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orchestrator-client.md

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orchestrator-client

orchestrator-client is a script that wraps API calls with convenient command line interface.

It can auto-determine the leader of an orchestrator setup and in such case forward all requests to the leader.

It closely mimics the orchestrator command line interface.

With orchestrator-client, you:

  • Do not need the orchestrator binary installed everywhere; only on hosts where the service runs
  • Do not need to deploy orchestrator configuration everywhere; only on service hosts
  • Do not need to make access to backend DB
  • Need to have access to the HTTP api
  • Need to set the ORCHESTRATOR_API environment variable.
    • Either provide a single endpoint for a proxy, e.g.
    export ORCHESTRATOR_API=https://orchestrator.myservice.com:3000/api
    • Or provide all orchestrator endpoints, and orchestrator-client will auto-pick the leader (no need for proxy), e.g.
    export ORCHESTRATOR_API="https://orchestrator.host1:3000/api https://orchestrator.host2:3000/api https://orchestrator.host3:3000/api"
  • You may set up the environment in /etc/profile.d/orchestrator-client.sh. If this file exists, it will be inlined by orchestrator-client.

Sample usage

Show currently known clusters (replication topologies):

orchestrator-client -c clusters

Discover, forget an instance:

orchestrator-client -c discover -i 127.0.0.1:22987
orchestrator-client -c forget -i 127.0.0.1:22987

Print an ASCII tree of topology instances. Pass a cluster name via -i (see clusters command above):

orchestrator-client -c topology -i 127.0.0.1:22987

Sample output:

127.0.0.1:22987
+ 127.0.0.1:22989
  + 127.0.0.1:22988
+ 127.0.0.1:22990

Move the replica around the topology:

orchestrator-client -c relocate -i 127.0.0.1:22988 -d 127.0.0.1:22987

Resulting topology:

127.0.0.1:22987
+ 127.0.0.1:22989
+ 127.0.0.1:22988
+ 127.0.0.1:22990

etc.

Behind the scenes

The command line interface makes for a nice wrapper to API calls, whose output is then transformed from JSON format to textual format.

As example, the command:

orchestrator-client -c discover -i 127.0.0.1:22987

Translates to (simplified here for convenience):

curl "$ORCHESTRATOR_API/discover/127.0.0.1/22987" | jq '.Details | .Key'

Meta commands

  • orchestrator-client -c help: list all available commands
  • orchestrator-client -c which-api: output the API endpoint orchestrator-client would use to invoke a command. This is useful when multiple endpoints are provided via $ORCHESTRATOR_API.
  • orchestrator-client -c api -path clusters: invoke a generic HTTP API call (in this case clusters) and return the raw JSON response.