Project: userver (App Definition and Development / Streaming & Messaging)
File: production_service.md

A good production ready service should have functionality for various cases: Overload Service should respond with HTTP 429 codes to some requests while still being able to handle the rest Debugging of a running service inspect logs get more logs from the suspiciously behaving service and then turn the logging level back profile memory usage see requests in flight Experiments Should be a way to turn on/off arbitrary functionality without restarting the service Metrics and Logs Functional testing This tutorial shows a configuration of a typical production ready service. For information about service interactions with other utilities and services in container see @ref scripts/docs/en/userver/deploy_env.md. Make sure that you can compile and run core tests and read a basic example @ref scripts/docs/en/userver/tutorial/hello_service.md. utils::DaemonMain initializes and starts the component system with the provided command line arguments: @snippet samples/productionservice/productionservice.cpp Production service sample - main A path to the static config file should be passed from a command line to start the service: ``` bash ./samples/userver-samples-productionservice --config /etc/production-service/staticconfig.yaml ``` Full static config could be seen at @ref samples/productionservice/staticconfig.yaml Important parts are described down below. Static configs tend to become quite big, so it is a good idea to move changing parts of it into variables. To do that, declare a `config_vars` field in the static config and point it to a file with variables. @snippet samples/productionservice/staticconfig.yaml Production service sample - static config - config vars A file with config variables could look @ref samples/productionservice/configvars.yaml "like this". Now in static config you could use `$variable-name` to refer to a variable, `*#fallback` fields are used if there is no variable with such name in the config variables file: @snippet samples/productionservice/staticconfig.yaml Production service sample - static config variables usage A good practice is to have at least 3 different task processors: @snippet samples/productionservice/staticconfig.yaml Production service sample - static config task processors Moving blocking operations into a separate task processor improves responsiveness and CPU usage of your service. Monitor task processor helps to get statistics and diagnostics from server under heavy load or from a server with a deadlocked threads in the main task processor. @warning This setup is for an abstract service on an abstract 8 core machine. Benchmark your service on your hardware and hand-tune the thread numbers to get optimal performance. Note the components::Server configuration: @snippet samples/productionservice/staticconfig.yaml Production service sample - static config server listen In this example we have two listeners. it is done to separate clients and utility/diagnostic handlers to listen on different ports or even interfaces. @anchor sampleprodserviceutilityhandlers Your server has the following utility handlers: to @ref scripts/docs/en/userver/requestsinflight.md "inspect in-flight request" - server::handlers::InspectRequests to @ref

"profile memory usage" - server::handlers::Jemalloc to @ref scripts/docs/en/userver/loglevelrunning_service.md "change logging level at runtime" - server::handlers::LogLevel and server::handlers::DynamicDebugLog to reopen log files after log rotation (you can also use @ref scripts/docs/en/userver/os_signals.md "signals") - server::handlers::OnLogRotate to @ref scripts/docs/en/userver/dns_control.md "control the DNS resolver" - server::handlers::DnsClientControl to @ref scripts/docs/en/userver/service_monitor.md "get statistics" from the service - server::handlers::ServerMonitor @snippet samples/productionservice/staticconfig.yaml Production service sample - static config utility handlers All those handlers live on a separate `components.server.listener-monitor` address, so you have to request them using the `listener-monitor` credentials: ``` bash $ curl http://localhost:8085/service/log-level/ {"init-log-level":"info","current-log-level":"info"} $ curl -X PUT 'http://localhost:8085/service/log-level/warning' {"init-log-level":"info","current-log-level":"warning"} ``` This is a server::handlers::Ping handle that returns 200 if the service is OK, 500 otherwise. Useful for balancers, that would stop sending traffic to the server if it responds with codes other than 200. @snippet samples/productionservice/staticconfig.yaml Production service sample - static config ping Note that the ping handler lives on the task processor of all the other handlers. Smart balancers may measure response times and send less traffic to the heavy loaded services. ``` bash $ curl --unix-socket service.socket http://localhost/ping -i HTTP/1.1 200 OK Date: Thu, 01 Jul 2021 12:46:07 UTC Content-Type: text/html; charset=utf-8 X-YaRequestId: 39e3f54b86984b8ca5235876dc566b27 Server: sample-production-service 1.0 X-YaTraceId: 4d7f8aa03e2d4e4d80a92a3ccecfbe6d Connection: keep-alive Content-Length: 0 ``` Here's a configuration of a dynamic config related components components::DynamicConfigClient, components::DynamicConfig, components::DynamicConfigClientUpdater. Service starts with some dynamic config values from `dynamic-config.fs-cache-path` file and updates dynamic values from a @ref scripts/docs/en/userver/tutorial/config_service.md "configs service" at startup. @snippet samples/productionservice/staticconfig.yaml Production service sample - static config dynamic configs @note Dynamic configs is an essential part of a reliable service with high availability. Those could be used as an emergency switch for new functionality, selector for experiments, limits/timeouts/log-level setup, proxy setup. See @ref scripts/docs/en/schemas/dynamic_configs.md for more info and @ref scripts/docs/en/userver/tutorial/config_service.md for insights on how to implement such service. congestion_control::Component limits the active requests count. In case of overload it responds with HTTP 429 codes to some requests, allowing your service to properly process handle the rest. All the significant parts of the component are configured by dynamic config options @ref USERVERRPSCCONTROL and @ref USERVERRPSCCONTROL_ENABLED @snippet samples/productionservice/staticconfig.yaml Production service sample - static config congestion-control It is a good idea to disable it in unit tests to avoid getting HTTP 429 on an overloaded CI server. @anchor tutorial_metrics Metrics is a convenient way to monitor the health of your service. Typical setup of components::SystemStatisticsCollector and components::StatisticsStorage is quite trivial: @snippet samples/productionservice/staticconfig.yaml Production service sample - static config metrics With such setup you could poll the metrics from handler server::handlers::ServerMonitor that we've configured in @ref sampleprodserviceutilityhandlers "previous

However a much more mature approach is to write a component that pushes the metrics directly into the remote metrics aggregation service or to write a handler that provides the metrics in the native aggregation service format. To produce metrics in declarative style use the utils::statistics::MetricTag or register your metrics writer in utils::statistics::Storage via RegisterWriter to produce metrics on per component basis. To test metrics refer to the @ref TESTSUITEMETRICSTESTING "testsuite metrics testing". List of userver built-in metrics could be found at @ref scripts/docs/en/userver/service_monitor.md. Alerts is a way to propagate critical errors from your service to a monitoring system. When the code identifies that something bad happened and a user should be notified about that, `alert_storage.FireAlert()` is called with the appropriate arguments. Then the alert subsystem notifies an external monitoring system (or a user) about the alert event though the specific HTTP handler. Storing sensitive data aside from the configs is a good practice that allows you to set different access rights for the two files. components::Secdist configuration is straightforward: @snippet samples/productionservice/staticconfig.yaml Production service sample - static config secdist Refer to the storages::secdist::SecdistConfig config for more information on the data retrieval. @anchor prodservicetestsuiterelatedcomponents server::handlers::TestsControl is a handle that allows controlling the service from test environments. That handle is used by the testsuite from @ref scripts/docs/en/userver/functional_testing.md "functional tests" to mock time, invalidate caches, testpoints and many other things. This component should be disabled in production environments. components::TestsuiteSupport is a lightweight storage to keep minor testsuite data. This component is required by many high-level components and it is safe to use this component in production environments. Dynamic configs are described in details at @ref scripts/docs/en/schemas/dynamic_configs.md . This sample requires @ref scripts/docs/en/userver/tutorial/config_service.md "configs service", so we build and start one from our previous tutorials. ``` bash mkdir build_release cd build_release cmake -DCMAKEBUILDTYPE=Release .. make userver-samples-config_service ./samples/userver-samples-config_service & make userver-samples-production_service python3 ../samples/tests/prepareproductionconfigs.py ./samples/userver-samples-productionservice --config /tmp/userver/productionservice/static_config.yaml ``` @ref scripts/docs/en/userver/functional_testing.md "Functional tests" are used to make sure that the service is working fine and implements the required functionality. A recommended practice is to build the service in Debug and Release modes and tests both of them, then deploy the Release build to the production, @ref "disabling all the tests related handlers". Debug builds of the userver provide numerous assertions that validate the framework usage and help to detect bugs at early stages. Typical functional tests for a service consist of a `conftest.py` file with mocks+configs for the sereffectivelyvice and a bunch of `test_*.py` files with actual tests. Such approach allows to reuse mocks and configurations in different tests. See the full example at @ref samples/productionservice/productionservice.cpp @ref samples/productionservice/staticconfig.yaml @ref samples/productionservice/configvars.yaml @ref samples/production_service/CMakeLists.txt @ref samples/production_service/tests/conftest.py @ref samples/productionservice/tests/testping.py @ref samples/productionservice/tests/testproduction.py @htmlonly <div class="bottom-nav"> @endhtmlonly @ref scripts/docs/en/userver/tutorial/configservice.md | @ref scripts/docs/en/userver/tutorial/tcpservice.md @htmlonly </div> @endhtmlonly @example samples/productionservice/productionservice.cpp @example samples/productionservice/staticconfig.yaml @example samples/productionservice/configvars.yaml @example samples/production_service/CMakeLists.txt @example samples/production_service/tests/conftest.py @example samples/productionservice/tests/testping.py @example samples/productionservice/tests/testproduction.py