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ah-fs.processor
Analyzes ah-fs data specifically for fs.readFile cases.
Last updated 3 years ago by thlorenz .
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Processes ah-fs data obtained from async resources related to file system opearations.

Installation

npm install ah-fs.processor

Table of Contents generated with DocToc

API

processFileSystem

Parameters

  • $0 Object
    • $0.activities Map<string, Object> a map of async activities hashed by id
    • $0.includeActivities boolean? if true the actual activities are appended to the output (optional, default false)

ReadFileProcessor

Instantiates an fs.readFile data processor to process data collected via nodesource/ah-fs

Parameters

  • $0 Object
  • includeActivities boolean? if true the actual activities are appended to the output (optional, default false)

readFileProcessor.process

Processes the supplied async activities and splits them into groups, and operations each representing a file read fs.readFile.

Groups

The returned value has a groups property which just lists the ids of async resources that were grouped together to form an operation indexed by the id of the open resource. Thus the groups is a map of sets. If no file read was encountered the groups are empty.

Operations

Additionally an operations property is included as well. Each operation represents one full fs.readFile execution. There will be one operation per group and they are indexed by the corresponding open resource id as well.

An operation has the following properties:

fs.readFile specific Operation Properties

Data about the async resources that were part of the operation, by default only id and triggerId are included:

  • open: contains data about opening the file
  • stat: contains data about getting file stats
  • read: contains data about reading the file
  • close: contains data about closing the file

General Operation Properties

The information below is the same for all operations and thus is only mentioned here and linked from the documentation of all other processors.

Data about the lifetime of the operation:

  • lifeCycle: contains three timestamps that detail when an operation was created, for how long it was alive and when it was destroyed.

    • created: the timestamp when the first resource of the operation was created
    • destroyed: the timestamp when the last resource of the operation was destroyed
    • timeAlive: the difference between the destroyed and created timestamps, i.e. how long the operation's resources were alive

    Each timestamp has the following two properties provided by utils.prettyNs.

    • ns: time in nanoseconds {Number}
    • ms: pretty printed time in milliseconds {String}

Data that links to user code that is responsible for the operation occurring.

  • createdAt: provides the line of code that called fs.readFile

  • userFunctions: depending on the settings (see constructor docs) each resource will include it's own array of userFunctions or they are separated out into one property with duplicates merged. The latter is the default behavior. In either case userFunctions is an Array of Objects with the following properties:

    • name: the function name
    • inferredName: the inferred function name, only needed if the name is not set
    • file: the file in which the function was defined
    • line: the line on which the functino was defined in that file
    • column: the column on which the functino was defined in that file
    • location: the file and line + column where the function was defined combined into a string
    • args: the err and information about the res of the operation with which the function was invoked
    • propertyPaths: the object paths at which the function was found, these could be multiple since the function could've been attached to multiple resources (only available if the functions were separated from the resources and merged)
    • propertyPath: the object path at which the function was found (only available if the functions weren't separated and thus are still part of each resource)

Sample Return Value

The sample return value was created with default options.

{ groups: Map { 10 => Set { 10, 11, 12, 13 } },
  operations:
    Map {
      10 => { lifeCycle:
        { created: { ms: '44.12ms', ns: 44119000 },
          destroyed: { ms: '85.95ms', ns: 85955000 },
          timeAlive: { ms: '41.84ms', ns: 41836000 } },
      createdAt: 'at Test.<anonymous> (/Volumes/d/dev/js/async-hooks/ah-fs/test/read-one-file.js:36:6)',
      open: { id: 10, triggerId: 1 },
      stat: { id: 11, triggerId: 10 },
      read: { id: 12, triggerId: 11 },
      close: { id: 13, triggerId: 12 },
      userFunctions:
        [ { file: '/Volumes/d/dev/js/async-hooks/ah-fs/test/read-one-file.js',
            line: 39,
            column: 17,
            inferredName: '',
            name: 'onread',
            location: 'onread (/Volumes/d/dev/js/async-hooks/ah-fs/test/read-one-file.js:39:17)',
            args:
            { '0': null,
              '1':
                { type: 'Buffer',
                  len: 6108,
                  included: 18,
                  val:
                  { utf8: 'const test = requi',
                    hex: '636f6e73742074657374203d207265717569' } },
              proto: 'Object' },
            propertyPaths:
            [ 'open.resource.context.callback',
              'stat.resource.context.callback',
              'read.resource.context.callback',
              'close.resource.context.callback' ] } ] } } }

Returns Object information about fs.readFile operations with the structure outlined above

ReadFileProcessor.operationSteps

The minimum number of steps, represented as an async resource each, involved to execute fs.readFile.

This can be used by higher level processors to group activities looking for larger operations first and then operations involving less steps.

Steps are: open, stat, read+, close

ReadFileProcessor.operation

Description of the operation: 'fs.readFile'.

ReadFileOperation

Processes a group of async activities that represent a fs read stream operation. It is used by the ReadFileProcessor as part of process.

Four operation steps are derived from the group, each providing some information about the operation in question.

Each step is processed into an operation in the corresponding private method, i.e. _processOpen. These methods are documented below for information's sake, they should not be called directly, nor should you have a need to directly instantiate a ReadFileOperation in the first place.

Parameters

  • group Map<Number, Set<Number>> the ids of the activities that were part of the operation
  • includeActivities Boolean? if true the activities are attached to each operation step (optional, default false)

readFileOperation._processOpen

The open resource tells us where in user code the fs.readFile originated via the second frame of the stack trace, as well as when the operation was created.

Additionally it has the same user functions attached as all the other resources.

Parameters

  • info Object information about the open step, pre-processed by the ReadFileProcessor.

readFileOperation._processStat

The stat resource gives us no interesting information. Therefore we just capture the id, triggerId and userFunctions and if so desired attach the activities.

Parameters

  • info Object information about the open step, pre-processed by the ReadFileProcessor.

readFileOperation._processRead

The read resource gives us no interesting information. Therefore we just capture the id, triggerId and userFunctions and if so desired attach the activities.

Parameters

  • info Object information about the read step, pre-processed by the ReadFileProcessor.

readFileOperation._processClose

The main information we pull from the close resource is the destroy timestamp.

Combined with the init timestamp of the open resource it allows us to deduce how long the file read took.

Parameters

  • info Object information about the close step, pre-processed by the ReadFileProcessor.

readFileOperation.summary

Returns the summary of processing the group into an operation.

The summary of all operations has a very similar structure, but includes some properties that are specific to this particular operation.

The general properties lifeCycle and createdAt are documented as part of the ReadFileProcessor. Therefore learn more here.

Properties Specific to fs.readFile

  • open: see readFileOperation._processOpen
  • stat: see readFileOperation._processStat
  • read: see readFileOperation._processRead
  • close: see readFileOperation._processClose

Parameters

  • $0 Object options
    • $0.separateFunctions Boolean? when true the user functions are separated out from the specific operations and attached as a userFunctions array directly to the returned result (optional, default true)
    • $0.mergeFunctions Boolean? if true when a duplicate function is found in the separated functions Array, they are merged into one while preserving all information from both version. Note that this setting only activates if separateFunctions is true as well. (optional, default true)

Returns Object all important information about the current operation

ReadStreamProcessor

Instantiates an fs.createReadStream data processor to process data collected via nodesource/ah-fs

Parameters

  • $0 Object
  • includeActivities boolean? if true the actual activities are appended to the output (optional, default false)

readStreamProcessor.process

Processes the supplied async activities and splits them into groups, and operations each representing a file read stream fs.createReadStream.

Groups

The returned value has a groups property which just lists the ids of async resources that were grouped together to form an operation indexed by the fd on which the readFile operated. Thus the groups is a map of sets. If no file read stream was encountered the groups are empty.

Operations

Additionally an operations property is included as well. Each operation represents one full fs.createReadStream execution. There will be one operation per group and they are indexed by the corresponding fd as well.

An operation has the following properties:

fs.createReadStream specific Operation Properties

Data about the async resources that were part of the operation, by default only id and triggerId are included:

  • open: contains data about opening the file
  • stream: contains data about how the stream was configured, including readable state and the path to the file being read, pipes count, encoding, etc.
  • reads: an Array of reads, each containing data about reading a chunk from the file including the time spent to complete reading the particular chunk
  • close: contains data about closing the file

General Operation Properties

Sample Return Value

The sample return value was created with default options.

{ groups: Map { 10 => Set { 10, 12, 13, 14, 16 } },
  operations:
  Map {
    10 => { lifeCycle:
      { created: { ms: '1.60ms', ns: 1600000 },
        destroyed: { ms: '14.33ms', ns: 14329000 },
        timeAlive: { ms: '12.73ms', ns: 12729000 } },
    createdAt: 'at Test.<anonymous> (/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js:94:6)',
    open: { id: 10, triggerId: 3 },
    stream:
      { id: 14,
        triggerId: 12,
        path: '/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js',
        flags: 'r',
        fd: 19,
        objectMode: false,
        highWaterMark: 65536,
        pipesCount: 0,
        defaultEncoding: 'utf8',
        encoding: null },
    reads:
      [ { id: 12,
          triggerId: 10,
          timeSpent: { ms: '0.83ms', ns: 830000 } },
        { id: 13,
          triggerId: 12,
          timeSpent: { ms: '0.24ms', ns: 240000 } } ],
    close: { id: 16, triggerId: 13 },
    userFunctions:
      [ { file: '/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js',
          line: 99,
          column: 16,
          inferredName: '',
          name: 'onend',
          location: 'onend (/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js:99:16)',
          args: null,
          propertyPaths: [ 'stream.resource.args[0]._events.end[1]' ] },
        { file: '/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js',
          line: 98,
          column: 17,
          inferredName: '',
          name: 'ondata',
          location: 'ondata (/Volumes/d/dev/js/async-hooks/ah-fs/test/readstream-one-file.js:98:17)',
          args: null,
          propertyPaths: [ 'stream.resource.args[0]._events.data' ] } ] } } }

Returns Object information about fs.createReadStream operations with the structure outlined above

ReadStreamProcessor.operationSteps

The minimum number of steps, represented as an async resource each, involved to execute fs.createReadStream.

This can be used by higher level processors to group activities looking for larger operations first and then operations involving less steps.

Steps are: open, stream+, read+, close

ReadStreamProcessor.operation.null

Description of the operation: 'fs.createReadStream'.

ReadStreamOperation

Processes a group of async activities that represent a fs read stream operation. It is used by the ReadStreamProcessor as part of process.

Four operation steps are derived from the group, each providing some information about the operation in question.

Each step is processed into an operation in the corresponding private method, i.e. _processOpen. These methods are documented below for information's sake, they should not be called directly, nor should you have a need to directly instantiate a ReadStreamOperation in the first place.

Parameters

  • group Map<Number, Set<Number>> the ids of the activities that were part of the operation
  • includeActivities Boolean? if true the activities are attached to each operation step (optional, default false)

readStreamOperation._processOpen

An open doesn't have too much info, but we can glean two very important data points:

  1. the init timestamp tells us when the stream was created
  2. the last frame of the init stack tells us where createReadStream was called.

Parameters

  • info Object information about the open step, pre-processed by the ReadStreamProcessor.

readStreamOperation._processTick

The ReadStream Tick gives us a lot of information. It has an args array with the ReadStream and its ReadableState respectively

The ReadStream provides us the following:

  1. the path to the file we are streaming
  2. the flags with which the file was opened
  3. the fd (assuming we are dealing with the tick triggered indirectly by the open)

All callbacks on the _events of the ReadStream have been removed, but are present inside the functions object (see below).

The ReadableState provides us the following:

  1. objectMode true|false
  2. highWaterMark
  3. pipesCount
  4. defaultEncoding, i.e. utf8
  5. encoding, i.e. utf8

The information extracted from the tick is attached to a stream property provided with the summary.

Parameters

  • info Object information about the tick step, pre-processed by the ReadStreamProcessor.

readStreamOperation._processRead

The read resource doesn't give us too much information.

The stack traces originate in core and we don't see any registred user callbacks, as those are present on the stream instead. However we can count the amount of reads that occurred and deduce how long each read took from the before and after timestamps.

Parameters

  • info Object information about the read step, pre-processed by the ReadStreamProcessor.

readStreamOperation._processClose

The main information we pull from the close resource is the destroy timestamp.

Combined with the init timestamp of the open resource it allows us to deduce how long the read stream was active.

Parameters

  • info Object information about the close step, pre-processed by the ReadStreamProcessor.

readStreamOperation.summary

Returns the summary of processing the group into an operation.

The summary of all operations has a very similar structure, but includes some properties that are specific to this particular operation.

The general properties lifeCycle and createdAt are documented as part of the ReadFileProcessor. Therefore learn more here.

Properties Specific to fs.createReadStream

  • open: see readStreamOperation._processOpen
  • stream: see readStreamOperation._processTick
  • read: see readStreamOperation._processRead
  • close: see readStreamOperation._processClose

Parameters

  • $0 Object options
    • $0.separateFunctions Boolean? when true the user functions are separated out from the specific operations and attached as a userFunctions array directly to the returned result (optional, default true)
    • $0.mergeFunctions Boolean? if true when a duplicate function is found in the separated functions Array, they are merged into one while preserving all information from both version. Note that this setting only activates if separateFunctions is true as well. (optional, default true)

Returns Object all important information about the current operation

openInitFrame0Rx

Sample initStack of writeFile open, calles as first operation of fs.writeFile. In order to be sure this is a writeFile open we need to check the two topmost frames.

"at Object.fs.open (fs.js:581:11)", "at Object.fs.writeFile (fs.js:1155:6)", "at Test.<anonymous> (/Volumes/d/dev/js/async-hooks/ah-fs/test/write-one-file.js:28:6)",

Code at fs.js:581:

binding.open(pathModule._makeLong(path), ...

Code at fs.js:1155:

fs.open(path, flag, options.mode, function(openErr, fd) ...

Bottom frame has info about where the call fs.writeFile originated.

writeInitFrame0Rx

Sample init stack of writeFile write, called afer fs.open completes:

"at Object.fs.write (fs.js:643:20)", "at writeAll (fs.js:1117:6)", "at writeFd (fs.js:1168:5)", "at fs.js:1159:7", "at FSReqWrap.oncomplete (fs.js:117:15)"

Code at fs.js:643:

binding.writeBuffer(fd, buffer, offset, length, position, req);

closeInitFrame0Rx

Sample initStack of writeFile close, called after last fs.write completes:

"at Object.fs.close (fs.js:555:11)", "at fs.js:1131:14", "at FSReqWrap.wrapper as oncomplete"

Code at fs.js:555:

binding.close(fd, req);

WriteFileProcessor

Instantiates an fs.writeFile data processor to process data collected via nodesource/ah-fs

Parameters

  • $0 Object
  • includeActivities boolean? if true the actual activities are appended to the output (optional, default false)

writeFileProcessor.process

Processes the supplied async activities and splits them into groups, and operations each representing a file read stream fs.createWriteFile.

Groups

The returned value has a groups property which just lists the ids of async resources that were grouped together to form an operation indexed by the id of the fs.open activity that was part of the fs.writeFile. Thus the groups is a map of sets. If no file write file was encountered the groups are empty.

Operations

Additionally an operations property is included as well. Each operation represents one full fs.writeFile execution. There will be one operation per group and they are indexed by the corresponding open id as well.

An operation has the following properties:

fs.createWriteFile specific Operation Properties

Data about the async resources that were part of the operation, by default only id and triggerId are included:

  • open: contains data about opening the file
  • writes: an Array of writes, each containing data about writing a chunk from the file including the time spent to complete writing the particular chunk
  • close: contains data about closing the file

General Operation Properties

Sample Return Value

The sample return value was created with default options.

{ groups: Map { 10 => Set { 10, 11, 12 } },
  operations:
  Map {
    10 => { lifeCycle:
      { created: { ms: '24.49ms', ns: 24491000 },
        destroyed: { ms: '33.96ms', ns: 33964000 },
        timeAlive: { ms: '9.47ms', ns: 9473000 } },
    createdAt: 'at Test.<anonymous> (/Volumes/d/dev/js/async-hooks/ah-fs/test/write-one-file.js:28:6)',
    open: { id: 10, triggerId: 1 },
    write: { id: 11, triggerId: 10 },
    close: { id: 12, triggerId: 11 } } } }

Returns Object information about fs.createWriteFile operations with the structure outlined above

WriteFileProcessor.operationSteps

The minimum number of steps, represented as an async resource each, involved to execute fs.writeFile.

This can be used by higher level processors to group activities looking for larger operations first and then operations involving less steps.

Steps are: open, write+, close

WriteFileProcessor.operation.null

Description of the operation: 'fs.writeFile'.

WriteFileOperation

Processes a group of async activities that represent a fs write file operation. It is used by the WriteFileProcessor as part of process.

Three operation steps are derived from the group, each providing some information about the operation in question.

Each step is processed into an operation in the corresponding private method, i.e. _processOpen. These methods are documented below for information's sake, they should not be called directly, nor should you have a need to directly instantiate a WriteFileOperation in the first place.

Parameters

  • group Map<Number, Set<Number>> the ids of the activities that were part of the operation
  • includeActivities Boolean? if true the activities are attached to each operation step (optional, default false)

writeFileOperation._processOpen

The open resource tells us where in user code the fs.writeFile originated via the second frame of the stack trace, as well as when the operation was created.

Parameters

  • info Object information about the open step, pre-processed by the WriteFileProcessor.

writeFileOperation._processWrite

The write resource gives us no interesting information. Therefore we just capture the id, triggerId and if so desired attach the activities.

Parameters

  • info Object information about the write step, pre-processed by the WriteFileProcessor.

writeFileOperation._processClose

The main information we pull from the close resource is the destroy timestamp.

Combined with the init timestamp of the open resource it allows us to deduce how long the file write took.

Parameters

  • info Object information about the close step, pre-processed by the WriteFileProcessor.

writeFileOperation.summary

Returns the summary of processing the group into an operation.

The summary of all operations has a very similar structure, but includes some properties that are specific to this particular operation.

The general properties lifeCycle and createdAt are documented as part of the WriteFileProcessor. Therefore learn more here.

Properties Specific to fs.writeFile

  • open: see writeFileOperation._processOpen
  • write: see writeFileOperation._processWrite
  • close: see writeFileOperation._processClose

Note this summary function takes no parameters (like the other Operations) since we don't find any user functions related to the write file operation and thus have nothing to process.

Returns Object all important information about the current operation

WriteStreamProcessor

Instantiates an fs.createWriteStream data processor to process data collected via nodesource/ah-fs

Parameters

  • $0 Object
    • $0.includeActivities boolean? if true the actual activities are appended to the output (optional, default false)
    • $0.separateFunctions Boolean? when true the user functions are separated out from the specific resources and attached as a userFunctions array directly to the returned operations (optional, default true)

writeStreamProcessor.process

Processes the supplied async activities and splits them into groups, and operations each representing a file write stream fs.createWriteStream.

Groups

The returned value has a groups property which just lists the ids of async resources that were grouped together to form an operation indexed by the fd on which the writeFile operated. Thus the groups is a map of sets. If no file write stream was encountered the groups are empty.

Operations

Additionally an operations property is included as well. Each operation represents one full fs.createWriteStream execution. There will be one operation per group and they are indexed by the corresponding fd as well.

An operation has the following properties:

fs.createWriteStream specific Operation Properties

Data about the async resources that were part of the operation, by default only id and triggerId are included:

  • open: contains data about opening the file
  • stream: contains data about how the stream was configured, including writeable state and the path to the file being write, pipes count, encoding, etc.
  • writes: an Array of writes, each containing data about writing a chunk from the file including the time spent to complete writeing the particular chunk
  • close: contains data about closing the file

General Operation Properties

Sample Return Value

The sample return value was created with default options.

{ groups: Map { 10 => Set { 14, 10, 16, 19 } },
  operations:
  Map {
    10 => { lifeCycle:
      { created: { ms: '1.12ms', ns: 1123000 },
        destroyed: { ms: '18.20ms', ns: 18205000 },
        timeAlive: { ms: '17.08ms', ns: 17082000 } },
    createdAt: 'at Test.<anonymous> (/Volumes/d/dev/js/async-hooks/ah-fs/test/read-stream-piped-into-write-stream.js:29:26)',
    open: { id: 10, triggerId: 3 },
    stream:
      { id: 16,
        triggerId: 13,
        path: '/dev/null',
        flags: 'w',
        fd: 19,
        mode: 438 },
    writes:
      [ { id: 14,
          triggerId: 13,
          timeSpent: { ms: '0.14ms', ns: 139000 } } ],
    close: { id: 19, triggerId: 15 },
    userFunctions:
      [ { file: '/Volumes/d/dev/js/async-hooks/ah-fs/test/read-stream-piped-into-write-stream.js',
          line: 32,
          column: 19,
          inferredName: '',
          name: 'onfinish',
          location: 'onfinish (/Volumes/d/dev/js/async-hooks/ah-fs/test/read-stream-piped-into-write-stream.js:32:19)',
          args: null,
          propertyPaths: [ 'stream.resource.args[1].pipes._events.finish[1]' ] } ] } } }

Returns Object information about fs.createWriteStream operations with the structure outlined above

writeStreamProcessor._separteIntoGroups

Here we try our best to piece together the parts of a WriteStream, Open | Write+ | WriteStreamTick | Close.

Since they aren't linked by a common file descriptor or similar we rely on async resource graph structure and the timestamps to take a best guess.

We just don't have the data available to piece this together with 100% certainty.

Below is a sample of collected async resources with all but types and ids removed.

 { type: 'FSREQWRAP', id: 10, tid: 3 }   open, write stream triggered by root
 { type: 'FSREQWRAP', id: 11, tid: 3 }   open, read stream triggered by root
 { type: 'TickObject', id: 12, tid: 3 }  read stream tick, triggered by root
 { type: 'FSREQWRAP', id: 13, tid: 11 }  read, triggerd by open of read steam
 { type: 'FSREQWRAP', id: 14, tid: 13 }  write, triggerd by read of read steam
 { type: 'FSREQWRAP', id: 15, tid: 13 }  read, next chunk, triggered by first read
 { type: 'TickObject', id: 16, tid: 13 } stream tick, triggerd by first read
 { type: 'FSREQWRAP', id: 18, tid: 15 }  close read stream, triggered by last read
 { type: 'FSREQWRAP', id: 19, tid: 15 }  close write stream, triggered by last read

We reason about that data as follows in order to piece together the WriteStream.

Connecting WriteSteam Write to WriteStream Close

Write (id: 14) is triggered by read of read stream (id: 13). The same read triggers the last read (id: 15). That last read triggers the close of the write stream (id: 19).

Therefore we can connect the write stream write to the write stream close since they have a common parent in their ancestry (the first read of the read stream).

           -- Read2:15 -- WriteStream:Close:19
         /
Read1:13
         \
           -- WriteStream:Write:14

However I would imagine that this breaks down once we have on read stream piped into multiple write streams as then the writes have the same Read parent.

Connecting WriteStream Open to WriteStream Write

There is no 100% way to get this right, but if we assume that the first write happens right after the opening of the write stream in the same context we can do the following.

We already know that the common parent of WriteStream:Write and WriteStream:Close is Read1:13. Therefore we find all WriteStream:Opens that share a parent with Read1:13. The ones with the closest parent win.

If we find more than one, we pick the one that was initialized closest to the WriteStream:Write timewise, assuming that we write to the stream immediately after opening it.

           -- ReadStream:Open:11 -- Read1:13 -- Read2:15 -- WriteStream:Close:19
         /                                   \
Parent:3                                       -- WriteStream:Write:14
         \
           -- WriteStream:Open:10

WriteStreamProcessor.operationSteps

The minimum number of steps, represented as an async resource each, involved to execute fs.createWriteStream.

This can be used by higher level processors to group activities looking for larger operations first and then operations involving less steps.

Steps are: open, stream, write+, close

WriteStreamProcessor.operation.null

Description of the operation: 'fs.createWriteStream'.

WriteStreamOperation

Processes a group of async activities that represent a fs write stream operation. It is used by the writeStreamProcessor as part of process.

Four operation steps are derived from the group, each providing some information about the operation in question.

Each step is processed into an operation in the corresponding private method, i.e. _processOpen. These methods are documented below for information's sake, they should not be called directly, nor should you have a need to directly instantiate a writeStreamOperation in the first place.

Parameters

  • group Map<Number, Set<Number>> the ids of the activities that were part of the operation
  • includeActivities Boolean? if true the activities are attached to each operation step (optional, default false)

writeStreamOperation._processOpen

An open doesn't have too much info, but we can glean two very important data points:

  1. the init timestamp tells us when the stream was created
  2. the last frame of the init stack tells us where createWriteStream was called.

Parameters

  • info Object information about the open step, pre-processed by the WriteStreamProcessor.

writeStreamOperation._processTick

The WriteStream Tick gives us a lot of information. It is the same tick object that we process in the ReadStreamOperation to glean data about the read stream. It has an args array with the ReadStream and its ReadableState respectively.

The ReadableState included the WritableState which the ah-fs pre-processor already plucked for us and added as the 3rd argument. Additionally it includes lots of functions including user functions registered with the WriteStream, i.e. on('finish').

Ergo the WriteStream provides us the following as part of the WritableState:

  1. the path to the file we are writing into
  2. the flags with which the file was opened
  3. the fd (assuming we are dealing with the tick triggered indirectly by the open)

All callbacks on the _events of the ReadStream and WriteStream have been removed, but are present inside the functions object (see below).

The information extracted from the tick is attached to a stream property provided with the summary.

Parameters

  • info Object information about the tick step, pre-processed by the WriteStreamProcessor.

writeStreamOperation._processwrite

The write resource doesn't give us too much information.

The stack traces originate in core and we don't see any registred user callbacks, as those are present on the stream instead. However we can count the amount of writes that occurred and deduce how long each write took from the before and after timestamps.

Parameters

  • info Object information about the write step, pre-processed by the WriteStreamProcessor.

writeStreamOperation._processClose

The main information we pull from the close resource is the destroy timestamp.

Combined with the init timestamp of the open resource it allows us to deduce how long the write stream was active.

Parameters

  • info Object information about the close step, pre-processed by the WriteStreamProcessor.

License

MIT

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  • 0.2.0                                ...           3 years ago
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