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 C++ Pub/Sub library versions, ranging from 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe document details the use of environment variables for configuring the library's behavior, specifically focusing on troubleshooting and testing scenarios.\u003c/p\u003e\n"],["\u003cp\u003eEndpoint overrides are supported via the \u003ccode\u003ePUBSUB_EMULATOR_HOST\u003c/code\u003e environment variable, which allows redirection to a custom endpoint, primarily for testing.\u003c/p\u003e\n"],["\u003cp\u003eTracing and logging for gRPC calls can be enabled and configured using \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_TRACING\u003c/code\u003e and \u003ccode\u003eGOOGLE_CLOUD_CPP_ENABLE_CLOG\u003c/code\u003e, respectively, with further customization options available via \u003ccode\u003eGOOGLE_CLOUD_CPP_TRACING_OPTIONS\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe environment variable \u003ccode\u003eGOOGLE_CLOUD_PROJECT\u003c/code\u003e is mentioned in the document for project configuration in examples and integration tests but is stated to have no direct effect within the library itself.\u003c/p\u003e\n"]]],[],null,["Version 2.28.0keyboard_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."]]
