enhancement(remap transform): add get_hostname function

.github/CODEOWNERS

@@ -68,6 +68,7 @@
 /docs/reference/remap/compact.cue @FungusHumungus
 /docs/reference/remap/exists.cue @FungusHumungus
 /docs/reference/remap/flatten.cue @FungusHumungus
+/docs/reference/remap/get_hostname.cue @fanatid
 /docs/reference/remap/ip_cidr_contains.cue @FungusHumungus
 /docs/reference/remap/ip_subnet.cue @FungusHumungus
 /docs/reference/remap/ip_to_ipv6.cue @FungusHumungus
@@ -103,6 +104,7 @@
 /lib/remap-functions/src/compact.rs @FungusHumungus
 /lib/remap-functions/src/exists.rs @FungusHumungus
 /lib/remap-functions/src/flatten.rs @FungusHumungus
+/lib/remap-functions/src/get_hostname.rs @fanatid
 /lib/remap-functions/src/ip_cidr_contains.rs @FungusHumungus
 /lib/remap-functions/src/ip_subnet.rs @FungusHumungus
 /lib/remap-functions/src/ip_to_ipv6.rs @FungusHumungus

docs/reference/remap/functions/get_hostname.cue

@@ -0,0 +1,21 @@
+package metadata
+
+remap: functions: get_hostname: {
+	arguments: []
+	internal_failure_reasons: []
+	return: types: ["string"]
+	category: "System"
+	description: #"""
+		Get system's hostname.
+		"""#
+	examples: [
+		{
+			title: "Get hostname"
+			input: log: {}
+			source: #"""
+				.hostname = get_hostname!()
+				"""#
+			output: log: hostname: "localhost.localdomain"
+		},
+	]
+}

lib/remap-functions/Cargo.toml

@@ -15,6 +15,7 @@ chrono = { version = "0.4", optional = true }
 cidr-utils = { version = "0.5", optional = true }
 grok = { version = "1", optional = true }
 hex = { version = "0.4", optional = true }
+hostname = { version = "0.3", optional = true }
 lazy_static = { version = "1", optional = true }
 md-5 = { version = "0.9", optional = true }
 nom = { version = "6.0.1", optional = true }
@@ -54,6 +55,7 @@ default = [
     "format_number",
     "format_timestamp",
     "get_env_var",
+    "get_hostname",
     "includes",
     "ip_cidr_contains",
     "ip_subnet",
@@ -122,6 +124,7 @@ floor = []
 format_number = ["rust_decimal"]
 format_timestamp = ["chrono"]
 get_env_var = []
+get_hostname = ["hostname"]
 includes = []
 ip_cidr_contains = ["cidr-utils"]
 ip_subnet = ["lazy_static", "regex"]

lib/remap-functions/src/get_hostname.rs

@@ -0,0 +1,58 @@
+use remap::prelude::*;
+
+#[derive(Clone, Copy, Debug)]
+pub struct GetHostname;
+
+impl Function for GetHostname {
+    fn identifier(&self) -> &'static str {
+        "get_hostname"
+    }
+
+    fn compile(&self, _: ArgumentList) -> Result<Box<dyn Expression>> {
+        Ok(Box::new(GetHostnameFn))
+    }
+}
+
+#[derive(Debug, Clone)]
+struct GetHostnameFn;
+
+impl Expression for GetHostnameFn {
+    fn execute(&self, _: &mut state::Program, _: &mut dyn Object) -> Result<Value> {
+        Ok(hostname::get()
+            .map_err(|error| format!("failed to get hostname: {}", error))?
+            .to_string_lossy()
+            .into())
+    }
+
+    fn type_def(&self, _: &state::Compiler) -> TypeDef {
+        TypeDef {
+            fallible: true,
+            kind: value::Kind::Bytes,
+            ..Default::default()
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::map;
+
+    remap::test_type_def![static_def {
+        expr: |_| GetHostnameFn,
+        def: TypeDef {
+            fallible: true,
+            kind: value::Kind::Bytes,
+            ..Default::default()
+        },
+    }];
+
+    #[test]
+    fn get_hostname() {
+        let mut state = state::Program::default();
+        let mut object: Value = map![].into();
+        let value = GetHostnameFn.execute(&mut state, &mut object).unwrap();
+
+        assert!(matches!(&value, Value::Bytes(_)));
+    }
+}

lib/remap-functions/src/lib.rs

@@ -34,6 +34,8 @@ mod format_number;
 mod format_timestamp;
 #[cfg(feature = "get_env_var")]
 mod get_env_var;
+#[cfg(feature = "get_hostname")]
+mod get_hostname;
 #[cfg(feature = "includes")]
 mod includes;
 #[cfg(feature = "ip_cidr_contains")]
@@ -173,6 +175,8 @@ pub use format_number::FormatNumber;
 pub use format_timestamp::FormatTimestamp;
 #[cfg(feature = "get_env_var")]
 pub use get_env_var::GetEnvVar;
+#[cfg(feature = "get_hostname")]
+pub use get_hostname::GetHostname;
 #[cfg(feature = "includes")]
 pub use includes::Includes;
 #[cfg(feature = "ip_cidr_contains")]
@@ -308,6 +312,8 @@ pub fn all() -> Vec<Box<dyn remap::Function>> {
         Box::new(FormatTimestamp),
         #[cfg(feature = "get_env_var")]
         Box::new(GetEnvVar),
+        #[cfg(feature = "get_hostname")]
+        Box::new(GetHostname),
         #[cfg(feature = "includes")]
         Box::new(Includes),
         #[cfg(feature = "ip_cidr_contains")]

tests/behavior/transforms/remap.toml

@@ -1918,3 +1918,23 @@
     [[tests.outputs.conditions]]
       type = "remap"
       source = '[.a, .b, .c] == [3, 2, 3]'
+
+[transforms.remap_function_get_hostname]
+  inputs = []
+  type = "remap"
+  source = """
+    .a = get_hostname!()
+  """
+[[tests]]
+  name = "remap_function_get_hostname"
+  [tests.input]
+    insert_at = "remap_function_get_hostname"
+    type = "log"
+    [tests.input.log_fields]
+  [[tests.outputs]]
+    extract_from = "remap_function_get_hostname"
+    [[tests.outputs.conditions]]
+      type = "remap"
+      source = '''
+        .a != ""
+      '''