wan
ff3f6732e9
SHOW() pretty-renders units (60s -> '1min'), which broke the post-up check after a successful apply. Compare pg_settings.setting (base-unit raw values) instead - rendering-proof.
106 lines
4.2 KiB
Bash
106 lines
4.2 KiB
Bash
#!/usr/bin/env bash
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# 010-tune-postgres - Memory & stability tuning for the 1GB e2-micro host
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# (B-tier of the 2026-08 tuning review). Settings land as a conf.d drop-in;
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# postgresql.conf itself stays pristine (include_dir = 'conf.d' is stock).
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#
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# max_connections 100 -> 30 each backend costs MBs; real
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# concurrency comes from PgBouncer
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# (013). 30 = pool 20 + admin headroom
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# effective_cache_size 4GB -> 768MB planner hint; box has 1GB, the 4GB
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# default overrates cache -> bad plans
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# work_mem 4MB (explicit, equals default; kept for determinism)
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# statement_timeout 0 -> 30s runaway-query guard; long migrations:
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# SET statement_timeout = 0; in-session
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# idle_in_transaction_session_timeout 0 -> 60s leaked transactions block
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# vacuum and hold locks; kill them
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# temp_file_limit -1 -> 2GB per-backend sort-spill cap so one bad
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# query cannot fill the 20G data disk
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# up: write drop-in; restart only if max_connections changes, else reload
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# down: remove drop-in; restart (restoring max_connections needs it)
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set -euo pipefail
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PGBIN=/etc/postgresql/18/main
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CONF=$PGBIN/conf.d/010-tune-postgres.conf
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CLUSTER=$(pg_lsclusters --no-header | awk 'NR==1{print $1"/"$2}')
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# desired state as "guc raw_value" pairs, compared against pg_settings.setting
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# (each GUC's base unit). Immune to SHOW()'s pretty unit rendering -
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# SHOW renders 60000ms as '1min', 2097152kB as '2GB', etc.
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# max_connections - effective_cache_size 8kB
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# work_mem kB *_timeout ms
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# temp_file_limit kB
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WANT=(
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'max_connections 30'
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'effective_cache_size 98304' # 768MB
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'work_mem 4096' # 4MB
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'statement_timeout 30000' # 30s
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'idle_in_transaction_session_timeout 60000' # 60s
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'temp_file_limit 2097152' # 2GB
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)
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pg() { runuser -u postgres -- psql -d postgres -v ON_ERROR_STOP=1 -tAc "$1"; }
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write_conf() {
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install -d -m 755 "$PGBIN/conf.d"
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cat > "$CONF" <<'EOF'
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# managed by sysmig 010-tune-postgres - memory & stability for 1GB e2-micro
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max_connections = 30
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effective_cache_size = 768MB
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work_mem = 4MB
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statement_timeout = 30s
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idle_in_transaction_session_timeout = 60s
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temp_file_limit = 2GB
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EOF
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chown root:postgres "$CONF"
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chmod 644 "$CONF"
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}
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case "${1:-}" in
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up)
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write_conf
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if [[ $(pg 'SHOW max_connections') != 30 ]]; then
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pg_ctlcluster "$CLUSTER" restart
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pg_isready -q
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echo " cluster restarted (max_connections requires it)"
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else
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pg_ctlcluster "$CLUSTER" reload
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echo " cluster reloaded"
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fi
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for kv in "${WANT[@]}"; do
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read -r guc want <<<"$kv"
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got=$(pg "SELECT setting FROM pg_settings WHERE name='$guc'")
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[[ $got == "$want" ]] || { echo "FATAL: $guc is '$got', expected '$want'" >&2; exit 1; }
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done
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echo " ${#WANT[@]} memory/stability settings active"
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;;
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status)
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if [[ $EUID -eq 0 ]]; then
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q() { runuser -u postgres -- psql -d postgres -v ON_ERROR_STOP=1 -tAc "$1"; }
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elif psql -d postgres -tAc 'SELECT 1' >/dev/null 2>&1; then
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q() { psql -d postgres -v ON_ERROR_STOP=1 -tAc "$1"; }
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else
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echo "? needs root or peer DB access to verify"
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exit 2
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fi
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[[ -f $CONF ]] || { echo "DRIFT drop-in $CONF missing"; exit 1; }
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bad=()
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for kv in "${WANT[@]}"; do
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read -r guc want <<<"$kv"
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got=$(q "SELECT setting FROM pg_settings WHERE name='$guc'" 2>/dev/null)
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[[ $got == "$want" ]] || bad+=("$guc=$got(want $want)")
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done
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if ((${#bad[@]})); then echo "DRIFT ${bad[*]}"; exit 1; fi
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echo "OK ${#WANT[@]} settings active (max_connections=30, timeouts, temp_file_limit)"
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;;
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down)
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rm -f "$CONF"
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if [[ $(pg 'SHOW max_connections') == 30 ]]; then
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pg_ctlcluster "$CLUSTER" restart
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echo " drop-in removed, cluster restarted (defaults restored)"
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else
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pg_ctlcluster "$CLUSTER" reload
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echo " drop-in removed, cluster reloaded"
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fi
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;;
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esac
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