我正在使用Java和Protoc 3.0编译器，我的proto文件在下面提到。 https://github.com/openconfig/public/blob/master/release/models/rpc/openconfig-rpc-api.yang
syntax = "proto3";
package Telemetry;
// Interface exported by Agent
service OpenConfigTelemetry {
// Request an inline subscription for data at the specified path.
// The device should send telemetry data back on the same
// connection as the subscription request.
rpc telemetrySubscribe(SubscriptionRequest) returns (stream OpenConfigData) {}
// Terminates and removes an exisiting telemetry subscription
rpc cancelTelemetrySubscription(CancelSubscriptionRequest) returns (CancelSubscriptionReply) {}
// Get the list of current telemetry subscriptions from the
// target. This command returns a list of existing subscriptions
// not including those that are established via configuration.
rpc getTelemetrySubscriptions(GetSubscriptionsRequest) returns (GetSubscriptionsReply) {}
// Get Telemetry Agent Operational States
rpc getTelemetryOperationalState(GetOperationalStateRequest) returns (GetOperationalStateReply) {}
// Return the set of data encodings supported by the device for
// telemetry data
rpc getDataEncodings(DataEncodingRequest) returns (DataEncodingReply) {}
}
// Message sent for a telemetry subscription request
message SubscriptionRequest {
// Data associated with a telemetry subscription
SubscriptionInput input = 1;
// List of data models paths and filters
// which are used in a telemetry operation.
repeated Path path_list = 2;
// The below configuration is not defined in Openconfig RPC.
// It is a proposed extension to configure additional
// subscription request features.
SubscriptionAdditionalConfig additional_config = 3;
}
// Data associated with a telemetry subscription
message SubscriptionInput {
// List of optional collector endpoints to send data for
// this subscription.
// If no collector destinations are specified, the collector
// destination is assumed to be the requester on the rpc channel.
repeated Collector collector_list = 1;
}
// Collector endpoints to send data specified as an ip+port combination.
message Collector {
// IP address of collector endpoint
string address = 1;
// Transport protocol port number for the collector destination.
uint32 port = 2;
}
// Data model path
message Path {
// Data model path of interest
// Path specification for elements of OpenConfig data models
string path = 1;
// Regular expression to be used in filtering state leaves
string filter = 2;
// If this is set to true, the target device will only send
// updates to the collector upon a change in data value
bool suppress_unchanged = 3;
// Maximum time in ms the target device may go without sending
// a message to the collector. If this time expires with
// suppress-unchanged set, the target device must send an update
// message regardless if the data values have changed.
uint32 max_silent_interval = 4;
// Time in ms between collection and transmission of the
// specified data to the collector platform. The target device
// will sample the corresponding data (e.g,. a counter) and
// immediately send to the collector destination.
//
// If sample-frequency is set to 0, then the network device
// must emit an update upon every datum change.
uint32 sample_frequency = 5;
}
// Configure subscription request additional features.
message SubscriptionAdditionalConfig {
// limit the number of records sent in the stream
int32 limit_records = 1;
// limit the time the stream remains open
int32 limit_time_seconds = 2;
}
// Reply to inline subscription for data at the specified path is done in
// two-folds.
// 1. Reply data message sent out using out-of-band channel.
// 2. Telemetry data send back on the same connection as the
// subscription request.
// 1. Reply data message sent out using out-of-band channel.
message SubscriptionReply {
// Response message to a telemetry subscription creation or
// get request.
SubscriptionResponse response = 1;
// List of data models paths and filters
// which are used in a telemetry operation.
repeated Path path_list = 2;
}
// Response message to a telemetry subscription creation or get request.
message SubscriptionResponse {
// Unique id for the subscription on the device. This is
// generated by the device and returned in a subscription
// request or when listing existing subscriptions
uint32 subscription_id = 1;
}
// 2. Telemetry data send back on the same connection as the
// subscription request.
message OpenConfigData {
// router name:export IP address
string system_id = 1;
// line card / RE (slot number)
uint32 component_id = 2;
// PFE (if applicable)
uint32 sub_component_id = 3;
// Path specification for elements of OpenConfig data models
string path = 4;
// Sequence number, monotonically increasing for each
// system_id, component_id, sub_component_id + path.
uint64 sequence_number = 5;
// timestamp (milliseconds since epoch)
uint64 timestamp = 6;
// List of key-value pairs
repeated KeyValue kv = 7;
}
// Simple Key-value, where value could be one of scalar types
message KeyValue {
// Key
string key = 1;
// One of possible values
oneof value {
double double_value = 5;
int64 int_value = 6;
uint64 uint_value = 7;
sint64 sint_value = 8;
bool bool_value = 9;
string str_value = 10;
bytes bytes_value = 11;
}
}
// Message sent for a telemetry subscription cancellation request
message CancelSubscriptionRequest {
// Subscription identifier as returned by the device when
// subscription was requested
uint32 subscription_id = 1;
}
// Reply to telemetry subscription cancellation request
message CancelSubscriptionReply {
// Return code
ReturnCode code = 1;
// Return code string
string code_str = 2;
};
// Result of the operation
enum ReturnCode {
SUCCESS = 0;
NO_SUBSCRIPTION_ENTRY = 1;
UNKNOWN_ERROR = 2;
}
// Message sent for a telemetry get request
message GetSubscriptionsRequest {
// Subscription identifier as returned by the device when
// subscription was requested
// --- or ---
// 0xFFFFFFFF for all subscription identifiers
uint32 subscription_id = 1;
}
// Reply to telemetry subscription get request
message GetSubscriptionsReply {
// List of current telemetry subscriptions
repeated SubscriptionReply subscription_list = 1;
}
// Message sent for telemetry agent operational states request
message GetOperationalStateRequest {
// Per-subscription_id level operational state can be requested.
//
// Subscription identifier as returned by the device when
// subscription was requested
// --- or ---
// 0xFFFFFFFF for all subscription identifiers including agent-level
// operational stats
// --- or ---
// If subscription_id is not present then sent only agent-level
// operational stats
uint32 subscription_id = 1;
// Control verbosity of the output
VerbosityLevel verbosity = 2;
}
// Verbosity Level
enum VerbosityLevel {
DETAIL = 0;
TERSE = 1;
BRIEF = 2;
}
// Reply to telemetry agent operational states request
message GetOperationalStateReply {
// List of key-value pairs where
// key = operational state definition
// value = operational state value
repeated KeyValue kv = 1;
}
// Message sent for a data encoding request
message DataEncodingRequest {
}
// Reply to data encodings supported request
message DataEncodingReply {
repeated EncodingType encoding_list = 1;
}
// Encoding Type Supported
enum EncodingType {
UNDEFINED = 0;
XML = 1;
JSON_IETF = 2;
PROTO3 = 3;
}
为了进行服务调用（rpc TelemetrySubscribe），我首先需要读取具有订阅ID的标头，然后开始阅读消息。现在，使用Java我能够连接服务，我确实介绍了拦截器但是当我打印/检索头时它是null。我的调用拦截器代码如下，
ClientInterceptor interceptor = new HeaderClientInterceptor();
originChannel = OkHttpChannelBuilder.forAddress(host, port)
.usePlaintext(true)
.build();
Channel channel = ClientInterceptors.intercept(originChannel, interceptor);
telemetryStub = OpenConfigTelemetryGrpc.newStub(channel);
这是读取元数据的拦截器代码。
@Override
public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method,
CallOptions callOptions, Channel next) {
return new SimpleForwardingClientCall<ReqT, RespT>(next.newCall(method, callOptions)) {
@Override
public void start(Listener<RespT> responseListener, Metadata headers) {
super.start(new SimpleForwardingClientCallListener<RespT>(responseListener) {
@Override
public void onHeaders(Metadata headers) {
Key<String> CUSTOM_HEADER_KEY = Metadata.Key.of("responseKEY", Metadata.ASCII_STRING_MARSHALLER);
System.out.println("Contains Key?? "+headers.containsKey(CUSTOM_HEADER_KEY));
想知道是否还有其他方法可以读取包含订阅ID的元数据或第一条消息？所有我需要阅读第一条有订阅ID的消息，并将相同的订阅ID返回给服务器，以便流可以启动我使用相同的原型文件的等效Python代码，它通过下面提到的代码与服务器通信仅供参考：
sub_req = SubscribeRequestMsg("host",port)
data_itr = stub.telemetrySubscribe(sub_req, _TIMEOUT_SECONDS)
metadata = data_itr.initial_metadata()
if metadata[0][0] == "responseKey":
metainfo = metadata[0][1]
print metainfo
subreply = agent_pb2.SubscriptionReply()
subreply.SetInParent()
google.protobuf.text_format.Merge(metainfo, subreply)
if subreply.response.subscription_id:
SUB_ID = subreply.response.subscription_id
从上面的python代码我可以轻松检索元数据对象，不知道如何使用Java检索它？
阅读metaData后，我得到的是：Metadata({content-type=[application/grpc], grpc-encoding=[identity], grpc-accept-encoding=[identity,deflate,gzip]})
但是我知道从元数据到另外一行，这是
response {
subscription_id: 2
}
如何从Header中提取包含订阅ID的最后一个响应。我确实尝试了很多选项，我迷失在这里。
答案 0 :(得分：6)
您使用的方法是请求元数据，而不是响应元数据：
public void start(Listener<RespT> responseListener, Metadata headers) {
对于响应元数据，您需要ClientCall.Listener并等待onHeaders回调：
public void onHeaders(Metadata headers)
我觉得您提到的元数据的使用似乎很奇怪。元数据通常用于其他错误详细信息或交叉功能，这些功能并不特定于RPC方法（如身份验证，跟踪等）。
答案 1 :(得分：4)
使用ClientInterceptor时常常不方便，因为您需要维护对它的引用才能将数据拉回来。在您的情况下，数据实际上是元数据。您可以更轻松地访问元数据的一种方法是将其放在Context。
例如，您可以为订阅ID创建Context.Key。在您的客户端拦截器中，您可以提取所需的Metadata标头，并使用Context将其放在Context.current().withValue(key, metadata)内。在StreamObserver内，您可以通过调用key.get(Context.current())来提取此内容。这假设您使用的是Async API，而不是阻止API。
更难的原因是因为元数据通常是有关呼叫的信息，但与呼叫本身没有直接关系。它适用于跟踪，编码，统计，取消等内容。如果某些内容改变了您处理请求的方式，则可能需要直接进入请求本身，而不是站在一边。