500 http status code when using SAML dynamic

[ashish1099]

Issue Summary

I have setup the SAML dynamic with our internal keycloak server. It works fine but sometime the request ends up with 500. As soon as I click on the "SAML Login" it hits this url https://redash.local/saml/login?next=%2F' and later dies with 502

I'm not sure why this is happening, but I can say that the request never reaches my keycloak

curl 'https://redash.local/saml/login?next=%2F' \
  -H 'authority: redash.local' \
  -H 'accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9' \
  -H 'accept-language: en-US,en;q=0.9' \
  -H 'cache-control: no-cache' \
  -H 'cookie: csrf_token=g37S1y0dp4; session=eyabeJbw' \
  -H 'dnt: 1' \
  -H 'pragma: no-cache' \
  -H 'referer: https://redash.local/login?next=https%3A%2F%2Fredash.local%2F' \
  -H 'sec-ch-ua: " Not A;Brand";v="99", "Chromium";v="100", "Google Chrome";v="100"' \
  -H 'sec-ch-ua-mobile: ?0' \
  -H 'sec-ch-ua-platform: "Linux"' \
  -H 'sec-fetch-dest: document' \
  -H 'sec-fetch-mode: navigate' \
  -H 'sec-fetch-site: same-origin' \
  -H 'sec-fetch-user: ?1' \
  -H 'upgrade-insecure-requests: 1' \
  -H 'user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.60 Safari/537.36' \
  --compressed

redash logs

[2022-04-05 06:08:15,486][PID:816][INFO][metrics] method=GET path=/saml/login endpoint=saml_auth_sp_initiated status=500 content_type=? content_length=-1 duration=30244.41 query_count=1 query_duration=0.96

in debug mode

[2022-04-05 10:12:10,682][PID:10][DEBUG][root] Current organization: default (1) (slug: default)
[2022-04-05 10:12:10,688][PID:10][DEBUG][saml2.httpbase] GET to https://keycloak.local/auth/realms/master/protocol/saml/descriptor
[2022-04-05 10:12:10,691][PID:10][DEBUG][urllib3.connectionpool] Starting new HTTPS connection (1): keycloak.local:443

Steps to Reproduce

1. simply install the redash via helm
2. setup the keycloak saml client
3. hit "SAML login" on the login page.

Technical details:

• Redash Version: 10.1.0.b50633 (docker tag)
• Browser/OS: 100.0.4896.60 (Google Chrome)
• How did you install Redash: (helm + argocd)