Log all queries in the official Postgres docker image

Setting log_destination back to stderr did the trick for me without creating a new image:

version: "2.2"
services:
  db:
    image: postgres:12-alpine
    command: ["postgres", "-c", "log_statement=all", "-c", "log_destination=stderr"]

And then I was able to trace the statements using docker-compose logs -f db.
Should work with other versions too, but I only tested it with postgres:12-alpine.

Edit: At the time of writing log_destination was not set to stderr in this image. This may have changed later on but this method still works for me even in newer images.

In case of running docker run directly from docker command, try follow command:

# single line to copy
docker run -d -e POSTGRES_USER=user -e POSTGRES_PASSWORD=pass -e POSTGRES_DB=postgres -p 5432:5432 --name db postgres:10 postgres -c log_statement=all

# split to read. 
docker run -d \
    -e POSTGRES_USER=user \
    -e POSTGRES_PASSWORD=pass \
    -e POSTGRES_DB=postgres \
    -p 5432:5432 \
    --name db \
    postgres:10 postgres \
    -c log_statement=all

The tailing part is overriding command as described here overriding docker file

Good luck!

Refer to this, you should enable logging_collector, then you can see incoming queries in log_directory's log_filename.

And to enable it in docker logs, you had to make some trick to make it, one solution is as follows:

wrapper.sh:

#!/usr/bin/env bash
mkdir /logs
touch /logs/postgresql.log
chmod -R 777 /logs
tail -f /logs/* &
/docker-entrypoint.sh "$@"

Above will use tail to monitor /logs/postgresql.log which will later be used by postgresql's logging_collector, and show it docker logs.

Dockerfile:

FROM postgres:11.1-alpine
COPY wrapper.sh /
RUN chmod +x /wrapper.sh
ENTRYPOINT ["/wrapper.sh"]
CMD ["postgres", "-c", "logging_collector=on", "-c", "log_directory=/logs", "-c", "log_filename=postgresql.log", "-c", "log_statement=all"]

Above will use customize wrapper.sh, it will first monitor the postgre log, print it, and then contiune to execute the default docker-entrypoint.sh to start postgresql server.

After container start, show logs before incoming queries:

orange@orange:~/abc$ docker build -t abc:1 .
orange@orange:~/abc$ docker run -idt abc:1
orange@orange:~/abc$ docker ps
CONTAINER ID        IMAGE                  COMMAND                  CREATED             STATUS              PORTS               NAMES
c9112eb785e5        abc:1                  "/wrapper.sh postgre…"   2 seconds ago       Up 1 second         5432/tcp            loving_joliot
orange@orange:~/abc$ docker logs loving_joliot
The files belonging to this database system will be owned by user "postgres".
......
2019-07-13 03:38:14.030 UTC [46] LOG:  database system was shut down at 2019-07-13 03:38:13 UTC
2019-07-13 03:38:14.034 UTC [10] LOG:  database system is ready to accept connections

Simulate some incoming queries, and see logs again:

orange@orange:~/abc$ docker exec -it -u postgres loving_joliot psql -c "SELECT datname FROM pg_database;"
  datname
-----------
 postgres
 template1
 template0
(3 rows)
orange@orange:~/abc$ docker logs loving_joliot
The files belonging to this database system will be owned by user "postgres".
......
2019-07-13 03:38:14.030 UTC [46] LOG:  database system was shut down at 2019-07-13 03:38:13 UTC
2019-07-13 03:38:14.034 UTC [10] LOG:  database system is ready to accept connections
2019-07-13 03:41:22.859 UTC [62] LOG:  statement: SELECT datname FROM pg_database;

You can see above we simulate a sql execute SELECT datname FROM pg_database;, and in docker logs we could already see this sql.

According to the documentation of the official Postgres image (section Database Configuration) you can either

• inject a custom configuration file (e.g. by means of adjusting the default configuration file) or
• start the container setting the configuration parameters required.

In the latter case simply start the container with

$ docker run -d --name some-postgres postgres -c log_statement=all

It makes use of Overriding Dockerfile image defaults.

If you'd like to enable additional logging options check out the Error reporting and Logging section of the PostgreSQL docs.