Improved Handling of DAYS_TO_RETAIN in Backup Script

postgres-appliance/scripts/postgres_backup.sh

@@ -1,17 +1,14 @@
 #!/bin/bash
 
-function log
-{
+# Log function to capture timestamped logs
+function log {
     echo "$(date "+%Y-%m-%d %H:%M:%S.%3N") - $0 - $*"
 }
 
-[[ -z $1 ]] && echo "Usage: $0 PGDATA" && exit 1
-
+# Check if the script is provided with the PGDATA argument
+[[ -z $1 ]] && log "Error: PGDATA is missing!" && echo "Usage: $0 PGDATA" && exit 1
 log "I was called as: $0 $*"
-
-
 readonly PGDATA=$1
-DAYS_TO_RETAIN=$BACKUP_NUM_TO_RETAIN
 
 IN_RECOVERY=$(psql -tXqAc "select pg_catalog.pg_is_in_recovery()")
 readonly IN_RECOVERY
@@ -21,52 +18,75 @@ elif [[ $IN_RECOVERY == "t" ]]; then
     [[ "$WALG_BACKUP_FROM_REPLICA" != "true" ]] && log "Cluster is in recovery, not running backup" && exit 0
 else
     log "ERROR: Recovery state unknown: $IN_RECOVERY" && exit 1
-fi
 
-# leave at least 2 days base backups before creating a new one
-[[ "$DAYS_TO_RETAIN" -lt 2 ]] && DAYS_TO_RETAIN=2
+# Ensure DAYS_TO_RETAIN is set, either externally or from BACKUP_NUM_TO_RETAIN
+if [[ -z $DAYS_TO_RETAIN ]]; then
+    DAYS_TO_RETAIN=$BACKUP_NUM_TO_RETAIN
+    log "DAYS_TO_RETAIN was not set. Using BACKUP_NUM_TO_RETAIN value: $DAYS_TO_RETAIN"
+
+    # Make sure there are at least 2 days of base backups before creating a new one
+    [[ "$DAYS_TO_RETAIN" -lt 2 ]] && DAYS_TO_RETAIN=2
+    log "Ensuring DAYS_TO_RETAIN is at least 2. Current value: $DAYS_TO_RETAIN"
+fi
 
+# Decide whether to use wal-g or wal-e for backup based on USE_WALG_BACKUP flag
 if [[ "$USE_WALG_BACKUP" == "true" ]]; then
     readonly WAL_E="wal-g"
+    log "Using wal-g for backup."
+
+    # Optionally set compression method for wal-g if provided
     [[ -z $WALG_BACKUP_COMPRESSION_METHOD ]] || export WALG_COMPRESSION_METHOD=$WALG_BACKUP_COMPRESSION_METHOD
     export PGHOST=/var/run/postgresql
 else
     readonly WAL_E="wal-e"
-
-    # Ensure we don't have more workes than CPU's
-    POOL_SIZE=$(grep -c ^processor /proc/cpuinfo 2>/dev/null || 1)
+    log "Using wal-e for backup."
+
+    # Determine pool size based on CPU count, but cap it at 4 to avoid excessive parallelism
+    POOL_SIZE=$(grep -c ^processor /proc/cpuinfo 2>/dev/null || echo 1)
     [ "$POOL_SIZE" -gt 4 ] && POOL_SIZE=4
     POOL_SIZE=(--pool-size "$POOL_SIZE")
+    log "POOL_SIZE set to $POOL_SIZE"
 fi
 
-BEFORE=""
-LEFT=0
-
+# Initialization
+BEFORE=""  # Backup candidate for deletion
+LEFT=0    # Counter for backups that will remain
 NOW=$(date +%s -u)
 readonly NOW
+
+log "Listing existing backups..."
+# Loop through the existing backups and check if they qualify for deletion
 while read -r name last_modified rest; do
     last_modified=$(date +%s -ud "$last_modified")
+
+    # If a backup's age exceeds DAYS_TO_RETAIN, consider it for deletion
     if [ $(((NOW-last_modified)/86400)) -ge $DAYS_TO_RETAIN ]; then
+        log "Backup $name is old enough for deletion."
         if [ -z "$BEFORE" ] || [ "$last_modified" -gt "$BEFORE_TIME" ]; then
             BEFORE_TIME=$last_modified
             BEFORE=$name
         fi
     else
-        # count how many backups will remain after we remove everything up to certain date
+        # Otherwise, increment the counter for backups that will remain
         ((LEFT=LEFT+1))
     fi
 done < <($WAL_E backup-list 2> /dev/null | sed '0,/^name\s*\(last_\)\?modified\s*/d')
 
-# we want keep at least N backups even if the number of days exceeded
-if [ -n "$BEFORE" ] && [ $LEFT -ge $DAYS_TO_RETAIN ]; then
+log "Total backups to retain: $LEFT. Target for deletion is: $BEFORE"
+
+# Ensure a certain number of backups remain, even if their age exceeds DAYS_TO_RETAIN
+if [ -n "$BEFORE" ] && [ $LEFT -ge $BACKUP_NUM_TO_RETAIN ]; then
+    log "Deleting backups before $BEFORE..."
+    # Use appropriate deletion command based on whether wal-g or wal-e is being used
     if [[ "$USE_WALG_BACKUP" == "true" ]]; then
-        $WAL_E delete before FIND_FULL "$BEFORE" --confirm
+        $WAL_E delete retain $LEFT --confirm
     else
         $WAL_E delete --confirm before "$BEFORE"
     fi
+else
+    log "No backups were deleted."
 fi
 
-# push a new base backup
-log "producing a new backup"
-# We reduce the priority of the backup for CPU consumption
+# Push a new base backup with reduced CPU priority
+log "Producing a new backup..."
 exec nice -n 5 $WAL_E backup-push "$PGDATA" "${POOL_SIZE[@]}"