Release 1.4.4

Sat 20 July 2013 by Monnand

This version contains some minor bug fixes and a huge improvement for APNS. I would like to give special thanks to cmabastar-gumi for his detailed bug reports. Please check the release note for detailed ChangeLog.

In this post, I will explain more about how I improved the performance for APNS.


Both issue 24 and issue 27 described a poor performance when pushing notification through APNS. After a brief profiling, I made three changes:

  • Checking Feedback Service less frequently.
  • Using a connection pool to send notifications in parallel.
  • Response the request immediately after sending the notification, without waiting for the error response from APNS.

Checking feedback service less frequently

Starting from version 1.4.2, uniqush-push supports Feedback Service for APNS. Both version 1.4.2 and version 1.4.3 have a very naive approach for Feedback Service: uniqush-push checks feedbacks after every push operation. This is very inefficient because it has to establish a new TCP connection every time.

In version 1.4.4, uniqush-push checks the feedback for every 10 minutes. Although it may be better to provide a parameter for user to set this time interval to other values, I see no strong benefit by providing this parameter. At this point of time, I would rather use a constant time interval (10 minutes) and keep a simple interface for users.

Using connection pools

Before version 1.4.4, uniqush-push maintains one single connection with APNS for each APNS key/certificate pair. Clearly, using a connection pool could improve the performance when we have concurrent request, since we can send notifications in parallel through several TCP connections. However, APNS' document does not clearly say how many connections we can have for each key/certificate pair. According to discussion on stackoverflow, 15 connections would be find in most cases. In version 1.4.4, we use at most 13 connections for each key/certificate pair.

As a byproduct, a general connection pool library in Go is available on github.

No wait for the error response

OK. This is a trade off we made here. As an asynchronous service, APNS cannot guarantee the response time for the error response. What's worse, it does not even guarantee that there will be a response.

Fortunately, most errors can be checked before sending notifications to APNS. In version 1.4.4, uniqush-push returns success immediately once the notification has been sent to APNS. Some error like invalid token can be processed later inside uniqush-push. In most cases, we are good.


After making the changes above, the performance for APNS is improved ~100x. Let's quote cmabastar-gumi's test results mentioned in reply to issue 27:

we were able to send 22k messages in less than 3mins and we were also able to test around 68k users to be subscribed in around 5mins. Thanks for this build! It's damn fast!