apache airflow: initdb vs resetdb

Question

What precisely is the difference between the "airflow initdb" command and the "airflow resetdb" command?

Is it really necessary to have 2 different commands?

When is it appropriate to use one vs the other?

The doc says ...

airflow initdb: Initialize the metadata database

airflow resetdb: Burn down and rebuild the metadata database

This doesn't tell me much.

My best guess is that

airflow initdb is to be used only the first time that the database is created from the airflow.cfg
airflow resetdb is to be used if any changes to that configuration are required.

When I run them, neither changes the timestamp on the sqlite database but resetdb seems to be much noisier.

airflow initdb:

(.sandbox) [airflow@localhost airflow]$ airflow initdb
[2020-01-01 21:49:21,603] {settings.py:252} INFO - settings.configure_orm(): Using pool settings. pool_size=5, max_overflow=10, pool_recycle=1800, pid=24917
DB: postgresql+psycopg2://airflow@localhost:5432/airflow_mdb
[2020-01-01 21:49:22,257] {db.py:368} INFO - Creating tables
INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Will assume transactional DDL.
Done.

airflow resetdb:

(.sandbox) [airflow@localhost airflow]$ airflow resetdb
[2020-01-01 21:49:46,579] {settings.py:252} INFO - settings.configure_orm(): Using pool settings. pool_size=5, max_overflow=10, pool_recycle=1800, pid=25045
DB: postgresql+psycopg2://airflow@localhost:5432/airflow_mdb
This will drop existing tables if they exist. Proceed? (y/n)y
[2020-01-01 21:49:49,984] {db.py:389} INFO - Dropping tables that exist
[2020-01-01 21:49:50,062] {migration.py:154} INFO - Context impl PostgresqlImpl.
[2020-01-01 21:49:50,063] {migration.py:161} INFO - Will assume transactional DDL.
[2020-01-01 21:49:50,070] {db.py:368} INFO - Creating tables
INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Will assume transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> e3a246e0dc1, current schema
INFO  [alembic.runtime.migration] Running upgrade e3a246e0dc1 -> 1507a7289a2f, create is_encrypted
INFO  [alembic.runtime.migration] Running upgrade 1507a7289a2f -> 13eb55f81627, maintain history for compatibility with earlier migrations
INFO  [alembic.runtime.migration] Running upgrade 13eb55f81627 -> 338e90f54d61, More logging into task_instance
INFO  [alembic.runtime.migration] Running upgrade 338e90f54d61 -> 52d714495f0, job_id indices
INFO  [alembic.runtime.migration] Running upgrade 52d714495f0 -> 502898887f84, Adding extra to Log
INFO  [alembic.runtime.migration] Running upgrade 502898887f84 -> 1b38cef5b76e, add dagrun
INFO  [alembic.runtime.migration] Running upgrade 1b38cef5b76e -> 2e541a1dcfed, task_duration
INFO  [alembic.runtime.migration] Running upgrade 2e541a1dcfed -> 40e67319e3a9, dagrun_config
INFO  [alembic.runtime.migration] Running upgrade 40e67319e3a9 -> 561833c1c74b, add password column to user
INFO  [alembic.runtime.migration] Running upgrade 561833c1c74b -> 4446e08588, dagrun start end
INFO  [alembic.runtime.migration] Running upgrade 4446e08588 -> bbc73705a13e, Add notification_sent column to sla_miss
INFO  [alembic.runtime.migration] Running upgrade bbc73705a13e -> bba5a7cfc896, Add a column to track the encryption state of the 'Extra' field in connection
INFO  [alembic.runtime.migration] Running upgrade bba5a7cfc896 -> 1968acfc09e3, add is_encrypted column to variable table
INFO  [alembic.runtime.migration] Running upgrade 1968acfc09e3 -> 2e82aab8ef20, rename user table
INFO  [alembic.runtime.migration] Running upgrade 2e82aab8ef20 -> 211e584da130, add TI state index
INFO  [alembic.runtime.migration] Running upgrade 211e584da130 -> 64de9cddf6c9, add task fails journal table
INFO  [alembic.runtime.migration] Running upgrade 64de9cddf6c9 -> f2ca10b85618, add dag_stats table
INFO  [alembic.runtime.migration] Running upgrade f2ca10b85618 -> 4addfa1236f1, Add fractional seconds to mysql tables
INFO  [alembic.runtime.migration] Running upgrade 4addfa1236f1 -> 8504051e801b, xcom dag task indices
INFO  [alembic.runtime.migration] Running upgrade 8504051e801b -> 5e7d17757c7a, add pid field to TaskInstance
INFO  [alembic.runtime.migration] Running upgrade 5e7d17757c7a -> 127d2bf2dfa7, Add dag_id/state index on dag_run table
INFO  [alembic.runtime.migration] Running upgrade 127d2bf2dfa7 -> cc1e65623dc7, add max tries column to task instance
INFO  [alembic.runtime.migration] Running upgrade cc1e65623dc7 -> bdaa763e6c56, Make xcom value column a large binary
INFO  [alembic.runtime.migration] Running upgrade bdaa763e6c56 -> 947454bf1dff, add ti job_id index
INFO  [alembic.runtime.migration] Running upgrade 947454bf1dff -> d2ae31099d61, Increase text size for MySQL (not relevant for other DBs' text types)
INFO  [alembic.runtime.migration] Running upgrade d2ae31099d61 -> 0e2a74e0fc9f, Add time zone awareness
INFO  [alembic.runtime.migration] Running upgrade d2ae31099d61 -> 33ae817a1ff4, kubernetes_resource_checkpointing
INFO  [alembic.runtime.migration] Running upgrade 33ae817a1ff4 -> 27c6a30d7c24, kubernetes_resource_checkpointing
INFO  [alembic.runtime.migration] Running upgrade 27c6a30d7c24 -> 86770d1215c0, add kubernetes scheduler uniqueness
INFO  [alembic.runtime.migration] Running upgrade 86770d1215c0, 0e2a74e0fc9f -> 05f30312d566, merge heads
INFO  [alembic.runtime.migration] Running upgrade 05f30312d566 -> f23433877c24, fix mysql not null constraint
INFO  [alembic.runtime.migration] Running upgrade f23433877c24 -> 856955da8476, fix sqlite foreign key
INFO  [alembic.runtime.migration] Running upgrade 856955da8476 -> 9635ae0956e7, index-faskfail
INFO  [alembic.runtime.migration] Running upgrade 9635ae0956e7 -> dd25f486b8ea, add idx_log_dag
INFO  [alembic.runtime.migration] Running upgrade dd25f486b8ea -> bf00311e1990, add index to taskinstance
INFO  [alembic.runtime.migration] Running upgrade 9635ae0956e7 -> 0a2a5b66e19d, add task_reschedule table
INFO  [alembic.runtime.migration] Running upgrade 0a2a5b66e19d, bf00311e1990 -> 03bc53e68815, merge_heads_2
INFO  [alembic.runtime.migration] Running upgrade 03bc53e68815 -> 41f5f12752f8, add superuser field
INFO  [alembic.runtime.migration] Running upgrade 41f5f12752f8 -> c8ffec048a3b, add fields to dag
INFO  [alembic.runtime.migration] Running upgrade c8ffec048a3b -> dd4ecb8fbee3, Add schedule interval to dag
INFO  [alembic.runtime.migration] Running upgrade dd4ecb8fbee3 -> 939bb1e647c8, task reschedule fk on cascade delete
INFO  [alembic.runtime.migration] Running upgrade c8ffec048a3b -> a56c9515abdc, Remove dag_stat table
INFO  [alembic.runtime.migration] Running upgrade 939bb1e647c8 -> 6e96a59344a4, Make TaskInstance.pool not nullable
INFO  [alembic.runtime.migration] Running upgrade 6e96a59344a4 -> 74effc47d867, change datetime to datetime2(6) on MSSQL tables
INFO  [alembic.runtime.migration] Running upgrade 939bb1e647c8 -> 004c1210f153, increase queue name size limit
(.sandbox) [airflow@localhost airflow]$ 

Of course you might move database from say sqlite to postgres.
It is unclear which is appropriate for that circumstance.
It is also unclear how the webserver and scheduler know where to look for the configuration?
Perhaps they look in airflow.cfg first to find out where the database is and then look into the database? This seems redundant.

Answer 1

db reset will delete all entries from the metadata database. This includes all dag runs, Variables and Connections.

db init is only run once, when airflow is installed.

Generally we aren't too worried about the dag runs. but the Variables and connections can be annoying to recreate as they often contain secret and sensitive data, which may not be duplicated as a matter of security best practice.

db init is also idempotent, so this can be run as often as you choose to, without needing to worry about the database changing.

Answer 2

The above explanation is right but the commands are wrong. A working command for reset is - airflow db reset A working command for init (set db) is - airflow db init