Add 'push-no-tls' feature, for push support when HTTPS is unnecessary.

Cargo.toml

@@ -22,7 +22,10 @@ default = ["protobuf"]
 gen = ["protobuf-codegen-pure"]
 nightly = ["libc"]
 process = ["libc", "procfs"]
-push = ["reqwest", "libc", "protobuf"]
+push = ["push-reqwest-ssl", "push-deps"]
+push-no-tls = ["push-deps"]
+push-reqwest-ssl = ["reqwest?/default-tls"]
+push-deps = ["reqwest", "libc", "protobuf"]
 
 [dependencies]
 cfg-if = "^1.0"
@@ -32,7 +35,7 @@ libc = { version = "^0.2", optional = true }
 parking_lot = "^0.12"
 protobuf = { version = "^2.0", optional = true }
 memchr = "^2.3"
-reqwest = { version = "^0.11", features = ["blocking"], optional = true }
+reqwest = { version = "^0.11", default-features = false, features = ["blocking"], optional = true }
 thiserror = "^1.0"
 
 [target.'cfg(target_os = "linux")'.dependencies]

src/lib.rs

@@ -158,7 +158,7 @@ mod errors;
 mod gauge;
 mod histogram;
 mod metrics;
-#[cfg(feature = "push")]
+#[cfg(feature = "push-deps")]
 mod push;
 mod registry;
 mod value;
@@ -219,7 +219,7 @@ pub use self::histogram::DEFAULT_BUCKETS;
 pub use self::histogram::{exponential_buckets, linear_buckets};
 pub use self::histogram::{Histogram, HistogramOpts, HistogramTimer, HistogramVec};
 pub use self::metrics::Opts;
-#[cfg(feature = "push")]
+#[cfg(feature = "push-deps")]
 pub use self::push::{
     hostname_grouping_key, push_add_collector, push_add_metrics, push_collector, push_metrics,
     BasicAuthentication,