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::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"]],[["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 document provides a comprehensive list of Pub/Sub library versions, ranging from the latest release candidate, 2.37.0-rc, down to version 2.11.0, each with links to their respective documentation.\u003c/p\u003e\n"],["\u003cp\u003eEnvironment variables like \u003ccode\u003ePUBSUB_EMULATOR_HOST\u003c/code\u003e are used for configuring the library's behavior, especially in testing, allowing users to specify an emulator endpoint instead of the default.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e and \u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e environment variables offer control over gRPC tracing, including the ability to log gRPC calls and modify the output's formatting.\u003c/p\u003e\n"],["\u003cp\u003e\u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e activates logging in the library by providing a default backend, and \u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is used for configuring the GCP project in examples and integration tests, but it does not directly affect the library.\u003c/p\u003e\n"],["\u003cp\u003eUsers can refer to the linked documentation for \u003ccode\u003egoogle::cloud::EndpointOption\u003c/code\u003e, \u003ccode\u003egoogle::cloud::LoggingComponentsOption\u003c/code\u003e, \u003ccode\u003egoogle::cloud::GrpcTracingOptionsOption\u003c/code\u003e, \u003ccode\u003egoogle::cloud::LogBackend\u003c/code\u003e, and \u003ccode\u003egoogle::cloud::LogSink\u003c/code\u003e to gain more detailed insights into library configuration and logging.\u003c/p\u003e\n"]]],[],null,["Version 2.34.0keyboard_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::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."]]
