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[JUJU-3777] Multiplex services to log targets using only a log-target.services field #252

Merged
merged 14 commits into from
Jul 3, 2023
Merged
39 changes: 39 additions & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -403,6 +403,45 @@ $ pebble run --verbose
...
```

<!--
TODO: uncomment this section once log forwarding is fully implemented
TODO: add log targets to the Pebble layer spec below

#### Log forwarding

Pebble supports forwarding its services' logs to a remote Loki server or syslog receiver (via UDP/TCP). In the `log-targets` section of the plan, you can specify destinations for log forwarding, for example:
```yaml
log-targets:
loki-example:
override: merge
type: loki
location: http://10.1.77.205:3100/loki/api/v1/push
services: [all]
syslog-example:
override: merge
type: syslog
location: tcp://192.168.10.241:1514
services: [svc1, svc2]
```

For each log target, use the `services` key to specify a list of services to collect logs from. In the above example, the `syslog-example` target will collect logs from `svc1` and `svc2`.

Use the special keyword `all` to match all services. In the above example, `loki-example` will collect logs from all services.
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To remove a service from a log target when merging, prefix the service name with a minus `-`. For example, if we have a base layer with
```yaml
my-target:
services: [svc1, svc2]
```
and override layer with
```yaml
my-target:
services: [-svc1]
override: merge
```
then in the merged layer, `my-target` will collect logs from only `svc2`. You can also use `-all` to remove all services from the list.
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-->

## Container usage

Pebble works well as a local service manager, but if running Pebble in a separate container, you can use the exec and file management APIs to coordinate with the remote system over the shared unix socket.
Expand Down
109 changes: 39 additions & 70 deletions internals/plan/plan.go
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (
"strings"
"time"

"github.com/canonical/pebble/internals/logger"
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"github.com/canonical/x-go/strutil/shlex"
"gopkg.in/yaml.v3"

Expand Down Expand Up @@ -89,9 +90,6 @@ type Service struct {
BackoffFactor OptionalFloat `yaml:"backoff-factor,omitempty"`
BackoffLimit OptionalDuration `yaml:"backoff-limit,omitempty"`
KillDelay OptionalDuration `yaml:"kill-delay,omitempty"`

// Log forwarding
LogTargets []string `yaml:"log-targets,omitempty"`
}

// Copy returns a deep copy of the service.
Expand Down Expand Up @@ -120,7 +118,6 @@ func (s *Service) Copy() *Service {
copied.OnCheckFailure[k] = v
}
}
copied.LogTargets = append([]string(nil), s.LogTargets...)
return &copied
}

Expand Down Expand Up @@ -188,23 +185,6 @@ func (s *Service) Merge(other *Service) {
if other.BackoffLimit.IsSet {
s.BackoffLimit = other.BackoffLimit
}
s.LogTargets = appendUnique(s.LogTargets, other.LogTargets...)
}

// appendUnique appends into a the elements from b which are not yet present
// and returns the modified slice.
// TODO: move this function into canonical/x-go/strutil
func appendUnique(a []string, b ...string) []string {
Outer:
for _, bn := range b {
for _, an := range a {
if an == bn {
continue Outer
}
}
a = append(a, bn)
}
return a
}

// Equal returns true when the two services are equal in value.
Expand Down Expand Up @@ -275,23 +255,22 @@ func CommandString(base, extra []string) string {
}

// LogsTo returns true if the logs from s should be forwarded to target t.
// This happens if:
// - t.Selection is "opt-out" or empty, and s.LogTargets is empty; or
// - t.Selection is not "disabled", and s.LogTargets contains t.
func (s *Service) LogsTo(t *LogTarget) bool {
if t.Selection == DisabledSelection {
return false
}
if len(s.LogTargets) == 0 {
if t.Selection == UnsetSelection || t.Selection == OptOutSelection {
// Iterate backwards through t.Services until we find something matching
// s.Name.
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for i := len(t.Services) - 1; i >= 0; i-- {
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switch t.Services[i] {
case s.Name:
return true
}
}
for _, targetName := range s.LogTargets {
if targetName == t.Name {
case ("-" + s.Name):
return false
case "all":
return true
case "-all":
return false
}
}
// Nothing matching the service name, so it was not specified.
return false
}

Expand Down Expand Up @@ -513,11 +492,11 @@ func (c *ExecCheck) Merge(other *ExecCheck) {

// LogTarget specifies a remote server to forward logs to.
type LogTarget struct {
Name string `yaml:"-"`
Type LogTargetType `yaml:"type"`
Location string `yaml:"location"`
Selection Selection `yaml:"selection,omitempty"`
Override Override `yaml:"override,omitempty"`
Name string `yaml:"-"`
Type LogTargetType `yaml:"type"`
Location string `yaml:"location"`
Services []string `yaml:"services"`
Override Override `yaml:"override,omitempty"`
}

// LogTargetType defines the protocol to use to forward logs.
Expand All @@ -529,19 +508,10 @@ const (
UnsetLogTarget LogTargetType = ""
)

// Selection describes which services' logs will be forwarded to this target.
type Selection string

const (
OptOutSelection Selection = "opt-out"
OptInSelection Selection = "opt-in"
DisabledSelection Selection = "disabled"
UnsetSelection Selection = ""
)

// Copy returns a deep copy of the log target configuration.
func (t *LogTarget) Copy() *LogTarget {
copied := *t
copied.Services = append([]string(nil), t.Services...)
return &copied
}

Expand All @@ -553,9 +523,7 @@ func (t *LogTarget) Merge(other *LogTarget) {
if other.Location != "" {
t.Location = other.Location
}
if other.Selection != "" {
t.Selection = other.Selection
}
t.Services = append(t.Services, other.Services...)
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}

// FormatError is the error returned when a layer has a format error, such as
Expand Down Expand Up @@ -796,35 +764,32 @@ func CombineLayers(layers ...*Layer) (*Layer, error) {
}
}

switch target.Selection {
case OptOutSelection, OptInSelection, DisabledSelection, UnsetSelection:
// valid, continue
default:
// Validate service names specified in log target
for _, serviceName := range target.Services {
if serviceName == "all" || serviceName == "-all" {
continue
}
if _, ok := combined.Services[serviceName]; ok {
continue
}
// Check if this is `-svc`
serviceName = strings.TrimPrefix(serviceName, "-")
if _, ok := combined.Services[serviceName]; ok {
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continue
}
return nil, &FormatError{
Message: fmt.Sprintf(`log target %q has invalid selection %q, must be %q, %q or %q`,
name, target.Selection, OptOutSelection, OptInSelection, DisabledSelection),
Message: fmt.Sprintf(`log target %q specifies unknown service %q`,
target.Name, serviceName),
}
}

if target.Location == "" && target.Selection != DisabledSelection {
if target.Location == "" && len(target.Services) > 0 {
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return nil, &FormatError{
Message: fmt.Sprintf(`plan must define "location" for log target %q`, name),
}
}
}

// Validate service log targets
for serviceName, service := range combined.Services {
for _, targetName := range service.LogTargets {
_, ok := combined.LogTargets[targetName]
if !ok {
return nil, &FormatError{
Message: fmt.Sprintf(`unknown log target %q for service %q`, targetName, serviceName),
}
}
}
}

// Ensure combined layers don't have cycles.
err := combined.checkCycles()
if err != nil {
Expand Down Expand Up @@ -963,6 +928,10 @@ func ParseLayer(order int, label string, data []byte) (*Layer, error) {
Message: fmt.Sprintf("cannot use reserved service name %q", name),
}
}
// Deprecated service names
if name == "all" || name == "default" || name == "none" {
logger.Noticef("WARNING: using %q as service name is deprecated", name)
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}
if service == nil {
return nil, &FormatError{
Message: fmt.Sprintf("service object cannot be null for service %q", name),
Expand Down
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