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 "http://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. Set it to 0 disables query splitting, but please note that caching is also disabled in this case.
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, only in-memory cache (fifo cache) is supported. An example config:
type: IN-MEMORY
config:
max_size: ""
max_size_items: 0
validity: 0s
Query Frontend supports --query-frontend.log_queries_longer_than flag to log queries running longer some duration.
Naming is hard :) Please check here to see why we chose query-frontend as the name.
usage: thanos query-frontend [<flags>]
query frontend
Flags:
-h, --help Show context-sensitive help (also try --help-long
and --help-man).
--version Show application version.
--log.level=info Log filtering level.
--log.format=logfmt Log format to use. Possible options: logfmt or
json.
--tracing.config-file=<file-path>
Path to YAML file with tracing configuration. See
format details:
https://thanos.io/tip/tracing.md/#configuration
--tracing.config=<content>
Alternative to 'tracing.config-file' flag (lower
priority). Content of YAML file with tracing
configuration. See format details:
https://thanos.io/tip/tracing.md/#configuration
--query-range.split-interval=24h
Split queries by an interval and execute in
parallel, 0 disables it.
--query-range.max-retries-per-request=5
Maximum number of retries for a single request;
beyond this, the downstream error is returned.
--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 queries will be scheduled in
parallel by the frontend.
--query-range.response-cache-max-freshness=1m
Most recent allowed cacheable result, to prevent
caching very recent results that might still be in
flux.
--query-range.partial-response
Enable partial response for queries if no
partial_response param is specified.
--no-query-range.partial-response for disabling.
--query-range.response-cache-config-file=<file-path>
Path to YAML file that contains response cache
configuration.
--query-range.response-cache-config=<content>
Alternative to
'query-range.response-cache-config-file' flag
(lower priority). Content of YAML file that
contains response cache configuration.
--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.
--query-frontend.downstream-url="http://localhost:9090"
URL of downstream Prometheus Query compatible API.
--query-frontend.compress-responses
Compress HTTP responses.
--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.
--log.request.decision=LogFinishCall
Request Logging for logging the start and end of
requests. LogFinishCall is enabled by default.
LogFinishCall : Logs the finish call of the
requests. LogStartAndFinishCall : Logs the start
and finish call of the requests. NoLogCall :
Disable request logging.