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_ENVIRONMENTS_ENDPOINT=...overrides theEndpointOption(which defaults to "composer.googleapis.com") used byMakeEnvironmentsConnection().
GOOGLE_CLOUD_CPP_IMAGE_VERSIONS_ENDPOINT=...overrides theEndpointOption(which defaults to "composer.googleapis.com") used byMakeImageVersionsConnection().
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::TracingComponentsOptionGOOGLE_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 release candidate version is 2.37.0-rc, and the current version displayed on the page is 2.21.0, with multiple versions available, ranging from 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables can be utilized to customize library behavior, particularly helpful for troubleshooting, and can be overridden in the code via functions.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_CPP_ENVIRONMENTS_ENDPOINT\u003c/code\u003e and \u003ccode\u003eGOOGLE_CLOUD_CPP_IMAGE_VERSIONS_ENDPOINT\u003c/code\u003e can override default endpoints for \u003ccode\u003eMakeEnvironmentsConnection()\u003c/code\u003e and \u003ccode\u003eMakeImageVersionsConnection()\u003c/code\u003e, respectively.\u003c/p\u003e\n"],["\u003cp\u003eTracing for gRPC calls can be activated with \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING=rpc\u003c/code\u003e, which prints each request and response, and \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG=yes\u003c/code\u003e is needed for output on the program's console.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e sets the GCP project in examples and integration tests but does not modify library behavior.\u003c/p\u003e\n"]]],[],null,["Version 2.21.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/composer/latest/composer-env)\n- [2.41.0](/cpp/docs/reference/composer/2.41.0/composer-env)\n- [2.40.0](/cpp/docs/reference/composer/2.40.0/composer-env)\n- [2.39.0](/cpp/docs/reference/composer/2.39.0/composer-env)\n- [2.38.0](/cpp/docs/reference/composer/2.38.0/composer-env)\n- [2.37.0](/cpp/docs/reference/composer/2.37.0/composer-env)\n- [2.36.0](/cpp/docs/reference/composer/2.36.0/composer-env)\n- [2.35.0](/cpp/docs/reference/composer/2.35.0/composer-env)\n- [2.34.0](/cpp/docs/reference/composer/2.34.0/composer-env)\n- [2.33.0](/cpp/docs/reference/composer/2.33.0/composer-env)\n- [2.32.0](/cpp/docs/reference/composer/2.32.0/composer-env)\n- [2.31.0](/cpp/docs/reference/composer/2.31.0/composer-env)\n- [2.30.0](/cpp/docs/reference/composer/2.30.0/composer-env)\n- [2.29.0](/cpp/docs/reference/composer/2.29.0/composer-env)\n- [2.28.0](/cpp/docs/reference/composer/2.28.0/composer-env)\n- [2.27.0](/cpp/docs/reference/composer/2.27.0/composer-env)\n- [2.26.0](/cpp/docs/reference/composer/2.26.0/composer-env)\n- [2.25.1](/cpp/docs/reference/composer/2.25.1/composer-env)\n- [2.24.0](/cpp/docs/reference/composer/2.24.0/composer-env)\n- [2.23.0](/cpp/docs/reference/composer/2.23.0/composer-env)\n- [2.22.1](/cpp/docs/reference/composer/2.22.1/composer-env)\n- [2.21.0](/cpp/docs/reference/composer/2.21.0/composer-env)\n- [2.20.0](/cpp/docs/reference/composer/2.20.0/composer-env)\n- [2.19.0](/cpp/docs/reference/composer/2.19.0/composer-env)\n- [2.18.0](/cpp/docs/reference/composer/2.18.0/composer-env)\n- [2.17.0](/cpp/docs/reference/composer/2.17.0/composer-env)\n- [2.16.0](/cpp/docs/reference/composer/2.16.0/composer-env)\n- [2.15.1](/cpp/docs/reference/composer/2.15.1/composer-env)\n- [2.14.0](/cpp/docs/reference/composer/2.14.0/composer-env)\n- [2.13.0](/cpp/docs/reference/composer/2.13.0/composer-env)\n- [2.12.0](/cpp/docs/reference/composer/2.12.0/composer-env)\n- [2.11.0](/cpp/docs/reference/composer/2.11.0/composer-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_ENVIRONMENTS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"composer.googleapis.com\") used by `MakeEnvironmentsConnection()`.\n- `GOOGLE_CLOUD_CPP_IMAGE_VERSIONS_ENDPOINT=...` overrides the `EndpointOption` (which defaults to \"composer.googleapis.com\") used by `MakeImageVersionsConnection()`.\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::TracingComponentsOption`](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1TracingComponentsOption.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."]]
