Added json_path function (#4225)

* Added json_path function * Add doc note about local.file * Update docs/sources/flow/reference/stdlib/json_path.md Co-authored-by: Clayton Cornell <[email protected]> --------- Co-authored-by: Clayton Cornell <[email protected]>
grafana · Jun 23, 2023 · fe2f702 · fe2f702
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -27,6 +27,8 @@ Main (unreleased)
   - `prometheus.exporter.squid` collects metrics from a squid server. (@armstrmi)
   - `prometheus.exporter.elasticsearch` collects metrics from Elasticsearch. (@marctc)
 
+- Added json_path function to river stdlib. (@jkroepke)
+
 ### Enhancements
 
 - Attributes and blocks set to their default values will no longer be shown in the Flow UI. (@rfratto)

diff --git a/docs/sources/flow/reference/stdlib/json_path.md b/docs/sources/flow/reference/stdlib/json_path.md
@@ -0,0 +1,41 @@
+---
+aliases:
+- ../../configuration-language/standard-library/json_path/
+title: json_path
+---
+
+# json_path
+
+The `json_path` function lookup values using [jsonpath](https://goessner.net/articles/JsonPath/) syntax.
+
+The function expects two strings. The first string is the JSON string used look up values. The second string is the jsonpath expression.
+
+`json_path` always returns a list of values. If the jsonpath expression does not match any values, an empty list is returned.
+
+A common use case of `json_path` is to decode and filter the output of a [`local.file`][] or [`remote.http`][] component to a River value.
+
+> Remember to escape double quotes when passing JSON string literals to `json_path`.
+>
+> For example, the JSON value `{"key": "value"}` is properly represented by the
+> string `"{\"key\": \"value\"}"`.
+
+## Examples
+
+```
+> json_path("{\"key\": \"value\"}", ".key")
+["value"]
+
+
+> json_path("[{\"name\": \"Department\",\"value\": \"IT\"},{\"name\":\"TestStatus\",\"value\":\"Pending\"}]", "[?(@.name == \"Department\")].value")
+["IT"]
+
+> json_path("{\"key\": \"value\"}", ".nonexists")
+[]
+
+> json_path("{\"key\": \"value\"}", ".key")[0]
+value
+
+```
+
+[`local.file`]: {{< relref "../components/local.file.md" >}}
+[`remote.http`]: {{< relref "../components/remote.http.md" >}}
diff --git a/go.mod b/go.mod
@@ -92,6 +92,7 @@ require (
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f
 	github.com/ncabatoff/process-exporter v0.7.10
 	github.com/nerdswords/yet-another-cloudwatch-exporter v0.51.0
+	github.com/ohler55/ojg v1.18.7
 	github.com/oklog/run v1.1.0
 	github.com/olekukonko/tablewriter v0.0.5
 	github.com/oliver006/redis_exporter v1.49.0

diff --git a/go.sum b/go.sum
@@ -1712,8 +1712,6 @@ github.com/grafana/ckit v0.0.0-20230518140533-fbd338b33964 h1:rJIMh9u7TBoq58tE8c
 github.com/grafana/ckit v0.0.0-20230518140533-fbd338b33964/go.mod h1:HcHGszFkeYCuFbWt6qt72rnZRHwbR2BhQBGHWqe4AqU=
 github.com/grafana/cloudflare-go v0.0.0-20230110200409-c627cf6792f2 h1:qhugDMdQ4Vp68H0tp/0iN17DM2ehRo1rLEdOFe/gB8I=
 github.com/grafana/cloudflare-go v0.0.0-20230110200409-c627cf6792f2/go.mod h1:w/aiO1POVIeXUQyl0VQSZjl5OAGDTL5aX+4v0RA1tcw=
-github.com/grafana/dnsmasq_exporter v0.2.1-0.20211118155541-751b01d21de9 h1:/ovWD85B27b/xytKaxhP/LvXF8fxWIhEwE55mFpCQsE=
-github.com/grafana/dnsmasq_exporter v0.2.1-0.20211118155541-751b01d21de9/go.mod h1:Jj5TSVVJE6t8Brq/ZkUbQ1n260dilriL0tWNaHjVDUs=
 github.com/grafana/dskit v0.0.0-20210908150159-fcf48cb19aa4/go.mod h1:m3eHzwe5IT5eE2MI3Ena2ooU8+Hek8IiVXb9yJ1+0rs=
 github.com/grafana/dskit v0.0.0-20211021180445-3bd016e9d7f1/go.mod h1:uPG2nyK4CtgNDmWv7qyzYcdI+S90kHHRWvHnBtEMBXM=
 github.com/grafana/dskit v0.0.0-20230201083518-528d8a7d52f2 h1:IOks+FXJ6iO/pfbaVEf4efNw+YzYBYNCkCabyrbkFTM=
@@ -2321,14 +2319,11 @@ github.com/mgutz/ansi v0.0.0-20170206155736-9520e82c474b/go.mod h1:01TrycV0kFyex
 github.com/microsoft/go-mssqldb v0.19.0 h1:LMRSgLcNMF8paPX14xlyQBmBH+jnFylPsYpVZf86eHM=
 github.com/microsoft/go-mssqldb v0.19.0/go.mod h1:ukJCBnnzLzpVF0qYRT+eg1e+eSwjeQ7IvenUv8QPook=
 github.com/miekg/dns v1.0.14/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
-github.com/miekg/dns v1.1.14/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
 github.com/miekg/dns v1.1.25/go.mod h1:bPDLeHnStXmXAq1m/Ch/hvfNHr14JKNPMBo3VZKjuso=
 github.com/miekg/dns v1.1.26/go.mod h1:bPDLeHnStXmXAq1m/Ch/hvfNHr14JKNPMBo3VZKjuso=
 github.com/miekg/dns v1.1.41/go.mod h1:p6aan82bvRIyn+zDIv9xYNUpwa73JcSh9BKwknJysuI=
 github.com/miekg/dns v1.1.43/go.mod h1:+evo5L0630/F6ca/Z9+GAqzhjGyn8/c+TBaOyfEl0V4=
 github.com/miekg/dns v1.1.50/go.mod h1:e3IlAVfNqAllflbibAZEWOXOQ+Ynzk/dDozDxY7XnME=
-github.com/miekg/dns v1.1.54 h1:5jon9mWcb0sFJGpnI99tOMhCPyJ+RPVz5b63MQG0VWI=
-github.com/miekg/dns v1.1.54/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=
 github.com/miekg/dns v1.1.55 h1:GoQ4hpsj0nFLYe+bWiCToyrBEJXkQfOOIvFGFy0lEgo=
 github.com/miekg/dns v1.1.55/go.mod h1:uInx36IzPl7FYnDcMeVWxj9byh7DutNykX4G9Sj60FY=
 github.com/miekg/pkcs11 v1.0.3/go.mod h1:XsNlhZGX73bx86s2hdc/FuaLm2CPZJemRLMA+WTFxgs=
@@ -2468,6 +2463,8 @@ github.com/nxadm/tail v1.4.8 h1:nPr65rt6Y5JFSKQO7qToXr7pePgD6Gwiw05lkbyAQTE=
 github.com/nxadm/tail v1.4.8/go.mod h1:+ncqLTQzXmGhMZNUePPaPqPvBxHAIsmXswZKocGu+AU=
 github.com/observiq/ctimefmt v1.0.0 h1:r7vTJ+Slkrt9fZ67mkf+mA6zAdR5nGIJRMTzkUyvilk=
 github.com/observiq/ctimefmt v1.0.0/go.mod h1:mxi62//WbSpG/roCO1c6MqZ7zQTvjVtYheqHN3eOjvc=
+github.com/ohler55/ojg v1.18.7 h1:sC7zy0usEiWa6bvx3NU1yZH4kCA2F3Qzs6iiDX4+xdk=
+github.com/ohler55/ojg v1.18.7/go.mod h1:uHcD1ErbErC27Zhb5Df2jUjbseLLcmOCo6oxSr3jZxo=
 github.com/oklog/oklog v0.3.2/go.mod h1:FCV+B7mhrz4o+ueLpx+KqkyXRGMWOYEvfiXtdGtbWGs=
 github.com/oklog/run v0.0.0-20180308005104-6934b124db28/go.mod h1:dlhp/R75TPv97u0XWUtDeV/lRKWPKSdTuV0TZvrmrQA=
 github.com/oklog/run v1.0.0/go.mod h1:dlhp/R75TPv97u0XWUtDeV/lRKWPKSdTuV0TZvrmrQA=
@@ -2812,8 +2809,6 @@ github.com/prometheus/procfs v0.2.0/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4O
 github.com/prometheus/procfs v0.6.0/go.mod h1:cz+aTbrPOrUb4q7XlbU9ygM+/jj0fzG6c1xBZuNvfVA=
 github.com/prometheus/procfs v0.7.3/go.mod h1:cz+aTbrPOrUb4q7XlbU9ygM+/jj0fzG6c1xBZuNvfVA=
 github.com/prometheus/procfs v0.8.0/go.mod h1:z7EfXMXOkbkqb9IINtpCn86r/to3BnA0uaxHdg830/4=
-github.com/prometheus/procfs v0.10.1 h1:kYK1Va/YMlutzCGazswoHKo//tZVlFpKYh+PymziUAg=
-github.com/prometheus/procfs v0.10.1/go.mod h1:nwNm2aOCAYw8uTR/9bWRREkZFxAUcWzPHWJq+XBB/FM=
 github.com/prometheus/procfs v0.11.0 h1:5EAgkfkMl659uZPbe9AS2N68a7Cc1TJbPEuGzFuRbyk=
 github.com/prometheus/procfs v0.11.0/go.mod h1:nwNm2aOCAYw8uTR/9bWRREkZFxAUcWzPHWJq+XBB/FM=
 github.com/prometheus/statsd_exporter v0.22.7/go.mod h1:N/TevpjkIh9ccs6nuzY3jQn9dFqnUakOjnEuMPJJJnI=

diff --git a/pkg/river/internal/stdlib/stdlib.go b/pkg/river/internal/stdlib/stdlib.go
@@ -7,6 +7,8 @@ import (
 
 	"github.com/grafana/agent/pkg/river/internal/value"
 	"github.com/grafana/agent/pkg/river/rivertypes"
+	"github.com/ohler55/ojg/jp"
+	"github.com/ohler55/ojg/oj"
 )
 
 // Identifiers holds a list of stdlib identifiers by name. All interface{}
@@ -79,6 +81,20 @@ var Identifiers = map[string]interface{}{
 		return res, nil
 	},
 
+	"json_path": func(jsonString string, path string) (interface{}, error) {
+		jsonPathExpr, err := jp.ParseString(path)
+		if err != nil {
+			return nil, err
+		}
+
+		jsonExpr, err := oj.ParseString(jsonString)
+		if err != nil {
+			return nil, err
+		}
+
+		return jsonPathExpr.Get(jsonExpr), nil
+	},
+
 	"coalesce": value.RawFunction(func(funcValue value.Value, args ...value.Value) (value.Value, error) {
 		if len(args) == 0 {
 			return value.Null, nil

diff --git a/pkg/river/vm/vm_stdlib_test.go b/pkg/river/vm/vm_stdlib_test.go
@@ -79,6 +79,32 @@ func TestStdlibCoalesce(t *testing.T) {
 	}
 }
 
+func TestStdlibJsonPath(t *testing.T) {
+	tt := []struct {
+		name   string
+		input  string
+		expect interface{}
+	}{
+		{"json_path with simple json", `json_path("{\"a\": \"b\"}", ".a")`, []string{"b"}},
+		{"json_path with simple json without results", `json_path("{\"a\": \"b\"}", ".nonexists")`, []string{}},
+		{"json_path with json array", `json_path("[{\"name\": \"Department\",\"value\": \"IT\"},{\"name\":\"ReferenceNumber\",\"value\":\"123456\"},{\"name\":\"TestStatus\",\"value\":\"Pending\"}]", "[?(@.name == \"Department\")].value")`, []string{"IT"}},
+		{"json_path with simple json and return first", `json_path("{\"a\": \"b\"}", ".a")[0]`, "b"},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			expr, err := parser.ParseExpression(tc.input)
+			require.NoError(t, err)
+
+			eval := vm.New(expr)
+
+			rv := reflect.New(reflect.TypeOf(tc.expect))
+			require.NoError(t, eval.Evaluate(nil, rv.Interface()))
+			require.Equal(t, tc.expect, rv.Elem().Interface())
+		})
+	}
+}
+
 func TestStdlib_Nonsensitive(t *testing.T) {
 	scope := &vm.Scope{
 		Variables: map[string]any{