Troubleshooting Phoenix Cloud App Access Errors

Michael H. · 2025-05-19T16:37:11.304Z

Having trouble accessing Phoenix cloud app - seeing this error after the page loading for a long while. Any suggested workaround? Let me know if other information would be helpful. Unexpected token ' <hea"... is not valid JSON

Troubleshooting Phoenix Cloud App Access Errors | Arize AI Community

4 comments

· Sorted by Oldest

RunLLM
APP
·
This error ("Unexpected token '<', ... is not valid JSON") is commonly caused by proxy or network misconfiguration, or by accessing a backend endpoint (like /v1/traces) directly instead of the main app URL. It can also occur if the Phoenix Cloud service is experiencing issues or if your browser cache is out of sync with the server. Workarounds include clearing your browser cache, ensuring you are visiting https://app.phoenix.arize.com (not a /v1/traces or other API path), and retrying after some time. If the issue persists, it may be related to a backend upgrade or temporary outage—upgrading to the latest Phoenix version or reaching out via the <https://arize-ai.slack.com/join/shared_invite/zt-11t1vbu4x-xkBIHmOREQnYnYDH1GDfCg?__hstc=259489365.a667dfafcfa0169c8aee4178d115dc81.1733501603539.1733501603539.1733501603539.1&__hssc=259489365.1.1733501603539&__hsfp=3822854628&submissionGuid=381a0676-8f38-437b-96f2-fc10875658df#/shared-invite/email|Phoenix Slack community> for support is recommended.If you are self-hosting or using a proxy (e.g., Istio, NGINX), ensure the PHOENIX_HOST_ROOT_PATH environment variable is set correctly and that your ingress/proxy is configured to rewrite paths as needed. Also, check that you are not running out of disk/database space, and try restarting the app. Let me know if you need more detailed troubleshooting steps or if you are using a specific deployment setup.Sources: - Unexpected token '<', "<!DOCTYPE "... is not valid JSON - error page on hosted phoenix - https://github.com/Arize-ai/phoenix/issues/4091 - https://github.com/Arize-ai/phoenix/issues/5254
💡 Hint: Mention RunLLM in the thread for followups.
Mikyo
·
Hey Michael H. - let me ping the infra team.
👍1
Mikyo
·
FYI Michael, phoenix cloud currently has IO limits due to them being 10 GB sqlite instances that don't handle high concurrent read/writes (because it's a single file). We're working on higher powered instances backed with a better DB to offer for free in the coming months but this might take a bit of time. The main solution to this is to either self-host or onboard with Arize Ax - the enterprise solution. We can certainly work with you on keeping your existing phoenix instance healthy but it does have inherent limitations due to it being a free instance (e.g. we have to manually bump your memory allocation and PVC) You can pretty easily self-host phoenix on things like railway and provision the resources you need (https://railway.com/template/PTHRoq) - https://docs.arize.com/phoenix/self-hosting
Michael H.
·
Got it. We're looking into self hosting. Thanks for your reply!
1

RunLLM
APP
·
This error ("Unexpected token '<', ... is not valid JSON") is commonly caused by proxy or network misconfiguration, or by accessing a backend endpoint (like /v1/traces) directly instead of the main app URL. It can also occur if the Phoenix Cloud service is experiencing issues or if your browser cache is out of sync with the server. Workarounds include clearing your browser cache, ensuring you are visiting https://app.phoenix.arize.com (not a /v1/traces or other API path), and retrying after some time. If the issue persists, it may be related to a backend upgrade or temporary outage—upgrading to the latest Phoenix version or reaching out via the <https://arize-ai.slack.com/join/shared_invite/zt-11t1vbu4x-xkBIHmOREQnYnYDH1GDfCg?__hstc=259489365.a667dfafcfa0169c8aee4178d115dc81.1733501603539.1733501603539.1733501603539.1&__hssc=259489365.1.1733501603539&__hsfp=3822854628&submissionGuid=381a0676-8f38-437b-96f2-fc10875658df#/shared-invite/email|Phoenix Slack community> for support is recommended.If you are self-hosting or using a proxy (e.g., Istio, NGINX), ensure the PHOENIX_HOST_ROOT_PATH environment variable is set correctly and that your ingress/proxy is configured to rewrite paths as needed. Also, check that you are not running out of disk/database space, and try restarting the app. Let me know if you need more detailed troubleshooting steps or if you are using a specific deployment setup.Sources: - Unexpected token '<', "<!DOCTYPE "... is not valid JSON - error page on hosted phoenix - https://github.com/Arize-ai/phoenix/issues/4091 - https://github.com/Arize-ai/phoenix/issues/5254
💡 Hint: Mention RunLLM in the thread for followups.
Mikyo
·
Hey Michael H. - let me ping the infra team.
👍1
Mikyo
·
FYI Michael, phoenix cloud currently has IO limits due to them being 10 GB sqlite instances that don't handle high concurrent read/writes (because it's a single file). We're working on higher powered instances backed with a better DB to offer for free in the coming months but this might take a bit of time. The main solution to this is to either self-host or onboard with Arize Ax - the enterprise solution. We can certainly work with you on keeping your existing phoenix instance healthy but it does have inherent limitations due to it being a free instance (e.g. we have to manually bump your memory allocation and PVC) You can pretty easily self-host phoenix on things like railway and provision the resources you need (https://railway.com/template/PTHRoq) - https://docs.arize.com/phoenix/self-hosting
Michael H.
·
Got it. We're looking into self hosting. Thanks for your reply!
1