# 33. Spark

AMPS contains a basic command-line client, `spark`, which can be used to run queries, place subscriptions, and publish data. While it provides support for each of these functions, `spark` is provided as a useful tool for informal testing and troubleshooting of AMPS instances and is not intended to be a replacement for a client library. For example, you can use `spark` to test whether an AMPS instance is reachable from a particular system, or use `spark` to perform ad hoc queries to inspect the data in AMPS. `spark` does not support all of the features available in AMPS client libraries, and does not display the headers or metadata returned by AMPS.

This chapter describes the commands available in the `spark` utility. For more information on the features available in AMPS, see the relevant chapters within this User Guide.

The `spark` utility is included in the `bin` directory of the AMPS install location. The `spark` client is written in Java, so running `spark` requires a Java Virtual Machine for Java 1.7 or later.

To run this client, simply type `./bin/spark` at the command line from the AMPS installation directory. AMPS will output the help screen as shown below, with a brief description of the `spark` client features.

    %> ./bin/spark
    ===============================
    - Spark - AMPS client utility -
    ===============================
    Usage:

        spark help [command]

    Supported Commands:

        help
        ping
        publish
        sow
        sow_and_subscribe
        sow_delete
        subscribe

    Example:

        %> ./spark help sow

    Returns the help and usage information for the 'sow' command.

Spark screen usage

## Getting Help with Spark

`spark` requires that a supported command is passed as an argument. Within each supported command, there are additional unique requirements and options available to change the behavior of `spark` and how it interacts with the AMPS engine.

For example, if more information was needed to run a `publish` command in `spark`, the following would display the help screen for the `spark` client’s `publish` feature.

    %>./spark help publish
    ===============================
    - Spark - AMPS client utility -
    ===============================
    Usage:

      spark publish [options]

    Required Parameters:

      server    -- AMPS server to connect to
      topic     -- topic to publish to

    Options:

      authenticator -- Custom AMPS authenticator factory to use
      delimiter     -- decimal value of message separator character
                       (default 10)
      delta         -- use delta publish
      file          -- file to publish records from, standard in when omitted
      proto         -- protocol to use (amps, fix, nvfix, xml)
                       (type, prot are synonyms for backward compatibility)
                       (default: amps)
      rate          -- decimal value used to send messages
                       at a fixed rate.  '.25' implies 1 message every
                       4 seconds. '1000' implies 1000 messages per second.

    Example:

      % ./spark publish -server localhost:9003 -topic Trades -file data.fix

        Connects to the AMPS instance listening on port 9003 and publishes records
        found in the 'data.fix' file to topic 'Trades'.

Usage of Spark publish command

## Spark Commands

Below, the commands supported by `spark` will be shown, along with some examples of how to use the various commands and descriptions of the most commonly used options. For the full range of options provided by `spark`, including options provided for compatibility with previous `spark` releases, use the `spark help` command as described above.

### Publish

The `publish` command is used to publish data to a topic on an AMPS server.

#### Common Options - Spark Publish

Spark publish options
Option | Definition
--- | ---
    server
| AMPS server to connect to.
    topic
| Topic to publish to.
delimiter | Decimal value of message separator character (default 10).
delta | Use delta publish (sends a `delta_publish` command to AMPS).
file | File to publish messages from, stdin when omitted. `spark` interprets each line in the input as a message. The file provided to this argument can be either uncompressed or compressed in ZIP format.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.
rate | Messages to publish per second. This is a decimal value, so values less than 1 can be provided to create a delay of more than a second between messages. ‘.25’ implies 1 message every 4 seconds. ‘1000’ implies 1000 messages per second.
type | For protocols and transports that accept multiple message types on a given transport, this specifies the message type to use.

#### Examples

The examples shown below will demonstrate how to publish records to AMPS using the `spark` client in one of the three following ways: a single record, a python script or by file.

Publish a Single Message

    %> echo '{ "id" : 1, "data": "hello, world!" }' |  \
       ./spark publish -server localhost:9007 -type json -topic order

       total messages published: 1 (50.00/s)

Publishing a single XML message

In the example shown above, a single record is published to AMPS using the `echo` command. If you are comfortable with creating records by hand this is a simple and effective way to test publishing in AMPS.

The JSON message is published to the topic order on the AMPS instance. This publish can be followed with a `sow` command in `spark` to test if the record was indeed published to the order topic.

Publish using Python

    %> python -c "for n in xrange(100): print '{\"id\":%d}' % n" | \
       ./spark publish -topic disorder -type json -rate 50 \
       -server localhost:9007

       total messages published: 100 (50.00/s)

Publish multiple messages using Python

In the example shown above, the `-c` flag is used to pass in a simple loop and print command to the python interpreter and have it print the results to `stdout`.

The python script generates 100 JSON messages of the form `{"id":0}`, `{"id":1}` ... `{"id":99}`. The output of this command is then piped to spark using the `|` character, which will publish the messages to the disorder topic inside the AMPS instance.

Publish from a File

    %> ./spark publish -server localhost:9007 -type json -topic chaos \
       -file data.json

       total messages published: 50 (12000.00/s)

Spark publish from a file

Generating a file of test data is a common way to test AMPS functionality. The example shown above demonstrates how to publish a file of data to the topic chaos in an AMPS server. As previously mentioned, `spark` interprets each line of the file as a distinct message.

### SOW

The `sow` command allows a `spark` client to query the latest messages which have been persisted to a topic. The SOW in AMPS acts as a database last update cache, and the `sow` command in `spark` is one of the ways to query the database. This `sow` command supports regular expression topic matching and content filtering, which allow a query to be very specific when looking for data.

For the `sow` command to succeed, the topic queried must provide a SOW. This includes SOW topics and views, queues, and conflated topics. These features of AMPS are discussed in more detail within this User Guide.

#### Common Options - Spark SOW

Spark sow options
Option | Definition
--- | ---
    server
| AMPS server to connect to.
    topic
| Topic to query.
batchsize | Batch Size to use during query. A batch size > 1 can help improve performance, as described in the chapter of the User Guide discussing the SOW.
filter | The content filter to use.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.
orderby | An expression that AMPS will use to order the results.
topn | Request AMPS to limit the query response to the first N records returned.
type | For protocols and transports that accept multiple message types on a given transport, this specifies the message type to use.
format | Optional format used for displaying messages. May contain literal separator characters mixed with format tags. Allowed tags are: `{bookmark}`, `{command}`, `{correlation_id}`, `{data}`, `{expiration}`, `{lease_period}`, `{length}`, `{sowkey}`, `{user_id}`, `{timestamp}`, `{topic}` Notice that not all headers may be available on every request, depending on the options provided to the request. See the AMPS Command Reference for details. Example: `-format "{command}:{data}"`

#### Examples

    %> ./spark sow -server localhost:9007 -type json -topic order -filter "/id = '1'"

    { "id" : 1, "data" : "hello, world" }
    Total messages received: 1 (Infinity/s)

Spark SOW Query

This `sow` command will query the order topic and filter results which match the xpath expression `/id = '1'`. This query will return the result published in the publish a single record example.

If the topic does not provide a SOW, the command returns an error indicating that the command is not valid for that topic.

### Subscribe

The `subscribe` command allows a `spark` client to query all incoming messages to a topic in real time. Similar to the `sow` command, the `subscribe` command supports regular expression topic matching and content filtering, which allow a query to be very specific when looking for data as it is published to AMPS. Unlike the `sow` command, a subscription can be placed on a topic which does not have a persistent SOW cache configured. This allows a `subscribe` command to be very flexible in the messages it can be configured to receive.

#### Common Options - Spark Subscribe

Option | Definition
--- | ---
    server
| AMPS server to connect to.
    topic
| Topic to subscribe to.
delta | Use delta subscription (sends a `delta_subscribe` command to AMPS).
filter | Content filter to use.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.
ack | Enable acknowledgments when receiving from a queue. Notice that, when this option is provided, `spark` acknowledges messages from the queue, signaling to AMPS that the message has been fully processed. (See the User Guide chapter on AMPS message queues for more information.)
backlog | Request a `max_backlog` of greater than 1 when receiving from a queue. (See the User Guide chapter on AMPS message queues for more information.)
type | For protocols and transports that accept multiple message types on a given transport, this specifies the message type to use.
format | Optional format used for displaying messages. May contain literal separator characters mixed with format tags. Allowed tags are: `{bookmark}`, `{command}`, `{correlation_id}`, `{data}`, `{expiration}`, `{lease_period}`, `{length}`, `{sowkey}`, `{user_id}`, `{timestamp}`, `{topic}` Notice that not all headers may be available on every request, depending on the options provided to the request. See the AMPS Command Reference for details. Example: `-format "{command}:{data}"`

Spark subscribe options

#### Examples

     %> ./spark subscribe -server localhost:9007 -topic chaos \
                            -type json -filter "/name = 'cup'"

    { "name" : "cup", "place" : "cupboard" }

Spark subscribe Example

The example above places a subscription on the chaos topic with a filter that will only return results for messages where `/name = 'cup'`. If we place this subscription before executing the `publish` command in the publish records from a file example, we will get the results listed above.

### sow_and_subscribe

The `sow_and_subscribe` command is a combination of the `sow` command and the `subscribe` command. When a `sow_and_subscribe` is requested, AMPS will first return all messages which match the query and are stored in the SOW. Once this has completed, all messages which match the subscription query will then be sent to the client.

The `sow_and_subscribe` command is a powerful tool to use when it is necessary to examine both the contents of the SOW, and the live subscription stream.

#### Common Options - Spark sow_and_subscribe

Spark sow_and_subscribe options
Option | Definition
--- | ---
    server
| AMPS server to connect to.
.code
    topic
| Topic to query and subscribe to.
batchsize | Batch Size to use during query.
delta | Request delta for subscriptions (sends a `sow_and_delta_subscribe` command to AMPS).
filter | Content filter to use.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.
orderby | An expression that AMPS will use to order the SOW query results.
topn | Request AMPS to limit the SOW query results to the first N records returned.
type | For protocols and transports that accept multiple message types on a given transport, this specifies the message type to use.
format | Optional format used for displaying messages. May contain literal separator characters mixed with format tags. Allowed tags are: `{bookmark}`, `{command}`, `{correlation_id}`, `{data}`, `{expiration}`, `{lease_period}`, `{length}`, `{sowkey}`, `{user_id}`, `{timestamp}`, `{topic}` Notice that not all headers may be available on every request, depending on the options provided to the request. See the AMPS Command Reference for details. Example: `-format "{command}:{data}"`

#### Examples

    %> ./spark sow_and_subscribe -server localhost:9007 -type json \
                                   -topic chaos -filter "/name = 'cup'"

    { "name" : "cup", "place" : "cupboard" }

Spark SOW and subscribe example

In the example above, the same topic and filter are being used as in the `subscribe` example in the spark subscribe example. The results of this query initially are similar also, since only the messages which are stored in the SOW are returned. If a publisher were started that published data to the topic that matched the content filter, those messages would then be printed out to the screen in the same manner as a `subscription`.

### sow_delete

The `sow_delete` command is used to remove records from the SOW topic in AMPS. If a filter is specified, only messages which match the filter will be removed. If a file is provided, the command reads messages from the file and sends those messages to AMPS. AMPS will delete the matching messages from the SOW. If no filter or file is specified, the command reads messages from standard input (one per line) and sends those messages to AMPS for deletion.

It can be useful to test a filter by first using the desired filter in a `sow` command and making sure the records returned match what is expected. If that is successful, then it is safe to use the filter for a `sow_delete`. Once records are deleted from the SOW, they are not recoverable.

#### Common Options - sow_delete

Spark sow_delete options
Option | Definition
--- | ---
    server
| AMPS server to connect to.
    topic
| Topic to delete records from.
filter | Content filter to use. Notice that a filter of `1=1` is true for every message and will delete the entire set of records in the SOW.
file | File from which to read messages to be deleted.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.
type | For protocols and transports that accept multiple message types on a given transport, this specifies the message type to use.

#### Examples

    %> ./spark sow_delete -server localhost:9007 \
       -topic chaos -type json -filter "/name = 'cup'"

       Deleted 1 records in 10ms.

Spark SOW delete example

With the `spark` command in the example above, we are asking for AMPS to delete records in the topic chaos which match the filter `/name = 'cup'`. In this example, we delete the record we published and queried previously in the `publish` and `sow_and_subscribe` examples. `spark` reports that one matching message was removed from the SOW topic.

### Ping

The spark `ping` command is used to connect to the amps instance and attempt to logon. This tool is useful to determine if an AMPS instance is running and responsive.

#### Common Options - Spark Ping

Spark ping options
Option | Definition
--- | ---
    server
| AMPS server to connect to.
proto | Protocol to use. In this release, `spark` supports `amps`, `fix`, `nvfix` and `xml`. Defaults to `amps`. `spark` also supports `json` as a synonym for `amps` in this release.

#### Examples

    %> ./spark ping -server localhost:9007 -type json
    Successfully connected to tcp://user@localhost:9007/amps/json

Successful ping using Spark

In the example above, `spark` was able to successfully log onto the AMPS instance that was located on port `9007`.

    %> ./spark ping -server localhost:9119
    Unable to connect to AMPS
    (com.crankuptheamps.client.exception.ConnectionRefusedException: Unable to
    connect to AMPS at localhost:9119).

Unsuccessful ping using spark

In the example above, `spark` was not able to successfully log onto the AMPS instance that was located on port `9119`. The error shows the exception thrown by `spark`, which in this case was a `ConnectionRefusedException` from Java.

## Spark Authentication

`spark` includes a way to provide credentials to AMPS for use with instances that are configured to require authentication. For example, to use a specific user ID and password to authenticate to AMPS, simply provide them in the URI in the format `user:password@host:port`.

The command below shows how to use spark to subscribe to a server, providing the specified username and password to AMPS.

    $AMPS_HOME/bin/spark subscribe -type json \
                                   -server username:password@localhost:9007

AMPS also provides the ability to implement custom authentication, and many production deployments use customized authentication methods. To support this, the `spark` authentication scheme is customizable. By default, the authentication scheme used by `spark` simply provides the username and password from the `-server` parameter, as described above.

Authentication schemes for `spark` are implemented in Java, as classes that implement `Authenticator` – the same method used by the AMPS Java client. To use a different authentication scheme with `spark`, you implement the `AuthenticatorFactory` interface in `spark` to return your custom authenticator, adjust the CLASSPATH to include the `.jar` file that contains the authenticator, and then provide the name of your `AuthenticatorFactory` on the command line. See the AMPS Java Client API documentation for details on implementing a custom `Authenticator`.

The command below explicitly loads the default factory, found in the `spark` package, without adjusting the CLASSPATH.

    $AMPS_HOME/bin/spark subscribe –server username:password@localhost:9007 \
                                   -type json -topic foo \
          -authenticator com.crankuptheamps.spark.DefaultAuthenticatorFactory