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debugging.md

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Debug graphite-clickhouse

General config

The debug section contains common parameters:

[debug]
directory = '/var/log/graphite-clickhouse/debug'  # where the additional debug information will be dumped.
directory-perm = '0644'  # file mode for the directory. It's applied only if directory does not exist.

Debug queries with external data

All queries to the data-table tables use external data. It reduces the SQL parsing time and allows to query big number of metrics without generating 100k+ characters SQL query.

Unfortunately, it requires some additional effort to reproduce the query in case of problems.

In PR #126 it's solved. All you need to do is set the additional config parameter in [debug] (see General config above):

[debug]
external-data-perm = '0640'  # to not read the metrics by anybody

And pass the HTTP header X-Gch-Debug-External-Data with any value in the /render or Prometheus request. It will produce the external data dump files in the debug directory and generate a curl command in the log on INFO level.

E.g. [2021-01-26T09:57:33.548+0100] INFO [render] external-data {"request_id": "7994db164f6eef7f2e4da20c54c089f2", "debug command": "curl -F 'metrics_list=@/tmp/ext-data-debug/ext-metrics_list:7994db164f6eef7f2e4da20c54c089f2.TSV;' 'http://graphite:[email protected]:8123/?cancel_http_readonly_queries_on_client_close=1&metrics_list_format=TSV&metrics_list_structure=Path+String&query=SELECT+Path%2C%0A%09arrayFilter%28x-%3EisNotNull%28x%29%2C+anyOrNullResample%281611590400%2C+1611594059%2C+60%29%28toUInt32%28intDiv%28Time%2C+60%29%2A60%29%2C+Time%29%29%2C%0A%09arrayFilter%28x-%3EisNotNull%28x%29%2C+avgOrNullResample%281611590400%2C+1611594059%2C+60%29%28Value%2C+Time%29%29%0AFROM+graphite.data%0APREWHERE+Date+%3E%3D%272021-01-25%27+AND+Date+%3C%3D+%272021-01-25%27%0AWHERE+%28Path+in+metrics_list%29+AND+%28Time+%3E%3D+1611590400+AND+Time+%3C%3D+1611594059%29%0AGROUP+BY+Path%0AFORMAT+RowBinary&query_id=7994db164f6eef7f2e4da20c54c089f2%3Adebug'"}

If URL contains user and password, it will be redacted to not expose the credentials.

Debug render data

All supported formats of /render handler are binary and may be difficult to debug. Although it's possible.

format=pickle

To get the data in text format you may pipe the output to the following command:
curl 'localhost:9090/render/?format=pickle&target=metric.name&from=1619777413&until=1619778013' | python3 -c 'import pickle, sys; print(pickle.loads(sys.stdin.buffer.read()))'

format=protobuf (or format=carbonapi_v2_pb)

The format is relatively easy to debug. You should have protoc binary installed. It's usually available in protobuf package. Then you can run the following command from the root of the repository:
curl 'localhost:9090/render/?format=protobuf&target=metric.name&from=1619777413&until=1619778013' | protoc --decode carbonapi_v2_pb.MultiFetchResponse -Ivendor/ vendor/github.com/go-graphite/protocol/carbonapi_v2_pb/carbonapi_v2_pb.proto

If the repository is not available, there's still a way to run protoc --decode_raw, but it's much less readable.

format=carbonapi_v3_pb

The format is the most efficient in the meaning of network traffic and memory. At the same time it is the least debug-able. The request itself is done by sending a POST body with carbonapi_v3_pb.MultiFetchRequest protobuf message. So, first one have to generate the request itself, pipe it to curl, and then decode the request. To do it one should run the following command in the root of the repository:

echo 'metrics{startTime: 1619777413, stopTime: 1619778013, pathExpression: "metric.name"}' | \
  protoc --encode=carbonapi_v3_pb.MultiFetchRequest -Ivendor/ vendor/github.com/go-graphite/protocol/carbonapi_v3_pb/carbonapi_v3_pb.proto | \
  curl -XGET --data-binary @- 'localhost:9090/render/?format=carbonapi_v3_pb' | \
  protoc --decode=carbonapi_v3_pb.MultiFetchResponse -Ivendor/ vendor/github.com/go-graphite/protocol/carbonapi_v3_pb/carbonapi_v3_pb.proto

To make it a little bit easier the JSON format is implemented.

format=json

The format exists only for debugging purpose and enabled by passing a header X-Gch-Debug-Output: any string. Here is a general way to debug the data:

  • Optional: make a request to the frontend (carbonapi) with additional header X-Gch-Debug-Output: a. Then in log a similar line will be generated:
    INFO [render.pb3parser] v3pb_request {"request_id": "051fe964d78d9f3d33827397df779ba0", "json": "{\"metrics\":[{\"name\":\"metric.name\",\"startTime\":1619777413,\"stopTime\":1619778013,\"pathExpression\":\"metric.name\",\"maxDataPoints\":700}]}"}
  • Get the request ID from the responses request, for example: X-Gch-Request-Id: 051fe964d78d9f3d33827397df779ba0
  • In logs either see the JSON body itself for the query ID, or look for [render.pb3parser] pb3_target record.
  • Now to make a request just run:
    curl -H 'Content-Type: application/json' -H 'Content-Type: application/json' -d "{\"metrics\":[{\"name\":\"metric.name\",\"startTime\":1619777413,\"stopTime\":1619778013,\"pathExpression\":\"metric.name\",\"maxDataPoints\":700}]}" 'localhost:9090/render/?format=json'

Marshal protobuf data with original marshallers

Both carbonapi_v2_pb and carbonapi_v3_proto have the optimized marshallers to convert ClickHouse data points to the protobuf response. But when it's necessary, it's possible to debug if the proper data is produced by passing X-Gch-Debug-Protobuf: 1 header.