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Fix message truncation, relates to #84

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This commit is contained in:
Philipp Heckel 2022-01-04 21:09:47 +01:00
parent 76d102f964
commit 2e40b895a7
2 changed files with 8 additions and 8 deletions
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10
server/server.go
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@ -138,7 +138,7 @@ var (
const (
firebaseControlTopic = "~control" // See Android if changed
emptyMessageBody = "triggered"
fcmMessageLimitReal = 4100 // see maybeTruncateFCMMessage for details
fcmMessageLimit = 4000 // see maybeTruncateFCMMessage for details
)
// New instantiates a new Server. It creates the cache and adds a Firebase
@ -230,15 +230,15 @@ func createFirebaseSubscriber(conf *Config) (subscriber, error) {
}
// maybeTruncateFCMMessage performs best-effort truncation of FCM messages.
// The docs says the limit is 4000 characters, but the real FCM message limit is 4100 of the
// serialized payload; I tested this diligently.
// The docs say the limit is 4000 characters, but during testing it wasn't quite clear
// what fields matter; so we're just capping the serialized JSON to 4000 bytes.
func maybeTruncateFCMMessage(m *messaging.Message) *messaging.Message {
s, err := json.Marshal(m)
if err != nil {
return m
}
if len(s) > fcmMessageLimitReal {
over := len(s) - fcmMessageLimitReal + 16 // = len("truncated":"1",), sigh ...
if len(s) > fcmMessageLimit {
over := len(s) - fcmMessageLimit + 16 // = len("truncated":"1",), sigh ...
message, ok := m.Data["message"]
if ok && len(message) > over {
m.Data["truncated"] = "1"

6
server/server_test.go
View file

@ -612,12 +612,12 @@ func TestServer_MaybeTruncateFCMMessage(t *testing.T) {
}
origMessageLength := len(origFCMMessage.Data["message"])
serializedOrigFCMMessage, _ := json.Marshal(origFCMMessage)
require.Greater(t, len(serializedOrigFCMMessage), fcmMessageLimitReal) // Pre-condition
require.Greater(t, len(serializedOrigFCMMessage), fcmMessageLimit) // Pre-condition
truncatedFCMMessage := maybeTruncateFCMMessage(origFCMMessage)
truncatedMessageLength := len(truncatedFCMMessage.Data["message"])
serializedTruncatedFCMMessage, _ := json.Marshal(truncatedFCMMessage)
require.Equal(t, fcmMessageLimitReal, len(serializedTruncatedFCMMessage))
require.Equal(t, fcmMessageLimit, len(serializedTruncatedFCMMessage))
require.Equal(t, "1", truncatedFCMMessage.Data["truncated"])
require.NotEqual(t, origMessageLength, truncatedMessageLength)
}
@ -639,7 +639,7 @@ func TestServer_MaybeTruncateFCMMessage_NotTooLong(t *testing.T) {
}
origMessageLength := len(origFCMMessage.Data["message"])
serializedOrigFCMMessage, _ := json.Marshal(origFCMMessage)
require.LessOrEqual(t, len(serializedOrigFCMMessage), fcmMessageLimitReal) // Pre-condition
require.LessOrEqual(t, len(serializedOrigFCMMessage), fcmMessageLimit) // Pre-condition
notTruncatedFCMMessage := maybeTruncateFCMMessage(origFCMMessage)
notTruncatedMessageLength := len(notTruncatedFCMMessage.Data["message"])