Struct TransportConfig 

pub struct TransportConfig {
    pub pool_max_idle_per_host: usize,
    pub pool_idle_timeout: Option<Duration>,
    pub tcp_keepalive: Option<Duration>,
    pub http2_prior_knowledge: bool,
    pub dns_cache_ttl: Option<Duration>,
    pub disable_proxies: bool,
}

HTTP transport configuration for reqwest::Client.

Manages connection pooling, DNS caching, TLS session resumption, and HTTP version negotiation. All fields have defaults that preserve the current behavior and do not require explicit configuration.

Fields

pool_max_idle_per_host: usize

Maximum number of idle connections per host in the connection pool.

Default: 32. Set to 0 to disable pooling.

pool_idle_timeout: Option<Duration>

How long an idle connection remains in the pool before being dropped.

Default: 90 seconds. Set to None to disable idle timeout.

tcp_keepalive: Option<Duration>

TCP keepalive interval for idle connections.

Default: 60 seconds. Set to None to disable. Helps detect stale connections on long-lived clients.

http2_prior_knowledge: bool

Enable HTTP/2 prior-knowledge.

When true, the client assumes the server supports HTTP/2 and skips the ALPN negotiation for HTTP/1.1 fallback. Saves a round-trip for endpoints that advertise HTTP/2 support (OpenAI, Anthropic).

Default: false (disable to avoid breaking custom base URLs).

dns_cache_ttl: Option<Duration>

DNS cache time-to-live.

Default: 30 seconds. DNS lookups are cached locally for this duration before re-resolving. Set to None to disable the local DNS cache and always re-resolve on each request.

disable_proxies: bool

Ignore ambient proxy settings (HTTP_PROXY, HTTPS_PROXY, ALL_PROXY and the system proxy configuration).

Any active outbound policy already disables proxies, so the guarded resolver sees every upstream host. Set this to rule out a machine-level proxy as a credential exposure path when the outbound policy is Off, without changing the process environment.

Redirects need no switch: the authenticated client never follows them, so credentials and request bodies cannot be forwarded to another origin.

Default: false.

Implementations

impl TransportConfig

pub fn new() -> Self

Create a new transport config with defaults.

pub fn with_pool_max_idle_per_host(self, count: usize) -> Self

Set the maximum idle connections per host.

pub fn with_pool_idle_timeout(self, timeout: Option<Duration>) -> Self

Set the idle connection timeout.

pub fn with_tcp_keepalive(self, interval: Option<Duration>) -> Self

Set the TCP keepalive interval.

pub fn with_http2_prior_knowledge(self, enabled: bool) -> Self

Enable or disable HTTP/2 prior-knowledge.

pub fn with_dns_cache_ttl(self, ttl: Option<Duration>) -> Self

Set the DNS cache TTL.

pub fn with_proxies_disabled(self, disabled: bool) -> Self

Ignore (or honor) ambient proxy settings from the environment.

pub fn apply_to_builder(&self, builder: ClientBuilder) -> ClientBuilder

Apply all transport settings to a reqwest::ClientBuilder.

This method converts transport fields into concrete reqwest builder calls. Call it once during client construction and chain the returned builder.

Not available on WASM targets: the browser fetch API controls transport settings and does not expose builder-level hooks.

Fields and their reqwest mapping

Field	reqwest method
pool_max_idle_per_host	.pool_max_idle_per_host(n)
pool_idle_timeout	.pool_idle_timeout(t)
tcp_keepalive	.tcp_keepalive(t)
http2_prior_knowledge	.http2_prior_knowledge() (when true)
dns_cache_ttl	.dns_resolver(...) during native client construction
enable_http3	.http3_prior_knowledge() (when true and http3 feature is on)
disable_proxies	.no_proxy() (when true)

DNS TTL

reqwest 0.13 exposes DNS customization through ClientBuilder::dns_resolver rather than a direct TTL setter. The native client construction path installs a resolver that combines this TTL with outbound-policy DNS validation, so DNS rebinding protection is preserved when both features are active.

Trait Implementations

impl Clone for TransportConfig

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TransportConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TransportConfig

fn default() -> Self

Returns the “default value” for a type.