Merge pull request #99 from fly-apps/add_repl_slot_admin

Add admin api to view Replication slots

Author: DAlperin

pkg/commands/admin.go

@@ -3,6 +3,8 @@ package commands
 import (
 	"encoding/json"
 	"fmt"
+	"github.com/fly-examples/postgres-ha/pkg/flypg"
+	"github.com/pkg/errors"
 	"io"
 	"net/http"
 	"os/exec"
@@ -174,3 +176,115 @@ func handleUpdateSettings(w http.ResponseWriter, r *http.Request) {
 
 	render.JSON(w, resp, http.StatusOK)
 }
+
+func handleReplicationStats(w http.ResponseWriter, r *http.Request) {
+	conn, close, err := localConnection(r.Context())
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+	defer close()
+
+	stats, err := admin.ResolveReplicationLag(r.Context(), conn)
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+
+	resp := &Response{Result: stats}
+
+	render.JSON(w, resp, http.StatusOK)
+}
+
+func handleStolonDBUid(w http.ResponseWriter, r *http.Request) {
+	env, err := util.BuildEnv()
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	data, err := stolon.FetchClusterData(env)
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	node, err := flypg.NewNode()
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	for _, db := range data.DBs {
+		if db.Spec.KeeperUID == node.KeeperUID {
+			resp := &Response{Result: db.UID}
+			render.JSON(w, resp, http.StatusOK)
+			return
+		}
+	}
+
+	render.Err(w, errors.New("can't find db"))
+}
+
+func handleEnableReadonly(w http.ResponseWriter, r *http.Request) {
+	conn, close, err := localConnection(r.Context())
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+	defer close()
+
+	err = admin.SetReadonly(r.Context(), conn, true)
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	args := []string{"root", "pkill", "haproxy"}
+
+	cmd := exec.Command("gosu", args...)
+
+	if err := cmd.Run(); err != nil {
+		render.Err(w, err)
+		return
+	}
+
+	if cmd.ProcessState.ExitCode() != 0 {
+		err := fmt.Errorf(cmd.ProcessState.String())
+		render.Err(w, err)
+		return
+	}
+
+	resp := &Response{Result: true}
+
+	render.JSON(w, resp, http.StatusOK)
+}
+
+func handleDisableReadonly(w http.ResponseWriter, r *http.Request) {
+	conn, close, err := localConnection(r.Context())
+	if err != nil {
+		render.Err(w, err)
+		return
+	}
+	defer close()
+
+	err = admin.SetReadonly(r.Context(), conn, false)
+	if err != nil {
+		render.Err(w, err)
+	}
+
+	args := []string{"root", "pkill", "haproxy"}
+
+	cmd := exec.Command("gosu", args...)
+
+	if err := cmd.Run(); err != nil {
+		render.Err(w, err)
+		return
+	}
+
+	if cmd.ProcessState.ExitCode() != 0 {
+		err := fmt.Errorf(cmd.ProcessState.String())
+		render.Err(w, err)
+		return
+	}
+
+	resp := &Response{Result: true}
+
+	render.JSON(w, resp, http.StatusOK)
+}

pkg/commands/handler.go

@@ -32,6 +32,10 @@ func Handler() http.Handler {
 		r.Get("/failover/trigger", handleFailoverTrigger)
 		r.Get("/restart", handleRestart)
 		r.Get("/settings/view", handleViewSettings)
+		r.Get("/replicationstats", handleReplicationStats)
+		r.Post("/readonly/enable", handleEnableReadonly)
+		r.Post("/readonly/disable", handleDisableReadonly)
+		r.Get("/dbuid", handleStolonDBUid)
 		r.Post("/settings/update", handleUpdateSettings)
 	})
 

pkg/flypg/admin/admin.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/md5"
 	"fmt"
+	"github.com/pkg/errors"
 	"os"
 	"strings"
 
@@ -252,6 +253,59 @@ func ResolveRole(ctx context.Context, pg *pgx.Conn) (string, error) {
 	return "leader", nil
 }
 
+type ReplicationStat struct {
+	Name string
+	Diff int
+}
+
+func ResolveReplicationLag(ctx context.Context, pg *pgx.Conn) ([]*ReplicationStat, error) {
+	sql := "select application_name, pg_current_wal_lsn() - flush_lsn as diff from pg_stat_replication;"
+
+	rows, err := pg.Query(ctx, sql)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var stats []*ReplicationStat
+	for rows.Next() {
+		var s ReplicationStat
+		if err := rows.Scan(&s.Name, &s.Diff); err != nil {
+			return nil, err
+		}
+		stats = append(stats, &s)
+	}
+	return stats, nil
+}
+
+func SetReadonly(ctx context.Context, pg *pgx.Conn, enable bool) error {
+	role, err := ResolveRole(ctx, pg)
+	if err != nil {
+		return err
+	}
+	if role != "leader" {
+		return errors.New("can't set non primary to read-only")
+	}
+
+	databases, err := ListDatabases(ctx, pg)
+	if err != nil {
+		return err
+	}
+
+	for _, db := range databases {
+		// exclude administrative dbs
+		if db.Name == "postgres" {
+			continue
+		}
+
+		sql := fmt.Sprintf("ALTER DATABASE %s SET default_transaction_read_only=%v;", db.Name, enable)
+		if _, err = pg.Exec(ctx, sql); err != nil {
+			return fmt.Errorf("failed to alter readonly state on db %s: %s", db.Name, err)
+		}
+	}
+
+	return nil
+}
+
 func ResolveSettings(ctx context.Context, pg *pgx.Conn, list []string) (*flypg.Settings, error) {
 	node, err := flypg.NewNode()
 	if err != nil {