stats.go: replace omitempty with omitzero

For some fields (like nested struct fields), omitempty has no effect
but omitzero does. Let's use it.

NOTE it might result in some compatibility issues since now
zero-only fields are not serialized.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

stats.go

@@ -2,30 +2,30 @@ package cgroups
 
 type ThrottlingData struct {
 	// Number of periods with throttling active
-	Periods uint64 `json:"periods,omitempty"`
+	Periods uint64 `json:"periods,omitzero"`
 	// Number of periods when the container hit its throttling limit.
-	ThrottledPeriods uint64 `json:"throttled_periods,omitempty"`
+	ThrottledPeriods uint64 `json:"throttled_periods,omitzero"`
 	// Aggregate time the container was throttled for in nanoseconds.
-	ThrottledTime uint64 `json:"throttled_time,omitempty"`
+	ThrottledTime uint64 `json:"throttled_time,omitzero"`
 }
 
 type BurstData struct {
 	// Number of periods bandwidth burst occurs
-	BurstsPeriods uint64 `json:"bursts_periods,omitempty"`
+	BurstsPeriods uint64 `json:"bursts_periods,omitzero"`
 	// Cumulative wall-time that any cpus has used above quota in respective periods
 	// Units: nanoseconds.
-	BurstTime uint64 `json:"burst_time,omitempty"`
+	BurstTime uint64 `json:"burst_time,omitzero"`
 }
 
 // CpuUsage denotes the usage of a CPU.
 // All CPU stats are aggregate since container inception.
 type CpuUsage struct {
 	// Total CPU time consumed.
 	// Units: nanoseconds.
-	TotalUsage uint64 `json:"total_usage,omitempty"`
+	TotalUsage uint64 `json:"total_usage,omitzero"`
 	// Total CPU time consumed per core.
 	// Units: nanoseconds.
-	PercpuUsage []uint64 `json:"percpu_usage,omitempty"`
+	PercpuUsage []uint64 `json:"percpu_usage,omitzero"`
 	// CPU time consumed per core in kernel mode
 	// Units: nanoseconds.
 	PercpuUsageInKernelmode []uint64 `json:"percpu_usage_in_kernelmode"`
@@ -48,26 +48,26 @@ type PSIData struct {
 }
 
 type PSIStats struct {
-	Some PSIData `json:"some,omitempty"`
-	Full PSIData `json:"full,omitempty"`
+	Some PSIData `json:"some,omitzero"`
+	Full PSIData `json:"full,omitzero"`
 }
 
 type CpuStats struct {
-	CpuUsage       CpuUsage       `json:"cpu_usage,omitempty"`
-	ThrottlingData ThrottlingData `json:"throttling_data,omitempty"`
-	PSI            *PSIStats      `json:"psi,omitempty"`
-	BurstData      BurstData      `json:"burst_data,omitempty"`
+	CpuUsage       CpuUsage       `json:"cpu_usage,omitzero"` //nolint:revive,staticcheck // Suppress "var-naming" warning.
+	ThrottlingData ThrottlingData `json:"throttling_data,omitzero"`
+	PSI            *PSIStats      `json:"psi,omitzero"`
+	BurstData      BurstData      `json:"burst_data,omitzero"`
 }
 
 type CPUSetStats struct {
 	// List of the physical numbers of the CPUs on which processes
 	// in that cpuset are allowed to execute
-	CPUs []uint16 `json:"cpus,omitempty"`
+	CPUs []uint16 `json:"cpus,omitzero"`
 	// cpu_exclusive flag
 	CPUExclusive uint64 `json:"cpu_exclusive"`
 	// List of memory nodes on which processes in that cpuset
 	// are allowed to allocate memory
-	Mems []uint16 `json:"mems,omitempty"`
+	Mems []uint16 `json:"mems,omitzero"`
 	// mem_hardwall flag
 	MemHardwall uint64 `json:"mem_hardwall"`
 	// mem_exclusive flag
@@ -87,122 +87,122 @@ type CPUSetStats struct {
 }
 
 type MemoryData struct {
-	Usage    uint64 `json:"usage,omitempty"`
-	MaxUsage uint64 `json:"max_usage,omitempty"`
+	Usage    uint64 `json:"usage,omitzero"`
+	MaxUsage uint64 `json:"max_usage,omitzero"`
 	Failcnt  uint64 `json:"failcnt"`
 	Limit    uint64 `json:"limit"`
 }
 
 type MemoryStats struct {
 	// memory used for cache
-	Cache uint64 `json:"cache,omitempty"`
+	Cache uint64 `json:"cache,omitzero"`
 	// usage of memory
-	Usage MemoryData `json:"usage,omitempty"`
+	Usage MemoryData `json:"usage,omitzero"`
 	// usage of memory + swap
-	SwapUsage MemoryData `json:"swap_usage,omitempty"`
+	SwapUsage MemoryData `json:"swap_usage,omitzero"`
 	// usage of swap only
-	SwapOnlyUsage MemoryData `json:"swap_only_usage,omitempty"`
+	SwapOnlyUsage MemoryData `json:"swap_only_usage,omitzero"`
 	// usage of kernel memory
-	KernelUsage MemoryData `json:"kernel_usage,omitempty"`
+	KernelUsage MemoryData `json:"kernel_usage,omitzero"`
 	// usage of kernel TCP memory
-	KernelTCPUsage MemoryData `json:"kernel_tcp_usage,omitempty"`
+	KernelTCPUsage MemoryData `json:"kernel_tcp_usage,omitzero"`
 	// usage of memory pages by NUMA node
 	// see chapter 5.6 of memory controller documentation
-	PageUsageByNUMA PageUsageByNUMA `json:"page_usage_by_numa,omitempty"`
+	PageUsageByNUMA PageUsageByNUMA `json:"page_usage_by_numa,omitzero"`
 	// if true, memory usage is accounted for throughout a hierarchy of cgroups.
 	UseHierarchy bool `json:"use_hierarchy"`
 
-	Stats map[string]uint64 `json:"stats,omitempty"`
-	PSI   *PSIStats         `json:"psi,omitempty"`
+	Stats map[string]uint64 `json:"stats,omitzero"`
+	PSI   *PSIStats         `json:"psi,omitzero"`
 }
 
 type PageUsageByNUMA struct {
 	// Embedding is used as types can't be recursive.
 	PageUsageByNUMAInner
-	Hierarchical PageUsageByNUMAInner `json:"hierarchical,omitempty"`
+	Hierarchical PageUsageByNUMAInner `json:"hierarchical,omitzero"`
 }
 
 type PageUsageByNUMAInner struct {
-	Total       PageStats `json:"total,omitempty"`
-	File        PageStats `json:"file,omitempty"`
-	Anon        PageStats `json:"anon,omitempty"`
-	Unevictable PageStats `json:"unevictable,omitempty"`
+	Total       PageStats `json:"total,omitzero"`
+	File        PageStats `json:"file,omitzero"`
+	Anon        PageStats `json:"anon,omitzero"`
+	Unevictable PageStats `json:"unevictable,omitzero"`
 }
 
 type PageStats struct {
-	Total uint64           `json:"total,omitempty"`
-	Nodes map[uint8]uint64 `json:"nodes,omitempty"`
+	Total uint64           `json:"total,omitzero"`
+	Nodes map[uint8]uint64 `json:"nodes,omitzero"`
 }
 
 type PidsStats struct {
 	// number of pids in the cgroup
-	Current uint64 `json:"current,omitempty"`
+	Current uint64 `json:"current,omitzero"`
 	// active pids hard limit
-	Limit uint64 `json:"limit,omitempty"`
+	Limit uint64 `json:"limit,omitzero"`
 }
 
 type BlkioStatEntry struct {
-	Major uint64 `json:"major,omitempty"`
-	Minor uint64 `json:"minor,omitempty"`
-	Op    string `json:"op,omitempty"`
-	Value uint64 `json:"value,omitempty"`
+	Major uint64 `json:"major,omitzero"`
+	Minor uint64 `json:"minor,omitzero"`
+	Op    string `json:"op,omitzero"`
+	Value uint64 `json:"value,omitzero"`
 }
 
 type BlkioStats struct {
 	// number of bytes transferred to and from the block device
-	IoServiceBytesRecursive []BlkioStatEntry `json:"io_service_bytes_recursive,omitempty"`
-	IoServicedRecursive     []BlkioStatEntry `json:"io_serviced_recursive,omitempty"`
-	IoQueuedRecursive       []BlkioStatEntry `json:"io_queue_recursive,omitempty"`
-	IoServiceTimeRecursive  []BlkioStatEntry `json:"io_service_time_recursive,omitempty"`
-	IoWaitTimeRecursive     []BlkioStatEntry `json:"io_wait_time_recursive,omitempty"`
-	IoMergedRecursive       []BlkioStatEntry `json:"io_merged_recursive,omitempty"`
-	IoTimeRecursive         []BlkioStatEntry `json:"io_time_recursive,omitempty"`
-	SectorsRecursive        []BlkioStatEntry `json:"sectors_recursive,omitempty"`
-	PSI                     *PSIStats        `json:"psi,omitempty"`
-	IoCostUsage             []BlkioStatEntry `json:"io_cost_usage,omitempty"`
-	IoCostWait              []BlkioStatEntry `json:"io_cost_wait,omitempty"`
-	IoCostIndebt            []BlkioStatEntry `json:"io_cost_indebt,omitempty"`
-	IoCostIndelay           []BlkioStatEntry `json:"io_cost_indelay,omitempty"`
+	IoServiceBytesRecursive []BlkioStatEntry `json:"io_service_bytes_recursive,omitzero"`
+	IoServicedRecursive     []BlkioStatEntry `json:"io_serviced_recursive,omitzero"`
+	IoQueuedRecursive       []BlkioStatEntry `json:"io_queue_recursive,omitzero"`
+	IoServiceTimeRecursive  []BlkioStatEntry `json:"io_service_time_recursive,omitzero"`
+	IoWaitTimeRecursive     []BlkioStatEntry `json:"io_wait_time_recursive,omitzero"`
+	IoMergedRecursive       []BlkioStatEntry `json:"io_merged_recursive,omitzero"`
+	IoTimeRecursive         []BlkioStatEntry `json:"io_time_recursive,omitzero"`
+	SectorsRecursive        []BlkioStatEntry `json:"sectors_recursive,omitzero"`
+	PSI                     *PSIStats        `json:"psi,omitzero"`
+	IoCostUsage             []BlkioStatEntry `json:"io_cost_usage,omitzero"`
+	IoCostWait              []BlkioStatEntry `json:"io_cost_wait,omitzero"`
+	IoCostIndebt            []BlkioStatEntry `json:"io_cost_indebt,omitzero"`
+	IoCostIndelay           []BlkioStatEntry `json:"io_cost_indelay,omitzero"`
 }
 
 type HugetlbStats struct {
 	// current res_counter usage for hugetlb
-	Usage uint64 `json:"usage,omitempty"`
+	Usage uint64 `json:"usage,omitzero"`
 	// maximum usage ever recorded.
-	MaxUsage uint64 `json:"max_usage,omitempty"`
+	MaxUsage uint64 `json:"max_usage,omitzero"`
 	// number of times hugetlb usage allocation failure.
 	Failcnt uint64 `json:"failcnt"`
 }
 
 type RdmaEntry struct {
-	Device     string `json:"device,omitempty"`
-	HcaHandles uint32 `json:"hca_handles,omitempty"`
-	HcaObjects uint32 `json:"hca_objects,omitempty"`
+	Device     string `json:"device,omitzero"`
+	HcaHandles uint32 `json:"hca_handles,omitzero"`
+	HcaObjects uint32 `json:"hca_objects,omitzero"`
 }
 
 type RdmaStats struct {
-	RdmaLimit   []RdmaEntry `json:"rdma_limit,omitempty"`
-	RdmaCurrent []RdmaEntry `json:"rdma_current,omitempty"`
+	RdmaLimit   []RdmaEntry `json:"rdma_limit,omitzero"`
+	RdmaCurrent []RdmaEntry `json:"rdma_current,omitzero"`
 }
 
 type MiscStats struct {
 	// current resource usage for a key in misc
-	Usage uint64 `json:"usage,omitempty"`
+	Usage uint64 `json:"usage,omitzero"`
 	// number of times the resource usage was about to go over the max boundary
-	Events uint64 `json:"events,omitempty"`
+	Events uint64 `json:"events,omitzero"`
 }
 
 type Stats struct {
-	CpuStats    CpuStats    `json:"cpu_stats,omitempty"`
-	CPUSetStats CPUSetStats `json:"cpuset_stats,omitempty"`
-	MemoryStats MemoryStats `json:"memory_stats,omitempty"`
-	PidsStats   PidsStats   `json:"pids_stats,omitempty"`
-	BlkioStats  BlkioStats  `json:"blkio_stats,omitempty"`
+	CpuStats    CpuStats    `json:"cpu_stats,omitzero"` //nolint:revive,staticcheck // Suppress "var-naming" warning.
+	CPUSetStats CPUSetStats `json:"cpuset_stats,omitzero"`
+	MemoryStats MemoryStats `json:"memory_stats,omitzero"`
+	PidsStats   PidsStats   `json:"pids_stats,omitzero"`
+	BlkioStats  BlkioStats  `json:"blkio_stats,omitzero"`
 	// the map is in the format "size of hugepage: stats of the hugepage"
-	HugetlbStats map[string]HugetlbStats `json:"hugetlb_stats,omitempty"`
-	RdmaStats    RdmaStats               `json:"rdma_stats,omitempty"`
+	HugetlbStats map[string]HugetlbStats `json:"hugetlb_stats,omitzero"`
+	RdmaStats    RdmaStats               `json:"rdma_stats,omitzero"`
 	// the map is in the format "misc resource name: stats of the key"
-	MiscStats map[string]MiscStats `json:"misc_stats,omitempty"`
+	MiscStats map[string]MiscStats `json:"misc_stats,omitzero"`
 }
 
 func NewStats() *Stats {