In Arcadia UI (browser) I am seeing this error OperationalError: disk I/O error (diskcache/

If you are accessing the Arcadia UI and hit a disk error like below it’s usually because there’s not more disk space left.


  1. Check the filesystem disk space and free up space as needed.
  2. Check is make sure there’s no limit on open files for the arcviz process
  3. Check the permission on the sqlite file located at /var/lib/arcadia
  4. Run the command mentioned here to clear the arcviz cache directory:
    Issue when downgrading from Arcadia 4.3+ to 4.2 and lower: Unsupported pickle protocol: 4


Operational> Error: disk I/O error


In the arcviz.INFO logs you might see errors like this:

 File "/opt/arcadia/lib/venv/lib64/python3.6/site-packages/diskcache/", line 597, in _execute_with_retry
    return sql(statement, *args, **kwargs)
sqlite3.OperationalError: disk I/O error
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Another alternative solution if the issue persists, is to change the Arcadia cache to use the File cache instead of the Disk cache backend. These changes can be applied via the Arcadia Visualization Server Safety Valve ( in Cloudera Manager, or Arcviz Settings in Ambari:

CACHES['default'] = {
  'BACKEND': 'vizlib.arcfilecache.FileBasedCache',
  'LOCATION': os.path.join(VARDIR, "cache"),
  'TIMEOUT': 31536000,
  'OPTIONS': {
    'MAX_ENTRIES': 10000

CACHES['default']['OPTIONS']['CULL_MINTIME'] = 3600*4