Error 503 When Accessing Tag History in SystemLink Server

Updated Nov 21, 2023

Reported In

Software

  • SystemLink Server

Issue Details

When I try to check the history of a tag in my SystemLink Server, I get the following error:

The request for tag history failed with error code 503.

error 503.png

Solution

One of the reasons for this to fail is an issue with the memory needed by several services, including MongoDB, to function correctly.
  • Make sure that the server machine meets the SystemLink software minimum requirements. These can be found in the readme file in the release notes for the corresponding version.
  • If the server is not meeting the resource requirements, assign more resources to it, or migrate the server to a machine that is able to meet the requirements.
  • Increasing the server's database cache size might temporarily fix the error, but after some time as data is processed, the same resource problem can be seen again. Other services could experience issues due to lack of memory as well.
  • Uninstalling unused software modules can help to temporarily fix this error.

Additional Information

The tag current values and aggregates are brokered by the Redis service, while the tag history is stored in MongoDB. If MongoDB is not able to use the necessary resources, tag history and other operations might fail.

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