transport/grpc: add support for GCP direct path
Tries direct path if the GOOGLE_CLOUD_ENABLE_DIRECT_PATH env var
contains a substring of the endpoint.
For example, if GOOGLE_CLOUD_ENABLE_DIRECT_PATH=spanner,pubsub
then grpc.Dial will attempt direct path when dialling spanner.googleapis.com.
Depends on a change to x/oauth2/google to determine whether the token
source is GCE metadata targeting the default service account, which is
the only supported token source for direct path.
See https://go-review.googlesource.com/c/oauth2/+/175877
Change-Id: I1051fd284073deb47f5c5d6364ad86efb57da172
Reviewed-on: https://code-review.googlesource.com/c/google-api-go-client/+/40950
Reviewed-by: Chris Broadfoot <cbro@google.com>
Reviewed-by: kokoro <noreply+kokoro@google.com>
diff --git a/go.mod b/go.mod
index f8559f7..59565d2 100644
--- a/go.mod
+++ b/go.mod
@@ -1,14 +1,20 @@
module google.golang.org/api
require (
- github.com/google/go-cmp v0.2.0
+ cloud.google.com/go v0.38.0 // indirect
+ github.com/golang/protobuf v1.3.1 // indirect
+ github.com/google/go-cmp v0.3.0
+ github.com/hashicorp/golang-lru v0.5.1 // indirect
go.opencensus.io v0.21.0
- golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f
- golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421
- golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6
- golang.org/x/tools v0.0.0-20190312170243-e65039ee4138
- google.golang.org/appengine v1.4.0
- google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19
- google.golang.org/grpc v1.19.0
- honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099
+ golang.org/x/lint v0.0.0-20190409202823-959b441ac422
+ golang.org/x/net v0.0.0-20190503192946-f4e77d36d62c // indirect
+ golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
+ golang.org/x/sync v0.0.0-20190423024810-112230192c58
+ golang.org/x/sys v0.0.0-20190507160741-ecd444e8653b // indirect
+ golang.org/x/text v0.3.2 // indirect
+ golang.org/x/tools v0.0.0-20190506145303-2d16b83fe98c
+ google.golang.org/appengine v1.5.0
+ google.golang.org/genproto v0.0.0-20190502173448-54afdca5d873
+ google.golang.org/grpc v1.20.1
+ honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a
)
diff --git a/go.sum b/go.sum
index d6f860f..3b85dc1 100644
--- a/go.sum
+++ b/go.sum
@@ -2,18 +2,32 @@
cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
cloud.google.com/go v0.34.0 h1:eOI3/cP2VTU6uZLDYAoic+eyzzB9YyGmJ7eIjl8rOPg=
cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+cloud.google.com/go v0.38.0 h1:ROfEUZz+Gh5pa62DJWXSaonyu3StP6EA6lPEXPI6mCo=
+cloud.google.com/go v0.38.0/go.mod h1:990N+gfupTy94rShfmMCWGDn0LpTmnzTp2qbd1dvSRU=
github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
+github.com/golang/mock v1.2.0/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
+github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
github.com/google/go-cmp v0.2.0 h1:+dTQ8DZQJz0Mb/HjFlkptS1FeQ4cWSnN941F8aEG4SQ=
github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
+github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
+github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
+github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57/go.mod h1:zfwlbNMJ+OItoe0UupaVj+oy1omPYYDuagoSzA8v9mc=
+github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
github.com/hashicorp/golang-lru v0.5.0 h1:CL2msUPvZTLb5O648aiLNJw3hnBxN2+1Jq8rCOH9wdo=
github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
+github.com/hashicorp/golang-lru v0.5.1 h1:0hERBMJE1eitiLkihrMvRVBYAkpHzc/J3QdDN+dAcgU=
+github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
+github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
go.opencensus.io v0.21.0 h1:mU6zScU4U1YAFPHEHYk+3JC4SY7JxgkqS10ZOSyksNg=
go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
@@ -23,39 +37,69 @@
golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f h1:hX65Cu3JDlGH3uEdK7I99Ii+9kjD6mvnnpfLdEAH0x4=
golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
+golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
+golang.org/x/lint v0.0.0-20190409202823-959b441ac422 h1:QzoH/1pFpZguR8NrRHLcO6jKqfv2zpuSqZLgdm7ZmjI=
+golang.org/x/lint v0.0.0-20190409202823-959b441ac422/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
golang.org/x/net v0.0.0-20190108225652-1e06a53dbb7e/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
golang.org/x/net v0.0.0-20190213061140-3a22650c66bd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
golang.org/x/net v0.0.0-20190311183353-d8887717615a h1:oWX7TPOiFAMXLq8o0ikBYfCJVlRHBcsciT5bXOrH628=
golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190503192946-f4e77d36d62c h1:uOCk1iQW6Vc18bnC13MfzScl+wdKBmM9Y9kU7Z83/lw=
+golang.org/x/net v0.0.0-20190503192946-f4e77d36d62c/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be h1:vEDujvNQGv4jgYKudGeI/+DAX4Jffq6hpD55MmoEvKs=
golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421 h1:Wo7BWFiOk0QRFMLYMqJGFMd9CgUAcGx7V+qEg/h5IBI=
golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
+golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45 h1:SVwTIAaPC2U/AvvLNZ2a7OVsmBpC8L5BlwK1whH3hm0=
+golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20181108010431-42b317875d0f h1:Bl/8QSvNqXvPGPGXa2z5xUTmV7VDcZyvRZ+QQXkXTZQ=
golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6 h1:bjcUS9ztw9kFmmIxJInhon/0Is3p+EHBKNgquIzo1OI=
golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190507160741-ecd444e8653b h1:ag/x1USPSsqHud38I9BAC88qdNLDHHtQ4mlgQIZPPNA=
+golang.org/x/sys v0.0.0-20190507160741-ecd444e8653b/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190114222345-bf090417da8b h1:qMK98NmNCRVDIYFycQ5yVRkvgDUFfdP8Ip4KqmDEB7g=
golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
+golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
golang.org/x/tools v0.0.0-20190312170243-e65039ee4138 h1:H3uGjxCR/6Ds0Mjgyp7LMK81+LvmbvWWEnJhzk1Pi9E=
golang.org/x/tools v0.0.0-20190312170243-e65039ee4138/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
+golang.org/x/tools v0.0.0-20190506145303-2d16b83fe98c h1:97SnQk1GYRXJgvwZ8fadnxDOWfKvkNQHH3CtZntPSrM=
+golang.org/x/tools v0.0.0-20190506145303-2d16b83fe98c/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
+google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
google.golang.org/appengine v1.4.0 h1:/wp5JvzpHIxhs/dumFmF7BXTf3Z+dd4uXta4kVyO508=
google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
+google.golang.org/appengine v1.5.0 h1:KxkO13IPW4Lslp2bz+KHP2E3gtFlrIGNThxkZQ3g+4c=
+google.golang.org/appengine v1.5.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19 h1:Lj2SnHtxkRGJDqnGaSjo+CCdIieEnwVazbOXILwQemk=
google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
+google.golang.org/genproto v0.0.0-20190418145605-e7d98fc518a7/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
+google.golang.org/genproto v0.0.0-20190502173448-54afdca5d873 h1:nfPFGzJkUDX6uBmpN/pSw7MbOAWegH5QDQuoXFHedLg=
+google.golang.org/genproto v0.0.0-20190502173448-54afdca5d873/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
google.golang.org/grpc v1.19.0 h1:cfg4PD8YEdSFnm7qLV4++93WcmhH2nIUhMjhdCvl3j8=
google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
+google.golang.org/grpc v1.20.1 h1:Hz2g2wirWK7H0qIIhGIqRGTuMwTE8HEKFnDZZ7lm9NU=
+google.golang.org/grpc v1.20.1/go.mod h1:10oTOabMzJvdu6/UiuZezV6QK5dSlG84ov/aaiqXj38=
honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099 h1:XJP7lxbSxWLOMNdBE4B/STaqVy6L73o0knwj2vIlxnw=
honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
+honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
+honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a h1:LJwr7TCTghdatWv40WobzlKXc9c4s8oGa7QKJUtHhWA=
+honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
diff --git a/transport/grpc/dial.go b/transport/grpc/dial.go
index 4f6b94d..7882100 100644
--- a/transport/grpc/dial.go
+++ b/transport/grpc/dial.go
@@ -21,13 +21,20 @@
"context"
"errors"
"log"
+ "os"
+ "strings"
"go.opencensus.io/plugin/ocgrpc"
+ "golang.org/x/oauth2"
"google.golang.org/api/internal"
"google.golang.org/api/option"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials"
+ grpcgoogle "google.golang.org/grpc/credentials/google"
"google.golang.org/grpc/credentials/oauth"
+
+ // Install grpclb, which is required for direct path.
+ _ "google.golang.org/grpc/balancer/grpclb"
)
// Set at init time by dial_appengine.go. If nil, we're not on App Engine.
@@ -60,9 +67,7 @@
if o.GRPCConn != nil {
return o.GRPCConn, nil
}
- grpcOpts := []grpc.DialOption{
- grpc.WithWaitForHandshake(),
- }
+ var grpcOpts []grpc.DialOption
if insecure {
grpcOpts = []grpc.DialOption{grpc.WithInsecure()}
} else if !o.NoAuth {
@@ -73,13 +78,31 @@
if err != nil {
return nil, err
}
- grpcOpts = []grpc.DialOption{
- grpc.WithPerRPCCredentials(grpcTokenSource{
- TokenSource: oauth.TokenSource{creds.TokenSource},
- quotaProject: o.QuotaProject,
- requestReason: o.RequestReason,
- }),
- grpc.WithTransportCredentials(credentials.NewClientTLSFromCert(nil, "")),
+ // Attempt Direct Path only if:
+ // * The endpoint is a host:port (or dns:///host:port).
+ // * Credentials are obtained via GCE metadata server, using the default
+ // service account.
+ // * Opted in via GOOGLE_CLOUD_ENABLE_DIRECT_PATH environment variable.
+ // For example, GOOGLE_CLOUD_ENABLE_DIRECT_PATH=spanner,pubsub
+ if isDirectPathEnabled(o.Endpoint) && isTokenSourceDirectPathCompatible(creds.TokenSource) {
+ if !strings.HasPrefix(o.Endpoint, "dns:///") {
+ o.Endpoint = "dns:///" + o.Endpoint
+ }
+ grpcOpts = []grpc.DialOption{
+ grpc.WithCredentialsBundle(
+ grpcgoogle.NewComputeEngineCredentials(),
+ ),
+ }
+ // TODO(cbro): add support for system parameters (quota project, request reason) via chained interceptor.
+ } else {
+ grpcOpts = []grpc.DialOption{
+ grpc.WithPerRPCCredentials(grpcTokenSource{
+ TokenSource: oauth.TokenSource{creds.TokenSource},
+ quotaProject: o.QuotaProject,
+ requestReason: o.RequestReason,
+ }),
+ grpc.WithTransportCredentials(credentials.NewClientTLSFromCert(nil, "")),
+ }
}
}
if appengineDialerHook != nil {
@@ -127,3 +150,44 @@
}
return metadata, nil
}
+
+func isTokenSourceDirectPathCompatible(ts oauth2.TokenSource) bool {
+ if ts == nil {
+ return false
+ }
+ tok, err := ts.Token()
+ if err != nil {
+ return false
+ }
+ if tok == nil {
+ return false
+ }
+ if source, _ := tok.Extra("oauth2.google.tokenSource").(string); source != "compute-metadata" {
+ return false
+ }
+ if acct, _ := tok.Extra("oauth2.google.serviceAccount").(string); acct != "default" {
+ return false
+ }
+ return true
+}
+
+func isDirectPathEnabled(endpoint string) bool {
+ // Only host:port is supported, not other schemes (e.g., "tcp://" or "unix://").
+ // Also don't try direct path if the user has chosen an alternate name resolver
+ // (i.e., via ":///" prefix).
+ //
+ // TODO(cbro): once gRPC has introspectible options, check the user hasn't
+ // provided a custom dialer in gRPC options.
+ if strings.Contains(endpoint, "://") && !strings.HasPrefix(endpoint, "dns:///") {
+ return false
+ }
+
+ // Only try direct path if the user has opted in via the environment variable.
+ whitelist := strings.Split(os.Getenv("GOOGLE_CLOUD_ENABLE_DIRECT_PATH"), ",")
+ for _, api := range whitelist {
+ if strings.Contains(endpoint, api) {
+ return true
+ }
+ }
+ return false
+}
