Datafile Debugger

In Case Of Disaster

AranagoDB uses append-only journals. Data corruption should only occur when thedatabase server is killed. In this case, the corruption should only occur in thelast object(s) that have being written to the journal.

If a corruption occurs within a normal datafile, then this can only happen if ahardware fault occurred.

If a journal or datafile is corrupt, shut down the database server and startthe program

  1. unix> arango-dfdb

in order to check the consistency of the datafiles and journals. This brings up

  1.     ___      _         __ _ _           ___  ___    ___ 
  2.    /   \__ _| |_ __ _ / _(_) | ___     /   \/ __\  / _ \
  3.   / /\ / _` | __/ _` | |_| | |/ _ \   / /\ /__\// / /_\/
  4.  / /_// (_| | || (_| |  _| | |  __/  / /_// \/  \/ /_\\ 
  5. /___,' \__,_|\__\__,_|_| |_|_|\___| /___,'\_____/\____/ 
  7. Available collections:
  8.   0: _structures
  9.   1: _users
  10.   2: _routing
  11.   3: _modules
  12.   4: _graphs
  13.   5: products
  14.   6: prices
  15.   *: all
  17. Collection to check:

You can now select which database and collection you want to check. After you selected one or all of the collections, a consistency check will be performed.

  1. Checking collection #1: _users
  3. Database
  4.   path: /usr/local/var/lib/arangodb
  6. Collection
  7.   name: _users
  8.   identifier: 82343
  10. Datafiles
  11.   # of journals: 1
  12.   # of compactors: 1
  13.   # of datafiles: 0
  15. Datafile
  16.   path: /usr/local/var/lib/arangodb/collection-82343/journal-1065383.db
  17.   type: journal
  18.   current size: 33554432
  19.   maximal size: 33554432
  20.   total used: 256
  21.   # of entries: 3
  22.   status: OK

If there is a problem with one of the datafiles, then the database debugger will print itand prompt for whether to attempt to fix it.

  1. WARNING: The journal was not closed properly, the last entries are corrupted.
  2.          This might happen ArangoDB was killed and the last entries were not
  3.          fully written to disk.
  5. Wipe the last entries (Y/N)?

If you answer Y, the corrupted entry will be removed.

If you see a corruption in a datafile (and not a journal), then something isterribly wrong. These files are immutable and never changed by ArangoDB. Acorruption in such file is an indication of a hard-disk failure.