How to fix liquibase.exception.LockException: Could not acquire change log lock

How to fix liquibase.exception.LockException: Could not acquire change log lock

This tutorial talks about Liquibase Lock exception during server startup.

Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Waiting for changelog lock....
Caused by: liquibase.exception.LockException: Could not acquire change log lock. Currently locked by
Liquibase Update Failed: Could not acquire change log lock.  Currently locked by S

This is the error when running database migration scripts or batch scripts and database is locked for updated.

First, Let’s understand the Liquibase Lock mechanism

How does Liquibase lock work?

Liquibase provides Lock services to maintain concurrency during multiple threads trying to update/modify the database. It allows to run a single thread always modify the database at a time using lokc mechanism.

Liquibase saves the changelog scripts changes in DATABASECHANGELOCK table by default. Applications configured to run a database migration scripts that runs during startup.

Liquibase does following things during startup,

  • First, It acquires the lock and lock the database, i.e It creates databasechangeloglock table and adds an record to it. Once Lock is acquired, Only one thread can modify the database state.

databasechangeloglock contains a locked column value true

  • Next, It runs the scripts configured in changeLogs
  • Once the scripts are succesfull, It release the locks by updating databasechangeloglock table with row locked to false.

Could not acquire change log lock issue occured if your application deployment is stopped once the lock is acquired.

The reason is Lock is still avialiable and not released.

Let’s see how to fix an error.

How to fix Liquibase Lock error

Database is still locked and need to release the lock to run the database scripts.

There are multiple ways to fix the issue

  • First way, remove database lock tables
    • First, Stop the application
    • Connect to database, remove databasechangelog and databasechangelog.lock tables in Database

TRUNCATE TABLE DATABASECHANGELOGLOCK

or
 drop table  DATABASECHANGELOGLOCK
or
 delete from   DATABASECHANGELOGLOCK

  • Restart the application

  • Second way, update the locked column value to zero

select * from DATABASECHANGELOGLOCK;

Outputs record that database is locked and Locked > 0

Find the id and updated the record with given id by below command

update DATABASECHANGELOGLOCK
set locked=0, lockgranted=null, lockedby=null
where id=value

Locked=0 might change based on database, It can be FALSE or f