Unable to access specific values in the alert object

[MaChengxin]

libtorrent version (or branch):
1.1.3.0

platform/architecture:
Ubuntu 16.04, x64

compiler and compiler version:
gcc (GCC) 5.4.0

Python version:
Python 2.7.12

please describe what symptom you see, what you would expect to see instead and
how to reproduce it.
I am trying to access session statistics and I am only interested in a few of them. It is suggested by the doc that "Always query the metrics first, to find out the index at which the value is stored".
However, the alert object returned by calling post_session_stats() doesn't support indexing.

TypeError: 'session_stats_alert' object has no attribute '_getitem_'

So here come two questions:

1. How do we use the returned index of lt.find_metric_idx("NAME_OF_STATS")?
2. Can we just use alert.values["NAME_OF_STATS"] to get the stats? (e.g. alert.values["ses.num_incoming_choke"])

[arvidn]

right, the python binding turns the array into a dictionary mapping the names to the values. i.e. in python you don't have to look up any index up-front

[arvidn]

This should probably be documented in the python binding documentation. if you're up for it, please submit pull request!

[MaChengxin]

Thanks for the answer.
Speaking of the python binding documentation, do you mean the following one?
https://github.com/arvidn/libtorrent/blob/master/docs/python_binding.rst

[arvidn]

yes

[MaChengxin]

So I tried to use alert.values["NAME_OF_STATS"] to get the stats that I am interested in:

alerts = ses.pop_alerts()
for a in alerts:
	if a.category() & lt.alert.category_t.error_notification:
		print(a)
	elif a.category() & lt.alert.category_t.stats_notification:
		'''
		total number of bytes sent and received by the session
		'''
		print("net.sent_bytes: ", a.values["net.sent_bytes"])
		print("net.sent_payload_bytes: ", a.values["net.sent_payload_bytes"])
		print("net.sent_ip_overhead_bytes: ", a.values["net.sent_ip_overhead_bytes"])
		print("net.sent_tracker_bytes: ", a.values["net.sent_tracker_bytes"])

		print("net.recv_bytes: ", a.values["net.recv_bytes"])
		print("net.recv_payload_bytes: ", a.values["net.recv_payload_bytes"])
		print("net.recv_ip_overhead_bytes: ", a.values["net.recv_ip_overhead_bytes"])
		print("net.recv_tracker_bytes: ", a.values["net.recv_tracker_bytes"])

		print("net.recv_failed_bytes: ", a.values["net.recv_failed_bytes"])
		print("net.recv_redundant_bytes: ", a.values["net.recv_redundant_bytes"])

It worked, but the result looks like incorrent:

net.sent_bytes:  6920
net.sent_payload_bytes:  0
net.sent_ip_overhead_bytes:  112076
net.sent_tracker_bytes:  379
net.recv_bytes:  2007475
net.recv_payload_bytes:  2004514
net.recv_ip_overhead_bytes:  110820
net.recv_tracker_bytes:  3765
net.recv_failed_bytes:  0
net.recv_redundant_bytes:  0

I was expecting sent_bytes = sent_payload_bytes + sent_ip_overhead_bytes + sent_tracker_bytes, but the result isn't.
Can you please explain why is that?

[arvidn]

payload refers to the actual content of the torrent. The difference between "bytes" and "payload" is the bittorrent protocol overhead (like, sending requests, heartbeats, haves etc.). In your case it looks like you're downloading, so the majority of those bytes are likely requests and haves. If you have a high churn of peers it may also be bitfields.

[MaChengxin]

Yes indeed, I am measuring downloading statistics.
From what you said, I infer that net.sent_bytes only includes net.sent_payload_bytes and protocol overhead, which isn't got explicitly, but rather requires a simple calculation (net.sent_bytes - net.sent_payload_bytes). Moreover, net.sent_ip_overhead_bytes and net.sent_tracker_bytes are not included in net.sent_bytes.
Am I right?

[arvidn]

I seem to recall sent_bytes including tracker traffic as well, but probably not the IP overhead.

[stale]

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