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package main

import (
// ... imports ...
)

// ... global variables ...

// Server is the main functionality of zoekt-sourcegraph-indexserver. It
// exists to conveniently use all the options passed in via func main.
type Server struct {
logger sglog.Logger

Sourcegraph Sourcegraph
BatchSize   int

// IndexDir is the index directory to use.
IndexDir string

// IndexConcurrency is the number of repositories we index at once.
IndexConcurrency int

// Interval is how often we sync with Sourcegraph.
Interval time.Duration

// CPUCount is the number of CPUs to use for indexing shards.
CPUCount int

queue Queue

// muIndexDir protects the index directory from concurrent access.
muIndexDir indexMutex

// If true, shard merging is enabled.
shardMerging bool

// deltaBuildRepositoriesAllowList is an allowlist for repositories that we
// use delta-builds for instead of normal builds
deltaBuildRepositoriesAllowList map[string]struct{}

// deltaShardNumberFallbackThreshold is an upper limit on the number of preexisting shards that can exist
// before attempting a delta build.
deltaShardNumberFallbackThreshold uint64

// repositoriesSkipSymbolsCalculationAllowList is an allowlist for repositories that
// we skip calculating symbols metadata for during builds
repositoriesSkipSymbolsCalculationAllowList map[string]struct{}

hostname string

mergeOpts mergeOpts

// timeout defines how long the index server waits before killing an indexing job.
timeout time.Duration
}

// ... functions ...

// Run the sync loop. This blocks forever.
func (s *Server) Run() {
// ... initialization ...

// Start a goroutine which updates the queue with commits to index.
go func() {
// ... continuously update the index queue ...
}()

// Start a goroutine which vacuums the index directory.
go func() {
// ... continuously vacuum the index directory ...
}()

// Start a goroutine which merges shards.
go func() {
// ... continuously merge shards ...
}()

// Start a number of goroutines to process the index queue.
for i := 0; i < s.IndexConcurrency; i++ {
go s.processQueue()
}

// block forever
select {}
}

// ... helper functions ...

// processQueue processes the index queue.
func (s *Server) processQueue() {
for {
// ... pop an IndexOptions from the queue ...
// ... index the repository using s.Index ...
// ... update the queue ...
}
}

// Index starts an index job for repo name at commit.
func (s *Server) Index(args *indexArgs) (state indexState, err error) {
// ... create a trace ...
// ... determine if delta build should be used ...
// ... determine if symbols calculation should be skipped ...
// ... determine the reason for indexing (forced, incremental, etc.) ...
// ... handle the different cases based on the incremental state ...
// ... create a gitIndexConfig ...
// ... call gitIndex to index the repository ...
// ... update the index status on Sourcegraph ...
// ... return the index state and any error ...
}

// ... helper functions for Index ...

// indexArgs is a struct containing all the arguments needed for indexing a repository.
type indexArgs struct {
IndexOptions
IndexDir                   string
Parallelism               int
Incremental               bool
UseDelta                  bool
DeltaShardNumberFallbackThreshold uint64
Symbols                   bool
FileLimit                  int64
}

// ... helper functions for Index ...

// ... other helper functions ...

// addDebugHandlers adds handlers specific to indexserver.
func (s *Server) addDebugHandlers(mux *http.ServeMux) {
// ... add handlers for debugging ...
}

// ... handler functions ...

// handleReindex triggers a reindex asynocronously.
func (s *Server) handleReindex(w http.ResponseWriter, r *http.Request) {
// ... handle the reindex request ...
}

// handleDebugList lists all repositories.
func (s *Server) handleDebugList(w http.ResponseWriter, r *http.Request) {
// ... handle the debug list request ...
}

// handleDebugMerge triggers a merge even if shard merging is not enabled.
func (s *Server) handleDebugMerge(w http.ResponseWriter, r *http.Request) {
// ... handle the debug merge request ...
}

// handleDebugIndexed lists all indexed repositories.
func (s *Server) handleDebugIndexed(w http.ResponseWriter, r *http.Request) {
// ... handle the debug indexed request ...
}

// forceIndex will run the index job for repo name now.
func (s *Server) forceIndex(id uint32) (string, error) {
// ... force index the repository ...
}

// listIndexed lists all indexed repositories.
func listIndexed(indexDir string) []uint32 {
// ... list all indexed repositories ...
}

// setupTmpDir sets up a temporary directory on the same volume as the
// indexes.
func setupTmpDir(logger sglog.Logger, main bool, index string) error {
// ... set up the temporary directory ...
}

// printMetaData prints the metadata of a shard.
func printMetaData(fn string) error {
// ... print the metadata ...
}

// printShardStats prints the statistics of a shard.
func printShardStats(fn string) error {
// ... print the statistics ...
}

// srcLogLevelIsDebug checks if the Sourcegraph log level is debug.
func srcLogLevelIsDebug() bool {
// ... check the log level ...
}

// getEnvWithDefaultInt64 gets an environment variable with a default value.
func getEnvWithDefaultInt64(k string, defaultVal int64) int64 {
// ... get the environment variable ...
}

// ... main function ...

Explanation:

The code you provided is for the zoekt-sourcegraph-indexserver, which is a service responsible for indexing repositories on Sourcegraph using the Zoekt search engine.

Key components:

• Server: This struct holds the main configuration and logic for the index server. It includes fields for:

• Logger: Used for logging.

• Sourcegraph: An interface to the Sourcegraph API.

• BatchSize: Controls the size of batches for indexing.

• IndexDir: The directory where indexes are stored.

• IndexConcurrency: The number of repositories indexed in parallel.

• Interval: The frequency for syncing with Sourcegraph.

• CPUCount: The number of CPUs to use for indexing shards.

• queue: A queue to store the repositories that need to be indexed.

• muIndexDir: A mutex for protecting the index directory from concurrent access.

• shardMerging: Whether shard merging is enabled.

• deltaBuildRepositoriesAllowList: A list of repositories to use delta builds for.

• deltaShardNumberFallbackThreshold: Threshold for using delta build instead of full build.

• repositoriesSkipSymbolsCalculationAllowList: A list of repositories to skip symbols calculation for.

• hostname: The hostname of the server.

• mergeOpts: Configuration for shard merging.

• timeout: Timeout for indexing jobs.

• Run(): This is the main function that starts the index server. It:

• Initializes the index directory.

• Starts goroutines for:

• Updating the index queue.

• Vacuuming the index directory.

• Merging shards.

• Starts a number of goroutines to process the index queue.

• Blocks forever.

• processQueue(): This function processes the index queue by:

• Popping an IndexOptions from the queue.

• Calling s.Index() to index the repository.

• Updating the queue with the new state of the repository.

• Index(): This function handles the indexing of a repository. It:

• Creates a trace for tracking the indexing process.

• Determines if delta build should be used and if symbols calculation should be skipped.

• Handles the different cases based on the incremental state of the index.

• Creates a gitIndexConfig for indexing.

• Calls gitIndex() to index the repository.

• Updates the index status on Sourcegraph.

• Returns the index state and any error.

• indexArgs: This struct holds the arguments for indexing a repository, including:

• IndexOptions: Options for indexing.

• IndexDir: The directory where indexes are stored.

• Parallelism: The number of shards to index in parallel.

• Incremental: Whether to do an incremental index.

• UseDelta: Whether to use delta build for indexing.

• DeltaShardNumberFallbackThreshold: Threshold for using delta build instead of full build.