OperationalError database is locked

Question

I have made some repetitive operations in my application  testing it   and suddenly I   m getting a weird error    OperationalError  database is locked   I ve restarted the server  but the error persists  What can it be all about

User · Accepted Answer

From django doc      SQLite is meant to be a lightweight   database  and thus can t support a   high level of concurrency    OperationalError  database is locked   errors indicate that your application   is experiencing more concurrency than   sqlite can handle in default   configuration  This error means that   one thread or process has an exclusive   lock on the database connection and   another thread timed out waiting for   the lock the be released       Python s SQLite wrapper has a default   timeout value that determines how long   the second thread is allowed to wait   on the lock before it times out and   raises the OperationalError  database   is locked error       If you re getting this error  you can   solve it by          Switching to another database backend  At a certain point SQLite becomes too  lite  for real-world applications  and these sorts of concurrency errors indicate you ve reached that point    Rewriting your code to reduce concurrency and ensure that database transactions are short-lived    Increase the default timeout value by setting the timeout database option      http   docs djangoproject com en dev ref databases  database-is-locked-errorsoption

User · Answer

I encountered this error message in a situation that is not  clearly  addressed by the help info linked in patrick s answer   When I used transaction atomic   to wrap a call to FooModel objects get or create   and called that code simultaneously from two different threads  only one thread would succeed  while the other would get the  database is locked  error  Changing the timeout database option had no effect on the behavior   I think this is due to the fact that sqlite cannot handle multiple simultaneous writers  so the application must serialize writes on their own   I solved the problem by using a threading RLock object instead of transaction atomic   when my Django app is running with a sqlite backend  That s not entirely equivalent  so you may need to do something else in your application   Here s my code that runs FooModel objects get or create simultaneously from two different threads  in case it is helpful   from concurrent futures import ThreadPoolExecutor  import configurations configurations setup    from django db import transaction from submissions models import ExerciseCollectionSubmission  def makeSubmission user id       try          with transaction atomic                e      ExerciseCollectionSubmission objects get or create                  student id user id  exercise collection id 172      except Exception as e          return f failed   e        e delete        return  success    futures       with ThreadPoolExecutor max workers 2  as executor      futures append executor submit makeSubmission  296       futures append executor submit makeSubmission  297    for future in futures      print future result

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In my case  It was because I open the database from SQLite Browser  When I close it from the browser  the problem is gone

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I had a similar error  right after the first instantiation of Django  v3 0 3   All recommendations here did not work apart from    deleted the db sqlite3 file and lose the data there  if any  python manage py makemigrations python manage py migrate     Btw  if you want to just test PostgreSQL   docker run --rm --name django-postgres     -e POSTGRES PASSWORD mypassword     -e PGPORT 5432     -e POSTGRES DB myproject     -p 5432 5432     postgres 9 6 17-alpine   Change the settings py to add this DATABASES   DATABASES          default              ENGINE    django db backends postgresql psycopg2            NAME    myproject            USER    postgres            PASSWORD    mypassword            HOST    localhost            PORT    5432                and add database adapter   pip install psycopg2-binary   Then the usual   python manage py makemigrations python manage py migrate

User · Answer

try this command   sudo fuser -k 8000 tcp

User · Answer

I disagree with  Patrick s answer which  by quoting this doc  implicitly links OP s problem  Database is locked  to this      Switching to another database backend  At a certain point SQLite becomes too  lite  for real-world applications  and these sorts of concurrency errors indicate you ve reached that point    This is a bit  too easy  to incriminate SQlite for this problem  which is very powerful when correctly used  it s not only a toy for small databases  fun fact  An SQLite database is limited in size to 140 terabytes     Unless you have a very busy server with thousands of connections at the same second  the reason for this Database is locked error is probably more a bad use of the API  than a problem inherent to SQlite which would be  too light   Here are more informations about Implementation Limits for SQLite     Now the solution   I had the same problem when I was using two scripts using the same database at the same time    one was accessing the DB with write operations the other was accessing the DB in read-only   Solution  always do cursor close   as soon as possible after having done a  even read-only  query   Here are more details

User · Answer

Just close  stop  and open  start  the database  This solved my problem

User · Answer

I found this worked for my needs   thread locking  YMMV conn   sqlite3 connect database  timeout 10  https   docs python org 3 library sqlite3 html sqlite3 connect database   timeout  detect types  isolation level  check same thread  factory  cached statements  uri   When a database is accessed by multiple connections  and one of the processes modifies the database  the SQLite database is locked until that transaction is committed  The timeout parameter specifies how long the connection should wait for the lock to go away until raising an exception  The default for the timeout parameter is 5 0  five seconds

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Already lot of Answers are available here  even I want to share my case   this may help someone   I have opened the connection in Python API to update values  I ll close connection only after receiving server response  Here what I did was I have opened connection to do some other operation in server as well before closing the connection in Python API

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Just reboot your server  it will clear all current processes that have your database locked

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In my case  I had not saved a database operation I performed within the SQLite Browser  Saving it solved the issue

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If you get this error while using manage py shell  one possible reason is that you have a development server running  manage py runserver  which is locking the database  Stoping the server while using the shell has always fixed the problem for me

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The practical reason for this is often that the python or django shells have opened a request to the DB and it wasn t closed properly  killing your terminal access often frees it up   I had this error on running command line tests today     Edit   I get periodic upvotes on this   If you d like to kill access without rebooting the terminal  then from commandline you can do    from django import db db connections close all

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As others have told  there is another process that is using the SQLite file and has not closed the connection  In case you are using Linux  you can see which processes are using the file  for example db sqlite3  using the fuser command as follows    sudo fuser -v db sqlite3                      USER        PID ACCESS COMMAND  path to db sqlite3                       user        955 F      apache2  If you want to stop the processes to release the lock  use fuser -k which sends the KILL signal to all processes accessing the file  sudo fuser -k db sqlite3  Note that this is dangerous as it might stop the web server process in a production server  Thanks to  cz-game for pointing out fuser

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I ve got the same error  One of the reasons was the DB connection was not closed   Therefore  check for unclosed DB connections  Also  check if you have committed the DB before closing the connection

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UPDATE django version 2 1 7  I got this error sqlite3 OperationalError  database is locked using pytest with django   Solution   If we are using  pytest mark django db decorator  What it does is create a in-memory-db for testing    Named  file memorydb default mode memory amp cache shared We can get this name with   from django db import connection db path   connection settings dict  NAME     To access this database and also edit it  do   Connect to the data base   with sqlite3 connect db path  uri True  as conn      c   conn cursor     Use uri True to specifies the disk file that is the SQLite database to be opened   To avoid the error activate transactions in the decorator    pytest mark django db transaction True    Final function   from django db import connection   pytest mark django db transaction True  def test mytest        db path   connection settings dict  NAME       with sqlite3 connect db path  uri True  as conn          c   conn cursor           c execute  my amazing query           conn commit       assert

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This also could happen if you are connected to your sqlite db via dbbrowser plugin through pycharm  Disconnection will solve the problem

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A very unusual scenario  which happened to me   There was infinite recursion  which kept creating the objects   More specifically  using DRF  I was overriding create method in a view  and I did  def create self  request   args    kwargs                          return self create request   args    kwargs

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For me it gets resolved once I closed the django shell which was opened using python manage py shell

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In my case  I added a new record manually saved and again through shell tried to add new record this time it works perfectly check it out  In  7   from main models import Flight  In  8   f   Flight origin  quot Florida quot   destination  quot Alaska quot   duration 10   In  9   f save    In  10   Flight objects all    Out 10    lt QuerySet   lt Flight  Flight object  1  gt    lt Flight  Flight object  2  gt    lt Flight  Flight object  3  gt    lt Flight  Flight object  4  gt   gt

[python] OperationalError: database is locked

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