PostgreSQL: connection refused error

Today, when I start a Rails app on local, the pg connection error was happened.

And restart the postgresql doesn’t resolve it.

brew services stop postgresql
brew services start postgresql

or

brew services restart postgresql

Through the postgresql log at /usr/local/var/log/postgres.log, the error message likes the following:

2019-12-23 18:08:35.962 CST [64396] HINT:  Is another postmaster (PID 410) running in data directory "/usr/local/var/postgres"?
2019-12-23 18:08:45.996 CST [64398] FATAL:  lock file "postmaster.pid" already exists
2019-12-23 18:08:45.996 CST [64398] HINT:  Is another postmaster (PID 410) running in data directory "/usr/local/var/postgres"?
2019-12-23 18:08:56.030 CST [64400] FATAL:  lock file "postmaster.pid" already exists
2019-12-23 18:08:56.030 CST [64400] HINT:  Is another postmaster (PID 410) running in data directory "/usr/local/var/postgres"?
2019-12-23 18:09:06.058 CST [64621] FATAL:  lock file "postmaster.pid" already exists
2019-12-23 18:09:06.058 CST [64621] HINT:  Is another postmaster (PID 410) running in data directory "/usr/local/var/postgres"?

Whoops, another postmaster progress exists which brings the connection refused error with me.

So, kill the exist postmaster to resolve it.

Get the PID

The above error log has display the PID info - postmaster (PID 410).

Also, you can find the details with following:

cat /usr/local/var/postgres/postmaster.pid

e.g.

410
/usr/local/var/postgres
1574126756
5432
/tmp
localhost
  5432001     65536
ready

Kill progress & restart pg

Then, kill it with kill -9.

kill -9 410

Restart the postgresql service via brew services restart postgresql.

The postgresql works fine now.

FYI:

Homebrew Services