go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/server/limiter/module.go (about)

     1  // Copyright 2020 The LUCI Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package limiter
    16  
    17  import (
    18  	"context"
    19  	"flag"
    20  	"fmt"
    21  	"time"
    22  
    23  	"go.chromium.org/luci/common/clock"
    24  	"go.chromium.org/luci/common/tsmon"
    25  
    26  	"go.chromium.org/luci/server/module"
    27  )
    28  
    29  // ModuleName can be used to refer to this module when declaring dependencies.
    30  var ModuleName = module.RegisterName("go.chromium.org/luci/server/limiter")
    31  
    32  const defaultMaxConcurrentRPCs = 100000 // e.g. unlimited
    33  
    34  // ModuleOptions contains configuration of the server module that installs
    35  // default limiters applied to all routes/services in the server.
    36  type ModuleOptions struct {
    37  	MaxConcurrentRPCs int64 // limit on a number of incoming concurrent RPCs (default is 100000, i.e. unlimited)
    38  	AdvisoryMode      bool  // if set, don't enforce MaxConcurrentRPCs, but still report violations
    39  }
    40  
    41  // Register registers the command line flags.
    42  func (o *ModuleOptions) Register(f *flag.FlagSet) {
    43  	if o.MaxConcurrentRPCs == 0 {
    44  		o.MaxConcurrentRPCs = defaultMaxConcurrentRPCs
    45  	}
    46  	f.Int64Var(
    47  		&o.MaxConcurrentRPCs,
    48  		"limiter-max-concurrent-rpcs",
    49  		o.MaxConcurrentRPCs,
    50  		fmt.Sprintf("Limit on a number of incoming concurrent RPCs (default is %d)", o.MaxConcurrentRPCs),
    51  	)
    52  	f.BoolVar(
    53  		&o.AdvisoryMode,
    54  		"limiter-advisory-mode",
    55  		o.AdvisoryMode,
    56  		"If set, don't enforce -limiter-max-concurrent-rpcs, but still report violations",
    57  	)
    58  }
    59  
    60  // NewModule returns a server module that installs default limiters applied to
    61  // all routes/services in the server.
    62  func NewModule(opts *ModuleOptions) module.Module {
    63  	if opts == nil {
    64  		opts = &ModuleOptions{}
    65  	}
    66  	return &serverModule{opts: opts}
    67  }
    68  
    69  // NewModuleFromFlags is a variant of NewModule that initializes options through
    70  // command line flags.
    71  //
    72  // Calling this function registers flags in flag.CommandLine. They are usually
    73  // parsed in server.Main(...).
    74  func NewModuleFromFlags() module.Module {
    75  	opts := &ModuleOptions{}
    76  	opts.Register(flag.CommandLine)
    77  	return NewModule(opts)
    78  }
    79  
    80  // serverModule implements module.Module.
    81  type serverModule struct {
    82  	opts       *ModuleOptions
    83  	rpcLimiter *Limiter // limits in-flight RPCs in the main port
    84  }
    85  
    86  // Name is part of module.Module interface.
    87  func (*serverModule) Name() module.Name {
    88  	return ModuleName
    89  }
    90  
    91  // Dependencies is part of module.Module interface.
    92  func (*serverModule) Dependencies() []module.Dependency {
    93  	return nil
    94  }
    95  
    96  // Initialize is part of module.Module interface.
    97  func (m *serverModule) Initialize(ctx context.Context, host module.Host, opts module.HostOptions) (context.Context, error) {
    98  	// Now that options are parsed by the server we can validate them and
    99  	// construct a limiter from them.
   100  	if m.opts.MaxConcurrentRPCs == 0 {
   101  		m.opts.MaxConcurrentRPCs = defaultMaxConcurrentRPCs
   102  	}
   103  	var err error
   104  	m.rpcLimiter, err = New(Options{
   105  		Name:                  "rpc",
   106  		AdvisoryMode:          m.opts.AdvisoryMode,
   107  		MaxConcurrentRequests: m.opts.MaxConcurrentRPCs,
   108  	})
   109  	if err != nil {
   110  		return nil, err
   111  	}
   112  
   113  	// We want limiter's metrics to be reported before every flush (so the flushed
   114  	// values are as fresh as possible) and also once per second (to make the
   115  	// limiter state observable through /admin/portal/tsmon/metrics debug UI).
   116  	tsmon.RegisterCallbackIn(ctx, m.rpcLimiter.ReportMetrics)
   117  	host.RunInBackground("luci.limiter.rpc", func(ctx context.Context) {
   118  		for {
   119  			m.rpcLimiter.ReportMetrics(ctx)
   120  			if r := <-clock.After(ctx, time.Second); r.Err != nil {
   121  				return // the context is canceled
   122  			}
   123  		}
   124  	})
   125  
   126  	// Actually add the limiter to the default interceptors chains.
   127  	intr := NewServerInterceptor(m.rpcLimiter)
   128  	host.RegisterUnaryServerInterceptors(intr.Unary())
   129  	host.RegisterStreamServerInterceptors(intr.Stream())
   130  	return ctx, nil
   131  }