gRPC

Package grpcpolaris grpc-go integrates with polaris-go

Package clientv3 implements the official Go etcd client for v3. Create client using `clientv3.New`: Make sure to close the client after using it. If the client is not closed, the connection will have leaky goroutines. To specify a client request timeout, wrap the context with context.WithTimeout: The Client has internal state (watchers and leases), so Clients should be reused instead of created as needed. Clients are safe for concurrent use by multiple goroutines. etcd client returns 2 types of errors: See https://github.com/etcd-io/etcd/blob/main/api/v3rpc/rpctypes/error.go Here is the example code to handle client errors: The grpc load balancer is registered statically and is shared across etcd clients. To enable detailed load balancer logging, set the ETCD_CLIENT_DEBUG environment variable. E.g. "ETCD_CLIENT_DEBUG=1".

Package grpc provides a grpc transport

Package grpctls provides helper structs and functions for grpc dialing with TLS options. See examples directory for common use. This package is a work in progress and makes no API stability promises.

Sample grpc-ping acts as an intermediary to the ping service.

Package transport provides a Transport for github.com/hashicorp/raft over gRPC.

Package cloud is the root of the packages used to access Google Cloud Services. See https://pkg.go.dev/cloud.google.com/go for a full list of sub-modules. All clients in sub-packages are configurable via client options. These options are described here: https://pkg.go.dev/google.golang.org/api/option. Endpoint configuration is used to specify the URL to which requests are sent. It is used for services that support or require regional endpoints, as well as for other use cases such as testing against fake servers. For example, the Vertex AI service recommends that you configure the endpoint to the location with the features you want that is closest to your physical location or the location of your users. There is no global endpoint for Vertex AI. See Vertex AI - Locations for more details. The following example demonstrates configuring a Vertex AI client with a regional endpoint: All of the clients support authentication via Google Application Default Credentials, or by providing a JSON key file for a Service Account. See examples below. Google Application Default Credentials (ADC) is the recommended way to authorize and authenticate clients. For information on how to create and obtain Application Default Credentials, see https://cloud.google.com/docs/authentication/production. If you have your environment configured correctly you will not need to pass any extra information to the client libraries. Here is an example of a client using ADC to authenticate: You can use a file with credentials to authenticate and authorize, such as a JSON key file associated with a Google service account. Service Account keys can be created and downloaded from https://console.cloud.google.com/iam-admin/serviceaccounts. This example uses the Secret Manger client, but the same steps apply to the all other client libraries this package as well. Example: In some cases (for instance, you don't want to store secrets on disk), you can create credentials from in-memory JSON and use the WithCredentials option. This example uses the Secret Manager client, but the same steps apply to all other client libraries as well. Note that scopes can be found at https://developers.google.com/identity/protocols/oauth2/scopes, and are also provided in all auto-generated libraries: for example, cloud.google.com/go/secretmanager/apiv1 provides DefaultAuthScopes. Example: By default, non-streaming methods, like Create or Get, will have a default deadline applied to the context provided at call time, unless a context deadline is already set. Streaming methods have no default deadline and will run indefinitely. To set timeouts or arrange for cancellation, use context. Transient errors will be retried when correctness allows. Here is an example of setting a timeout for an RPC using context.WithTimeout: Here is an example of setting a timeout for an RPC using github.com/googleapis/gax-go/v2.WithTimeout: Here is an example of how to arrange for an RPC to be canceled, use context.WithCancel: Do not attempt to control the initial connection (dialing) of a service by setting a timeout on the context passed to NewClient. Dialing is non-blocking, so timeouts would be ineffective and would only interfere with credential refreshing, which uses the same context. Regardless of which transport is used, request headers can be set in the same way using [`callctx.SetHeaders`]setheaders. Here is a generic example: ## Google-reserved headers There are a some header keys that Google reserves for internal use that must not be ovewritten. The following header keys are broadly considered reserved and should not be conveyed by client library users unless instructed to do so: * `x-goog-api-client` * `x-goog-request-params` Be sure to check the individual package documentation for other service-specific reserved headers. For example, Storage supports a specific auditing header that is mentioned in that [module's documentation]storagedocs. ## Google Cloud system parameters Google Cloud services respect system parameterssystem parameters that can be used to augment request and/or response behavior. For the most part, they are not needed when using one of the enclosed client libraries. However, those that may be necessary are made available via the [`callctx`]callctx package. If not present there, consider opening an issue on that repo to request a new constant. Connection pooling differs in clients based on their transport. Cloud clients either rely on HTTP or gRPC transports to communicate with Google Cloud. Cloud clients that use HTTP rely on the underlying HTTP transport to cache connections for later re-use. These are cached to the http.MaxIdleConns and http.MaxIdleConnsPerHost settings in http.DefaultTransport by default. For gRPC clients, connection pooling is configurable. Users of Cloud Client Libraries may specify option.WithGRPCConnectionPool(n) as a client option to NewClient calls. This configures the underlying gRPC connections to be pooled and accessed in a round robin fashion. Minimal container images like Alpine lack CA certificates. This causes RPCs to appear to hang, because gRPC retries indefinitely. See https://github.com/googleapis/google-cloud-go/issues/928 for more information. For tips on how to write tests against code that calls into our libraries check out our Debugging Guide. For tips on how to write tests against code that calls into our libraries check out our Testing Guide. Most of the errors returned by the generated clients are wrapped in an github.com/googleapis/gax-go/v2/apierror.APIError and can be further unwrapped into a google.golang.org/grpc/status.Status or google.golang.org/api/googleapi.Error depending on the transport used to make the call (gRPC or REST). Converting your errors to these types can be a useful way to get more information about what went wrong while debugging. APIError gives access to specific details in the error. The transport-specific errors can still be unwrapped using the APIError. If the gRPC transport was used, the google.golang.org/grpc/status.Status can still be parsed using the google.golang.org/grpc/status.FromError function. Semver is used to communicate stability of the sub-modules of this package. Note, some stable sub-modules do contain packages, and sometimes features, that are considered unstable. If something is unstable it will be explicitly labeled as such. Example of package does in an unstable package: Clients that contain alpha and beta in their import path may change or go away without notice. Clients marked stable will maintain compatibility with future versions for as long as we can reasonably sustain. Incompatible changes might be made in some situations, including:

Package storage provides an easy way to work with Google Cloud Storage. Google Cloud Storage stores data in named objects, which are grouped into buckets. More information about Google Cloud Storage is available at https://cloud.google.com/storage/docs. See https://pkg.go.dev/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. To start working with this package, create a Client: The client will use your default application credentials. Clients should be reused instead of created as needed. The methods of Client are safe for concurrent use by multiple goroutines. You may configure the client by passing in options from the google.golang.org/api/option package. You may also use options defined in this package, such as WithJSONReads. If you only wish to access public data, you can create an unauthenticated client with To use an emulator with this library, you can set the STORAGE_EMULATOR_HOST environment variable to the address at which your emulator is running. This will send requests to that address instead of to Cloud Storage. You can then create and use a client as usual: Please note that there is no official emulator for Cloud Storage. A Google Cloud Storage bucket is a collection of objects. To work with a bucket, make a bucket handle: A handle is a reference to a bucket. You can have a handle even if the bucket doesn't exist yet. To create a bucket in Google Cloud Storage, call BucketHandle.Create: Note that although buckets are associated with projects, bucket names are global across all projects. Each bucket has associated metadata, represented in this package by BucketAttrs. The third argument to BucketHandle.Create allows you to set the initial BucketAttrs of a bucket. To retrieve a bucket's attributes, use BucketHandle.Attrs: An object holds arbitrary data as a sequence of bytes, like a file. You refer to objects using a handle, just as with buckets, but unlike buckets you don't explicitly create an object. Instead, the first time you write to an object it will be created. You can use the standard Go io.Reader and io.Writer interfaces to read and write object data: Objects also have attributes, which you can fetch with ObjectHandle.Attrs: Listing objects in a bucket is done with the BucketHandle.Objects method: Objects are listed lexicographically by name. To filter objects lexicographically, [Query.StartOffset] and/or [Query.EndOffset] can be used: If only a subset of object attributes is needed when listing, specifying this subset using Query.SetAttrSelection may speed up the listing process: Both objects and buckets have ACLs (Access Control Lists). An ACL is a list of ACLRules, each of which specifies the role of a user, group or project. ACLs are suitable for fine-grained control, but you may prefer using IAM to control access at the project level (see Cloud Storage IAM docs. To list the ACLs of a bucket or object, obtain an ACLHandle and call ACLHandle.List: You can also set and delete ACLs. Every object has a generation and a metageneration. The generation changes whenever the content changes, and the metageneration changes whenever the metadata changes. Conditions let you check these values before an operation; the operation only executes if the conditions match. You can use conditions to prevent race conditions in read-modify-write operations. For example, say you've read an object's metadata into objAttrs. Now you want to write to that object, but only if its contents haven't changed since you read it. Here is how to express that: You can obtain a URL that lets anyone read or write an object for a limited time. Signing a URL requires credentials authorized to sign a URL. To use the same authentication that was used when instantiating the Storage client, use BucketHandle.SignedURL. You can also sign a URL without creating a client. See the documentation of SignedURL for details. A type of signed request that allows uploads through HTML forms directly to Cloud Storage with temporary permission. Conditions can be applied to restrict how the HTML form is used and exercised by a user. For more information, please see the XML POST Object docs as well as the documentation of BucketHandle.GenerateSignedPostPolicyV4. If the GoogleAccessID and PrivateKey option fields are not provided, they will be automatically detected by BucketHandle.SignedURL and BucketHandle.GenerateSignedPostPolicyV4 if any of the following are true: Detecting GoogleAccessID may not be possible if you are authenticated using a token source or using option.WithHTTPClient. In this case, you can provide a service account email for GoogleAccessID and the client will attempt to sign the URL or Post Policy using that service account. To generate the signature, you must have: Errors returned by this client are often of the type googleapi.Error. These errors can be introspected for more information by using errors.As with the richer googleapi.Error type. For example: Methods in this package may retry calls that fail with transient errors. Retrying continues indefinitely unless the controlling context is canceled, the client is closed, or a non-transient error is received. To stop retries from continuing, use context timeouts or cancellation. The retry strategy in this library follows best practices for Cloud Storage. By default, operations are retried only if they are idempotent, and exponential backoff with jitter is employed. In addition, errors are only retried if they are defined as transient by the service. See the Cloud Storage retry docs for more information. Users can configure non-default retry behavior for a single library call (using BucketHandle.Retryer and ObjectHandle.Retryer) or for all calls made by a client (using Client.SetRetry). For example: You can add custom headers to any API call made by this package by using callctx.SetHeaders on the context which is passed to the method. For example, to add a custom audit logging header: This package includes support for the Cloud Storage gRPC API. The implementation uses gRPC rather than the Default JSON & XML APIs to make requests to Cloud Storage. The Go Storage gRPC client is generally available. The Notifications, Serivce Account HMAC and GetServiceAccount RPCs are not supported through the gRPC client. To create a client which will use gRPC, use the alternate constructor: Using the gRPC API inside GCP with a bucket in the same region can allow for Direct Connectivity (enabling requests to skip some proxy steps and reducing response latency). A warning is emmitted if gRPC is not used within GCP to warn that Direct Connectivity could not be initialized. Direct Connectivity is not required to access the gRPC API. Dependencies for the gRPC API may slightly increase the size of binaries for applications depending on this package. If you are not using gRPC, you can use the build tag `disable_grpc_modules` to opt out of these dependencies and reduce the binary size. The gRPC client emits metrics by default and will export the gRPC telemetry discussed in gRFC/66 and gRFC/78 to Google Cloud Monitoring. The metrics are accessible through Cloud Monitoring API and you incur no additional cost for publishing the metrics. Google Cloud Support can use this information to more quickly diagnose problems related to GCS and gRPC. Sending this data does not incur any billing charges, and requires minimal CPU (a single RPC every minute) or memory (a few KiB to batch the telemetry). To access the metrics you can view them through Cloud Monitoring metric explorer with the prefix `storage.googleapis.com/client`. Metrics are emitted every minute. You can disable metrics using the following example when creating a new gRPC client using WithDisabledClientMetrics. The metrics exporter uses Cloud Monitoring API which determines project ID and credentials doing the following: * Project ID is determined using OTel Resource Detector for the environment otherwise it falls back to the project provided by google.FindCredentials. * Credentials are determined using Application Default Credentials. The principal must have `roles/monitoring.metricWriter` role granted. If not a logged warning will be emitted. Subsequent are silenced to prevent noisy logs. Certain control plane and long-running operations for Cloud Storage (including Folder and Managed Folder operations) are supported via the autogenerated Storage Control client, which is available as a subpackage in this module. See package docs at cloud.google.com/go/storage/control/apiv2 or reference the Storage Control API docs.

Package pubsub provides an easy way to publish and receive Google Cloud Pub/Sub messages, hiding the details of the underlying server RPCs. Pub/Sub is a many-to-many, asynchronous messaging system that decouples senders and receivers. More information about Pub/Sub is available at https://cloud.google.com/pubsub/docs See https://godoc.org/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. Pub/Sub messages are published to topics. A Topic may be created using Client.CreateTopic like so: Messages may then be published to a Topic: Topic.Publish queues the message for publishing and returns immediately. When enough messages have accumulated, or enough time has elapsed, the batch of messages is sent to the Pub/Sub service. Topic.Publish returns a PublishResult, which behaves like a future: its Get method blocks until the message has been sent to the service. The first time you call Topic.Publish on a Topic, goroutines are started in the background. To clean up these goroutines, call Topic.Stop: To receive messages published to a Topic, clients create a Subscription for the topic. There may be more than one subscription per topic ; each message that is published to the topic will be delivered to all associated subscriptions. A Subscription may be created like so: Messages are then consumed from a Subscription via callback. The callback is invoked concurrently by multiple goroutines, maximizing throughput. To terminate a call to Subscription.Receive, cancel its context. Once client code has processed the Message, it must call Message.Ack or Message.Nack; otherwise the Message will eventually be redelivered. Ack/Nack MUST be called within the Subscription.Receive handler function, and not from a goroutine. Otherwise, flow control (e.g. ReceiveSettings.MaxOutstandingMessages) will not be respected, and messages can get orphaned when cancelling Receive. If the client cannot or doesn't want to process the message, it can call Message.Nack to speed redelivery. For more information and configuration options, see Ack Deadlines below. Note: It is possible for a Message to be redelivered even if Message.Ack has been called. Client code must be robust to multiple deliveries of messages. Note: This uses pubsub's streaming pull feature. This feature has properties that may be surprising. Please take a look at https://cloud.google.com/pubsub/docs/pull#streamingpull for more details on how streaming pull behaves compared to the synchronous pull method. The number of StreamingPull connections can be configured by setting NumGoroutines in ReceiveSettings. The default value of 10 means the client library will maintain 10 StreamingPull connections. This is more than sufficient for most use cases, as StreamingPull connections can handle up to 10 MB/s https://cloud.google.com/pubsub/quotas#resource_limits. In some cases, using too many streams can lead to client library behaving poorly as the application becomes I/O bound. By default, the number of connections in the gRPC conn pool is min(4,GOMAXPROCS). Each connection supports up to 100 streams. Thus, if you have 4 or more CPU cores, the default setting allows a maximum of 400 streams which is already excessive for most use cases. If you want to change the limits on the number of streams, you can change the number of connections in the gRPC connection pool as shown below: The default pubsub deadlines are suitable for most use cases, but may be overridden. This section describes the tradeoffs that should be considered when overriding the defaults. Behind the scenes, each message returned by the Pub/Sub server has an associated lease, known as an "ack deadline". Unless a message is acknowledged within the ack deadline, or the client requests that the ack deadline be extended, the message will become eligible for redelivery. As a convenience, the pubsub client will automatically extend deadlines until either: Ack deadlines are extended periodically by the client. The period between extensions, as well as the length of the extension, automatically adjusts based on the time it takes the subscriber application to ack messages (based on the 99th percentile of ack latency). By default, this extension period is capped at 10m, but this limit can be configured by the "MaxExtensionPeriod" setting. This has the effect that subscribers that process messages quickly have their message ack deadlines extended for a short amount, whereas subscribers that process message slowly have their message ack deadlines extended for a large amount. The net effect is fewer RPCs sent from the client library. For example, consider a subscriber that takes 3 minutes to process each message. Since the library has already recorded several 3-minute "ack latencies"s in a percentile distribution, future message extensions are sent with a value of 3 minutes, every 3 minutes. Suppose the application crashes 5 seconds after the library sends such an extension: the Pub/Sub server would wait the remaining 2m55s before re-sending the messages out to other subscribers. Please note that by default, the client library does not use the subscription's AckDeadline for the MaxExtension value. For use cases where message processing exceeds 30 minutes, we recommend using the base client in a pull model, since long-lived streams are periodically killed by firewalls. See the example at https://godoc.org/cloud.google.com/go/pubsub/apiv1#example-SubscriberClient-Pull-LengthyClientProcessing To use an emulator with this library, you can set the PUBSUB_EMULATOR_HOST environment variable to the address at which your emulator is running. This will send requests to that address instead of to Pub/Sub. You can then create and use a client as usual:

Package cloud is the root of the packages used to access Google Cloud Services. See https://godoc.org/cloud.google.com/go for a full list of sub-packages. All clients in sub-packages are configurable via client options. These options are described here: https://godoc.org/google.golang.org/api/option. All the clients in sub-packages support authentication via Google Application Default Credentials (see https://cloud.google.com/docs/authentication/production), or by providing a JSON key file for a Service Account. See the authentication examples in this package for details. By default, all requests in sub-packages will run indefinitely, retrying on transient errors when correctness allows. To set timeouts or arrange for cancellation, use contexts. See the examples for details. Do not attempt to control the initial connection (dialing) of a service by setting a timeout on the context passed to NewClient. Dialing is non-blocking, so timeouts would be ineffective and would only interfere with credential refreshing, which uses the same context. Connection pooling differs in clients based on their transport. Cloud clients either rely on HTTP or gRPC transports to communicate with Google Cloud. Cloud clients that use HTTP (bigquery, compute, storage, and translate) rely on the underlying HTTP transport to cache connections for later re-use. These are cached to the default http.MaxIdleConns and http.MaxIdleConnsPerHost settings in http.DefaultTransport. For gRPC clients (all others in this repo), connection pooling is configurable. Users of cloud client libraries may specify option.WithGRPCConnectionPool(n) as a client option to NewClient calls. This configures the underlying gRPC connections to be pooled and addressed in a round robin fashion. Minimal docker images like Alpine lack CA certificates. This causes RPCs to appear to hang, because gRPC retries indefinitely. See https://github.com/GoogleCloudPlatform/google-cloud-go/issues/928 for more information. To see gRPC logs, set the environment variable GRPC_GO_LOG_SEVERITY_LEVEL. See https://godoc.org/google.golang.org/grpc/grpclog for more information. For HTTP logging, set the GODEBUG environment variable to "http2debug=1" or "http2debug=2". Google Application Default Credentials is the recommended way to authorize and authenticate clients. For information on how to create and obtain Application Default Credentials, see https://developers.google.com/identity/protocols/application-default-credentials. To arrange for an RPC to be canceled, use context.WithCancel. You can use a file with credentials to authenticate and authorize, such as a JSON key file associated with a Google service account. Service Account keys can be created and downloaded from https://console.developers.google.com/permissions/serviceaccounts. This example uses the Datastore client, but the same steps apply to the other client libraries underneath this package. In some cases (for instance, you don't want to store secrets on disk), you can create credentials from in-memory JSON and use the WithCredentials option. The google package in this example is at golang.org/x/oauth2/google. This example uses the PubSub client, but the same steps apply to the other client libraries underneath this package. To set a timeout for an RPC, use context.WithTimeout.

Package promgrpc is an instrumentation package that allows capturing metrics of your gRPC based services, both the server and the client side. The main goal of version 4 was to make it modular without sacrificing the simplicity of use. It is still possible to integrate the package in just a few lines. However, if necessary, metrics can be added, removed or modified freely. The package does not introduce any new concepts to an already complicated environment. Instead, it focuses on providing implementations of interfaces exported by gRPC and Prometheus libraries. It causes no side effects nor has global state. Instead, it comes with handy one-liners to reduce integration overhead. The package achieved high modularity by using Inversion of Control. We can define three layers of abstraction, where each is configurable or if necessary replaceable. Collectors serve one purpose, storing metrics. These are types well known from Prometheus ecosystem, like counters, gauges, histograms or summaries. This package comes with a set of predefined functions that create a specific instances for each use case. For example: Level higher consist of stats handlers. This layer is responsible for metrics collection. It is aware of a collector and knows how to use it to record event occurrences. Each implementation satisfies stats.Handler and prometheus.Collector interface and knows how to monitor a single dimension, e.g. a total number of received/sent requests: Above all, there is a coordinator. StatsHandler combines multiple stats handlers into a single instance. The package comes with eighteen predefined metrics — nine for server and nine for client side: The package does not require any configuration whatsoever but makes it possible. It is beneficial for different reasons. Having all metrics enabled could not be desirable. Some, like histograms, can create significant overhead on the producer side. If performance is critical, it advisable to reduce the set of metrics. To do that, implement a custom version of coordinator constructor, ClientStatsHandler and/or ServerStatsHandler. Another good reason to change default settings is backward compatibility. Migration of Grafana dashboards is not an easy nor quick task. If the discrepancy is small and, e.g. the only necessary adjustment is changing the namespace, it is achievable by passing CollectorWithNamespace to a collector constructor. It is the same very known pattern from the gRPC package, with some enhancements. What makes it different is that both StatsHandlerOption and CollectorOption have a shareable variant, called ShareableCollectorOption and ShareableStatsHandlerOption respectively. Thanks to that, it is possible to pass options related to stats handlers and collectors to coordinator constructors. Constructors take care of moving options to the correct receivers. Mixing both strategies described above will give even greater freedom. However, if that is even not enough, it is possible to reimplement an entire stack for a given metric or metrics.

Package otlpexporter exports data by using the OTLP format to a gRPC endpoint.

Package jaegerexporter sends trace data to a Jaeger Collector gRPC endpoint.

Package oauth2clientauthextension implements `cauth.Client` This extension provides OAuth2 Client Credentials flow authenticator for HTTP and gRPC based exporters. The extension fetches and refreshes the token after expiry For further details about OAuth2 Client Credentials flow refer https://datatracker.ietf.org/doc/html/rfc6749#section-4.4

Package pubsublite provides an easy way to publish and receive messages using the Pub/Sub Lite service. Google Pub/Sub services are designed to provide reliable, many-to-many, asynchronous messaging between applications. Publisher applications can send messages to a topic and other applications can subscribe to that topic to receive the messages. By decoupling senders and receivers, Google Pub/Sub allows developers to communicate between independently written applications. Compared to Cloud Pub/Sub, Pub/Sub Lite provides partitioned data storage with predefined throughput and storage capacity. Guidance on how to choose between Cloud Pub/Sub and Pub/Sub Lite is available at https://cloud.google.com/pubsub/docs/choosing-pubsub-or-lite. More information about Pub/Sub Lite is available at https://cloud.google.com/pubsub/lite. See https://pkg.go.dev/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. Examples can be found at https://pkg.go.dev/cloud.google.com/go/pubsublite#pkg-examples and https://pkg.go.dev/cloud.google.com/go/pubsublite/pscompat#pkg-examples. Complete sample programs can be found at https://github.com/GoogleCloudPlatform/golang-samples/tree/master/pubsublite. The cloud.google.com/go/pubsublite/pscompat subpackage contains clients for publishing and receiving messages, which have similar interfaces to their pubsub.Topic and pubsub.Subscription counterparts in cloud.google.com/go/pubsub. The following examples demonstrate how to declare common interfaces: https://pkg.go.dev/cloud.google.com/go/pubsublite/pscompat#example-NewPublisherClient-Interface and https://pkg.go.dev/cloud.google.com/go/pubsublite/pscompat#example-NewSubscriberClient-Interface. The following imports are required for code snippets below: Messages are published to topics. Pub/Sub Lite topics may be created like so: Close must be called to release resources when an AdminClient is no longer required. See https://cloud.google.com/pubsub/lite/docs/topics for more information about how Pub/Sub Lite topics are configured. See https://cloud.google.com/pubsub/lite/docs/locations for the list of locations where Pub/Sub Lite is available. Pub/Sub Lite uses gRPC streams extensively for high throughput. For more differences, see https://pkg.go.dev/cloud.google.com/go/pubsublite/pscompat. To publish messages to a topic, first create a PublisherClient: Then call Publish: Publish queues the message for publishing and returns immediately. When enough messages have accumulated, or enough time has elapsed, the batch of messages is sent to the Pub/Sub Lite service. Thresholds for batching can be configured in PublishSettings. Publish returns a PublishResult, which behaves like a future; its Get method blocks until the message has been sent (or has failed to be sent) to the service: Once you've finishing publishing all messages, call Stop to flush all messages to the service and close gRPC streams. The PublisherClient can no longer be used after it has been stopped or has terminated due to a permanent error. PublisherClients are expected to be long-lived and used for the duration of the application, rather than for publishing small batches of messages. Stop must be called to release resources when a PublisherClient is no longer required. See https://cloud.google.com/pubsub/lite/docs/publishing for more information about publishing. To receive messages published to a topic, create a subscription to the topic. There may be more than one subscription per topic; each message that is published to the topic will be delivered to all of its subscriptions. Pub/Sub Lite subscriptions may be created like so: See https://cloud.google.com/pubsub/lite/docs/subscriptions for more information about how subscriptions are configured. To receive messages for a subscription, first create a SubscriberClient: Messages are then consumed from a subscription via callback. The callback may be invoked concurrently by multiple goroutines (one per partition that the subscriber client is connected to). Receive blocks until either the context is canceled or a permanent error occurs. To terminate a call to Receive, cancel its context: Clients must call pubsub.Message.Ack() or pubsub.Message.Nack() for every message received. Pub/Sub Lite does not have ACK deadlines. Pub/Sub Lite also does not actually have the concept of NACK. The default behavior terminates the SubscriberClient. In Pub/Sub Lite, only a single subscriber for a given subscription is connected to any partition at a time, and there is no other client that may be able to handle messages. See https://cloud.google.com/pubsub/lite/docs/subscribing for more information about receiving messages. Pub/Sub Lite utilizes gRPC streams extensively. gRPC allows a maximum of 100 streams per connection. Internally, the library uses a default connection pool size of 8, which supports up to 800 topic partitions. To alter the connection pool size, pass a ClientOption to pscompat.NewPublisherClient and pscompat.NewSubscriberClient:

Package grpc provides a grpc transport

* Package multiresolver allows you to Dial to multiple hosts/IPs as a single ClientConn. * * Usage: multi:///127.0.0.1:1234,dns://example.org:1234 * Note the triple slash at the beginning. * * Make sure to import this package: * ``` * import _ "github.com/codeallergy/grpc-multi-resolver" * ```