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
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
24h. When caching is enabled it should be greater than
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), memcached, and redis are supported.
dedup=false. Read more about deduplication in Dedup documentation.
Cache-Control=no-storein the response:
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_items are not set, then the cache would not be created.
If either of
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.
set operation is skipped because of the item size is larger than
max_item_size, this event is tracked by a counter metric
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
The default redis config is:
type: REDIS config: addr: "" username: "" password: "" db: 0 dial_timeout: 5s read_timeout: 3s write_timeout: 3s pool_size: 100 min_idle_conns: 10 idle_timeout: 5m0s max_conn_age: 0s max_get_multi_concurrency: 100 get_multi_batch_size: 100 max_set_multi_concurrency: 100 set_multi_batch_size: 100 expiration: 24h0m0s
expiration specifies redis cache valid time. If set to 0s, so using a default of 24 hours expiration time.
Other cache configuration parameters, you can refer to redis-index-cache.
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-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
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.
--query-frontend.forward-header flag provides list of request headers forwarded by query frontend to downstream queriers.
If downstream queriers need basic authentication to access, we can run query-frontend:
thanos query-frontend \ --http-address "0.0.0.0:9090" \ --query-frontend.forward-header "Authorization" --query-frontend.downstream-url="<thanos-querier>:<querier-http-port>"
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.forward-header=<http-header-name> ... List of headers forwarded by the query-frontend to downstream queriers, default is empty --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-frontend.vertical-shards=QUERY-FRONTEND.VERTICAL-SHARDS Number of shards to use when distributing shardable PromQL queries. For more details, you can refer to the Vertical query sharding proposal: https://thanos.io/tip/proposals-accepted/202205-vertical-query-sharding.md --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.horizontal-shards=0 Split queries in this many requests when query duration is below query-range.max-split-interval. --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.max-split-interval=0 Split query range below this interval in query-range.horizontal-shards. Queries with a range longer than this value will be split in multiple requests of this length. --query-range.min-split-interval=0 Split query range requests above this interval in query-range.horizontal-shards requests of equal range. Using this parameter is not allowed with query-range.split-interval. One should also set query-range.split-min-horizontal-shards to a value greater than 1 to enable splitting. --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://thanos.io/tip/thanos/logging.md/#configuration --request.logging-config-file=<file-path> Path to YAML file with request logging configuration. See format details: https://thanos.io/tip/thanos/logging.md/#configuration --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.