Statistics collector¶
Module stats
gathers various counters from the query resolution
and server internals, and offers them as a key-value storage.
These metrics can be either exported to Graphite/InfluxDB/Metronome,
exposed as Prometheus metrics endpoint, or processed using user-provided script
as described in chapter Asynchronous events.
Note
Please remember that each Knot Resolver instance keeps its own statistics, and instances can be started and stopped dynamically. This might affect your data postprocessing procedures if you are using Multiple instances.
Built-in statistics¶
Built-in counters keep track of number of queries and answers matching specific criteria.
Global request counters |
|
request.total |
total number of DNS requests (including internal client requests) |
request.internal |
internal requests generated by Knot Resolver (e.g. DNSSEC trust anchor updates) |
request.udp |
external requests received over plain UDP (RFC 1035) |
request.tcp |
external requests received over plain TCP (RFC 1035) |
request.dot |
external requests received over DNS-over-TLS (RFC 7858) |
request.doh |
external requests received over DNS-over-HTTP (RFC 8484) |
request.xdp |
external requests received over plain UDP via an AF_XDP socket |
Global answer counters |
|
answer.total |
total number of answered queries |
answer.cached |
queries answered from cache |
answer.stale |
queries that utilized stale data |
Answers categorized by RCODE |
|
answer.noerror |
NOERROR answers |
answer.nodata |
NOERROR, but empty answers |
answer.nxdomain |
NXDOMAIN answers |
answer.servfail |
SERVFAIL answers |
Answer latency |
|
answer.1ms |
completed in 1ms |
answer.10ms |
completed in 10ms |
answer.50ms |
completed in 50ms |
answer.100ms |
completed in 100ms |
answer.250ms |
completed in 250ms |
answer.500ms |
completed in 500ms |
answer.1000ms |
completed in 1000ms |
answer.1500ms |
completed in 1500ms |
answer.slow |
completed in more than 1500ms |
answer.sum_ms |
sum of all latencies in ms |
Answer flags |
|
answer.aa |
authoritative answer |
answer.tc |
truncated answer |
answer.ra |
recursion available |
answer.rd |
recursion desired (in answer!) |
answer.ad |
authentic data (DNSSEC) |
answer.cd |
checking disabled (DNSSEC) |
answer.do |
DNSSEC answer OK |
answer.edns0 |
EDNS0 present |
Query flags |
|
query.edns |
queries with EDNS present |
query.dnssec |
queries with DNSSEC DO=1 |
Example:
modules.load('stats')
-- Enumerate metrics
> stats.list()
[answer.cached] => 486178
[iterator.tcp] => 490
[answer.noerror] => 507367
[answer.total] => 618631
[iterator.udp] => 102408
[query.concurrent] => 149
-- Query metrics by prefix
> stats.list('iter')
[iterator.udp] => 105104
[iterator.tcp] => 490
-- Fetch most common queries
> stats.frequent()
[1] => {
[type] => 2
[count] => 4
[name] => cz.
}
-- Fetch most common queries (sorted by frequency)
> table.sort(stats.frequent(), function (a, b) return a.count > b.count end)
-- Show recently contacted authoritative servers
> stats.upstreams()
[2a01:618:404::1] => {
[1] => 26 -- RTT
}
[128.241.220.33] => {
[1] => 31 - RTT
}
-- Set custom metrics from modules
> stats['filter.match'] = 5
> stats['filter.match']
5
Module reference¶
- stats.get(key)¶
- Parameters:
key (string) – i.e.
"answer.total"
- Returns:
number
Return nominal value of given metric.
- stats.set('key val')¶
Set nominal value of given metric.
Example:
stats.set('answer.total 5')
-- or syntactic sugar
stats['answer.total'] = 5
- stats.list([prefix])¶
- Parameters:
prefix (string) – optional metric prefix, i.e.
"answer"
shows only metrics beginning with “answer”
Outputs collected metrics as a JSON dictionary.
- stats.upstreams()¶
Outputs a list of recent upstreams and their RTT. It is sorted by time and stored in a ring buffer of
a fixed size. This means it’s not aggregated and readable by multiple consumers, but also that
you may lose entries if you don’t read quickly enough. The default ring size is 512 entries, and may be overridden on compile time by -DUPSTREAMS_COUNT=X
.
- stats.frequent()¶
Outputs list of most frequent iterative queries as a JSON array. The queries are sampled probabilistically, and include subrequests. The list maximum size is 5000 entries, make diffs if you want to track it over time.
- stats.clear_frequent()¶
Clear the list of most frequent iterative queries.
Graphite/InfluxDB/Metronome¶
The graphite
sends statistics over the Graphite protocol to either Graphite, Metronome, InfluxDB or any compatible storage. This allows powerful visualization over metrics collected by Knot Resolver.
Tip
The Graphite server is challenging to get up and running, InfluxDB combined with Grafana are much easier, and provide richer set of options and available front-ends. Metronome by PowerDNS alternatively provides a mini-graphite server for much simpler setups.
Example configuration:
Only the host
parameter is mandatory.
By default the module uses UDP so it doesn’t guarantee the delivery, set tcp = true
to enable Graphite over TCP. If the TCP consumer goes down or the connection with Graphite is lost, resolver will periodically attempt to reconnect with it.
modules = {
graphite = {
prefix = hostname() .. worker.id, -- optional metric prefix
host = '127.0.0.1', -- graphite server address
port = 2003, -- graphite server port
interval = 5 * sec, -- publish interval
tcp = false -- set to true if you want TCP mode
}
}
The module supports sending data to multiple servers at once.
modules = {
graphite = {
host = { '127.0.0.1', '1.2.3.4', '::1' },
}
}
Dependencies¶
lua cqueues package.
Prometheus metrics endpoint¶
The HTTP module exposes /metrics
endpoint that serves metrics
from Statistics collector in Prometheus text format.
You can use it as soon as HTTP module is configured:
$ curl -k https://localhost:8453/metrics | tail
# TYPE latency histogram
latency_bucket{le=10} 2.000000
latency_bucket{le=50} 2.000000
latency_bucket{le=100} 2.000000
latency_bucket{le=250} 2.000000
latency_bucket{le=500} 2.000000
latency_bucket{le=1000} 2.000000
latency_bucket{le=1500} 2.000000
latency_bucket{le=+Inf} 2.000000
latency_count 2.000000
latency_sum 11.000000
You can namespace the metrics in configuration, using http.prometheus.namespace attribute:
modules.load('http')
-- Set Prometheus namespace
http.prometheus.namespace = 'resolver_'
You can also add custom metrics or rewrite existing metrics before they are returned to Prometheus client.
modules.load('http')
-- Add an arbitrary metric to Prometheus
http.prometheus.finalize = function (metrics)
table.insert(metrics, 'build_info{version="1.2.3"} 1')
end