[[grpc-component]]
== gRPC Component

*Available as of Camel version 2.19*

The gRPC component allows you to call or expose Remote Procedure Call (RPC) services
using https://developers.google.com/protocol-buffers/docs/overview[Protocol Buffers (protobuf)] 
exchange format over HTTP/2 transport.

Maven users will need to add the following dependency to their `pom.xml`
for this component:

[source,xml]
------------------------------------------------------------
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-grpc</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
------------------------------------------------------------

Starting with Camel *2.22* gRCP requires strong own of the Google Guava version. It's necessary to
add following configuration property to the maven file

[source,xml]
------------------------------------------------------------
<properties>
    <google-guava-version>${grpc-guava-version}</google-guava-version>
<properties>
------------------------------------------------------------

### URI format

[source,java]
-------------------------------------
grpc://service[?options]
-------------------------------------

### Endpoint Options

// component options: START
The gRPC component has no options.
// component options: END

// endpoint options: START
The gRPC endpoint is configured using URI syntax:

----
grpc:host:port/service
----

with the following path and query parameters:

==== Path Parameters (3 parameters):


[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *host* | *Required* The gRPC server host name. This is localhost or 0.0.0.0 when being a consumer or remote server host name when using producer. |  | String
| *port* | *Required* The gRPC local or remote server port |  | int
| *service* | *Required* Fully qualified service name from the protocol buffer descriptor file (package dot service definition name) |  | String
|===


==== Query Parameters (25 parameters):


[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *flowControlWindow* (common) | The HTTP/2 flow control window size (MiB) | 1048576 | int
| *maxMessageSize* (common) | The maximum message size allowed to be received/sent (MiB) | 4194304 | int
| *bridgeErrorHandler* (consumer) | Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. | false | boolean
| *consumerStrategy* (consumer) | This option specifies the top-level strategy for processing service requests and responses in streaming mode. If an aggregation strategy is selected, all requests will be accumulated in the list, then transferred to the flow, and the accumulated responses will be sent to the sender. If a propagation strategy is selected, request is sent to the stream, and the response will be immediately sent back to the sender. | PROPAGATION | GrpcConsumerStrategy
| *forwardOnCompleted* (consumer) | Determines if onCompleted events should be pushed to the Camel route. | false | boolean
| *forwardOnError* (consumer) | Determines if onError events should be pushed to the Camel route. Exceptions will be set as message body. | false | boolean
| *maxConcurrentCallsPer Connection* (consumer) | The maximum number of concurrent calls permitted for each incoming server connection | 2147483647 | int
| *exceptionHandler* (consumer) | To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored. |  | ExceptionHandler
| *exchangePattern* (consumer) | Sets the exchange pattern when the consumer creates an exchange. |  | ExchangePattern
| *method* (producer) | gRPC method name |  | String
| *producerStrategy* (producer) | The mode used to communicate with a remote gRPC server. In SIMPLE mode a single exchange is translated into a remote procedure call. In STREAMING mode all exchanges will be sent within the same request (input and output of the recipient gRPC service must be of type 'stream'). | SIMPLE | GrpcProducerStrategy
| *streamRepliesTo* (producer) | When using STREAMING client mode, it indicates the endpoint where responses should be forwarded. |  | String
| *userAgent* (producer) | The user agent header passed to the server |  | String
| *synchronous* (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean
| *authenticationType* (security) | Authentication method type in advance to the SSL/TLS negotiation | NONE | GrpcAuthType
| *jwtAlgorithm* (security) | JSON Web Token sign algorithm | HMAC256 | JwtAlgorithm
| *jwtIssuer* (security) | JSON Web Token issuer |  | String
| *jwtSecret* (security) | JSON Web Token secret |  | String
| *jwtSubject* (security) | JSON Web Token subject |  | String
| *keyCertChainResource* (security) | The X.509 certificate chain file resource in PEM format link |  | String
| *keyPassword* (security) | The PKCS#8 private key file password |  | String
| *keyResource* (security) | The PKCS#8 private key file resource in PEM format link |  | String
| *negotiationType* (security) | Identifies the security negotiation type used for HTTP/2 communication | PLAINTEXT | NegotiationType
| *serviceAccountResource* (security) | Service Account key file in JSON format resource link supported by the Google Cloud SDK |  | String
| *trustCertCollectionResource* (security) | The trusted certificates collection file resource in PEM format for verifying the remote endpoint's certificate |  | String
|===
// endpoint options: END
// spring-boot-auto-configure options: START
=== Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-grpc-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>
----


The component supports 2 options, which are listed below.



[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *camel.component.grpc.enabled* | Enable grpc component | true | Boolean
| *camel.component.grpc.resolve-property-placeholders* | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | Boolean
|===
// spring-boot-auto-configure options: END


### Transport security and authentication support (available from *Camel 2.20*)

The following https://grpc.io/docs/guides/auth.html[authentication] mechanisms are built-in to gRPC and available in this component:

* *SSL/TLS:* gRPC has SSL/TLS integration and promotes the use of SSL/TLS to authenticate the server, and to encrypt all the data exchanged between the client and the server. Optional mechanisms are available for clients to provide certificates for mutual authentication.
* *Token-based authentication with Google:* gRPC provides a generic mechanism to attach metadata based credentials to requests and responses. Additional support for acquiring access tokens while accessing Google APIs through gRPC is provided. In general this mechanism must be used as well as SSL/TLS on the channel.

To enable these features the following component properties combinations must be configured:

[width="100%",cols="10%,20%,25%,15%,30%",options="header",]
|=======================================================================
|Num.|Option |Parameter|Value|Required/Optional
|1|*SSL/TLS*|negotiationType|TLS|Required
|||keyCertChainResource||Required
|||keyResource||Required
|||keyPassword||Optional
|||trustCertCollectionResource||Optional
|2|*Token-based authentication with Google API*|authenticationType|GOOGLE|Required
|||negotiationType|TLS|Required
|||serviceAccountResource||Required
|3|*Custom JSON Web Token implementation authentication*|authenticationType|JWT|Required
|||negotiationType|NONE or TLS|Optional. The TLS/SSL not checking for this type, but strongly recommended.
|||jwtAlgorithm|HMAC256(default) or (HMAC384,HMAC512)|Optional
|||jwtSecret||Required
|||jwtIssuer||Optional
|||jwtSubject||Optional
|=======================================================================
TLS with OpenSSL is currently the recommended approach for using gRPC over TLS component.
Using the JDK for ALPN is generally much slower and may not support the necessary ciphers for HTTP2. This function is not implemented in the component.

### gRPC producer resource type mapping

The table below shows the types of objects in the message body, depending on the types (simple or stream) of incoming and outgoing parameters, as well as the invocation style (synchronous or asynchronous). Please note, that invocation of the procedures with incoming stream parameter in asynchronous style are not allowed.

[width="100%",cols="15%,15%,15%,25%,25%",options="header",]
|=======================================================================
|Invocation style |Request type|Response type|Request Body Type|Result Body Type

|*synchronous*|simple|simple|Object|Object
|*synchronous*|simple|stream|Object|List<Object>
|synchronous|stream|simple|not allowed|not allowed
|synchronous|stream|stream|not allowed|not allowed

|*asynchronous*|simple|simple|Object|List<Object>
|*asynchronous*|simple|stream|Object|List<Object>
|*asynchronous*|stream|simple|Object or List<Object>|List<Object>
|*asynchronous*|stream|stream|Object or List<Object>|List<Object>

|=======================================================================

### gRPC consumer headers (will be installed after the consumer invocation)

[width="100%",cols="25%,50,25%",options="header",]
|=======================================================================
|Header name |Description|Possible values

|*CamelGrpcMethodName*|Method name handled by the consumer service|
|*CamelGrpcEventType*|Received event type from the sent request|onNext, onCompleted or onError
|*CamelGrpcUserAgent*|If provided, the given agent will prepend the gRPC library's user agent information|

|=======================================================================

### Examples

Below is a simple synchronous method invoke with host and port parameters

[source,java]
-------------------------------------------------------------------------------
from("direct:grpc-sync")
.to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=sendPing&synchronous=true");
-------------------------------------------------------------------------------

[source,java]
---------------------------------------------------------------------------------------
<route>
    <from uri="direct:grpc-sync" />
    <to uri="grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=sendPing&synchronous=true"/>
</route>
---------------------------------------------------------------------------------------

An asynchronous method invoke

[source,java]
-------------------------------------------------------------------------------
from("direct:grpc-async")
.to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=pingAsyncResponse");
-------------------------------------------------------------------------------

gRPC service consumer with propagation consumer strategy

[source,java]
-------------------------------------------------------------------------------
from("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?consumerStrategy=PROPAGATION")
.to("direct:grpc-service");
-------------------------------------------------------------------------------

gRPC service producer with streaming producer strategy (requires a service that uses "stream" mode as input and output)

[source,java]
-------------------------------------------------------------------------------
from("direct:grpc-request-stream")
.to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=PingAsyncAsync&producerStrategy=STREAMING&streamRepliesTo=direct:grpc-response-stream");

from("direct:grpc-response-stream")
.log("Response received: ${body}");
-------------------------------------------------------------------------------

gRPC service consumer TLS/SLL security negotiation enable

[source,java]
-------------------------------------------------------------------------------
from("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?consumerStrategy=PROPAGATION&negotiationType=TLS&keyCertChainResource=file:src/test/resources/certs/server.pem&keyResource=file:src/test/resources/certs/server.key&trustCertCollectionResource=file:src/test/resources/certs/ca.pem")
.to("direct:tls-enable")
-------------------------------------------------------------------------------

gRPC service producer with custom JSON Web Token implementation authentication

[source,java]
-------------------------------------------------------------------------------
from("direct:grpc-jwt")
.to("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?method=pingSyncSync&synchronous=true&authenticationType=JWT&jwtSecret=supersecuredsecret");
-------------------------------------------------------------------------------

### Configuration

It's it is recommended to use Maven Protocol Buffers Plugin which calls Protocol Buffer Compiler (protoc) tool to generate Java source files from .proto (protocol buffer definition) files for the custom project. This plugin will generate procedures request and response classes, their builders and gRPC procedures stubs classes as well.

Following steps are required:

Insert operating system and CPU architecture detection extension inside **<build>** tag of the project pom.xml or set ${os.detected.classifier} parameter manually 
[source,xml]
-------------------------------------------------------------------------
<extensions>
  <extension>
    <groupId>kr.motd.maven</groupId>
    <artifactId>os-maven-plugin</artifactId>
    <version>1.4.1.Final</version>
  </extension>
</extensions>
-------------------------------------------------------------------------

Insert gRPC and protobuf Java code generator plugin **<plugins>** tag of the project pom.xml
[source,xml]
-------------------------------------------------------------------------
<plugin>
  <groupId>org.xolstice.maven.plugins</groupId>
  <artifactId>protobuf-maven-plugin</artifactId>
  <version>0.5.0</version>
  <configuration>
    <protocArtifact>com.google.protobuf:protoc:${protobuf-version}:exe:${os.detected.classifier}</protocArtifact>
    <pluginId>grpc-java</pluginId>
    <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc-version}:exe:${os.detected.classifier}</pluginArtifact>
  </configuration>
  <executions>
    <execution>
      <goals>
        <goal>compile</goal>
        <goal>compile-custom</goal>
        <goal>test-compile</goal>
        <goal>test-compile-custom</goal>
      </goals>
    </execution>
  </executions>
</plugin>
-------------------------------------------------------------------------

### For more information, see these resources

http://www.grpc.io/[gRPC project site]

https://www.xolstice.org/protobuf-maven-plugin[Maven Protocol Buffers Plugin]

### See Also

* Getting Started
* Configuring Camel
* Component
* Endpoint
* <<protobuf-dataformat,Protocol Buffers Data Format>>
