chore(entrypoint.sh): improve shell script

Author: kosheeta

entrypoint.sh

@@ -1,72 +1,63 @@
 #! /bin/sh
 
-if [[ -z "$POSTGRES_HOST" ]]; then
-  echo "POSTGRES_HOST environment variable is required"
-  exit 1
-fi
-
-POSTGRES_PORT="${POSTGRES_PORT:-5432}"
-
-if [[ -z "$POSTGRES_USER" ]]; then
-  echo "POSTGRES_USER environment variable is required"
-  exit 1
-fi
-
-if [[ -z "$POSTGRES_PASSWORD" ]]; then
-  echo "POSTGRES_PASSWORD environment variable is required"
-  exit 1
-fi
-
-if [[ -z "$S3_ENDPOINT" ]]; then
-  echo "S3_ENDPOINT environment variable is required"
-  exit 1
-fi
-
-if [[ -z "$S3_ACCESS_KEY" ]]; then
-  echo "S3_ACCESS_KEY environment variable is required"
-  exit 1
-fi
-
-if [[ -z "$S3_SECRET_KEY" ]]; then
-  echo "S3_SECRET_KEY environment variable is required"
-  exit 1
-fi
-
-if [[ -z "$S3_BUCKET" ]]; then
-  echo "S3_BUCKET environment variable is required"
-  exit 1
-fi
-
-S3_FILE_PREFIX="${S3_FILE_PREFIX:-backup-}"
-
+# with these settings, certain common errors will cause the script to immediately fail, explicitly and loudly
+set -euo pipefail
+
+# required environment variables
+: "${POSTGRES_HOST}"
+: "${POSTGRES_USER}"
+: "${POSTGRES_PASSWORD}"
+: "${S3_ENDPOINT}"
+: "${S3_ACCESS_KEY}"
+: "${S3_SECRET_KEY}"
+: "${S3_BUCKET}"
+
+# not required environment variables with default values
+: "${POSTGRES_PORT:=5432}"
+: "${S3_FILE_PREFIX:=backup-}"
+: "${PG_DUMPALL_EXTRA_ARGS:=}"
+: "${OPENSSL_ENC_EXTRA_ARGS:=}"
+: "${AWS_S3_CP_EXTRA_ARGS:=}"
+
+# print pg_dumpall version
 pg_dumpall -V
+
 echo "Creating a dump of all databases..."
 
-SOURCE_FILE="output.bak.gz"
-DESTINATION_FILE="${S3_FILE_PREFIX}$(date +"%Y-%m-%dT%H:%M:%SZ").bak.gz"
+LOCAL_FILE="output.bak.gz"
+REMOTE_FILE="${S3_FILE_PREFIX}$(date +"%Y-%m-%dT%H:%M:%SZ").bak.gz"
 
+# PGPASSWORD is required for pg_dumpall
 export PGPASSWORD=$POSTGRES_PASSWORD
-pg_dumpall -h $POSTGRES_HOST -p $POSTGRES_PORT -U $POSTGRES_USER $PG_DUMPALL_EXTRA_ARGS | gzip > $SOURCE_FILE
+
+# dump all databases and gzip to file
+pg_dumpall -h $POSTGRES_HOST -p $POSTGRES_PORT -U $POSTGRES_USER $PG_DUMPALL_EXTRA_ARGS | gzip > $LOCAL_FILE
 
 echo "Dump created"
 
+# if encryption password is set and not an empty string
 if [[ -z "$ENCRYPTION_PASSWORD" ]]; then
   echo "Encryption disabled"
 else
   echo "Encryption of the dump..."
 
-  openssl enc -aes-256-cbc -pbkdf2 -iter 20000 -in $SOURCE_FILE -out ${SOURCE_FILE}.enc -k $ENCRYPTION_PASSWORD $OPENSSL_ENC_EXTRA_ARGS
+  # encrypt local dump
+  openssl enc -aes-256-cbc -pbkdf2 -iter 20000 -in $LOCAL_FILE -out ${LOCAL_FILE}.enc -k $ENCRYPTION_PASSWORD $OPENSSL_ENC_EXTRA_ARGS
 
-  SOURCE_FILE="${SOURCE_FILE}.enc"
-  DESTINATION_FILE="${DESTINATION_FILE}.enc"
+  # update file extensions
+  LOCAL_FILE="${LOCAL_FILE}.enc"
+  REMOTE_FILE="${REMOTE_FILE}.enc"
 
   echo "Dump encrypted"
 fi
 
 echo "Uploading the dump to S3..."
 
+# AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY is required for aws
 export AWS_ACCESS_KEY_ID=$S3_ACCESS_KEY
 export AWS_SECRET_ACCESS_KEY=$S3_SECRET_KEY
-aws s3 cp $SOURCE_FILE s3://$S3_BUCKET/$DESTINATION_FILE --endpoint-url $S3_ENDPOINT $AWS_S3_CP_EXTRA_ARGS
+
+# upload local dump to s3
+aws s3 cp $LOCAL_FILE s3://$S3_BUCKET/$REMOTE_FILE --endpoint-url $S3_ENDPOINT $AWS_S3_CP_EXTRA_ARGS
 
 echo "Dump uploaded"