gRPC
Since Camel 2.19
Both producer and consumer are supported
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>
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>${grpc-guava-version}</google-guava-version>
<properties>
Configuring Options
Camel components are configured on two separate levels:
-
component level
-
endpoint level
Configuring Component Options
The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.
Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.
Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.
Configuring Endpoint Options
Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.
Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.
A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.
The following two sections lists all the options, firstly for the component followed by the endpoint.
Component Options
The gRPC component supports 3 options, which are listed below.
Name | Description | Default | Type |
---|---|---|---|
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 |
|
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
boolean |
|
Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. |
true |
boolean |
Endpoint Options
The gRPC endpoint is configured using URI syntax:
grpc:host:port/service
with the following path and query parameters:
Path Parameters (3 parameters)
Name | Description | Default | Type |
---|---|---|---|
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 |
||
Required The gRPC local or remote server port. |
int |
||
Required Fully qualified service name from the protocol buffer descriptor file (package dot service definition name). |
String |
Query Parameters (28 parameters)
Name | Description | Default | Type |
---|---|---|---|
Setting the autoDiscoverClientInterceptors mechanism, if true, the component will look for a ClientInterceptor instance in the registry automatically otherwise it will skip that checking. |
true |
boolean |
|
The HTTP/2 flow control window size (MiB). |
1048576 |
int |
|
The maximum message size allowed to be received/sent (MiB). |
4194304 |
int |
|
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 |
|
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. Enum values:
|
PROPAGATION |
GrpcConsumerStrategy |
|
Determines if onCompleted events should be pushed to the Camel route. |
false |
boolean |
|
Determines if onError events should be pushed to the Camel route. Exceptions will be set as message body. |
false |
boolean |
|
The maximum number of concurrent calls permitted for each incoming server connection. |
2147483647 |
int |
|
Lets the route to take control over stream observer. If this value is set to true, then the response observer of gRPC call will be set with the name GrpcConstants.GRPC_RESPONSE_OBSERVER in the Exchange object. <p> Please note that the stream observer’s onNext(), onError(), onCompleted() methods should be called in the route. |
false |
boolean |
|
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 |
||
Sets the exchange pattern when the consumer creates an exchange. Enum values:
|
ExchangePattern |
||
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
boolean |
|
gRPC method name. |
String |
||
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'). Enum values:
|
SIMPLE |
GrpcProducerStrategy |
|
When using STREAMING client mode, it indicates the endpoint where responses should be forwarded. |
String |
||
The user agent header passed to the server. |
String |
||
Sets whether synchronous processing should be strictly used. |
false |
boolean |
|
Authentication method type in advance to the SSL/TLS negotiation. Enum values:
|
NONE |
GrpcAuthType |
|
JSON Web Token sign algorithm. Enum values:
|
HMAC256 |
JwtAlgorithm |
|
JSON Web Token issuer. |
String |
||
JSON Web Token secret. |
String |
||
JSON Web Token subject. |
String |
||
The X.509 certificate chain file resource in PEM format link. |
String |
||
The PKCS#8 private key file password. |
String |
||
The PKCS#8 private key file resource in PEM format link. |
String |
||
Identifies the security negotiation type used for HTTP/2 communication. Enum values:
|
PLAINTEXT |
NegotiationType |
|
Service Account key file in JSON format resource link supported by the Google Cloud SDK. |
String |
||
The trusted certificates collection file resource in PEM format for verifying the remote endpoint’s certificate. |
String |
Transport security and authentication support
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 |
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.
There might be a need to install additional libraries according to the Operating System of choice. For more information consult the Security page of gRPC.
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> |
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 |
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: ${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");
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 ${os.detected.classifier} parameter manually
<extensions>
<extension>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.4.1.Final</version>
</extension>
</extensions>
Insert gRPC and protobuf Java code generator plugin <plugins> tag of the project pom.xml
<plugin>
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.5.0</version>
<configuration>
<protocArtifact>com.google.protobuf:protoc:${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>
Spring Boot Auto-Configuration
When using grpc with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:
<dependency>
<groupId>org.apache.camel.springboot</groupId>
<artifactId>camel-grpc-starter</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
The component supports 4 options, which are listed below.
Name | Description | Default | Type |
---|---|---|---|
Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. |
true |
Boolean |
|
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 |
|
Whether to enable auto configuration of the grpc component. This is enabled by default. |
Boolean |
||
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
Boolean |