Projection management

The various gRPC client APIs include dedicated clients that allow you to manage projections.

WARNING

Currently not all clients fully expose all operations.

For a detailed explanation of projections, see the server documentation.

You can find the full sample code from this documentation page in the respective clients repositories.

Required packages

Install the client SDK package to your project.

# From Pypi
$ pip install esdbclient

# With Poetry
$ poetry add esdbclient

# Yarn
$ yarn add @eventstore/db-client

# NPM
$ npm install --save @eventstore/db-client

# TypeScript Declarations are included in the package.

# Yarn
$ yarn add @eventstore/db-client

# NPM
$ npm install --save @eventstore/db-client

# Maven
<dependency>
  <groupId>com.eventstore</groupId>
  <artifactId>db-client-java</artifactId>
  <version>5.2.0</version>
</dependency>

# Gradle
implementation 'com.eventstore:db-client-java:5.2.0'

dotnet add package EventStore.Client.Grpc.ProjectionManagement --version 23.*

// This is currently not available in the Go client

No additional configuration is needed having Rust installed. Go check https://rustup.rs.

Creating a client

Projection management operations are exposed through a dedicated client.

client = EventStoreDBClient(
    uri="{connectionString}"
)

const client = EventStoreDBClient.connectionString`
  esdb+discover://${ADMIN}:${PASSWORD}@${ENDPOINT}?nodePreference=leader

const client = EventStoreDBClient.connectionString`
  esdb+discover://${ADMIN}:${PASSWORD}@${ENDPOINT}?nodePreference=leader

EventStoreDBClientSettings settings = EventStoreDBConnectionString.parseOrThrow(connection);
EventStoreDBProjectionManagementClient client = EventStoreDBProjectionManagementClient.create(settings);

var settings = EventStoreClientSettings.Create(connection);
settings.ConnectionName     = "Projection management client";
settings.DefaultCredentials = new UserCredentials("admin", "changeit");
var managementClient = new EventStoreProjectionManagementClient(settings);

// This is currently not available in the Go client

// This is currently not available in the Rust client

Create a projection

Creates a projection that runs until the last event in the store, and then continues processing new events as they are appended to the store. The query parameter contains the JavaScript you want created as a projection. Projections have explicit names, and you can enable or disable them via this name.

# This is currently not available in the Python client

const name = `countEvents_Create_${uuid()}`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .outputState();

await client.createProjection(name, projection);

const name = `countEvents_Create_${uuid()}`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .outputState();

await client.createProjection(name, projection);

String js =
        "fromAll()" +
        ".when({" +
        "    $init: function() {" +
        "        return {" +
        "            count: 0" +
        "        };" +
        "    }," +
        "    $any: function(s, e) {" +
        "        s.count += 1;" +
        "    }" +
        "})" +
        ".outputState();";

String name = "countEvents_Create_" + java.util.UUID.randomUUID();

client.create(name, js).get();

const string js = @"fromAll()
                            .when({
                                $init: function() {
                                    return {
                                        count: 0
                                    };
                                },
                                $any: function(s, e) {
                                    s.count += 1;
                                }
                            })
                            .outputState();";

var name = $"countEvents_Create_{Guid.NewGuid()}";
await managementClient.CreateContinuousAsync(name, js);

// This is currently not available in the Go client

// This is currently not available in the Rust client

Trying to create projections with the same name will result in an error:

# This is currently not available in the Python client

try {
  await client.createProjection(name, projection);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("Conflict"))
    throw err;
  console.log(`${name} already exists`);
}

try {
  await client.createProjection(name, projection);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("Conflict"))
    throw err;
  console.log(`${name} already exists`);
}

try {
    client.create(name, js).get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("Conflict")) {
        System.out.println(name + " already exists");
    }
}

await managementClient.CreateContinuousAsync(name, js);
try {
    await managementClient.CreateContinuousAsync(name, js);
}
catch (RpcException e) when (e.StatusCode is StatusCode.AlreadyExists) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("Conflict")) { // will be removed in a future release
    var format = $"{name} already exists";
    Console.WriteLine(format);
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Restart the subsystem

Restarts the entire projection subsystem. The user must be in the $ops or $admin group to perform this operation

# This is currently not available in the Python client

await client.restartSubsystem();

await client.restartSubsystem();

client.restartSubsystem().get();

await managementClient.RestartSubsystemAsync();

// This is currently not available in the Go client

// This is currently not available in the Rust client

Enable a projection

Enables an existing projection by name. Once enabled, the projection will start to process events even after restarting the server or the projection subsystem. You must have access to a projection to enable it, see the ACL documentation

# This is currently not available in the Python client

await client.enableProjection("$by_category");

await client.enableProjection("$by_category");

client.enable("$by_category").get();

await managementClient.EnableAsync("$by_category");

// This is currently not available in the Go client

// This is currently not available in the Rust client

You can only enable an existing projection. When you try to enable a non-existing projection, you'll get an error:

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.enableProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.enableProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.disable("projection that does not exists").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println(ex.getMessage());
    }
}

try {
    await managementClient.EnableAsync("projection that does not exists");
}
catch (RpcException e) when (e.StatusCode is StatusCode.NotFound) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("NotFound")) { // will be removed in a future release
    Console.WriteLine(e.Message);
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Disable a projection

Disables a projection, this will save the projection checkpoint. Once disabled, the projection will not process events even after restarting the server or the projection subsystem. You must have access to a projection to disable it, see the ACL documentation.

# This is currently not available in the Python client

await client.disableProjection("$by_category");

await client.disableProjection("$by_category");

client.disable("$by_category").get();

await managementClient.DisableAsync("$by_category");

// This is currently not available in the Go client

// This is currently not available in the Rust client

You can only disable an existing projection. When you try to disable a non-existing projection, you'll get an error:

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.disableProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.disableProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.disable("projection that does not exists").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println(ex.getMessage());
    }
}

try {
    await managementClient.DisableAsync("projection that does not exists");
}
catch (RpcException e) when (e.StatusCode is StatusCode.NotFound) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("NotFound")) { // will be removed in a future release
    Console.WriteLine(e.Message);
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Delete a projection

Deletes a projection

# This is currently not available in the Python client

// A projection must be disabled to allow it to be deleted.
await client.disableProjection(name);

// The projection can now be deleted
await client.deleteProjection(name);

// A projection must be disabled to allow it to be deleted.
await client.disableProjection(name);

// The projection can now be deleted
await client.deleteProjection(name);

// A projection must be disabled to allow it to be deleted.
client.disable(name).get();
// The projection can now be deleted
client.delete(name).get();

// this is not yet available in the .net grpc client

// This is currently not available in the Go client

// This is currently not available in the Rust client

You can only delete an existing projection. When you try to delete a non-existing projection, you'll get an error:

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.deleteProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.deleteProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.delete("projection that does not exists").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println(ex.getMessage());
    }
}

// This is currently not available in the .Net client

// This is currently not available in the Go client

// This is currently not available in the Rust client

Abort a projection

Aborts a projection, this will not save the projection's checkpoint.

# This is currently not available in the Python client

await client.abortProjection(name);

await client.abortProjection(name);

client.abort("$by_category").get();

// The .net clients prior to version 21.6 had an incorrect behavior: they will save the checkpoint.
await managementClient.AbortAsync("countEvents_Abort");

// This is currently not available in the Go client

// This is currently not available in the Rust client

You can only abort an existing projection. When you try to abort a non-existing projection, you'll get an error:

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.abortProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.abortProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.abort("projection that does not exists").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println(ex.getMessage());
    }
}

try {
    await managementClient.AbortAsync("projection that does not exists");
}
catch (RpcException e) when (e.StatusCode is StatusCode.NotFound) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("NotFound")) { // will be removed in a future release
    Console.WriteLine(e.Message);
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Reset a projection

Resets a projection. This will re-emit events. Streams that are written to from the projection will also be soft deleted.

# This is currently not available in the Python client

await client.resetProjection(name);

await client.resetProjection(name);

client.reset("$by_category").get();

// Checkpoint will be written prior to resetting the projection
await managementClient.ResetAsync("countEvents_Reset");

// This is currently not available in the Go client

// This is currently not available in the Rust client

Resetting a projection that does not exist will result in an error.

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.resetProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.resetProjection(projectionName);
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.reset("projection that does not exists").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println(ex.getMessage());
    }
}

try {
    await managementClient.ResetAsync("projection that does not exists");
}
catch (RpcException e) when (e.StatusCode is StatusCode.NotFound) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("NotFound")) { // will be removed in a future release
    Console.WriteLine(e.Message);
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Update a projection

Updates a projection. The name parameter is the name of the projection to be updated. The query parameter contains the new JavaScript.

# This is currently not available in the Python client

const name = `countEvents_Update_${uuid()}`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .outputState();

await client.createProjection(name, "fromAll().when()");
await client.updateProjection(name, projection);

const name = `countEvents_Update_${uuid()}`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .outputState();

await client.createProjection(name, "fromAll().when()");
await client.updateProjection(name, projection);

String name = "countEvents_Update_" + java.util.UUID.randomUUID();
String js =
        "fromAll()" +
                ".when({" +
                "    $init: function() {" +
                "        return {" +
                "            count: 0" +
                "        };" +
                "    }," +
                "    $any: function(s, e) {" +
                "        s.count += 1;" +
                "    }" +
                "})" +
                ".outputState();";

client.create(name, "fromAll().when()").get();
client.update(name, js).get();

const string js = @"fromAll()
                            .when({
                                $init: function() {
                                    return {
                                        count: 0
                                    };
                                },
                                $any: function(s, e) {
                                    s.count += 1;
                                }
                            })
                            .outputState();";

var name = $"countEvents_Update_{Guid.NewGuid()}";

await managementClient.CreateContinuousAsync(name, "fromAll().when()");
await managementClient.UpdateAsync(name, js);

// This is currently not available in the Go client

// This is currently not available in the Rust client

You can only update an existing projection. When you try to update a non-existing projection, you'll get an error:

# This is currently not available in the Python client

const projectionName = "projection that does not exist";

try {
  await client.updateProjection(projectionName, "fromAll().when()");
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

const projectionName = "projection that does not exist";

try {
  await client.updateProjection(projectionName, "fromAll().when()");
} catch (err) {
  if (!isCommandError(err) || !err.message.includes("NotFound"))
    throw err;
  console.log(`${projectionName} does not exist`);
}

try {
    client.update("Update Not existing projection", "fromAll().when()").get();
} catch (ExecutionException ex) {
    if (ex.getMessage().contains("NotFound")) {
        System.out.println("'Update Not existing projection' does not exists and can not be updated");
    }
}

try {
    await managementClient.UpdateAsync("Update Not existing projection", "fromAll().when()");
}
catch (RpcException e) when (e.StatusCode is StatusCode.NotFound) {
    Console.WriteLine(e.Message);
}
catch (RpcException e) when (e.Message.Contains("NotFound")) { // will be removed in a future release
    Console.WriteLine("'Update Not existing projection' does not exists and can not be updated");
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

List all projections

Returns a list of all projections, user defined & system projections. See the projection details section for an explanation of the returned values

# This is currently not available in the Python client

// This is currently not available in the nodejs client

// This is currently not available in the nodejs client

List<ProjectionDetails> details = client.list().get();

for (ProjectionDetails detail: details) {
    System.out.println(
        detail.getName() + ", " +
        detail.getStatus() + ", " +
        detail.getCheckpointStatus() + ", " +
        detail.getMode() + ", " +
        detail.getProgress());
}

var details = managementClient.ListAllAsync();
await foreach (var detail in details)
    Console.WriteLine(
        $@"{detail.Name}, {detail.Status}, {detail.CheckpointStatus}, {detail.Mode}, {detail.Progress}"
    );

// This is currently not available in the Go client

// This is currently not available in the Rust client

List continuous projections

Returns a list of all continuous projections. See the projection details section for an explanation of the returned values

# This is currently not available in the Python client

const projections = await client.listProjections();

for (const { name, status, checkpointStatus, progress } of projections) {
  console.log(name, status, checkpointStatus, progress);
}

const projections = await client.listProjections();

for (const { name, status, checkpointStatus, progress } of projections) {
  console.log(name, status, checkpointStatus, progress);
}

List<ProjectionDetails> details = client.list().get();

for (ProjectionDetails detail: details) {
    System.out.println(
        detail.getName() + ", " +
        detail.getStatus() + ", " +
        detail.getCheckpointStatus() + ", " +
        detail.getMode() + ", " +
        detail.getProgress());
}

var details = managementClient.ListContinuousAsync();
await foreach (var detail in details)
    Console.WriteLine(
        $@"{detail.Name}, {detail.Status}, {detail.CheckpointStatus}, {detail.Mode}, {detail.Progress}"
    );

// This is currently not available in the Go client

// This is currently not available in the Rust client

Get Status

Gets the status of a named projection. See the projection details section for an explanation of the returned values

# This is currently not available in the Python client

const projection = await client.getProjectionStatus(name);

console.log(
  projection.name,
  projection.status,
  projection.checkpointStatus,
  projection.progress
);

const projection = await client.getProjectionStatus(name);

console.log(
  projection.name,
  projection.status,
  projection.checkpointStatus,
  projection.progress
);

String name = "get_result_example";
String js =
    "fromAll()" +
    ".when({" +
    "    $init() {" +
    "        return {" +
    "            count: 0," +
    "        };" +
    "    }," +
    "    $any(s, e) {" +
    "        s.count += 1;" +
    "    }" +
    "})" +
    ".transformBy((state) => state.count)" +
    ".outputState();";

client.create(name, js).get();

Thread.sleep(500); //give it some time to process and have a state.

int result = client
        .getResult(name, int.class)
        .get();

System.out.println(result);

await managementClient.CreateContinuousAsync(name, js);
var status = await managementClient.GetStatusAsync(name);
Console.WriteLine(
    $@"{status?.Name}, {status?.Status}, {status?.CheckpointStatus}, {status?.Mode}, {status?.Progress}"
);

// This is currently not available in the Go client

// This is currently not available in the Rust client

Get state

Retrieves the state of a projection.

# This is currently not available in the Python client

  const name = `get_state_example`;
  const projection = `
    fromAll()
        .when({
            $init() {
                return {
                    count: 0,
                };
            },
            $any(s, e) {
                s.count += 1;
            }
        })
        .transformBy((state) => state.count)
        .outputState();
`;

  await client.createProjection(name, projection);

  // Give it some time to count event
  await delay(500);

  const state = await client.getProjectionState(name);

  console.log(`Counted ${state.count} events.`);

interface CountProjectionState {
  count: number;
}

const name = `get_state_example`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .transformBy((state) => state.count)
      .outputState();


await client.createProjection(name, projection);

// Give it some time to count event
await delay(500);

const state = await client.getProjectionState<CountProjectionState>(name);

console.log(`Counted ${state.count} events.`);

String name = "get_result_example";
String js =
    "fromAll()" +
    ".when({" +
    "    $init() {" +
    "        return {" +
    "            count: 0," +
    "        };" +
    "    }," +
    "    $any(s, e) {" +
    "        s.count += 1;" +
    "    }" +
    "})" +
    ".transformBy((state) => state.count)" +
    ".outputState();";

client.create(name, js).get();

Thread.sleep(500); //give it some time to process and have a state.

int result = client
        .getResult(name, int.class)
        .get();

System.out.println(result);

const string js =
    "fromAll().when({$init:function(){return {count:0};},$any:function(s, e){s.count += 1;}}).outputState();";

var name = $"countEvents_State_{Guid.NewGuid()}";

await managementClient.CreateContinuousAsync(name, js);
//give it some time to process and have a state.
await Task.Delay(500);

var stateDocument = await managementClient.GetStateAsync(name);
var result        = await managementClient.GetStateAsync<Result>(name);

Console.WriteLine(DocToString(stateDocument));
Console.WriteLine(result);

static async Task<string> DocToString(JsonDocument d) {
    await using var stream = new MemoryStream();
    var             writer = new Utf8JsonWriter(stream, new JsonWriterOptions { Indented = false });
    d.WriteTo(writer);
    await writer.FlushAsync();
    return Encoding.UTF8.GetString(stream.ToArray());
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Get result

Retrieves the result of the named projection and partition.

# This is currently not available in the Python client

const name = `get_result_example`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .transformBy((state) => state.count)
      .outputState();


await client.createProjection(name, projection);

// Give it some time to have a result.
await delay(500);

const result = await client.getProjectionResult(name);

console.log(`Counted ${result} events.`);

const name = `get_result_example`;
const projection = `
  fromAll()
      .when({
          $init() {
              return {
                  count: 0,
              };
          },
          $any(s, e) {
              s.count += 1;
          }
      })
      .transformBy((state) => state.count)
      .outputState();


await client.createProjection(name, projection);

// Give it some time to have a result.
await delay(500);

const result = await client.getProjectionResult<number>(name);

console.log(`Counted ${result} events.`);

String name = "get_result_example";
String js =
    "fromAll()" +
    ".when({" +
    "    $init() {" +
    "        return {" +
    "            count: 0," +
    "        };" +
    "    }," +
    "    $any(s, e) {" +
    "        s.count += 1;" +
    "    }" +
    "})" +
    ".transformBy((state) => state.count)" +
    ".outputState();";

client.create(name, js).get();

Thread.sleep(500); //give it some time to process and have a state.

int result = client
        .getResult(name, int.class)
        .get();

System.out.println(result);

const string js = @"fromAll()
                            .when({
                                $init: function() {
                                    return {
                                        count: 0
                                    };
                                },
                                $any: function(s, e) {
                                    s.count += 1;
                                }
                            })
                            .outputState();";

var name = $"countEvents_Result_{Guid.NewGuid()}";

await managementClient.CreateContinuousAsync(name, js);
await Task.Delay(500); //give it some time to have a result.

// Results are retrieved either as  JsonDocument or a typed result 
var document = await managementClient.GetResultAsync(name);
var result   = await managementClient.GetResultAsync<Result>(name);

Console.WriteLine(DocToString(document));
Console.WriteLine(result);

static string DocToString(JsonDocument d) {
    using var stream = new MemoryStream();
    using var writer = new Utf8JsonWriter(stream, new JsonWriterOptions { Indented = false });
    d.WriteTo(writer);
    writer.Flush();
    return Encoding.UTF8.GetString(stream.ToArray());
}

// This is currently not available in the Go client

// This is currently not available in the Rust client

Projection Details

List all, list continuous and get status all return the details and statistics of projections

Field	Description
Name, EffectiveName	The name of the projection
Status	A human readable string of the current statuses of the projection (see below)
StateReason	A human readable string explaining the reason of the current projection state
CheckpointStatus	A human readable string explaining the current operation performed on the checkpoint : requested, writing
Mode	Continuous, OneTime , Transient
CoreProcessingTime	The total time, in ms, the projection took to handle events since the last restart
Progress	The progress, in %, indicates how far this projection has processed event, in case of a restart this could be -1% or some number. It will be updated as soon as a new event is appended and processed
WritesInProgress	The number of write requests to emitted streams currently in progress, these writes can be batches of events
ReadsInProgress	The number of read requests currently in progress
PartitionsCached	The number of cached projection partitions
Position	The Position of the last processed event
LastCheckpoint	The Position of the last checkpoint of this projection
EventsProcessedAfterRestart	The number of events processed since the last restart of this projection
BufferedEvents	The number of events in the projection read buffer
WritePendingEventsBeforeCheckpoint	The number of events waiting to be appended to emitted streams before the pending checkpoint can be written
WritePendingEventsAfterCheckpoint	The number of events to be appended to emitted streams since the last checkpoint
Version	This is used internally, the version is increased when the projection is edited or reset
Epoch	This is used internally, the epoch is increased when the projection is reset

The Status string is a combination of the following values. The first 3 are the most common one, as the other one are transient values while the projection is initialised or stopped

Value	Description
Running	The projection is running and processing events
Stopped	The projection is stopped and is no longer processing new events
Faulted	An error occurred in the projection, StateReason will give the fault details, the projection is not processing events
Initial	This is the initial state, before the projection is fully initialised
Suspended	The projection is suspended and will not process events, this happens while stopping the projection
LoadStateRequested	The state of the projection is being retrieved, this happens while the projection is starting
StateLoaded	The state of the projection is loaded, this happens while the projection is starting
Subscribed	The projection has successfully subscribed to its readers, this happens while the projection is starting
FaultedStopping	This happens before the projection is stopped due to an error in the projection
Stopping	The projection is being stopped
CompletingPhase	This happens while the projection is stopping
PhaseCompleted	This happens while the projection is stopping