Istio http2

Istio http2 DEFAULT

istio / istio Public

@johnjjung I'm hitting this same issue which for me appears to be #9429; The browsers are over aggressively using open connections. Trying to find a work around.

Yea, we had traditional LB for services in parallel and our uptime checks had LB's up but Istio Gateways/Virtual Services down, and ended reverting back to GCP-load balancers for our services. It's strange the latency from our uptime checks went down significantly as well. We'll be experimenting on our sandbox-cluster:

  • We had wild card certs as a secret (this broke when we upgraded to the latest istio version)
  • We reverted to Secure Gateway File Mount. For this it caused a bunch of issues where only one virtual service would work. So if you had and only one of the two would work on the browser (curl and rest clients worked fine). We confirmed this with multiple machines that it was the browsers that it would just pick one of the two domains and 404. After a lot of research it seems to be http2 reusing connections. We also tried making two separate gateways with two different file mounts using the one wildcard certificate and one not-wild certificate, and it would still not work so we ended up using GCP-load balancers :(

Protocol Selection

 2 minute read 

Istio supports proxying any TCP traffic. This includes HTTP, HTTPS, gRPC, as well as raw TCP protocols. In order to provide additional capabilities, such as routing and rich metrics, the protocol must be determined. This can be done automatically or explicitly specified.

Non-TCP based protocols, such as UDP, are not proxied. These protocols will continue to function as normal, without any interception by the Istio proxy but cannot be used in proxy-only components such as ingress or egress gateways.

Automatic protocol selection

Istio can automatically detect HTTP and HTTP/2 traffic. If the protocol cannot automatically be determined, traffic will be treated as plain TCP traffic.

Server First protocols, such as MySQL, are incompatible with automatic protocol selection. See Server first protocols for more information.

Explicit protocol selection

Protocols can be specified manually in the Service definition.

This can be configured in two ways:

  • By the name of the port: .
  • In Kubernetes 1.18+, by the field: .

The following protocols are supported:

  • *
  • *
  • (UDP will not be proxied, but the port can be explicitly declared as UDP)

* These protocols are disabled by default to avoid accidentally enabling experimental features. To enable them, configure the corresponding Pilot environment variables.

Below is an example of a Service that defines a port by and an port by name:

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 12 minute read 

describes a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections. The specification describes a set of ports that should be exposed, the type of protocol to use, SNI configuration for the load balancer, etc.

For example, the following Gateway configuration sets up a proxy to act as a load balancer exposing port 80 and 9080 (http), 443 (https), 9443(https) and port 2379 (TCP) for ingress. The gateway will be applied to the proxy running on a pod with labels . While Istio will configure the proxy to listen on these ports, it is the responsibility of the user to ensure that external traffic to these ports are allowed into the mesh.

The Gateway specification above describes the L4-L6 properties of a load balancer. A can then be bound to a gateway to control the forwarding of traffic arriving at a particular host or gateway port.

For example, the following VirtualService splits traffic for , , , into two versions (prod and qa) of an internal reviews service on port 9080. In addition, requests containing the cookie “user: dev-123” will be sent to special port 7777 in the qa version. The same rule is also applicable inside the mesh for requests to the “” service. This rule is applicable across ports 443, 9080. Note that gets redirected to (i.e. 80 redirects to 443).

The following VirtualService forwards traffic arriving at (external) port 27017 to internal Mongo server on port 5555. This rule is not applicable internally in the mesh as the gateway list omits the reserved name .

It is possible to restrict the set of virtual services that can bind to a gateway server using the namespace/hostname syntax in the hosts field. For example, the following Gateway allows any virtual service in the ns1 namespace to bind to it, while restricting only the virtual service with host in the ns2 namespace to bind to it.


Gateway describes a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections.


A list of server specifications.


One or more labels that indicate a specific set of pods/VMs on which this gateway configuration should be applied. By default workloads are searched across all namespaces based on label selectors. This implies that a gateway resource in the namespace “foo” can select pods in the namespace “bar” based on labels. This behavior can be controlled via the environment variable in istiod. If this variable is set to true, the scope of label search is restricted to the configuration namespace in which the the resource is present. In other words, the Gateway resource must reside in the same namespace as the gateway workload instance. If selector is nil, the Gateway will be applied to all workloads.



describes the properties of the proxy on a given load balancer port. For example,

Another example

The following is an example of TLS configuration for port 443


The Port on which the proxy should listen for incoming connections.


The ip or the Unix domain socket to which the listener should be bound to. Format: or or (Linux abstract namespace). When using Unix domain sockets, the port number should be 0. This can be used to restrict the reachability of this server to be gateway internal only. This is typically used when a gateway needs to communicate to another mesh service e.g. publishing metrics. In such case, the server created with the specified bind will not be available to external gateway clients.


One or more hosts exposed by this gateway. While typically applicable to HTTP services, it can also be used for TCP services using TLS with SNI. A host is specified as a with an optional prefix. The should be specified using FQDN format, optionally including a wildcard character in the left-most component (e.g., ). Set the to to select all hosts from the specified namespace (e.g.,).

The can be set to or , representing any or the current namespace, respectively. For example, selects the service from any available namespace while only selects the service from the namespace of the sidecar. The default, if no is specified, is , that is, select services from any namespace. Any associated in the selected namespace will also be used.

A must be bound to the gateway and must have one or more hosts that match the hosts specified in a server. The match could be an exact match or a suffix match with the server’s hosts. For example, if the server’s hosts specifies , a with hosts or will match. However, a with host or will not match.

NOTE: Only virtual services exported to the gateway’s namespace (e.g., value of ) can be referenced. Private configurations (e.g., set to ) will not be available. Refer to the setting in , , and configurations for details.


Set of TLS related options that govern the server’s behavior. Use these options to control if all http requests should be redirected to https, and the TLS modes to use.


An optional name of the server, when set must be unique across all servers. This will be used for variety of purposes like prefixing stats generated with this name etc.



Port describes the properties of a specific port of a service.


A valid non-negative integer port number.


The protocol exposed on the port. MUST BE one of HTTP|HTTPS|GRPC|HTTP2|MONGO|TCP|TLS. TLS implies the connection will be routed based on the SNI header to the destination without terminating the TLS connection.


Label assigned to the port.


The port number on the endpoint where the traffic will be received. Applicable only when used with ServiceEntries.




If set to true, the load balancer will send a 301 redirect for all http connections, asking the clients to use HTTPS.


Optional: Indicates whether connections to this port should be secured using TLS. The value of this field determines how TLS is enforced.


REQUIRED if mode is or . The path to the file holding the server-side TLS certificate to use.


REQUIRED if mode is or . The path to the file holding the server’s private key.


REQUIRED if mode is . The path to a file containing certificate authority certificates to use in verifying a presented client side certificate.


For gateways running on Kubernetes, the name of the secret that holds the TLS certs including the CA certificates. Applicable only on Kubernetes. The secret (of type ) should contain the following keys and values: and . For mutual TLS, can be provided in the same secret or a separate secret named . Secret of type tls for server certificates along with ca.crt key for CA certificates is also supported. Only one of server certificates and CA certificate or credentialName can be specified.


A list of alternate names to verify the subject identity in the certificate presented by the client.


An optional list of base64-encoded SHA-256 hashes of the SKPIs of authorized client certificates. Note: When both verifycertificatehash and verifycertificatespki are specified, a hash matching either value will result in the certificate being accepted.


An optional list of hex-encoded SHA-256 hashes of the authorized client certificates. Both simple and colon separated formats are acceptable. Note: When both verifycertificatehash and verifycertificatespki are specified, a hash matching either value will result in the certificate being accepted.


Optional: Minimum TLS protocol version.


Optional: Maximum TLS protocol version.


Optional: If specified, only support the specified cipher list. Otherwise default to the default cipher list supported by Envoy.



TLS modes enforced by the proxy


The SNI string presented by the client will be used as the match criterion in a VirtualService TLS route to determine the destination service from the service registry.

Secure connections with standard TLS semantics.

Secure connections to the downstream using mutual TLS by presenting server certificates for authentication.

Similar to the passthrough mode, except servers with this TLS mode do not require an associated VirtualService to map from the SNI value to service in the registry. The destination details such as the service/subset/port are encoded in the SNI value. The proxy will forward to the upstream (Envoy) cluster (a group of endpoints) specified by the SNI value. This server is typically used to provide connectivity between services in disparate L3 networks that otherwise do not have direct connectivity between their respective endpoints. Use of this mode assumes that both the source and the destination are using Istio mTLS to secure traffic. In order for this mode to be enabled, the gateway deployment must be configured with the environment variable.

Secure connections from the downstream using mutual TLS by presenting server certificates for authentication. Compared to Mutual mode, this mode uses certificates, representing gateway workload identity, generated automatically by Istio for mTLS authentication. When this mode is used, all other fields in should be empty.


TLS protocol versions.


Automatically choose the optimal TLS version.

TLS version 1.0

TLS version 1.1

TLS version 1.2

TLS version 1.3

gRPC July Meetup/ How to configure Istio to support your gRPC web applications- by Casey Wylie

How to upgrade Istio Service Mesh from http to http2?

We are on Kubernetes and use Istio Service Mesh. Currently, there is SSL Termination for HTTPS in Gateway. I see in the istio-proxy logs that the HTTP protocol is HTTP 1.1.

I want to upgrade HTTP 1.1 to HTTP2 due to its various advantages. Clients should call our services HTTP2 over SSL/TLS.

I am using this blog for an internal demo on this topic.

These are the bottlenecks:

1) I want to propose a plan which will causes least amount of changes. I understand I need to update the Gateway from


based on the examples I see in the Istio's Gateway documentation.

I want to know: Will this allow HTTP2 over TLS connections from browsers (which support only this mode)? Can I provide tls details for HTTP2, like I did with HTTPS?

2) What are some of the other Istio configurations to update?

3) Will this change be break Microservices which are using http protocol currently? How can I mitigate this?

4) I was reading about DestinationRule and upgrade policy. Is this a good fit?

asked Jan 6 '20 at 5:00


Http2 istio


gRPC is a communication protocol for services, built on HTTP/2. Unlike REST over HTTP/1, which is based on resources, gRPC is based on Service Definitions. You specify service definitions in a format called protocol buffers (“proto”), which can be serialized into an small binary format for transmission.

With gRPC, you can generate boilerplate code from files into multiple programming languages, making gRPC an ideal choice for polyglot microservices.

While gRPC supports some networking use cases like TLS and client-side load balancing, adding Istio to a gRPC architecture can be useful for collecting telemetry, adding traffic rules, and setting RPC-level authorization. Istio can also provide a useful management layer if your traffic is a mix of HTTP, TCP, gRPC, and database protocols, because you can use the same Istio APIs for all traffic types.

Istio and its data plane proxy, Envoy, both support gRPC. Let's see how to manage gRPC traffic with Istio.


Here, we're running two gRPC Services, and . makes an RPC call to the 's function every 2 seconds.

Adding Istio to gRPC Kubernetes services has one pre-requisite: labeling your Kubernetes Service ports. The server's port is labeled as follows:

Once we deploy the app, we can see this traffic between client and server in a service graph:


We can also view the server's gRPC traffic metrics in Grafana:

Then, we can apply an Istio traffic rule to inject a 10-second delay fault into . You might apply this rule in a chaos testing scenario, to test the resiliency of this application.

This causes the client RPC to time out ():

To learn more about gRPC and Istio:

Istio in Production: Day 2 Traffic Routing (Cloud Next '19)


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