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 the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeApplicationsConnection().
GOOGLE_CLOUD_CPP_AUTHORIZED_CERTIFICATES_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeAuthorizedCertificatesConnection().
GOOGLE_CLOUD_CPP_AUTHORIZED_DOMAINS_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeAuthorizedDomainsConnection().
GOOGLE_CLOUD_CPP_DOMAIN_MAPPINGS_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeDomainMappingsConnection().
GOOGLE_CLOUD_CPP_FIREWALL_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeFirewallConnection().
GOOGLE_CLOUD_CPP_INSTANCES_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeInstancesConnection().
GOOGLE_CLOUD_CPP_SERVICES_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeServicesConnection().
GOOGLE_CLOUD_CPP_VERSIONS_ENDPOINT=... overrides the EndpointOption (which defaults to "appengine.googleapis.com") used by MakeVersionsConnection().
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.
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"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 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."]]
