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
PUBSUB_EMULATOR_HOST=host:port: tells the library to connect to the specified emulator rather than the default endpoint. Intended for testing only.
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 webpage provides documentation for various versions of a C++ Pub/Sub library, ranging from version 2.11.0 up to the latest release candidate, 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables, such as \u003ccode\u003ePUBSUB_EMULATOR_HOST\u003c/code\u003e, can be used to modify library behavior, including overriding the default endpoint for testing purposes.\u003c/p\u003e\n"],["\u003cp\u003eTracing for gRPC calls can be enabled by setting \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING=rpc\u003c/code\u003e, with additional options for modifying tracing behavior available via \u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG=yes\u003c/code\u003e environment variable enables logging output to the console, which the library can utilize for internal logs.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e can be set for project configuration in examples and tests, but it does not directly affect library operation.\u003c/p\u003e\n"]]],[],null,["Version 2.24.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/pubsub/latest/pubsub-env)\n- [2.41.0](/cpp/docs/reference/pubsub/2.41.0/pubsub-env)\n- [2.40.0](/cpp/docs/reference/pubsub/2.40.0/pubsub-env)\n- [2.39.0](/cpp/docs/reference/pubsub/2.39.0/pubsub-env)\n- [2.38.0](/cpp/docs/reference/pubsub/2.38.0/pubsub-env)\n- [2.37.0](/cpp/docs/reference/pubsub/2.37.0/pubsub-env)\n- [2.36.0](/cpp/docs/reference/pubsub/2.36.0/pubsub-env)\n- [2.35.0](/cpp/docs/reference/pubsub/2.35.0/pubsub-env)\n- [2.34.0](/cpp/docs/reference/pubsub/2.34.0/pubsub-env)\n- [2.33.0](/cpp/docs/reference/pubsub/2.33.0/pubsub-env)\n- [2.32.0](/cpp/docs/reference/pubsub/2.32.0/pubsub-env)\n- [2.31.0](/cpp/docs/reference/pubsub/2.31.0/pubsub-env)\n- [2.30.0](/cpp/docs/reference/pubsub/2.30.0/pubsub-env)\n- [2.29.0](/cpp/docs/reference/pubsub/2.29.0/pubsub-env)\n- [2.28.0](/cpp/docs/reference/pubsub/2.28.0/pubsub-env)\n- [2.27.0](/cpp/docs/reference/pubsub/2.27.0/pubsub-env)\n- [2.26.0](/cpp/docs/reference/pubsub/2.26.0/pubsub-env)\n- [2.25.1](/cpp/docs/reference/pubsub/2.25.1/pubsub-env)\n- [2.24.0](/cpp/docs/reference/pubsub/2.24.0/pubsub-env)\n- [2.23.0](/cpp/docs/reference/pubsub/2.23.0/pubsub-env)\n- [2.22.1](/cpp/docs/reference/pubsub/2.22.1/pubsub-env)\n- [2.21.0](/cpp/docs/reference/pubsub/2.21.0/pubsub-env)\n- [2.20.0](/cpp/docs/reference/pubsub/2.20.0/pubsub-env)\n- [2.19.0](/cpp/docs/reference/pubsub/2.19.0/pubsub-env)\n- [2.18.0](/cpp/docs/reference/pubsub/2.18.0/pubsub-env)\n- [2.17.0](/cpp/docs/reference/pubsub/2.17.0/pubsub-env)\n- [2.16.0](/cpp/docs/reference/pubsub/2.16.0/pubsub-env)\n- [2.15.1](/cpp/docs/reference/pubsub/2.15.1/pubsub-env)\n- [2.14.0](/cpp/docs/reference/pubsub/2.14.0/pubsub-env)\n- [2.13.0](/cpp/docs/reference/pubsub/2.13.0/pubsub-env)\n- [2.12.0](/cpp/docs/reference/pubsub/2.12.0/pubsub-env)\n- [2.11.0](/cpp/docs/reference/pubsub/2.11.0/pubsub-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`PUBSUB_EMULATOR_HOST=host:port`: tells the library to connect to the specified emulator rather than the default endpoint. Intended for testing only.\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`](about:invalid#zCSafez)`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."]]
