The thanos query-frontend command implements a service that can be put in front of Thanos Queriers to improve the read path. It is based on the Cortex Query Frontend component so you can find some common features like Splitting and Results Caching.
Query Frontend is fully stateless and horizontally scalable.
Example command to run Query Frontend:
thanos query-frontend \
--http-address "0.0.0.0:9090" \
--query-frontend.downstream-url="<thanos-querier>:<querier-http-port>"
_NOTE: Currently only range queries (/api/v1/query_range API call) are actually processed through Query Frontend. All other API calls just directly go to the downstream Querier, which means only range queries are split and cached. But we are planning to support instant queries as well.
For more information please check out initial design proposal.
Query Frontend splits a long query into multiple short queries based on the configured --query-range.split-interval flag. The default value of --query-range.split-interval is 24h. When caching is enabled it should be greater than 0.
There are some benefits from query splitting:
Query Frontend supports a retry mechanism to retry query when HTTP requests are failing. There is a --query-range.max-retries-per-request flag to limit the maximum retry times.
Query Frontend supports caching query results and reuses them on subsequent queries. If the cached results are incomplete, Query Frontend calculates the required subqueries and executes them in parallel on downstream queriers. Query Frontend can optionally align queries with their step parameter to improve the cacheability of the query results. Currently, in-memory cache (fifo cache) and memcached are supported.
type: IN-MEMORY
config:
max_size: ""
max_size_items: 0
validity: 0s
max_size: Maximum memory size of the cache in bytes. A unit suffix (KB, MB, GB) may be applied.
_NOTE: If both max_size and max_size_items are not set, then the cache would not be created.
If either of max_size or max_size_items is set, then there is no limit on other field. For example - only set max_size_item to 1000, then max_size is unlimited. Similarly, if only max_size is set, then max_size_items is unlimited.
Example configuration: kube-thanos
type: MEMCACHED
config:
addresses: []
timeout: 0s
max_idle_connections: 0
max_async_concurrency: 0
max_async_buffer_size: 0
max_get_multi_concurrency: 0
max_item_size: 0
max_get_multi_batch_size: 0
dns_provider_update_interval: 0s
auto_discovery: false
expiration: 0s
expiration specifies memcached cache valid time. If set to 0s, so using a default of 24 hours expiration time.
If a set operation is skipped because of the item size is larger than max_item_size, this event is tracked by a counter metric cortex_memcache_client_set_skip_total.
Other cache configuration parameters, you can refer to memcached-index-cache.
The default memcached config is:
type: MEMCACHED
config:
addresses: [your-memcached-addresses]
timeout: 500ms
max_idle_connections: 100
max_item_size: 1MiB
max_async_concurrency: 10
max_async_buffer_size: 10000
max_get_multi_concurrency: 100
max_get_multi_batch_size: 0
dns_provider_update_interval: 10s
expiration: 24h
Query Frontend supports --query-frontend.log-queries-longer-than flag to log queries running longer than some duration.
Naming is hard :) Please check here to see why we chose query-frontend as the name.
You can configure the parameters of the HTTP client that query-frontend uses for the downstream URL with parameters --query-frontend.downstream-tripper-config and --query-frontend.downstream-tripper-config-file. If it is pointing to a single host, most likely a load-balancer, then it is highly recommended to increase max_idle_conns_per_host via these parameters to at least 100 because otherwise query-frontend will not be able to leverage HTTP keep-alive connections, and the latency will be 10 - 20% higher. By default, the Go HTTP client will only keep two idle connections per each host.
Keys which denote a duration are strings that can end with s or m to indicate seconds or minutes respectively. All of the other keys are integers. Supported keys are:
idle_conn_timeout - timeout of idle connections (string);response_header_timeout - maximum duration to wait for a response header (string);tls_handshake_timeout - maximum duration of a TLS handshake (string);expect_continue_timeout - Go source code (string);max_idle_conns - maximum number of idle connections to all hosts (integer);max_idle_conns_per_host - maximum number of idle connections to each host (integer);max_conns_per_host - maximum number of connections to each host (integer);You can find the default values here.
usage: thanos query-frontend [<flags>]
Query frontend command implements a service deployed in front of queriers to
improve query parallelization and caching.
Flags:
--cache-compression-type=""
Use compression in results cache. Supported
values are: 'snappy' and ” (disable
compression).
-h, --help Show context-sensitive help (also try
--help-long and --help-man).
--http-address="0.0.0.0:10902"
Listen host:port for HTTP endpoints.
--http-grace-period=2m Time to wait after an interrupt received for
HTTP Server.
--http.config="" [EXPERIMENTAL] Path to the configuration file
that can enable TLS or authentication for all
HTTP endpoints.
--labels.default-time-range=24h
The default metadata time range duration for
retrieving labels through Labels and Series API
when the range parameters are not specified.
--labels.max-query-parallelism=14
Maximum number of labels requests will be
scheduled in parallel by the Frontend.
--labels.max-retries-per-request=5
Maximum number of retries for a single
label/series API request; beyond this, the
downstream error is returned.
--labels.partial-response Enable partial response for labels requests if
no partial_response param is specified.
--no-labels.partial-response for disabling.
--labels.response-cache-config=<content>
Alternative to
'labels.response-cache-config-file' flag
(mutually exclusive). Content of YAML file that
contains response cache configuration.
--labels.response-cache-config-file=<file-path>
Path to YAML file that contains response cache
configuration.
--labels.response-cache-max-freshness=1m
Most recent allowed cacheable result for labels
requests, to prevent caching very recent
results that might still be in flux.
--labels.split-interval=24h
Split labels requests by an interval and
execute in parallel, it should be greater than
0 when labels.response-cache-config is
configured.
--log.format=logfmt Log format to use. Possible options: logfmt or
json.
--log.level=info Log filtering level.
--log.request.decision= Deprecation Warning - This flag would be soon
deprecated, and replaced with
`request.logging-config`. Request Logging for
logging the start and end of requests. By
default this flag is disabled. LogFinishCall :
Logs the finish call of the requests.
LogStartAndFinishCall : Logs the start and
finish call of the requests. NoLogCall :
Disable request logging.
--query-frontend.compress-responses
Compress HTTP responses.
--query-frontend.downstream-tripper-config=<content>
Alternative to
'query-frontend.downstream-tripper-config-file'
flag (mutually exclusive). Content of YAML file
that contains downstream tripper configuration.
If your downstream URL is localhost or
127.0.0.1 then it is highly recommended to
increase max_idle_conns_per_host to at least
100.
--query-frontend.downstream-tripper-config-file=<file-path>
Path to YAML file that contains downstream
tripper configuration. If your downstream URL
is localhost or 127.0.0.1 then it is highly
recommended to increase max_idle_conns_per_host
to at least 100.
--query-frontend.downstream-url="http://localhost:9090"
URL of downstream Prometheus Query compatible
API.
--query-frontend.log-queries-longer-than=0
Log queries that are slower than the specified
duration. Set to 0 to disable. Set to < 0 to
enable on all queries.
--query-frontend.org-id-header=<http-header-name> ...
Request header names used to identify the
source of slow queries (repeated flag). The
values of the header will be added to the org
id field in the slow query log. If multiple
headers match the request, the first matching
arg specified will take precedence. If no
headers match 'anonymous' will be used.
--query-range.align-range-with-step
Mutate incoming queries to align their start
and end with their step for better
cache-ability. Note: Grafana dashboards do that
by default.
--query-range.max-query-length=0
Limit the query time range (end - start time)
in the query-frontend, 0 disables it.
--query-range.max-query-parallelism=14
Maximum number of query range requests will be
scheduled in parallel by the Frontend.
--query-range.max-retries-per-request=5
Maximum number of retries for a single query
range request; beyond this, the downstream
error is returned.
--query-range.partial-response
Enable partial response for query range
requests if no partial_response param is
specified. --no-query-range.partial-response
for disabling.
--query-range.request-downsampled
Make additional query for downsampled data in
case of empty or incomplete response to range
request.
--query-range.response-cache-config=<content>
Alternative to
'query-range.response-cache-config-file' flag
(mutually exclusive). Content of YAML file that
contains response cache configuration.
--query-range.response-cache-config-file=<file-path>
Path to YAML file that contains response cache
configuration.
--query-range.response-cache-max-freshness=1m
Most recent allowed cacheable result for query
range requests, to prevent caching very recent
results that might still be in flux.
--query-range.split-interval=24h
Split query range requests by an interval and
execute in parallel, it should be greater than
0 when query-range.response-cache-config is
configured.
--request.logging-config=<content>
Alternative to 'request.logging-config-file'
flag (mutually exclusive). Content of YAML file
with request logging configuration. See format
details:
https://gist.github.com/yashrsharma44/02f5765c5710dd09ce5d14e854f22825
--request.logging-config-file=<file-path>
Path to YAML file with request logging
configuration. See format details:
https://gist.github.com/yashrsharma44/02f5765c5710dd09ce5d14e854f22825
--tracing.config=<content>
Alternative to 'tracing.config-file' flag
(mutually exclusive). Content of YAML file with
tracing configuration. See format details:
https://thanos.io/tip/thanos/tracing.md/#configuration
--tracing.config-file=<file-path>
Path to YAML file with tracing configuration.
See format details:
https://thanos.io/tip/thanos/tracing.md/#configuration
--version Show application version.
--web.disable-cors Whether to disable CORS headers to be set by
Thanos. By default Thanos sets CORS headers to
be allowed by all.
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