Services added to web applications load slowly in ArcGIS Web AppBuilder web apps

Description

In ArGIS Web AppBuilder, services such as feature services and map services can be added to the map via the Add Data widget. However, these services may take a long time to load data in the web app, especially when compared to the loading times of the same services in ArcGIS Online or Portal for ArcGIS Map Viewer.

Cause

This issue occurs in services containing a large amounts of features, and when a sizable amount of users are attempting to access the web app containing the feature service. In these cases, the service in question can be assigned with a higher number of instances, which is useful in pooling a higher amount of system resources, such as physical memory (RAM) and CPU cores towards the service. However, increasing the number of instances to a point where it exceeds the amount of resources available also causes an overall reduction in system performance, thus increasing load times in web apps.

To summarize, the following are reasons why services may take time to load on a map in a web app:

• Insufficient RAM to handle many instances. Refer to Problem: The number of ArcSOC instances causes ArcGIS Server stability issues for more information.
• The number of instance are more than double the CPU cores on the server machine. Refer to ArcGIS Server: Configure the shared instance pool for more information.
• Services containing large datasets.
• A large amount of end users accessing the web app.

Solution or Workaround

The following are best practices to improve service performance in web apps.

• Increase the memory of the server machine to accommodate larger feature services and a large number of end users accessing the web app. Upgrading to a CPU with a higher core count can also allow for a higher number of instances set for a particular service. Refer to ArcGIS Enterprise: ArcGIS Server 11.0 system requirements for more information.
• Services can be fine tuned to increase web app performance, reduce wait-times and prevent timeout. For example, frequently used services can be configured to have more instances, and infrequently used services can be configured to have up to zero instances to free up resources. Refer to ArcGIS Server: Configure service instance settings for more information and instructions on pooling instances between services.
• Prioritize using map services over feature services in web apps if the goal is to display data. Map services offer better load times, but at the cost of not being able to perform analysis and queries on features. Refer to FAQ: What is the difference between a map service, feature service, and a hosted feature layer? for more information.
• Map services encountering issues can be monitored and analyzed using server logs and reports of server statistics. Refer to ArcGIS Server: Troubleshoot map service performance with server logs for troubleshooting map services and ArcGIS Server: Work with server statistics for generating map and feature service statistics.