Chapter 128. gRPC Component Available as of Camel version 2.19 The gRPC component allows you to call or expose Remote Procedure Call (RPC) services using 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: <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 <properties> <google-guava-version>USD{grpc-guava-version}</google-guava-version> <properties> 128.1. URI format grpc://service[?options] 128.2. Endpoint Options The gRPC component has no options. The gRPC endpoint is configured using URI syntax: with the following path and query parameters: 128.2.1. Path Parameters (3 parameters): 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 128.2.2. Query Parameters (25 parameters): 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 128.3. Spring Boot Auto-Configuration The component supports 2 options, which are listed below. 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 128.4. Transport security and authentication support (available from Camel 2.20 ) The following 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: 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. 128.5. 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. 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> 128.6. gRPC consumer headers (will be installed after the consumer invocation) 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 128.7. Examples Below is a simple synchronous method invoke with host and port parameters from("direct:grpc-sync") .to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=sendPing&synchronous=true"); <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 from("direct:grpc-async") .to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=pingAsyncResponse"); gRPC service consumer with propagation consumer strategy 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) 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: USD{body}"); gRPC service consumer TLS/SLL security negotiation enable 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 from("direct:grpc-jwt") .to("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?method=pingSyncSync&synchronous=true&authenticationType=JWT&jwtSecret=supersecuredsecret"); 128.8. 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 USD{os.detected.classifier} parameter manually <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 <plugin> <groupId>org.xolstice.maven.plugins</groupId> <artifactId>protobuf-maven-plugin</artifactId> <version>0.5.0</version> <configuration> <protocArtifact>com.google.protobuf:protoc:USD{protobuf-version}:exe:USD{os.detected.classifier}</protocArtifact> <pluginId>grpc-java</pluginId> <pluginArtifact>io.grpc:protoc-gen-grpc-java:USD{grpc-version}:exe:USD{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> 128.9. For more information, see these resources gRPC project site Maven Protocol Buffers Plugin 128.10. See Also Getting Started Configuring Camel Component Endpoint Protocol Buffers Data Format

Commands:
<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>
<properties> <google-guava-version>USD{grpc-guava-version}</google-guava-version> <properties>
grpc://service[?options]
grpc:host:port/service
from("direct:grpc-sync") .to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=sendPing&synchronous=true");
<route> <from uri="direct:grpc-sync" /> <to uri="grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=sendPing&synchronous=true"/> </route>
from("direct:grpc-async") .to("grpc://remotehost:1101/org.apache.camel.component.grpc.PingPong?method=pingAsyncResponse");
from("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?consumerStrategy=PROPAGATION") .to("direct:grpc-service");
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: USD{body}");
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")
from("direct:grpc-jwt") .to("grpc://localhost:1101/org.apache.camel.component.grpc.PingPong?method=pingSyncSync&synchronous=true&authenticationType=JWT&jwtSecret=supersecuredsecret");
<extensions> <extension> <groupId>kr.motd.maven</groupId> <artifactId>os-maven-plugin</artifactId> <version>1.4.1.Final</version> </extension> </extensions>
<plugin> <groupId>org.xolstice.maven.plugins</groupId> <artifactId>protobuf-maven-plugin</artifactId> <version>0.5.0</version> <configuration> <protocArtifact>com.google.protobuf:protoc:USD{protobuf-version}:exe:USD{os.detected.classifier}</protocArtifact> <pluginId>grpc-java</pluginId> <pluginArtifact>io.grpc:protoc-gen-grpc-java:USD{grpc-version}:exe:USD{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>