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\u003eThis page lists various versions of the C++ Pub/Sub library, ranging from the latest release candidate [2.37.0-rc] down to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables can be set to configure the library's behavior, offering an alternative to in-code configuration, and they can be useful in troubleshooting.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003ePUBSUB_EMULATOR_HOST\u003c/code\u003e variable is used to redirect the library's connection to a specified emulator, typically for testing purposes.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e activates tracing for gRPC calls, and \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e is needed to display any of this information, providing insights into the library's operations.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is used in examples and integration tests to configure the project, but it does not have any impact when in the library.\u003c/p\u003e\n"]]],[],null,["Version 2.18.0keyboard_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`](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."]]
