nats.zig/deps/nats.c/examples/micro-sequence.c
torque 41fbdf886b
git subrepo pull --branch=v3.7.0 deps/nats.c
subrepo:
  subdir:   "deps/nats.c"
  merged:   "5d057f6"
upstream:
  origin:   "https://github.com/nats-io/nats.c.git"
  branch:   "v3.7.0"
  commit:   "5d057f6"
git-subrepo:
  version:  "0.4.6"
  commit:   "affc4c01a"
2023-10-14 13:22:13 -07:00

192 lines
5.9 KiB
C

// Copyright 2023 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "examples.h"
// Sequence NATS microservice example.
//
// This example illustrates multiple NATS microservices communicating with each
// other.
//
// The main service (c-sequence) calculates the sum of 1/f(1) + 1/f(2)... up to
// N (included). It exposes one (default) endpoint, "sequence". The inputs are
// f (the function name) and N. name, can be "factorial", "fibonacci", or
// "power2").
//
// c-sequence parses the request, then calculates the sequence by calling the
// c-functions microservice to calculate f(1), f(2), etc. The c-functions
// service in turn uses c-arithmetics microservice for all arithmetic
// operations.
//
// Requires NATS server and CLI, and the nats.c examples fully built. See
// https://github.com/nats-io/nats.c#building
//
// RUN:
// ```sh
// $NATS_SERVER & # NATS_SERVER points to the NATS server binary
// nats_pid=$!
// sleep 2 # wait for server to start
// ./examples/nats-micro-sequence &
// sequence_pid=$!
// ./examples/nats-micro-func &
// func_pid=$!
// ./examples/nats-micro-arithmetics &
// arithmetics_pid=$!
// sleep 2 # wait for microservice to start
// nats request -r 'sequence' '"factorial" 10'
// nats request -r 'sequence' '"power2" 10'
// nats request -r 'sequence' '"fibonacci" 10'
// kill $sequence_pid $func_pid $arithmetics_pid $nats_pid
// ```
//
// OUTPUT:
// ```
// 2.718282
// 1.999023
// 3.341705
// ```
static microError *
call_function(long double *result, natsConnection *nc, const char *subject, int n)
{
microError *err = NULL;
microClient *client = NULL;
natsMsg *response = NULL;
microArgs *args = NULL;
char buf[256];
char sbuf[256];
int len;
len = snprintf(buf, sizeof(buf), "%d", n);
snprintf(sbuf, sizeof(sbuf), "f.%s", subject);
err = micro_NewClient(&client, nc, NULL);
if (err == NULL)
err = microClient_DoRequest(&response, client, sbuf, buf, len);
if (err == NULL)
err = micro_ParseArgs(&args, natsMsg_GetData(response), natsMsg_GetDataLength(response));
if (err == NULL)
err = microArgs_GetFloat(result, args, 0);
microClient_Destroy(client);
natsMsg_Destroy(response);
return err;
}
// calculates the sum of X/f(1) + X/f(2)... up to N (included). The inputs are X
// (float), f name (string), and N (int). E.g.: '10.0 "power2" 10' will
// calculate 10/2 + 10/4 + 10/8 + 10/16 + 10/32 + 10/64 + 10/128 + 10/256 +
// 10/512 + 10/1024 = 20.998046875
static microError *handle_sequence(microRequest *req)
{
microError *err = NULL;
natsConnection *nc = microRequest_GetConnection(req);
microArgs *args = NULL;
int n = 0;
int i;
const char *function;
long double initialValue = 1.0;
long double value = 1.0;
long double denominator = 0;
char result[64];
int result_len = 0;
err = micro_ParseArgs(&args, microRequest_GetData(req), microRequest_GetDataLength(req));
if ((err == NULL) && (microArgs_Count(args) != 2))
{
err = micro_Errorf("Invalid number of arguments, expected 2 got %d", microArgs_Count(args));
}
if (err == NULL)
err = microArgs_GetString(&function, args, 0);
if ((err == NULL) &&
(strcmp(function, "factorial") != 0) &&
(strcmp(function, "power2") != 0) &&
(strcmp(function, "fibonacci") != 0))
{
err = micro_Errorf("Invalid function name '%s', must be 'factorial', 'power2', or 'fibonacci'", function);
}
if (err == NULL)
err = microArgs_GetInt(&n, args, 1);
if ((err == NULL) && (n < 1))
{
err = micro_Errorf("Invalid number of iterations %d, must be at least 1", n);
}
for (i = 1; (err == NULL) && (i <= n); i++)
{
if (err == NULL)
err = call_function(&denominator, nc, function, i);
if ((err == NULL) && (denominator == 0))
{
err = micro_Errorf("division by zero at step %d", i);
}
if (err == NULL)
value = value + initialValue / denominator;
}
if (err == NULL)
result_len = snprintf(result, sizeof(result), "%Lf", value);
if (err == NULL)
err = microRequest_Respond(req, result, result_len);
microArgs_Destroy(args);
return err;
}
int main(int argc, char **argv)
{
natsStatus s = NATS_OK;
microError *err = NULL;
natsConnection *conn = NULL;
natsOptions *opts = NULL;
microService *m = NULL;
char errorbuf[1024];
microEndpointConfig sequence_cfg = {
.Subject = "sequence",
.Name = "sequence-service",
.Handler = handle_sequence,
};
microServiceConfig cfg = {
.Description = "Sequence adder - NATS microservice example in C",
.Name = "c-sequence",
.Version = "1.0.0",
.Endpoint = &sequence_cfg,
};
opts = parseArgs(argc, argv, "");
s = natsConnection_Connect(&conn, opts);
if (s != NATS_OK)
{
printf("Error: %u - %s\n", s, natsStatus_GetText(s));
nats_PrintLastErrorStack(stderr);
natsOptions_Destroy(opts);
return 1;
}
err = micro_AddService(&m, conn, &cfg);
if (err == NULL)
err = microService_Run(m);
microService_Destroy(m);
natsOptions_Destroy(opts);
natsConnection_Destroy(conn);
if (err != NULL)
{
printf("Error: %s\n", microError_String(err, errorbuf, sizeof(errorbuf)));
microError_Destroy(err);
return 1;
}
return 0;
}