Re: [SPDK] jsonrpc API

* Re: [SPDK] jsonrpc API
@ 2019-07-10 17:04 Khoussi, Siham
  0 siblings, 0 replies; 5+ messages in thread
From: Khoussi, Siham @ 2019-07-10 17:04 UTC (permalink / raw)
  To: spdk

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Thank you Tomek for your reply. Indeed, I was based on the rpc_get_methods example to write my client.

From your reply, I understand that in order to attach parameters to the request  I need to encode them using the spdk_json_write_*(). So in this case, I tried the following:

	w = spdk_jsonrpc_begin_request(request, 1, NULL);
	spdk_json_write_object_begin(w);
	spdk_json_write_named_string(w, "method", "construct_nvme_bdev");
	spdk_json_write_named_object_begin(w, "params");
	spdk_json_write_named_string(w, "trtype", "pcie");
	spdk_json_write_named_string(w, "name", "nvme01n1");
	spdk_json_write_named_string(w, "traddr", "0000:03:00.0");
	spdk_json_write_object_end(w);
	spdk_json_write_object_end(w);
	spdk_jsonrpc_end_request(request, w);
	int s = spdk_jsonrpc_client_send_request(client, request);

I'm getting an error [*ERROR*: jsonrpc parse request failed] which is due to [SPDK_JSON_PARSE_INCOMPLETE] in [int spdk_jsonrpc_parse_request()]. Did I encode the request right? Or do you think I need to include all the parameters with omitting some?

Thank you again,
Siham

-----Original Message-----
From: SPDK <spdk-bounces(a)lists.01.org> On Behalf Of Zawadzki, Tomasz
Sent: Wednesday, July 10, 2019 4:56 AM
To: Storage Performance Development Kit <spdk(a)lists.01.org>
Subject: Re: [SPDK] jsonrpc API

Hi Siham,

Description for steps you were able to work out, show that you are already familiar with rpc_client_test.c. This is our example of using jsonrpc client library.
At this point you are able to send the JSON request to SPDK and receive response. The creation of request is still up to the app that sends the jsonrpc.
Various modules do the reverse of what you are attempting - gets requests and sends a response. For examples of decoding JSON requests and sending responses see *_rpc.c files throughout SPDK.

In order to issue proper construct_nvme_bdev RPC, best pointer on expected fields would be docs https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspdk.io%2Fdoc%2Fjsonrpc.html%23rpc_construct_nvme_bdev&amp;data=02%7C01%7Csiham.khoussi%40nist.gov%7C272722a4241740002dd208d705148896%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C1%7C636983458067397193&amp;sdata=Zzx46RosGFPSLhWmM3t3l678w4TsNmVt%2FEDd4WvY9ow%3D&amp;reserved=0 or directly in C code the rpc_construct_nvme_decoders structure in bdev_nvme_rpc.c.
Filling out of this structure would follow the same scheme you've already done for rpc_get_methods, but with additional spdk_json_write_*() between spdk_jsonrpc_begin_request() and spdk_jsonrpc_client_send_request(). The request sent in this manner will be processed on SPDK side by spdk_rpc_construct_nvme_bdev() in  bdev_nvme_rpc.c.

For decoding the response, expected fields are provided in the documentation as well. First spdk_json_object_decoder needs to be created, matching the expected fields. Response can be decoded then with spdk_json_decode_object() filling out all the structure. construct_nvme_bdev method in particular returns array of strings with created nvme bdev names.

Thanks,
Tomek

> -----Original Message-----
> From: SPDK [mailto:spdk-bounces(a)lists.01.org] On Behalf Of Khoussi, 
> Siham
> (IntlAssoc)
> Sent: Tuesday, July 9, 2019 9:41 PM
> To: Storage Performance Development Kit <spdk(a)lists.01.org>
> Subject: [SPDK] jsonrpc API
> 
> Hello all,
> 
> I'm looking to use the jsonrpc api to create a client in C rather than python.
> And so far I was able to create a client, send a request "rpc_get_methods"
> using [spdk_jsonrpc_begin_request(request, 1, "rpc_get_methods")], 
> receive a response using [spdk_jsonrpc_client_get_response(client)] 
> and decode the response with  [spdk_json_decode_array(result, 
> spdk_json_decode_string, resp->method_names, RPC_MAX_METHODS, 
> &resp->method_num, sizeof(char *))].
> 
> However, I was wondering if anyone could tell me how to create a 
> request with parameters using the same API (e.g construct_nvme_bdev -b
> nvme01n1 -t pcie -a 0000:03:00.0)? And how to decode it, maybe using 
> the spdk_json_object_decoder structure? Are there existing examples in C?
> 
> Thank you again,
> Siham
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