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 a comprehensive list of Pub/Sub C++ library versions, ranging from the latest release candidate 2.37.0-rc down to version 2.11.0, with corresponding documentation links for each.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables can be utilized to customize the behavior of the Pub/Sub C++ library, offering a method for troubleshooting and configuration adjustments.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003ePUBSUB_EMULATOR_HOST\u003c/code\u003e environment variable enables connecting the library to a specific emulator for testing purposes, instead of the standard endpoint.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e variable activates gRPC call tracing, and, in conjunction with \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e, facilitates the output of tracing information to the console.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is an environment variable that, while not impacting the library, is used in examples and integration testing to determine the Google Cloud Project.\u003c/p\u003e\n"]]],[],null,["Version 2.19.0keyboard_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."]]
