Drop database users prior to DROP/CREATE database.

This fixes an annoying issue where one tries to rebuild the database,
and it fails due to there being existing connections.

The one thing that is potentially scary about this implementation is
that it means it's now a lot easier to accidentally drop your
production database by running the wrong script; might be worth adding
a "--force" flag controlling this behavior or something.

Thanks to Nemanja Stanarevic and Neeraj Wahi for prototypes of this
implementation!  They did most of the work and testing for this.

scripts/setup/postgres-init-db

@@ -1,8 +1,14 @@
-#!/bin/sh -xe
+#!/bin/bash
+set -e
+set -x
 
 # Make sure the current working directory is readable
 cd /
 
+# Drop any open connections to any old database.  Hackishly call using
+# source because postgres user can't read /root/zulip/scripts/setup.
+source "$(dirname "$0")/terminate-psql-sessions" postgres zulip zulip_base
+
 su postgres -c psql <<EOF
 CREATE USER zulip;
 ALTER ROLE zulip SET search_path TO zulip,public;
@@ -15,6 +21,7 @@ CREATE SCHEMA zulip AUTHORIZATION zulip;
 CREATE EXTENSION tsearch_extras SCHEMA zulip;
 EOF
 
+# Clear memcached to avoid contamination from previous database state
 sh "$(dirname "$0")/flush-memcached"
 
 echo "Database created"

scripts/setup/terminate-psql-sessions

@@ -0,0 +1,31 @@
+#!/bin/bash
+set -e
+set -x
+
+cd /
+if [ "$EUID" -eq 0 ]; then
+    version=$(su postgres -c 'psql -A -t -d postgres -c "show server_version"')
+else
+    version=$(psql -A -t -d postgres -c "show server_version")
+fi
+
+major=$(echo $version | cut -d. -f1,2)
+pid_style=$(echo "$major > 9.1" | bc -l)
+username=$1
+shift
+tables=$(echo "'$@'" | sed "s/ /','/g")
+if [ "$pid_style" = "1" ]; then
+    pidname="pid"
+else
+    pidname="procpid"
+fi
+
+if [ "$EUID" -eq 0 ]; then
+    su postgres -c psql postgres postgres <<EOF
+SELECT pg_terminate_backend($pidname) FROM pg_stat_activity WHERE datname IN ($tables);
+EOF
+else
+    psql -h localhost postgres "$username" <<EOF
+SELECT pg_terminate_backend($pidname) FROM pg_stat_activity WHERE datname IN ($tables);
+EOF
+fi

tools/do-destroy-rebuild-database

@@ -1,5 +1,7 @@
 #!/bin/sh -xe
 
+"$(dirname "$0")/../scripts/setup/terminate-psql-sessions" zulip zulip zulip_base
+
 psql -h localhost postgres zulip <<EOF
 DROP DATABASE IF EXISTS zulip;
 CREATE DATABASE zulip TEMPLATE zulip_base;

tools/generate-fixtures

@@ -11,6 +11,7 @@ if [ "$template_grep_error_code" == "0" ]; then
     if [ -e zerver/fixtures/migration-status ] &&
         cmp -s zerver/fixtures/available-migrations zerver/fixtures/migration-status &&
         [ "$1" != "--force" ]; then
+        "$(dirname "$0")/../scripts/setup/terminate-psql-sessions" zulip zulip_test zulip_test_base zulip_test_template
         psql -h localhost postgres zulip_test << EOF
 DROP DATABASE IF EXISTS zulip_test;
 CREATE DATABASE zulip_test TEMPLATE zulip_test_template;
@@ -22,6 +23,8 @@ fi
 
 mkdir -p zerver/fixtures
 
+"$(dirname "$0")/../scripts/setup/terminate-psql-sessions" zulip zulip_test zulip_test_base zulip_test_template
+
 psql -h localhost postgres zulip_test <<EOF
 DROP DATABASE IF EXISTS zulip_test;
 CREATE DATABASE zulip_test TEMPLATE zulip_test_base;

tools/postgres-init-dev-db

@@ -49,6 +49,8 @@ else
 fi
 chmod go-rw ~/.pgpass
 
+"$(dirname "$0")/../scripts/setup/terminate-psql-sessions" "$USERNAME" "$DBNAME" "$DBNAME_BASE"
+
 psql -h localhost postgres "$USERNAME" <<EOF
 DROP DATABASE IF EXISTS $DBNAME;
 DROP DATABASE IF EXISTS $DBNAME_BASE;