Rate limit refactorings

- Swap unmaintained gopkg.in/mail.v2 for Shopify/gomail
- Better rate-limiting with time windows/frequency for APIs and mail
- Rate limit Gmail for 20 per hour (non-public information)

go.mod

@@ -4,8 +4,9 @@ go 1.21.6
 
 require (
 	github.com/BurntSushi/toml v1.3.2
-	github.com/KimMachineGun/automemlimit v0.4.0
+	github.com/KimMachineGun/automemlimit v0.5.0
 	github.com/PuerkitoBio/goquery v1.8.1
+	github.com/Shopify/gomail v0.0.0-20220729171026-0784ece65e69
 	github.com/araddon/dateparse v0.0.0-20210429162001-6b43995a97de
 	github.com/avast/retry-go/v4 v4.5.1
 	github.com/blang/semver/v4 v4.0.0
@@ -32,7 +33,6 @@ require (
 	go.uber.org/ratelimit v0.3.0
 	golang.org/x/oauth2 v0.16.0
 	google.golang.org/api v0.157.0
-	gopkg.in/mail.v2 v2.3.1
 )
 
 require (
@@ -79,6 +79,7 @@ require (
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/opencontainers/runtime-spec v1.1.0 // indirect
+	github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58 // indirect
 	github.com/pelletier/go-toml/v2 v2.1.1 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect

go.sum

@@ -6,10 +6,12 @@ cloud.google.com/go/compute/metadata v0.2.3/go.mod h1:VAV5nSsACxMJvgaAuX6Pk2Aawl
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/BurntSushi/toml v1.3.2 h1:o7IhLm0Msx3BaB+n3Ag7L8EVlByGnpq14C4YWiu/gL8=
 github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
-github.com/KimMachineGun/automemlimit v0.4.0 h1:qOjSDbAUENEL6fiKmRKuAVhPaLijpoEHFDTE+I+prp0=
-github.com/KimMachineGun/automemlimit v0.4.0/go.mod h1:pJhTW/nWJMj6SnWSU2TEKSlCaM+1N5Mej+IfS/5/Ol0=
+github.com/KimMachineGun/automemlimit v0.5.0 h1:BeOe+BbJc8L5chL3OwzVYjVzyvPALdd5wxVVOWuUZmQ=
+github.com/KimMachineGun/automemlimit v0.5.0/go.mod h1:di3GCKiu9Y+1fs92erCbUvKzPkNyViN3mA0vti/ykEQ=
 github.com/PuerkitoBio/goquery v1.8.1 h1:uQxhNlArOIdbrH1tr0UXwdVFgDcZDrZVdcpygAcwmWM=
 github.com/PuerkitoBio/goquery v1.8.1/go.mod h1:Q8ICL1kNUJ2sXGoAhPGUdYDJvgQgHzJsnnd3H7Ho5jQ=
+github.com/Shopify/gomail v0.0.0-20220729171026-0784ece65e69 h1:gPoXdwo3sKq8qcfMu/Nc/wkJMLKwe7kaG9Uo8tOj3cU=
+github.com/Shopify/gomail v0.0.0-20220729171026-0784ece65e69/go.mod h1:RS+Gaowa0M+gCuiFAiRMGBCMqxLrNA7TESTU/Wbblm8=
 github.com/andybalholm/cascadia v1.3.1/go.mod h1:R4bJ1UQfqADjvDa4P6HZHLh/3OxWWEqc0Sk8XGwHqvA=
 github.com/andybalholm/cascadia v1.3.2 h1:3Xi6Dw5lHF15JtdcmAHD3i1+T8plmv7BQ/nsViSLyss=
 github.com/andybalholm/cascadia v1.3.2/go.mod h1:7gtRlve5FxPPgIgX36uWBX58OdBsSS6lUvCFb+h7KvU=
@@ -198,6 +200,8 @@ github.com/modern-go/reflect2 v1.0.2 h1:xBagoLtFs94CBntxluKeaWgTMpvLxC4ur3nMaC9G
 github.com/modern-go/reflect2 v1.0.2/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
 github.com/opencontainers/runtime-spec v1.1.0 h1:HHUyrt9mwHUjtasSbXSMvs4cyFxh+Bll4AjJ9odEGpg=
 github.com/opencontainers/runtime-spec v1.1.0/go.mod h1:jwyrGlmzljRJv/Fgzds9SsS/C5hL+LL3ko9hs6T5lQ0=
+github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58 h1:onHthvaw9LFnH4t2DcNVpwGmV9E1BkGknEliJkfwQj0=
+github.com/pbnjay/memory v0.0.0-20210728143218-7b4eea64cf58/go.mod h1:DXv8WO4yhMYhSNPKjeNKa5WY9YCIEBRbNzFFPJbWO6Y=
 github.com/pelletier/go-toml/v2 v2.1.1 h1:LWAJwfNvjQZCFIDKWYQaM62NcYeYViCmWIwmOStowAI=
 github.com/pelletier/go-toml/v2 v2.1.1/go.mod h1:tJU2Z3ZkXwnxa4DPO899bsyIoywizdUvyaeZurnPPDc=
 github.com/peterbourgon/ff/v4 v4.0.0-alpha.4 h1:aiqS8aBlF9PsAKeMddMSfbwp3smONCn3UO8QfUg0Z7Y=

messenger/calendar.go

@@ -42,7 +42,8 @@ import (
 
 const (
 	CalendarAPILimit    = 5 // 5 req/s per user
-	CalendarMinDelay    = 1 * time.Second / CalendarAPILimit
+	CalendarWindow      = 1 * time.Second
+	CalendarMinDelay    = CalendarWindow / CalendarAPILimit
 	CalendarMaxResults  = 100
 	CalendarCredentials = "assets/calendar_credentials.json" // embedded Google Calendar credentials file
 
@@ -76,7 +77,7 @@ func Calendar(ctx context.Context, ch <-chan interface{}, name, tokFile string,
 	logger.Debug().Msg("Creating exams with Google Calendar API")
 
 	now := time.Now()
-	rl := ratelimit.New(CalendarAPILimit)
+	rl := ratelimit.New(CalendarAPILimit, ratelimit.Per(CalendarWindow))
 
 	// process all messages
 	for o := range ch {

messenger/discord.go

@@ -38,7 +38,8 @@ import (
 
 const (
 	DiscordAPILimit = 50 // 50 API req/s per user/IP
-	DiscordMinDelay = 1 * time.Second / DiscordAPILimit
+	DiscordWindow   = 1 * time.Second
+	DiscordMinDelay = DiscordWindow / DiscordAPILimit
 )
 
 var (
@@ -83,7 +84,7 @@ func Discord(ctx context.Context, ch <-chan interface{}, token string, userIDs [
 
 	logger.Debug().Msg("Sending a message through Discord")
 
-	rl := ratelimit.New(DiscordAPILimit)
+	rl := ratelimit.New(DiscordAPILimit, ratelimit.Per(DiscordWindow))
 
 	// process all messages
 	for o := range ch {

messenger/mail.go

@@ -27,17 +27,18 @@ import (
 	"strconv"
 	"time"
 
+	mail "github.com/Shopify/gomail"
 	"github.com/avast/retry-go/v4"
 	"github.com/dkorunic/e-dnevnik-bot/format"
 	"github.com/dkorunic/e-dnevnik-bot/logger"
 	"github.com/dkorunic/e-dnevnik-bot/msgtypes"
 	"go.uber.org/ratelimit"
-	"gopkg.in/mail.v2"
 )
 
 const (
-	MailSendLimit = 50 // 50 emails per second
-	MailMinDelay  = 1 * time.Second / MailSendLimit
+	MailSendLimit = 20 // 20 emails per 1 hour
+	MailWindow    = 1 * time.Hour
+	MailMinDelay  = MailWindow / MailSendLimit
 	MailSubject   = "Nova ocjena iz e-Dnevnika"
 )
 
@@ -71,7 +72,7 @@ func Mail(ctx context.Context, ch <-chan interface{}, server, port, username, pa
 		portInt = 465
 	}
 
-	rl := ratelimit.New(MailSendLimit)
+	rl := ratelimit.New(MailSendLimit, ratelimit.Per(MailWindow))
 
 	// process all messages
 	for o := range ch {

messenger/slack.go

@@ -37,7 +37,8 @@ import (
 
 const (
 	SlackAPILImit = 1 // typically 1 req/s per user
-	SlackMinDelay = 1 * time.Second / SlackAPILImit
+	SlackWindow   = 1 * time.Second
+	SlackMinDelay = SlackWindow / SlackAPILImit
 )
 
 var (
@@ -68,7 +69,7 @@ func Slack(ctx context.Context, ch <-chan interface{}, token string, chatIDs []s
 
 	logger.Debug().Msg("Sending message through Slack")
 
-	rl := ratelimit.New(SlackAPILImit)
+	rl := ratelimit.New(SlackAPILImit, ratelimit.Per(SlackWindow))
 
 	var err error
 

messenger/telegram.go

@@ -38,7 +38,8 @@ import (
 
 const (
 	TelegramAPILimit = 30 // 30 API req/s per user
-	TelegramMinDelay = 1 * time.Second / TelegramAPILimit
+	TelegramWindow   = 1 * time.Second
+	TelegramMinDelay = TelegramWindow / TelegramAPILimit
 )
 
 var (
@@ -77,7 +78,7 @@ func Telegram(ctx context.Context, ch <-chan interface{}, apiKey string, chatIDs
 
 	logger.Debug().Msg("Sending message through Telegram")
 
-	rl := ratelimit.New(TelegramAPILimit)
+	rl := ratelimit.New(TelegramAPILimit, ratelimit.Per(TelegramWindow))
 
 	// process all messages
 	for o := range ch {