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_APPLICATIONS_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeApplicationsConnection().
GOOGLE_CLOUD_CPP_AUTHORIZED_CERTIFICATES_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeAuthorizedCertificatesConnection().
GOOGLE_CLOUD_CPP_AUTHORIZED_DOMAINS_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeAuthorizedDomainsConnection().
GOOGLE_CLOUD_CPP_DOMAIN_MAPPINGS_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeDomainMappingsConnection().
GOOGLE_CLOUD_CPP_FIREWALL_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeFirewallConnection().
GOOGLE_CLOUD_CPP_INSTANCES_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeInstancesConnection().
GOOGLE_CLOUD_CPP_SERVICES_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeServicesConnection().
GOOGLE_CLOUD_CPP_VERSIONS_ENDPOINT=...overrides theEndpointOption(which defaults to "appengine.googleapis.com") used byMakeVersionsConnection().
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 latest version of the App Engine C++ library is 2.37.0-rc, and the page provides links to documentation for versions ranging from 2.11.0 up to the latest.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables can be used to configure the behavior of the library, especially useful for troubleshooting.\u003c/p\u003e\n"],["\u003cp\u003eSpecific environment variables can override the default endpoints for various connections such as Applications, Authorized Certificates, and more, all of which default to "appengine.googleapis.com".\u003c/p\u003e\n"],["\u003cp\u003eTracing and logging for gRPC calls can be enabled and configured via \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e, \u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e, and \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e environment variables.\u003c/p\u003e\n"],["\u003cp\u003eWhile \u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is used in examples and tests to configure the GCP project, it has no effect within the library's operation itself.\u003c/p\u003e\n"]]],[],null,["Version latestkeyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/appengine/latest/appengine-env)\n- [2.41.0](/cpp/docs/reference/appengine/2.41.0/appengine-env)\n- [2.40.0](/cpp/docs/reference/appengine/2.40.0/appengine-env)\n- [2.39.0](/cpp/docs/reference/appengine/2.39.0/appengine-env)\n- [2.38.0](/cpp/docs/reference/appengine/2.38.0/appengine-env)\n- [2.37.0](/cpp/docs/reference/appengine/2.37.0/appengine-env)\n- [2.36.0](/cpp/docs/reference/appengine/2.36.0/appengine-env)\n- [2.35.0](/cpp/docs/reference/appengine/2.35.0/appengine-env)\n- [2.34.0](/cpp/docs/reference/appengine/2.34.0/appengine-env)\n- [2.33.0](/cpp/docs/reference/appengine/2.33.0/appengine-env)\n- [2.32.0](/cpp/docs/reference/appengine/2.32.0/appengine-env)\n- [2.31.0](/cpp/docs/reference/appengine/2.31.0/appengine-env)\n- [2.30.0](/cpp/docs/reference/appengine/2.30.0/appengine-env)\n- [2.29.0](/cpp/docs/reference/appengine/2.29.0/appengine-env)\n- [2.28.0](/cpp/docs/reference/appengine/2.28.0/appengine-env)\n- [2.27.0](/cpp/docs/reference/appengine/2.27.0/appengine-env)\n- [2.26.0](/cpp/docs/reference/appengine/2.26.0/appengine-env)\n- [2.25.1](/cpp/docs/reference/appengine/2.25.1/appengine-env)\n- [2.24.0](/cpp/docs/reference/appengine/2.24.0/appengine-env)\n- [2.23.0](/cpp/docs/reference/appengine/2.23.0/appengine-env)\n- [2.22.1](/cpp/docs/reference/appengine/2.22.1/appengine-env)\n- [2.21.0](/cpp/docs/reference/appengine/2.21.0/appengine-env)\n- [2.20.0](/cpp/docs/reference/appengine/2.20.0/appengine-env)\n- [2.19.0](/cpp/docs/reference/appengine/2.19.0/appengine-env)\n- [2.18.0](/cpp/docs/reference/appengine/2.18.0/appengine-env)\n- [2.17.0](/cpp/docs/reference/appengine/2.17.0/appengine-env)\n- [2.16.0](/cpp/docs/reference/appengine/2.16.0/appengine-env)\n- [2.15.1](/cpp/docs/reference/appengine/2.15.1/appengine-env)\n- [2.14.0](/cpp/docs/reference/appengine/2.14.0/appengine-env)\n- [2.13.0](/cpp/docs/reference/appengine/2.13.0/appengine-env)\n- [2.12.0](/cpp/docs/reference/appengine/2.12.0/appengine-env)\n- [2.11.0](/cpp/docs/reference/appengine/2.11.0/appengine-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_APPLICATIONS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeApplicationsConnection()`.\n- `GOOGLE_CLOUD_CPP_AUTHORIZED_CERTIFICATES_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeAuthorizedCertificatesConnection()`.\n- `GOOGLE_CLOUD_CPP_AUTHORIZED_DOMAINS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeAuthorizedDomainsConnection()`.\n- `GOOGLE_CLOUD_CPP_DOMAIN_MAPPINGS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeDomainMappingsConnection()`.\n- `GOOGLE_CLOUD_CPP_FIREWALL_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeFirewallConnection()`.\n- `GOOGLE_CLOUD_CPP_INSTANCES_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeInstancesConnection()`.\n- `GOOGLE_CLOUD_CPP_SERVICES_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeServicesConnection()`.\n- `GOOGLE_CLOUD_CPP_VERSIONS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"appengine.googleapis.com\") used by `MakeVersionsConnection()`.\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."]]
