* moved https://og2k.com/pub/configure/software/db/postgresql/postgres@rpi.md to https://github.com/InstallAndUse/RPi

read_temperature_from_DS18x20_sensors/README.md

@@ -1,4 +1,5 @@
 #
+# 2020 06 12  + init /A
 # 2022 03 18  + published on https://github.com/InstallAndUse/RPi /A
 #
 
@@ -31,12 +32,60 @@
 # check you have python installed (probabaly on RPi it is)
  which python
      /usr/bin/python
+
+# eventually, run first read
  root@(host):/home/pi/meter# ./read_ds18x20.py
      /sys/bus/w1/devices/10-000800e489b3;27000
      /sys/bus/w1/devices/10-00080280a759;29500#
 
 
- change DB credentials in shell script (user) and (pass)
+# prepare PostgreSQL database for telemetry gathering (satellite)
+#
+
+# install postgres
+sudo su
+apt install postgresql
+
+# start cluster
+pg_ctlcluster 11 main start
+
+# connect to DB
+su - postgres
+psql
+
+# create user (user is named accordingly to hostname to simplicity in future replication configuration)
+CREATE USER (user) WITH PASSWORD '(pass)';
+\du
+
+# create database (there is only one DB named telemetry to avoid confusion)
+CREATE DATABASE telemetry;
+\l
+
+# grant access to (user)
+GRANT ALL ON DATABASE telemetry TO (user) ;
+\l telemetry
+
+# connect to DB and create table
+# tables are named individually to keep order for replication
+# telemetry_hostname represents table with telemetry for hostname
+\c telemetry
+CREATE TABLE telemetry_host();
+\d
+\d telemetry_host
+
+# adding columns to table
+# it is importnant to set NOT NULL, because we do not want to keep DB clean and tidy
+ALTER TABLE telemetry_host ADD COLUMN timestamp TIMESTAMPTZ PRIMARY KEY;
+ALTER TABLE telemetry_host ADD COLUMN sensor CHAR(64) NOT NULL;
+ALTER TABLE telemetry_host ADD COLUMN value INTEGER NOT NULL;
+\d telemetry_host
+
+# grant access on table to (user)
+???
+
+
+
+# change DB credentials in shell script (user) and (pass)
  nano ./read_ds18x20.sh
  pi@(host):~/meter $ ./read_ds18x20.py | ./read_ds18x20.sh
      INSERT 0 1

setup_replication_of_historical_data_from_sensors_to_server_using_PostgreSQL/README.md

@@ -1,2 +1,90 @@
 # In this project we shall setup replication between PostgreSQL DataBases (DBs) to move historical data of DS18x20 sensors from measurement units to server.
+
+# 2020 06 12  + init /A
 # 2022 03 19  + published on https://github.com/InstallAndUse/RPi /A
+
+
+# set publication (logical replication)
+# first we need to create user who will be subscribed to this publication
+# (again, to keep it simple, (user2) is a name of (host2) which will login)
+CREATE USER (user2) WITH PASSWORD '(pass2)';
+\du
+CREATE PUBLICATION telemetry_host FOR TABLE telemetry_host;
+SELECT * FROM pg_catalog.pg_publication;
+\d telemetry_host
+
+# grant readonly access on subscription to (user2)
+ALTER ROLE (user2) REPLICATION ;
+GRANT SELECT ON telemetry_host TO (user2);
+\c telemetry
+GRANT ALL ON TABLE public.telemetry_lab5rp41 TO lab5rp41 ;
+
+# exit to console and insert into DB first entry
+exit
+psql -h localhost -U lab5rp41 -d telemetry -c "INSERT INTO telemetry_lab5rp41 (timestamp, sensor, value) VALUES (now(), 'test_sensor', '12345')"
+    Password for user (user):
+    INSERT 0 1
+
+# check select with (user2)
+psql -h localhost -U (user2) -d telemetry -c "SELECT * FROM telemetry_host"
+    Password for user (user2):
+               timestamp           | value |                              sensor
+    -------------------------------+-------+------------------------------------------------------------------
+     2020-06-12 08:58:36.732033+01 | 12345 | test_sensor
+    (1 row)
+
+# open access to database from network
+# trying access DB to IP address (not to localhost), should denied access
+ip a
+psql -h (host_ip) -U (user2) -d telemetry -c "SELECT * FROM telemetry_host"
+    psql: could not connect to server: Connection refused
+      Is the server running on host "192.168.xxx.xxx" and accepting
+      TCP/IP connections on port 5432?
+# become root (logout postgres)
+exit
+sudo
+
+# on moment of writing, configs for postgres on RPi are here, may differ for different linux distros
+# enable listening on all interfaces
+nano /etc/postgresql/11/main/postgresql.conf
+    # - Connection Settings -
+    listen_addresses = '*'
+    wal_level = logical
+
+# enable auth method
+nano /etc/postgresql/11/main/pg_hba.conf
+# we need to open network access for IPv4 and IPv6 (as RPi obtain IPv6 from DHCP as well)
+# in this case, I am opening only access to DB telemetry and only for user (user2)
+    # IPv4 local connections:
+    host    all             all            127.0.0.1/32            md5
+    host    replication     (user2)        0.0.0.0/0               md5
+    host    telemetry       (user2)        0.0.0.0/0               md5
+    # IPv6 local connections:
+    host    all             all            ::1/128                 md5
+    host    replication     (user2)        ::0/0                   md5
+    host    telemetry       (user2)        ::0/0                   md5
+
+# save, and restart postresql cluster
+systemctl | grep sql
+systemctl restart postgresql@11-main.service
+
+# check that postgres is listening on network interfaces
+netstat -ntap | grep 5432
+    # postgres listens only on localhost
+    tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      1796/postgres
+    tcp6       0      0 ::1:5432                :::*                    LISTEN      1796/postgres
+
+# now try again
+psql -h (host_ip) -U (user2) -d telemetry -c "SELECT * FROM telemetry_host"
+    Password for user lab5dle4:
+               timestamp           | value |                              sensor
+    -------------------------------+-------+------------------------------------------------------------------
+     2020-06-12 08:58:36.732033+01 | 12345 | test_sensor
+    (1 row)
+# it is important to set it up correctly to this point to avoid confusion later on setting up subsciber-side
+
+# open firewall, if needed for tcp/5432 (by default it is opened)
+iptables -L -n -v --line-numbers | grep 5432
+
+
+# reboot and retry last SELECT command, everything should work