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[tor-commits] [sbws/master] fix: docs: Move torflow scaling docstring to docs
commit 54a1128af9670380d0c47d1f4d92994a662c1f3f
Author: juga0 <juga@xxxxxxxxxx>
Date: Tue May 19 15:19:11 2020 +0000
fix: docs: Move torflow scaling docstring to docs
so that it has its own page as it is too long as docstring and is
harder to write latex with the docstring syntax.
---
docs/source/torflow_aggr.rst | 150 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 150 insertions(+)
diff --git a/docs/source/torflow_aggr.rst b/docs/source/torflow_aggr.rst
new file mode 100644
index 0000000..6fc8fd1
--- /dev/null
+++ b/docs/source/torflow_aggr.rst
@@ -0,0 +1,150 @@
+.. _torflow_aggr:
+
+Torflow measurements aggregation
+==================================
+
+From Torflow's README.spec.txt (section 2.2)::
+
+ In this way, the resulting network status consensus bandwidth values # NOQA
+ are effectively re-weighted proportional to how much faster the node # NOQA
+ was as compared to the rest of the network.
+
+The variables and steps used in Torflow:
+
+**strm_bw**::
+
+ The strm_bw field is the average (mean) of all the streams for the relay # NOQA
+ identified by the fingerprint field.
+ strm_bw = sum(bw stream x)/|n stream|
+
+**filt_bw**::
+
+ The filt_bw field is computed similarly, but only the streams equal to # NOQA
+ or greater than the strm_bw are counted in order to filter very slow # NOQA
+ streams due to slow node pairings.
+
+**filt_sbw and strm_sbw**::
+
+ for rs in RouterStats.query.filter(stats_clause).\
+ options(eagerload_all('router.streams.circuit.routers')).all(): # NOQA
+ tot_sbw = 0
+ sbw_cnt = 0
+ for s in rs.router.streams:
+ if isinstance(s, ClosedStream):
+ skip = False
+ #for br in badrouters:
+ # if br != rs:
+ # if br.router in s.circuit.routers:
+ # skip = True
+ if not skip:
+ # Throw out outliers < mean
+ # (too much variance for stddev to filter much)
+ if rs.strm_closed == 1 or s.bandwidth() >= rs.sbw:
+ tot_sbw += s.bandwidth()
+ sbw_cnt += 1
+
+ if sbw_cnt: rs.filt_sbw = tot_sbw/sbw_cnt
+ else: rs.filt_sbw = None
+
+**filt_avg, and strm_avg**::
+
+ Once we have determined the most recent measurements for each node, we # NOQA
+ compute an average of the filt_bw fields over all nodes we have measured. # NOQA
+
+::
+
+ filt_avg = sum(map(lambda n: n.filt_bw, nodes.itervalues()))/float(len(nodes)) # NOQA
+ strm_avg = sum(map(lambda n: n.strm_bw, nodes.itervalues()))/float(len(nodes)) # NOQA
+
+**true_filt_avg and true_strm_avg**::
+
+ for cl in ["Guard+Exit", "Guard", "Exit", "Middle"]:
+ true_filt_avg[cl] = filt_avg
+ true_strm_avg[cl] = strm_avg
+
+In the non-pid case, all types of nodes get the same avg
+
+**n.fbw_ratio and n.fsw_ratio**::
+
+ for n in nodes.itervalues():
+ n.fbw_ratio = n.filt_bw/true_filt_avg[n.node_class()]
+ n.sbw_ratio = n.strm_bw/true_strm_avg[n.node_class()]
+
+**n.ratio**::
+
+ These averages are used to produce ratios for each node by dividing the # NOQA
+ measured value for that node by the network average.
+
+::
+
+ # Choose the larger between sbw and fbw
+ if n.sbw_ratio > n.fbw_ratio:
+ n.ratio = n.sbw_ratio
+ else:
+ n.ratio = n.fbw_ratio
+
+**desc_bw**:
+
+It is the minimum of all the descriptor bandwidth values::
+
+ bws = map(int, g)
+ bw_observed = min(bws)
+
+ return Router(ns.idhex, ns.nickname, bw_observed, dead, exitpolicy,
+ ns.flags, ip, version, os, uptime, published, contact, rate_limited, # NOQA
+ ns.orhash, ns.bandwidth, extra_info_digest, ns.unmeasured)
+
+ self.desc_bw = max(bw,1) # Avoid div by 0
+
+**new_bw**::
+
+ These ratios are then multiplied by the most recent observed descriptor # NOQA
+ bandwidth we have available for each node, to produce a new value for # NOQA
+ the network status consensus process.
+
+::
+
+ n.new_bw = n.desc_bw*n.ratio
+
+The descriptor observed bandwidth is multiplied by the ratio.
+
+**Limit the bandwidth to a maximum**::
+
+ NODE_CAP = 0.05
+
+::
+
+ if n.new_bw > tot_net_bw*NODE_CAP:
+ plog("INFO", "Clipping extremely fast "+n.node_class()+" node "+n.idhex+"="+n.nick+ # NOQA
+ " at "+str(100*NODE_CAP)+"% of network capacity ("+
+ str(n.new_bw)+"->"+str(int(tot_net_bw*NODE_CAP))+") "+
+ " pid_error="+str(n.pid_error)+
+ " pid_error_sum="+str(n.pid_error_sum))
+ n.new_bw = int(tot_net_bw*NODE_CAP)
+
+However, tot_net_bw does not seems to be updated when not using pid.
+This clipping would make faster relays to all have the same value.
+
+All of that can be expressed as:
+
+.. math::
+
+ bwn_i =& min\\left(bwnew_i,
+ \\sum_{i=1}^{n}bwnew_i \\times 0.05\\right) \\
+
+ &= min\\left(
+ \\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times r_i\\right),
+ \\sum_{i=1}^{n}\\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times r_i\\right)
+ \\times 0.05\\right)\\
+
+ &= min\\left(
+ \\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times max\\left(rf_i, rs_i\\right)\\right),
+ \\sum_{i=1}^{n}\\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times
+ max\\left(rf_i, rs_i\\right)\\right) \\times 0.05\\right)\\
+
+ &= min\\left(
+ \\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times max\\left(\\frac{bwfilt_i}{bwfilt},
+ \\frac{bw_i}{bwstrm}\\right)\\right),
+ \\sum_{i=1}^{n}\\left(min\\left(bwobs_i, bwavg_i, bwbur_i \\right) \\times
+ max\\left(\\frac{bwfilt_i}{bwfilt},
+ \\frac{bw_i}{bwstrm}\\right)\\right) \\times 0.05\\right)
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