open-nomad/api/services.go
Seth Hoenig 0e44094d1a client: enable configuring enable_tag_override for services
Consul provides a feature of Service Definitions where the tags
associated with a service can be modified through the Catalog API,
overriding the value(s) configured in the agent's service configuration.

To enable this feature, the flag enable_tag_override must be configured
in the service definition.

Previously, Nomad did not allow configuring this flag, and thus the default
value of false was used. Now, it is configurable.

Because Nomad itself acts as a state machine around the the service definitions
of the tasks it manages, it's worth describing what happens when this feature
is enabled and why.

Consider the basic case where there is no Nomad, and your service is provided
to consul as a boring JSON file. The ultimate source of truth for the definition
of that service is the file, and is stored in the agent. Later, Consul performs
"anti-entropy" which synchronizes the Catalog (stored only the leaders). Then
with enable_tag_override=true, the tags field is available for "external"
modification through the Catalog API (rather than directly configuring the
service definition file, or using the Agent API). The important observation
is that if the service definition ever changes (i.e. the file is changed &
config reloaded OR the Agent API is used to modify the service), those
"external" tag values are thrown away, and the new service definition is
once again the source of truth.

In the Nomad case, Nomad itself is the source of truth over the Agent in
the same way the JSON file was the source of truth in the example above.
That means any time Nomad sets a new service definition, any externally
configured tags are going to be replaced. When does this happen? Only on
major lifecycle events, for example when a task is modified because of an
updated job spec from the 'nomad job run <existing>' command. Otherwise,
Nomad's periodic re-sync's with Consul will now no longer try to restore
the externally modified tag values (as long as enable_tag_override=true).

Fixes #2057
2020-02-10 08:00:55 -06:00

182 lines
4.9 KiB
Go

package api
import (
"fmt"
"time"
)
// CheckRestart describes if and when a task should be restarted based on
// failing health checks.
type CheckRestart struct {
Limit int `mapstructure:"limit"`
Grace *time.Duration `mapstructure:"grace"`
IgnoreWarnings bool `mapstructure:"ignore_warnings"`
}
// Canonicalize CheckRestart fields if not nil.
func (c *CheckRestart) Canonicalize() {
if c == nil {
return
}
if c.Grace == nil {
c.Grace = timeToPtr(1 * time.Second)
}
}
// Copy returns a copy of CheckRestart or nil if unset.
func (c *CheckRestart) Copy() *CheckRestart {
if c == nil {
return nil
}
nc := new(CheckRestart)
nc.Limit = c.Limit
if c.Grace != nil {
g := *c.Grace
nc.Grace = &g
}
nc.IgnoreWarnings = c.IgnoreWarnings
return nc
}
// Merge values from other CheckRestart over default values on this
// CheckRestart and return merged copy.
func (c *CheckRestart) Merge(o *CheckRestart) *CheckRestart {
if c == nil {
// Just return other
return o
}
nc := c.Copy()
if o == nil {
// Nothing to merge
return nc
}
if o.Limit > 0 {
nc.Limit = o.Limit
}
if o.Grace != nil {
nc.Grace = o.Grace
}
if o.IgnoreWarnings {
nc.IgnoreWarnings = o.IgnoreWarnings
}
return nc
}
// ServiceCheck represents the consul health check that Nomad registers.
type ServiceCheck struct {
//FIXME Id is unused. Remove?
Id string
Name string
Type string
Command string
Args []string
Path string
Protocol string
PortLabel string `mapstructure:"port"`
AddressMode string `mapstructure:"address_mode"`
Interval time.Duration
Timeout time.Duration
InitialStatus string `mapstructure:"initial_status"`
TLSSkipVerify bool `mapstructure:"tls_skip_verify"`
Header map[string][]string
Method string
CheckRestart *CheckRestart `mapstructure:"check_restart"`
GRPCService string `mapstructure:"grpc_service"`
GRPCUseTLS bool `mapstructure:"grpc_use_tls"`
TaskName string `mapstructure:"task"`
}
// Service represents a Consul service definition.
type Service struct {
//FIXME Id is unused. Remove?
Id string
Name string
Tags []string
CanaryTags []string `mapstructure:"canary_tags"`
EnableTagOverride bool `mapstructure:"enable_tag_override"`
PortLabel string `mapstructure:"port"`
AddressMode string `mapstructure:"address_mode"`
Checks []ServiceCheck
CheckRestart *CheckRestart `mapstructure:"check_restart"`
Connect *ConsulConnect
Meta map[string]string
CanaryMeta map[string]string
}
// Canonicalize the Service by ensuring its name and address mode are set. Task
// will be nil for group services.
func (s *Service) Canonicalize(t *Task, tg *TaskGroup, job *Job) {
if s.Name == "" {
if t != nil {
s.Name = fmt.Sprintf("%s-%s-%s", *job.Name, *tg.Name, t.Name)
} else {
s.Name = fmt.Sprintf("%s-%s", *job.Name, *tg.Name)
}
}
// Default to AddressModeAuto
if s.AddressMode == "" {
s.AddressMode = "auto"
}
// Canonicalize CheckRestart on Checks and merge Service.CheckRestart
// into each check.
for i, check := range s.Checks {
s.Checks[i].CheckRestart = s.CheckRestart.Merge(check.CheckRestart)
s.Checks[i].CheckRestart.Canonicalize()
}
}
// ConsulConnect represents a Consul Connect jobspec stanza.
type ConsulConnect struct {
Native bool
SidecarService *ConsulSidecarService `mapstructure:"sidecar_service"`
SidecarTask *SidecarTask `mapstructure:"sidecar_task"`
}
// ConsulSidecarService represents a Consul Connect SidecarService jobspec
// stanza.
type ConsulSidecarService struct {
Tags []string
Port string
Proxy *ConsulProxy
}
// SidecarTask represents a subset of Task fields that can be set to override
// the fields of the Task generated for the sidecar
type SidecarTask struct {
Name string
Driver string
User string
Config map[string]interface{}
Env map[string]string
Resources *Resources
Meta map[string]string
KillTimeout *time.Duration `mapstructure:"kill_timeout"`
LogConfig *LogConfig `mapstructure:"logs"`
ShutdownDelay *time.Duration `mapstructure:"shutdown_delay"`
KillSignal string `mapstructure:"kill_signal"`
}
// ConsulProxy represents a Consul Connect sidecar proxy jobspec stanza.
type ConsulProxy struct {
LocalServiceAddress string `mapstructure:"local_service_address"`
LocalServicePort int `mapstructure:"local_service_port"`
Upstreams []*ConsulUpstream
Config map[string]interface{}
}
// ConsulUpstream represents a Consul Connect upstream jobspec stanza.
type ConsulUpstream struct {
DestinationName string `mapstructure:"destination_name"`
LocalBindPort int `mapstructure:"local_bind_port"`
}