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\u003eThis page provides documentation for various versions of the C++ App Engine library, ranging from version 2.11.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables can be used to override default endpoints for different App Engine services, such as Applications, AuthorizedCertificates, and more, using variables like \u003ccode\u003eGOOGLE_CLOUD_CPP_APPLICATIONS_ENDPOINT\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e environment variable can be set to "rpc" to enable detailed tracing of gRPC calls, which can be paired with \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e to show the outputs on the program's console.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e allows customization of gRPC tracing behavior, such as formatting and truncation of string/bytes fields in messages.\u003c/p\u003e\n"],["\u003cp\u003eSetting the environment variable \u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e can be used to set the GCP project, primarily in examples and integration tests, but not having any effect within the library itself.\u003c/p\u003e\n"]]],[],null,["Version 2.32.0keyboard_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."]]
