gRPCurl
grpcurl
is a command-line tool that lets you interact with gRPC servers. It's
basically curl
for gRPC servers.
The main purpose for this tool is to invoke RPC methods on a gRPC server from the
command-line. gRPC servers use a binary encoding on the wire
(protocol buffers, or "protobufs"
for short). So they are basically impossible to interact with using regular curl
(and older versions of curl
that do not support HTTP/2 are of course non-starters).
This program accepts messages using JSON encoding, which is much more friendly for both
humans and scripts.
With this tool you can also browse the schema for gRPC services, either by querying
a server that supports service reflection,
by reading proto source files, or by loading in compiled "protoset" files (files that contain encoded file
descriptor protos).
In fact, the way the tool transforms JSON request data into a binary encoded protobuf
is using that very same schema. So, if the server you interact with does not support
reflection, you will either need the proto source files that define the service or need
protoset files that grpcurl
can use.
Examples for how to set up server reflection can be found here.
This repo also provides a library package, github.com/fullstorydev/grpcurl
, that has
functions for simplifying the construction of other command-line tools that dynamically
invoke gRPC endpoints. This code is a great example of how to use the various packages of
the protoreflect library, and shows
off what they can do.
Features
grpcurl
supports all kinds of RPC methods, including streaming methods. You can even
operate bi-directional streaming methods interactively by running grpcurl
from an
interactive terminal and using stdin as the request body!
grpcurl
supports both plain-text and TLS servers and has numerous options for TLS
configuration. It also supports mutual TLS, where the client is required to present a
client certificate.
As mentioned above, grpcurl
works seamlessly if the server supports the reflection
service. If not, you can supply the .proto
source files or you can supply protoset
files (containing compiled descriptors, produced by protoc
) to grpcurl
.
Installation
You can use the go
tool to install grpcurl
:
go get github.com/fullstorydev/grpcurl
go install github.com/fullstorydev/grpcurl/cmd/grpcurl
This installs the command into the bin
sub-folder of wherever your $GOPATH
environment variable points. If this directory is already in your $PATH
, then
you should be good to go.
If you have already pulled down this repo to a location that is not in your
$GOPATH
and want to build from the sources, you can cd
into the repo and then
run make install
.
If you encounter compile errors, you could have out-dated versions of grpcurl
's
dependencies. You can update the dependencies by running make updatedeps
.
Usage
The usage doc for the tool explains the numerous options:
grpcurl -help
In the sections below, you will find numerous examples demonstrating how to use
grpcurl
.
Invoking RPCs
Invoking an RPC on a trusted server (e.g. TLS without self-signed key or custom CA)
that requires no client certs and supports service reflection is the simplest thing to
do with grpcurl
. This minimal invocation sends an empty request body:
grpcurl grpc.server.com:443 my.custom.server.Service/Method
To send a non-empty request, use the -d
argument. Note that all arguments must come
before the server address and method name:
grpcurl -d '{"id": 1234, "tags": ["foo","bar"]}' \
grpc.server.com:443 my.custom.server.Service/Method
As can be seen in the example, the supplied body must be in JSON format. The body will be parsed and then transmitted to the server in the protobuf binary format.
If you want to include grpcurl
in a command pipeline, such as when using jq
to
create a request body, you can use -d @
, which tells grpcurl
to read the actual
request body from stdin:
grpcurl -d @ grpc.server.com:443 my.custom.server.Service/Method <<<EOM
{
"id": 1234,
"tags": [
"foor",
"bar"
]
}
EOM
Listing Services
To list all services exposed by a server, use the "list" verb. When using .proto
source
or protoset files instead of server reflection, this lists all services defined in the
source or protoset files.
# Server supports reflection
grpcurl localhost:8787 list
# Using compiled protoset files
grpcurl -protoset my-protos.bin list
# Using proto sources
grpcurl -import-path ../protos -proto my-stuff.proto list
The "list" verb also lets you see all methods in a particular service:
grpcurl localhost:8787 list my.custom.server.Service
Describing Elements
The "describe" verb will print the type of any symbol that the server knows about or that is found in a given protoset file and also print the full descriptor for the symbol, in JSON.
# Server supports reflection
grpcurl localhost:8787 describe my.custom.server.Service.MethodOne
# Using compiled protoset files
grpcurl -protoset my-protos.bin describe my.custom.server.Service.MethodOne
# Using proto sources
grpcurl -import-path ../protos -proto my-stuff.proto describe my.custom.server.Service.MethodOne
Proto Source Files
To use grpcurl
on servers that do not support reflection, you can use .proto
source
files.
In addition to using -proto
flags to point grpcurl
at the relevant proto source file(s),
you may also need to supply -import-path
flags to tell grpcurl
the folders from which
dependencies can be imported.
Just like when compiling with protoc
, you do not need to provide an import path for the
location of the standard protos included with protoc
(which contain various "well-known
types" with a package definition of google.protobuf
). These files are "known" by grpcurl
as a snapshot of their descriptors is built into the grpcurl
binary.
Protoset Files
You can also use compiled protoset files with grpcurl
. If you are scripting grpcurl
and
need to re-use the same proto sources for many invocations, you will see better performance
by using protoset files (since it skips the parsing and compilation steps with each
invocation).
Protoset files contain binary encoded google.protobuf.FileDescriptorSet
protos. To create
a protoset file, invoke protoc
with the *.proto
files that describe the service:
protoc --proto_path=. \
--descriptor_set_out=myservice.protoset \
--include_imports \
my/custom/server/service.proto
The --descriptor_set_out
argument is what tells protoc
to produce a protoset,
and the --include_imports
argument is necessary for the protoset to contain
everything that grpcurl
needs to process and understand the schema.