, the registered URL of each model needs to be replaced with its current URL.
+
+To replace the URL of each model, execute the following commands:
+
+1. Open bash in the mongo DB docker container: 
+
+    ```bash 
+    sudo docker exec -it clearml-mongo /bin/bash
+    ```
+
+1. Inside the docker shell, create the following script. Make sure to replace `<old-bucket-name>` and `<new-bucket-name>`, 
+   as well as the URL protocol if you aren't using `s3`. 
+    ```bash
+    cat <<EOT >> script.js
+    db.model.find({uri:{$regex:/^s3/}}).forEach(function(e,i) {
+    e.uri = e.uri.replace("s3://<old-bucket-name>/","s3://<new-bucket-name>/");
+    db.model.save(e);});
+    EOT 
+    ```
+
+1. Run the script against the backend DB:
+
+   ```bash
+   mongo backend script.js
+   ```
+<br/>
+
+**Models are not accessible from the UI after I moved them (different bucket / server). How do I fix this?** <a id="relocate_models"></a>
+
+This can happen if your models were uploaded to the ClearML files server, since the value registered was their full URL 
+at the time of registration (e.g. `https://files.<OLD_DOMAIN>/path/to/model`).
+
+To fix this, the registered URL of each model needs to be replaced with its current URL:
+
+1. Open bash in the mongo DB Docker container: 
+
+   ```bash
+   sudo docker exec -it clearml-mongo /bin/bash
+   ```
+
+1. Inside the Docker shell, create the following script. Make sure to replace `<old-bucket-name>` and `<new-bucket-name>`, as well as the URL protocol prefixes if you aren't using S3. 
+    ```bash
+    cat <<EOT >> script.js
+    db.model.find({uri:{$regex:/^s3/}}).forEach(function(e,i) {
+    e.uri = e.uri.replace("s3://<old-bucket-name>/","s3://<new-bucket-name>/");
+    db.model.save(e);});
+    EOT 
+    ```
+
+1. Run the script against the backend DB:
+
+    ```bash
+    mongo backend script.js
+    ```
+
 ## Experiments
 
 **I noticed I keep getting the message "warning: uncommitted code". What does it mean?** <a id="uncommitted-code-warning"></a>
@@ -521,6 +586,56 @@ see [ClearML Configuration Reference](configs/clearml_conf.md).
 Yes! Since this is such a common occurrence, we created a PyCharm plugin that allows a remote debugger to grab your local 
 repository / commit ID. For detailed information about using the plugin, see the [ClearML PyCharm Plugin](guides/ide/integration_pycharm.md).
 
+<br/>
+
+**Debug images and/or artifacts are not loading in the UI after I migrated ClearML Server to a new domain. How do I fix this?**  <a id="migrate_server_debug"></a>  
+
+This can happen if your debug images and / or artifacts were uploaded to the ClearML file server, since the value
+registered was their full URL at the time of registration (e.g. `https://files.<OLD_DOMAIN>/path/to/artifact`).
+
+To fix this, the registered URL of each debug image and / or artifact needs to be replaced with its current URL.
+
+* For **debug images**, use the following command. Make sure to insert the old domain and the new domain that will replace it
+    ```bash
+    curl --header "Content-Type: application/json" \
+    --request POST \
+    --data '{
+        "script": {
+            "source": "ctx._source.url = ctx._source.url.replace('https://files.<OLD_DOMAIN>', 'https://files.<NEW_DOMAIN>')",
+            "lang": "painless"
+        },
+        "query": {
+            "match_all": {}
+        }
+    }' \
+    ```
+
+* For **artifacts**, you can do the following: 
+
+    1. Open bash in the mongo DB docker container:
+
+    ```bash 
+    sudo docker exec -it clearml-mongo /bin/bash
+    ```
+
+    1. Inside the docker shell, create the following script. Make sure to replace `<old-bucket-name>` and `<new-bucket-name>`, 
+   as well as the URL protocol prefixes if you aren't using `s3`. 
+   
+    ```bash
+    cat <<EOT >> script.js
+    db.model.find({uri:{$regex:/^s3/}}).forEach(function(e,i) {
+    e.uri = e.uri.replace("s3://<old-bucket-name>/","s3://<new-bucket-name>/");
+    db.model.save(e);});
+    EOT 
+    ```
+
+    1. Run the script against the backend DB:
+
+    ```bash
+    mongo backend script.js
+    ```
+   
+
 ## Jupyter
 
 **I am using Jupyter Notebook. Is this supported?** <a id="jupyter-notebook"></a>
@@ -880,6 +995,7 @@ api {
 ```
 
 
+
 ## ClearML Agent
 
 **How can I execute ClearML Agent without installing packages each time?** <a className="tr_top_negative" id="system_site_packages"></a>