Table of Contents

Sidecar #

The thanos sidecar command runs a component that gets deployed along with a Prometheus instance. This allows sidecar to optionally upload metrics to object storage and allow Queriers to query Prometheus data with common, efficient StoreAPI.

In details:

  • It implements Thanos’ Store API on top of Prometheus’ remote-read API. This allows Queriers to treat Prometheus servers as yet another source of time series data without directly talking to its APIs.

  • Optionally, the sidecar uploads TSDB blocks to an object storage bucket as Prometheus produces them every 2 hours. This allows Prometheus servers to be run with relatively low retention while their historic data is made durable and queryable via object storage.

    NOTE: This still does NOT mean that Prometheus can be fully stateless, because if it crashes and restarts you will lose ~2 hours of metrics, so persistent disk for Prometheus is highly recommended. The closest to stateless you can get is using remote write (which Thanos supports, see Receiver. Remote write has other risks and consequences, and still if crashed you loose in positive case seconds of metrics data, so persistent disk is recommended in all cases.

  • Optionally Thanos sidecar is able to watch Prometheus rules and configuration, decompress and substitute environment variables if needed and ping Prometheus to reload them. Read more about this in here

Prometheus servers connected to the Thanos cluster via the sidecar are subject to a few limitations and recommendations for safe operations:

  • The recommended Prometheus version is 2.2.1 or greater (including newest releases). This is due to Prometheus instability in previous versions as well as lack of flags endpoint.

  • (!) The Prometheus external_labels section of the Prometheus configuration file has unique labels in the overall Thanos system. Those external labels will be used by the sidecar and then Thanos in many places:

    • Querier to filter out store APIs to touch during query requests.
    • Many object storage readers like compactor and store gateway which groups the blocks by Prometheus source. Each produced TSDB block by Prometheus is labelled with external label by sidecar before upload to object storage.
  • The --web.enable-admin-api flag is enabled to support sidecar to get metadata from Prometheus like external labels.

  • The --web.enable-lifecycle flag is enabled if you want to use sidecar reloading features (--reload.* flags).

If you choose to use the sidecar to also upload data to object storage:

  • Must specify object storage (--objstore.* flags)
  • It only uploads uncompacted Prometheus blocks. For compacted blocks, see Upload compacted blocks.
  • The --storage.tsdb.min-block-duration and --storage.tsdb.max-block-duration must be set to equal values to disable local compaction on order to use Thanos sidecar upload, otherwise leave local compaction on if sidecar just exposes StoreAPI and your retention is normal. The default of 2h is recommended. Mentioned parameters set to equal values disable the internal Prometheus compaction, which is needed to avoid the uploaded data corruption when Thanos compactor does its job, this is critical for data consistency and should not be ignored if you plan to use Thanos compactor. Even though you set mentioned parameters equal, you might observe Prometheus internal metric prometheus_tsdb_compactions_total being incremented, don’t be confused by that: Prometheus writes initial head block to filesytem via its internal compaction mechanism, but if you have followed recommendations - data won’t be modified by Prometheus before the sidecar uploads it. Thanos sidecar will also check sanity of the flags set to Prometheus on the startup and log errors or warning if they have been configured improperly (#838).
  • The retention is recommended to not be lower than three times the min block duration, so 6 hours. This achieves resilience in the face of connectivity issues to the object storage since all local data will remain available within the Thanos cluster. If connectivity gets restored the backlog of blocks gets uploaded to the object storage.

Reloader Configuration #

Thanos can watch changes in Prometheus configuration and refresh Prometheus configuration if --web.enable-lifecycle enabled.

You can configure watching for changes in directory via --reloader.rule-dir=DIR_NAME flag.

Thanos sidecar can watch --reloader.config-file=CONFIG_FILE configuration file, replace environment variables found in there in $(VARIABLE) format, and produce generated config in --reloader.config-envsubst-file=OUT_CONFIG_FILE file.

Example basic deployment #

prometheus \
  --storage.tsdb.max-block-duration=2h \
  --storage.tsdb.min-block-duration=2h \
thanos sidecar \
    --tsdb.path        "/path/to/prometheus/data/dir" \
    --prometheus.url   "http://localhost:9090" \
    --objstore.config-file  "bucket.yml"

The example content of bucket.yml:

type: GCS
  bucket: example-bucket

Upload compacted blocks (EXPERIMENTAL) #

If you want to migrate from a pure Prometheus setup to Thanos and have to keep the historical data, you can use the flag --shipper.upload-compacted. This will also upload blocks that were compacted by Prometheus. Values greater than 1 in the compaction.level field of a Prometheus block’s meta.json file indicate level of compaction.

To use this, the Prometheus compaction needs to be disabled. This can be done by setting the following flags for Prometheus:

  • --storage.tsdb.min-block-duration=2h
  • --storage.tsdb.max-block-duration=2h

Flags #

usage: thanos sidecar [<flags>]

sidecar for Prometheus server

  -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
                                 Path to YAML file with tracing configuration.
                                 See format details:
                                 Alternative to 'tracing.config-file' flag
                                 (lower priority). Content of YAML file with
                                 tracing configuration. See format details:
                                 Listen host:port for HTTP endpoints.
      --http-grace-period=2m     Time to wait after an interrupt received for
                                 HTTP Server.
                                 Listen ip:port address for gRPC endpoints
                                 (StoreAPI). Make sure this address is routable
                                 from other components.
      --grpc-grace-period=2m     Time to wait after an interrupt received for
                                 GRPC Server.
      --grpc-server-tls-cert=""  TLS Certificate for gRPC server, leave blank to
                                 disable TLS
      --grpc-server-tls-key=""   TLS Key for the gRPC server, leave blank to
                                 disable TLS
                                 TLS CA to verify clients against. If no client
                                 CA is specified, there is no client
                                 verification on server side. (tls.NoClientCert)
                                 URL at which to reach Prometheus's API. For
                                 better performance use local network.
                                 Maximum time to wait for the Prometheus
                                 instance to start up
                                 Controls the http MaxIdleConns. Default is 0,
                                 which is unlimited
                                 Controls the http MaxIdleConnsPerHost
      --tsdb.path="./data"       Data directory of TSDB.
      --reloader.config-file=""  Config file watched by the reloader.
                                 Output file for environment variable
                                 substituted config file.
      --reloader.rule-dir=RELOADER.RULE-DIR ...
                                 Rule directories for the reloader to refresh
                                 (repeated field).
                                 Path to YAML file that contains object store
                                 configuration. See format details:
                                 Alternative to 'objstore.config-file' flag
                                 (lower priority). Content of YAML file that
                                 contains object store configuration. See format
                                 If true shipper will try to upload compacted
                                 blocks as well. Useful for migration purposes.
                                 Works only if compaction is disabled on
                                 Prometheus. Do it once and then disable the
                                 flag when done.
                                 Start of time range limit to serve. Thanos
                                 sidecar will serve only metrics, which happened
                                 later than this value. Option can be a constant
                                 time in RFC3339 format or time duration
                                 relative to current time, such as -1d or 2h45m.
                                 Valid duration units are ms, s, m, h, d, w, y.