A number of environment variables can be used to configure the behavior of the library. There are also functions to configure this behavior in code. The environment variables are convenient when troubleshooting problems.
Endpoint Overrides
GOOGLE_CLOUD_CPP_APP_HUB_ENDPOINT=...overrides theEndpointOption(which defaults to "apphub.googleapis.com") used byMakeAppHubConnection().
GOOGLE_CLOUD_CPP_ENABLE_TRACING=rpc: turns on tracing for most gRPC calls. The library injects an additional Stub decorator that prints each gRPC request and response. Unless you have configured your own logging backend, you should also setGOOGLE_CLOUD_CPP_ENABLE_CLOGto produce any output on the program's console.
See Also
google::cloud::LoggingComponentsOptionGOOGLE_CLOUD_CPP_TRACING_OPTIONS=...: modifies the behavior of gRPC tracing, including whether messages will be output on multiple lines, or whether string/bytes fields will be truncated.
See Also
google::cloud::GrpcTracingOptionsOptionGOOGLE_CLOUD_CPP_ENABLE_CLOG=yes: turns on logging in the library, basically the library always "logs" but the logging infrastructure has no backend to actually print anything until the application sets a backend or they set this environment variable.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[[["\u003cp\u003eThe webpage provides documentation for various versions of the AppHub library, ranging from version 2.23.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables such as \u003ccode\u003eGOOGLE_CLOUD_CPP_APP_HUB_ENDPOINT\u003c/code\u003e can be used to override default settings and customize library behavior, like the endpoint used by \u003ccode\u003eMakeAppHubConnection()\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eTracing for gRPC calls can be enabled with \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING=rpc\u003c/code\u003e, which also requires \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e to be set for output to be visible on the console.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e is used to modify gRPC tracing behavior, such as output format and field truncation.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is an environment variable that is used in examples and tests to set the GCP project but has no effect within the library.\u003c/p\u003e\n"]]],[],null,["Version 2.36.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/apphub/latest/apphub-env)\n- [2.41.0](/cpp/docs/reference/apphub/2.41.0/apphub-env)\n- [2.40.0](/cpp/docs/reference/apphub/2.40.0/apphub-env)\n- [2.39.0](/cpp/docs/reference/apphub/2.39.0/apphub-env)\n- [2.38.0](/cpp/docs/reference/apphub/2.38.0/apphub-env)\n- [2.37.0](/cpp/docs/reference/apphub/2.37.0/apphub-env)\n- [2.36.0](/cpp/docs/reference/apphub/2.36.0/apphub-env)\n- [2.35.0](/cpp/docs/reference/apphub/2.35.0/apphub-env)\n- [2.34.0](/cpp/docs/reference/apphub/2.34.0/apphub-env)\n- [2.33.0](/cpp/docs/reference/apphub/2.33.0/apphub-env)\n- [2.32.0](/cpp/docs/reference/apphub/2.32.0/apphub-env)\n- [2.31.0](/cpp/docs/reference/apphub/2.31.0/apphub-env)\n- [2.30.0](/cpp/docs/reference/apphub/2.30.0/apphub-env)\n- [2.29.0](/cpp/docs/reference/apphub/2.29.0/apphub-env)\n- [2.28.0](/cpp/docs/reference/apphub/2.28.0/apphub-env)\n- [2.27.0](/cpp/docs/reference/apphub/2.27.0/apphub-env)\n- [2.26.0](/cpp/docs/reference/apphub/2.26.0/apphub-env)\n- [2.25.1](/cpp/docs/reference/apphub/2.25.1/apphub-env)\n- [2.24.0](/cpp/docs/reference/apphub/2.24.0/apphub-env)\n- [2.23.0](/cpp/docs/reference/apphub/2.23.0/apphub-env) \n\nEnvironment Variables\n=====================\n\nA number of environment variables can be used to configure the behavior of the library. There are also functions to configure this behavior in code. The environment variables are convenient when troubleshooting problems.\n\nEndpoint Overrides\n------------------\n\n- `GOOGLE_CLOUD_CPP_APP_HUB_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"apphub.googleapis.com\") used by `MakeAppHubConnection()`.\n\n###### See Also\n\n[`google::cloud::EndpointOption`](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1EndpointOption.html)\n\nLogging\n-------\n\n`GOOGLE_CLOUD_CPP_ENABLE_TRACING=rpc`: turns on tracing for most gRPC calls. The library injects an additional Stub decorator that prints each gRPC request and response. Unless you have configured your own logging backend, you should also set `GOOGLE_CLOUD_CPP_ENABLE_CLOG` to produce any output on the program's console.\n\n###### See Also\n\n[`google::cloud::LoggingComponentsOption`](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1LoggingComponentsOption.html)`GOOGLE_CLOUD_CPP_TRACING_OPTIONS=...`: modifies the behavior of gRPC tracing, including whether messages will be output on multiple lines, or whether string/bytes fields will be truncated.\n\n###### See Also\n\n[`google::cloud::GrpcTracingOptionsOption`](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1GrpcTracingOptionsOption.html)`GOOGLE_CLOUD_CPP_ENABLE_CLOG=yes`: turns on logging in the library, basically the library always \"logs\" but the logging infrastructure has no backend to actually print anything until the application sets a backend or they set this environment variable.\n\n###### See Also\n\n[`google::cloud::LogBackend`](https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1LogBackend.html)\n\n###### See Also\n\n[`google::cloud::LogSink`](https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1LogSink.html)\n\nSetting the Default Project\n---------------------------\n\n`GOOGLE_CLOUD_PROJECT=...`: is used in examples and integration tests to configure the GCP project. This has no effect in the library."]]
