Parse command line arguments

The control flow of picodata looks as following:

Picodata binary -> exec tarantool -l picodata -> libpicodata.so -> ...

Since the libpicodata is a shared lib loaded by tarantool, we can't pass
it arguments as usual. At first, tarantool parses them by itself and
rejects uknown arguments. Secondly, it spoils argv array.

To overcome these two issues, this patch introduces argparse on behalf
of the picodata binary, and puts parsed values into the environment
variables.

P.S. Thihs is how command line args look from within libpicodata:

```console
$ tarantool -l picodata /dev/null --opt1 foo --opt2 bar
Hello from rust lib
arg[0] tarantool
arg[1] /dev/null
arg[2] --opt1
arg[3] foo
arg[4] --opt2
arg[5] bar
arg[6] --opt2
arg[7] bar
```

Cargo.toml

@@ -6,6 +6,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+clap = {version = "2.33", features = ["yaml"]}
 libc = "0.2.108"
 errno = "0.2.8"
 

src/cli.yml

+name: picodata
+version: "0.1"
+args: []
+subcommands:
+  - run:
+      about: run the picodata instance
+      args:
+        - listen:
+            # short: l
+            long: listen
+            help: Socket bind address
+            takes_value: true
+            default_value: "0.0.0.0:3301"
+            value_name: "[host:]port"
+
+        - peer:
+            # short: p
+            long: peer
+            help: Address of another instance(s)
+            multiple: true
+            takes_value: true
+            value_name: "host:port"
+
+        - cluster-id:
+            long: cluster-id
+            help: Name of the cluster
+            value_name: "name"
+            takes_value: true
+
+        - instance-id:
+            long: instance-id
+            help: Name of the instance
+            value_name: "name"
+            takes_value: true
+
+        - replicaset-id:
+            long: replicaset-id
+            help: Name of the replicaset
+            value_name: "name"
+            takes_value: true
+
+        - tarantool-exec:
+            short: e
+            help: Execute tarantool script
+            value_name: expr
+
+        # - advertise-peer:
+        #     help: URI advertised to other instances in cluster
+        #     long: advertise

src/lib.rs

@@ -3,5 +3,10 @@ use std::os::raw::c_int;
 #[no_mangle]
 pub extern "C" fn luaopen_picodata(_l: std::ffi::c_void) -> c_int {
     println!("Hello from rust lib");
+    for (key, value) in std::env::vars() {
+        if key.starts_with("PICODATA_") {
+            println!("{}: {}", key, value);
+        }
+    }
     0
 }

src/main.rs

+use clap::App;
 use std::collections::HashMap;
 use std::ffi::CString;
 
+#[macro_use]
+extern crate clap;
+
 mod execve;
 
 macro_rules! CString {
@@ -10,6 +14,23 @@ macro_rules! CString {
 }
 
 fn main() {
+    let yml = load_yaml!("cli.yml");
+    let matches = App::from_yaml(yml).version(crate_version!()).get_matches();
+    println!("{:?}", matches);
+
+    if matches.subcommand_name().is_none() {
+        println!("{}", matches.usage());
+        std::process::exit(0);
+    }
+
+    if let Some(matches) = matches.subcommand_matches("run") {
+        return main_run(matches);
+    }
+
+    unreachable!();
+}
+
+fn main_run(matches: &clap::ArgMatches) {
     let tarantool_path: String = match execve::which("tarantool") {
         Some(v) => v
             .into_os_string()
@@ -21,11 +42,12 @@ fn main() {
         }
     };
 
-    let args = [&tarantool_path, "-l", "picodata"];
-    let argv = std::iter::empty()
-        .chain(args.iter().map(|&s| CString!(s)))
-        .chain(std::env::args().skip(1).map(|s| CString!(s)))
-        .collect();
+    let mut args: Vec<&str> = vec![&tarantool_path, "-l", "picodata"];
+    if let Some(script) = matches.value_of("tarantool-exec") {
+        args.push("-e");
+        args.push(script);
+    }
+    let argv = args.iter().map(|&s| CString!(s)).collect();
 
     let mut envp = HashMap::new();
     for (k, v) in std::env::vars() {
@@ -34,6 +56,19 @@ fn main() {
         }
     }
 
+    if let Some(peer) = matches.values_of("peer") {
+        let append = |s: String, str| if s.is_empty() {s + str} else {s + "," + str};
+        let peer = peer.fold(String::new(), append);
+        envp.insert("PICODATA_PEER".to_owned(), peer);
+    }
+
+    for arg in ["listen", "instance-id", "replicaset-id", "cluster-id"] {
+        if let Some(v) = matches.value_of(arg) {
+            let k = format!("PICODATA_{}", arg.to_uppercase().replace("-", "_"));
+            envp.insert(k, v.to_owned());
+        }
+    }
+
     // In order to make libpicodata loaded we should provide
     // its path in the LUA_CPATH env variable.
     let cpath: String = {

tests/cli.rs

@@ -5,12 +5,14 @@ use tempfile::tempdir;
 #[test]
 fn positive() {
     let mut cmd = Command::cargo_bin("picodata").unwrap();
+    cmd.arg("run");
     cmd.assert().success();
 }
 
 #[test]
 fn missing_tarantool() {
     let mut cmd = Command::cargo_bin("picodata").unwrap();
+    cmd.arg("run");
     cmd.env("PATH", "/nowhere");
     cmd.assert()
         .failure()
@@ -24,6 +26,7 @@ fn broken_tarantool() {
     File::create(temp_path.join("tarantool")).unwrap();
 
     let mut cmd = Command::cargo_bin("picodata").unwrap();
+    cmd.arg("run");
     cmd.env("PATH", temp_path);
     cmd.assert().failure().stderr(format!(
         "{}/tarantool: {}\n",
@@ -35,6 +38,7 @@ fn broken_tarantool() {
 #[test]
 fn pass_arguments() {
     let mut cmd = Command::cargo_bin("picodata").unwrap();
+    cmd.arg("run");
     cmd.args(["-e", "error('xxx', 0)"]);
     cmd.assert().failure().stderr(
         "LuajitError: xxx\n\
@@ -45,10 +49,17 @@ fn pass_arguments() {
 #[test]
 fn pass_environment() {
     let mut cmd = Command::cargo_bin("picodata").unwrap();
+    cmd.arg("run");
     cmd.env("LUA_CPATH", "/dev/null/?");
     cmd.env("CUSTOM_VAR", "keep me");
     cmd.env("TARANTOOL_VAR", "purge me");
     cmd.env("TT_VAR", "purge me too");
+    cmd.args(["--listen", "127.0.0.1:3301"]);
+    cmd.args(["--cluster-id", "sam"]);
+    cmd.args(["--replicaset-id", "r1"]);
+    cmd.args(["--instance-id", "i1"]);
+    cmd.args(["--peer", "i1,i2"]);
+    cmd.args(["--peer", "i3"]);
     cmd.arg("-e").arg(
         r#"
         cpath = os.environ()['LUA_CPATH']
@@ -62,6 +73,11 @@ fn pass_environment() {
         assert_eq(os.environ()['CUSTOM_VAR'], 'keep me')
         assert_eq(os.environ()['TARANTOOL_VAR'], nil)
         assert_eq(os.environ()['TT_VAR'], nil)
+        assert_eq(os.environ()['PICODATA_LISTEN'], "127.0.0.1:3301")
+        assert_eq(os.environ()['PICODATA_CLUSTER_ID'], "sam")
+        assert_eq(os.environ()['PICODATA_REPLICASET_ID'], "r1")
+        assert_eq(os.environ()['PICODATA_INSTANCE_ID'], "i1")
+        assert_eq(os.environ()['PICODATA_PEER'], "i1,i2,i3")
     "#,
     );
     cmd.assert().success();