Implementation details
Writing bandwidth files atomically
To avoid inconsistent reads, implementations SHOULD write bandwidth files atomically. If the file is transferred from another host, it SHOULD be written to a temporary path, then renamed to the V3BandwidthsFile path.
sbws versions 0.7.0 and later write the bandwidth file to an archival location, create a temporary symlink to that location, then atomically rename the symlink to the configured V3BandwidthsFile path.
Torflow does not write bandwidth files atomically.
Additional KeyValue pair definitions
KeyValue pairs in RelayLines that current implementations generate.
Simple Bandwidth Scanner
sbws RelayLines contain these keys:
"node_id" hexdigest
As above.
"bw" Bandwidth
As above.
"nick" nickname
[Exactly once.]
The relay nickname.
Torflow also has a "nick" KeyValue.
"rtt" Int
[Zero or one time.]
The Round Trip Time in milliseconds to obtain 1 byte of data.
This KeyValue was added in version 1.1.0 of this specification. It became optional in version 1.3.0 or 1.4.0 of this specification.
"time" DateTime
[Exactly once.]
The date and time timestamp in ISO 8601 format and UTC time zone when the last bandwidth was obtained.
This KeyValue was added in version 1.1.0 of this specification. The Torflow equivalent is "measured_at".
"success" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay were successful.
This KeyValue was added in version 1.1.0 of this specification.
"error_circ" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay failed because of circuit failures.
This KeyValue was added in version 1.1.0 of this specification. The Torflow equivalent is "circ_fail".
"error_stream" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay failed because of stream failures.
This KeyValue was added in version 1.1.0 of this specification.
"error_destination" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay failed because the destination Web server was not available.
This KeyValue was added in version 1.4.0 of this specification.
"error_second_relay" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay failed because sbws could not find a second relay for the test circuit.
This KeyValue was added in version 1.4.0 of this specification.
"error_misc" Int
[Zero or one time.]
The number of times that the bandwidth measurements for this relay failed because of other reasons.
This KeyValue was added in version 1.1.0 of this specification.
"bw_mean" Int
[Zero or one time.]
The measured bandwidth mean for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"bw_median" Int
[Zero or one time.]
The measured bandwidth median for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"desc_bw_avg" Int
[Zero or one time.]
The descriptor average bandwidth for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"desc_bw_obs_last" Int
[Zero or one time.]
The last descriptor observed bandwidth for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"desc_bw_obs_mean" Int
[Zero or one time.]
The descriptor observed bandwidth mean for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"desc_bw_bur" Int
[Zero or one time.]
The descriptor burst bandwidth for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"consensus_bandwidth" Int
[Zero or one time.]
The consensus bandwidth for this relay in bytes per second.
This KeyValue was added in version 1.2.0 of this specification.
"consensus_bandwidth_is_unmeasured" Bool
[Zero or one time.]
If the consensus bandwidth for this relay was not obtained from three or more bandwidth authorities, this KeyValue is True or False otherwise.
This KeyValue was added in version 1.2.0 of this specification.
"relay_in_recent_consensus_count" Int
[Zero or one time.]
The number of times this relay was found in a consensus in the last data_period days. (Unless otherwise stated, data_period is 5 by default.)
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_priority_list_count" Int
[Zero or one time.]
The number of times this relay has been prioritized to be measured in the last data_period days.
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurement_attempt_count" Int
[Zero or one time.]
The number of times this relay was tried to be measured in the last data_period days.
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurement_failure_count" Int
[Zero or one time.]
The number of times this relay was tried to be measured in the last data_period days, but it was not possible to obtain a measurement.
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurements_excluded_error_count" Int
[Zero or one time.]
The number of recent relay measurement attempts that failed. Measurements are recent if they are in the last data_period days (5 by default).
(See the note in section 1.4, version 1.4.0, about excluded relays.)
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurements_excluded_near_count" Int
[Zero or one time.]
When all of a relay's recent successful measurements were performed in a period of time that was too short (by default 1 day), the relay is excluded. This KeyValue contains the number of recent successful measurements for the relay that were ignored for this reason.
(See the note in section 1.4, version 1.4.0, about excluded relays.)
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurements_excluded_old_count" Int
[Zero or one time.]
The number of successful measurements for this relay that are too old (more than data_period days, 5 by default).
Excludes measurements that are already counted in relay_recent_measurements_excluded_near_count.
(See the note in section 1.4, version 1.4.0, about excluded relays.)
This KeyValue was added in version 1.4.0 of this specification.
"relay_recent_measurements_excluded_few_count" Int
[Zero or one time.]
The number of successful measurements for this relay that were ignored because the relay did not have enough successful measurements (fewer than 2, by default).
Excludes measurements that are already counted in relay_recent_measurements_excluded_near_count or relay_recent_measurements_excluded_old_count.
(See the note in section 1.4, version 1.4.0, about excluded relays.)
This KeyValue was added in version 1.4.0 of this specification.
"under_min_report" bool
[Zero or one time.]
If the value is 1, there are not enough eligible relays in the bandwidth file, and Tor bandwidth authorities MAY NOT vote on this relay. (Current Tor versions do not change their behaviour based on the "under_min_report" key.)
If the value is 0 or the KeyValue is not present, there are enough relays in the bandwidth file.
Because Tor versions released before April 2019 (see section 1.4. for the full list of versions) ignore "vote=0", generator implementations MUST NOT change the bandwidths for under_min_report relays. Using the same bw value makes authorities that do not understand "vote=0" or "under_min_report=1" produce votes that don't change relay weights too much. It also avoids flapping when the reporting threshold is reached.
This KeyValue was added in version 1.4.0 of this specification.
"unmeasured" bool
[Zero or one time.]
If the value is 1, this relay was not successfully measured and Tor bandwidth authorities MAY NOT vote on this relay. (Current Tor versions do not change their behaviour based on the "unmeasured" key.)
If the value is 0 or the KeyValue is not present, this relay was successfully measured.
Because Tor versions released before April 2019 (see section 1.4. for the full list of versions) ignore "vote=0", generator implementations MUST set "bw=1" for unmeasured relays. Using the minimum bw value makes authorities that do not understand "vote=0" or "unmeasured=1" produce votes that don't change relay weights too much.
This KeyValue was added in version 1.4.0 of this specification.
"vote" bool
[Zero or one time.]
If the value is 0, Tor directory authorities SHOULD ignore the relay's entry in the bandwidth file. They SHOULD vote for the relay the same way they would vote for a relay that is not present in the file.
This MAY be the case when this relay was not successfully measured but it is included in the Bandwidth File, to diagnose why they were not measured.
If the value is 1 or the KeyValue is not present, Tor directory authorities MUST use the relay's bw value in any votes for that relay.
Implementations MUST also set "bw=1" for unmeasured relays. But they MUST NOT change the bw for under_min_report relays. (See the explanations under "unmeasured" and "under_min_report" for more details.)
This KeyValue was added in version 1.4.0 of this specification.
"xoff_recv" Int
[Zero or one time.]
The number of times this relay received XOFF_RECV stream events while
being measured in the last data_period days.
This KeyValue was added in version 1.6.0 of this specification.
"xoff_sent" Int
[Zero or one time.]
The number of times this relay received XOFF_SENT stream events while
being measured in the last data_period days.
This KeyValue was added in version 1.6.0 of this specification.
"r_strm" Float
[Zero or one time.]
The stream ratio of this relay calculated as explained in B4.3.
This KeyValue was added in version 1.7.0 of this specification.
"r_strm_filt" Float
[Zero or one time.]
The filtered stream ratio of this relay calculated as explained in B4.3.
This KeyValue was added in version 1.7.0 of this specification.
Torflow
Torflow RelayLines include node_id and bw, and other KeyValue pairs [2].
References:
- https://gitlab.torproject.org/tpo/network-health/torflow
- https://gitlab.torproject.org/tpo/network-health/torflow/-/blob/main/NetworkScanners/BwAuthority/README.spec.txt?ref_type=heads#L332 The Torflow specification is outdated, and does not match the current implementation. See section A.1. for the format produced by Torflow.
- The Tor Directory Protocol
- How Tor Version Numbers Work In Tor
- https://semver.org/