redis operation with ruby is blocking in ppoll - ruby

Question

Our project use this apns provider that runing on centos 6.4 to push the oofline msg .
The apns provider just read from redis queue with brpop, then reformat the data and send to the apns msg to apple push service.
Recently, I faced an problem that the apn provider DO NOT read the msg from redis queue, I just strace the process:
The abnormal strace result:
tcp 0 0 ::1:39688 ::1:6379 ESTABLISHED 29452/ruby
[root#server]# strace -p 29452
Process 29452 attached - interrupt to quit
ppoll([{fd=56, events=POLLIN}], 1, NULL, NULL, 8
The normal strace result:
clock_gettime(CLOCK_MONOTONIC, {9266059, 349937955}) = 0
select(9, [8], NULL, NULL, {6, 0}) = 1 (in [8], left {3, 976969})
fcntl64(8, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)
read(8, "*-1\r\n", 1024) = 5
write(8, "*3\r\n$5\r\nbrpop\r\n$9\r\napn_queue\r\n$1"..., 37) = 37
fcntl64(8, F_GETFL) = 0x802 (flags O_RDWR|O_NONBLOCK)
read(8, 0x9a0e5d8, 1024) = -1 EAGAIN (Resource temporarily unavailable)
clock_gettime(CLOCK_MONOTONIC, {9266061, 374086306}) = 0
select(9, [8], NULL, NULL, {6, 0}^C <unfinished ...>
Process 20493 detached
here is the related code:
loop do
begin
message = #redis.brpop(self.queue, 1)
if message
APN.log(:info, "---------->#{message} ----------->\n")
#notification = APN::Notification.new(JSON.parse(message.last,:symbolize_names => true))
send_notification
end
rescue Exception => e
if e.class == Interrupt || e.class == SystemExit
APN.log(:info, 'Shutting down...')
exit(0)
end
APN.log(:error, "class: #{e.class} Encountered error: #{e}, backtrace #{e.backtrace}")
APN.log(:info, 'Trying to reconnect...')
client.connect!
APN.log(:info, 'Reconnected')
client.push(#notification)
end
end
This problem occur aperiodically , the period time may be one or two month.
I think the code logic is right, guess the system network may affect the normal runnning of programming.
When I use pkill [pid] to kill the programm, it just restore the normal condiction starting read the msg from queue.
Now I don't know how to analyse the problem, so I have to use cron to reboot or send kill signal to the program every dawn periodcally. :(
Can everyone have the idea to handle the problem?

Answer 1

You used in your abnormal strace result ppoll with null timeout .
correct way is
const struct timespec timeout = { .tv_sec = 10, .tv_nsec = 0 };
struct pollfd myfds;
myfds.fd = fd;
myfds.events = POLLIN;
myfds.revents = 0;
retresult = ppoll(&myfds, 1,&timeout,NULL);
This will give 10sec delay once 10sec is finish its return to next code.