Skip layers with specified WMS errors

[PhilAnzel]

WMS client layers may fail with HTTP errors such as "404", "408" or "504" due to transient network or server problems. In case of such a failure, no layers are drawn and an exception is thrown. It would be better to be able to specify on a per-layer basis those layers that can simply be skipped if an error occurs. This might be by means of a CONFIGURE statement that specifies the error to ignore, such as

  CONFIG ON_WMS_ERROR "IGNORE=404"
  CONFIG ON_WMS_ERROR "IGNORE=408,504"

(thanks to Steve W for this suggested usage).

[dmorissette]

To remain consistent with the other config info used for CONNECTIONTYPE WMS and WFS layers which are provided through "ows_...", "wms_...", "wfs_..." metadata entries, we should probably use metadata for this as well instead of CONFIG options.

We'd also need to think about which actions other than IGNORE we need to support. In http://mapserver.org/development/rfc/ms-rfc-47.html for IGNORE_MISSING_DATA the actions were IGNORE, LOG or FAIL, with FAIL being the default.

Finally, we need to take into consideration that we cannot have multiple metadata entries with the same key.

Perhaps something as follows would do?

METADATA
  "ows_onerror"     "LOG"    # Set new default behavior to log and skip all errors unless explicitly specified otherwise
  "ows_onerror_404" "FAIL"   # FAIL on 404 errors
  "ows_onerror_408" "IGNORE" # Silently ignore request timeout errors
  "ows_onerror_504" "IGNORE" # Silently ignore proxy timeout errors
END

[PhilAnzel]

Thank you, Daniel, that would certainly make for a more robust server. - Phil

[dmorissette]

Unfortunately this will have to wait for 6.4. I'll assign this ticket to @aboudreault. Please ping us again after the 6.2 release is out to make sure we don't forget.

[tbonfort]

too late for 6.4, demilestoning

[PhilAnzel]

Ping: a reminder, this would still be handy to have.

[dmorissette]

Agreed this would be nice to have. Unfortunately I don't see myself having time anytime soon, so hopefully another dev can take it.

[mapserver-bot]

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