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Add a mechanism to get GCE custom metadata in cloudprober config. #363

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manugarg merged 1 commit into from
Jan 30, 2020
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Add a mechanism to get GCE custom metadata in cloudprober config. #363

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185 changes: 99 additions & 86 deletions config/config.go
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Copyright 2017 Google Inc.
// Copyright 2017-2020 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
Expand Down Expand Up @@ -26,85 +26,94 @@ Macros

Cloudprober configs support some macros to make configs construction easier:

*) env: get the value of an environment variable. A common use-case for this
is using it inside a kubernetes cluster. Example:

# Use an environment variable in probe config
probe {
name: "dns_google_jp"
type: DNS
targets {
host_names: "1.1.1.1"
}
dns_probe {
resolved_domain: "{{env "TEST_DOM"}}"
}
interval_msec: 5000 # 5s
timeout_msec: 1000 # 1s
}

# Then run cloudprober as:
TEST_DOM=google.co.jp ./cloudprober --config_file=cloudprober.cfg

*) extractSubstring - extract substring from a string using regex. Example use in config:

# Sharded VM-to-VM connectivity checks over internal IP
# Instance name format: ig-<zone>-<shard>-<random-characters>, e.g. ig-asia-east1-a-00-ftx1
{{$shard := .instance | extractSubstring "[^-]+-[^-]+-[^-]+-[^-]+-([^-]+)-.*" 1}}
probe {
name: "vm-to-vm-{{$shard}}"
type: PING
targets {
gce_targets {
instances {}
}
regex: "{{$targets}}"
}
run_on: "{{$run_on}}"
}

*) mkMap - mkMap returns a map built from the arguments. It's useful as Go
templates take only one argument. With this function, we can create a map of
multiple values and pass it to a template. Example use in config:

{{define "probeTmpl"}}
probe {
type: {{.typ}}
name: "{{.name}}"
targets {
host_names: "www.google.com"
}
}
{{end}}

{{template "probeTmpl" mkMap "typ" "PING" "name" "ping_google"}}
{{template "probeTmpl" mkMap "typ" "HTTP" "name" "http_google"}}


*) mkSlice - mkSlice returns a slice consisting of the arguments. Example use in config:

# Sharded VM-to-VM connectivity checks over internal IP
# Instance name format: ig-<zone>-<shard>-<random-characters>, e.g. ig-asia-east1-a-00-ftx1

{{with $shards := mkSlice "00" "01" "02" "03"}}
{{range $_, $shard := $shards}}
{{$targets := printf "^ig-([^-]+-[^-]+-[^-]+)-%s-[^-]+$" $shard}}
{{$run_on := printf "^ig-([^-]+-[^-]+-[^-]+)-%s-[^-.]+(|[.].*)$" $shard}}

probe {
name: "vm-to-vm-{{$shard}}"
type: PING
targets {
gce_targets {
instances {}
}
regex: "{{$targets}}"
}
run_on: "{{$run_on}}"
}

{{end}}
{{end}}
env
Get the value of an environment variable.

Example:

probe {
name: "dns_google_jp"
type: DNS
targets {
host_names: "1.1.1.1"
}
dns_probe {
resolved_domain: "{{env "TEST_DOM"}}"
}
}

# Then run cloudprober as:
TEST_DOM=google.co.jp ./cloudprober --config_file=cloudprober.cfg

gceCustomMetadata
Get value of a GCE custom metadata key. It first looks for the given key in
the instance's custom metadata and if it is not found there, it looks for it
in the project's custom metaata.

# Get load balancer IP from metadata.
probe {
name: "http_lb"
type: HTTP
targets {
host_names: "{{ gceCustomMetadata lb_ip }}"
}
}

extractSubstring
Extract substring from a string using regex. Example use in config:

# Sharded VM-to-VM connectivity checks over internal IP
# Instance name format: ig-<zone>-<shard>-<random-characters>, e.g. ig-asia-east1-a-00-ftx1
{{$shard := .instance | extractSubstring "[^-]+-[^-]+-[^-]+-[^-]+-([^-]+)-.*" 1}}
probe {
name: "vm-to-vm-{{$shard}}"
type: PING
targets {
gce_targets {
instances {}
}
regex: "{{$targets}}"
}
run_on: "{{$run_on}}"
}

mkMap
Returns a map built from the arguments. It's useful as Go templates take only
one argument. With this function, we can create a map of multiple values and
pass it to a template. Example use in config:

{{define "probeTmpl"}}
probe {
type: {{.typ}}
name: "{{.name}}"
targets {
host_names: "www.google.com"
}
}
{{end}}

{{template "probeTmpl" mkMap "typ" "PING" "name" "ping_google"}}
{{template "probeTmpl" mkMap "typ" "HTTP" "name" "http_google"}}


mkSlice
Returns a slice consisting of the arguments. It can be used with the built-in
'range' function to replicate text.


{{with $regions := mkSlice "us=central1" "us-east1"}}
{{range $_, $region := $regions}}

probe {
name: "service-a-{{$region}}"
type: HTTP
targets {
host_names: "service-a.{{$region}}.corp.xx.com"
}
}

{{end}}
{{end}}
*/
package config

Expand All @@ -124,18 +133,18 @@ import (
// ReadFromGCEMetadata reads the config from the GCE metadata. To allow for
// instance level as well as project-wide config, we look for the config in
// metadata in the following manner:
// a. If cloudprober_config is set in the instance's custom metadata, its
// value is returned.
// b. If (and only if), the key is not found in the step above, we look for
// the same key in the project's custom metadata.
// a. If the given key is set in the instance's custom metadata, its value is
// returned.
// b. If (and only if), the key is not found in the step above, we look for
// the same key in the project's custom metadata.
func ReadFromGCEMetadata(metadataKeyName string) (string, error) {
config, err := metadata.Get("instance/attributes/" + metadataKeyName)
config, err := metadata.InstanceAttributeValue(metadataKeyName)
// If instance level config found, return
if _, notFound := err.(metadata.NotDefinedError); !notFound {
return config, err
}
// Check project level config next
return metadata.Get("project/attributes/" + metadataKeyName)
return metadata.ProjectAttributeValue(metadataKeyName)
}

// DefaultConfig returns the default config string.
Expand All @@ -155,6 +164,9 @@ func ParseTemplate(config string, sysVars map[string]string) (string, error) {
}
return value
},

"gceCustomMetadata": ReadFromGCEMetadata,

// extractSubstring allows us to extract substring from a string using regex
// matching groups.
"extractSubstring": func(re string, n int, s string) (string, error) {
Expand Down Expand Up @@ -183,6 +195,7 @@ func ParseTemplate(config string, sysVars map[string]string) (string, error) {
}
return m, nil
},

// mkSlice makes a slice from its arguments.
"mkSlice": func(args ...interface{}) []interface{} {
return args
Expand Down